gallery/vendor/i-slint-core/input.rs

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

// cSpell: ignore altgr rpos Unapply
/*! Module handling mouse events
*/
#![warn(missing_docs)]

use crate::cursor::MouseCursorInner;
use crate::item_tree::ItemTreeRc;
use crate::item_tree::{ItemRc, ItemWeak, VisitChildrenResult};
use crate::items::{
    AllowedDragActions, BuiltInMouseCursor, DropEvent, ItemRef, OperatingSystemType,
    TextCursorDirection,
};
pub use crate::items::{FocusReason, KeyEvent, KeyboardModifiers, PointerEventButton};
use crate::lengths::{ItemTransform, LogicalPoint, LogicalVector};
use crate::window::{WindowAdapter, WindowInner};
use crate::{Coord, Property, SharedString};
use alloc::rc::Rc;
use alloc::vec::Vec;
use const_field_offset::FieldOffsets;
use core::cell::Cell;
use core::fmt::Display;
use core::pin::Pin;
use core::time::Duration;

/// A mouse or touch event
///
/// The only difference with [`crate::platform::WindowEvent`] is that it uses untyped `Point`
/// TODO: merge with platform::WindowEvent
#[repr(C)]
#[derive(Debug, Clone, PartialEq)]
pub enum MouseEvent {
    /// The mouse or finger was pressed
    Pressed {
        /// The position of the pointer when the event happened.
        position: LogicalPoint,
        /// The button that was pressed.
        button: PointerEventButton,
        /// The current click count reported for this press.
        click_count: u8,
        /// The touch ID if the event originated from touch input.
        touch_finger_id: i32,
    },
    /// The mouse or finger was released
    Released {
        /// The position of the pointer when the event happened.
        position: LogicalPoint,
        /// The button that was released.
        button: PointerEventButton,
        /// The current click count reported for this release.
        click_count: u8,
        /// The touch ID if the event originated from touch input.
        touch_finger_id: i32,
    },
    /// The position of the pointer has changed
    Moved {
        /// The new position of the pointer.
        position: LogicalPoint,
        /// The touch ID if the event originated from touch input.
        touch_finger_id: i32,
    },
    /// Wheel was operated.
    Wheel {
        /// The position of the pointer when the event happened.
        position: LogicalPoint,
        /// The horizontal scroll delta in logical pixels.
        delta_x: Coord,
        /// The vertical scroll delta in logical pixels.
        delta_y: Coord,
        /// The gesture phase reported for the wheel event.
        phase: TouchPhase,
    },
    /// The mouse is being dragged over this item.
    /// [`InputEventResult::EventIgnored`] means that the item does not handle the drag operation
    /// and [`InputEventResult::EventAccepted`] means that the item can accept it.
    DragMove {
        /// The dragged payload and its current position/proposed action.
        event: DropEvent,
        /// The actions the drag source permits.
        allowed: AllowedDragActions,
    },
    /// The mouse is released while dragging over this item.
    Drop {
        /// The dragged payload and its current position/proposed action.
        event: DropEvent,
        /// The actions the drag source permits.
        allowed: AllowedDragActions,
    },
    /// A platform-recognized pinch gesture (macOS/iOS trackpad, Qt).
    PinchGesture {
        /// The focal position of the gesture.
        position: LogicalPoint,
        /// The incremental scale delta for this gesture update.
        delta: f32,
        /// The gesture phase reported by the platform.
        phase: TouchPhase,
    },
    /// A platform-recognized rotation gesture (macOS/iOS trackpad, Qt).
    RotationGesture {
        /// The focal position of the gesture.
        position: LogicalPoint,
        /// The incremental rotation in degrees, where positive means clockwise.
        delta: f32,
        /// The gesture phase reported by the platform.
        phase: TouchPhase,
    },
    /// The mouse exited the item or component
    Exit,
}

impl MouseEvent {
    /// The touch ID if the event originated from touch input.
    pub fn touch_finger_id(&self) -> i32 {
        match self {
            MouseEvent::Pressed { touch_finger_id, .. } => *touch_finger_id,
            MouseEvent::Released { touch_finger_id, .. } => *touch_finger_id,
            MouseEvent::Moved { touch_finger_id, .. } => *touch_finger_id,
            _ => 0,
        }
    }

    /// Whether the event originates from a touch screen rather than a mouse.
    pub fn is_from_touch(&self) -> bool {
        // touch events carry the finger id + 1, events from a mouse carry 0
        self.touch_finger_id() != 0
    }

    /// The position of the cursor for this event, if any
    pub fn position(&self) -> Option<LogicalPoint> {
        match self {
            MouseEvent::Pressed { position, .. } => Some(*position),
            MouseEvent::Released { position, .. } => Some(*position),
            MouseEvent::Moved { position, .. } => Some(*position),
            MouseEvent::Wheel { position, .. } => Some(*position),
            MouseEvent::PinchGesture { position, .. } => Some(*position),
            MouseEvent::RotationGesture { position, .. } => Some(*position),
            MouseEvent::DragMove { event: e, .. } | MouseEvent::Drop { event: e, .. } => {
                Some(crate::lengths::logical_point_from_api(e.position))
            }
            MouseEvent::Exit => None,
        }
    }

    /// Translate the position by the given value
    pub fn translate(&mut self, vec: LogicalVector) {
        let pos = match self {
            MouseEvent::Pressed { position, .. } => Some(position),
            MouseEvent::Released { position, .. } => Some(position),
            MouseEvent::Moved { position, .. } => Some(position),
            MouseEvent::Wheel { position, .. } => Some(position),
            MouseEvent::PinchGesture { position, .. } => Some(position),
            MouseEvent::RotationGesture { position, .. } => Some(position),
            MouseEvent::DragMove { event: e, .. } | MouseEvent::Drop { event: e, .. } => {
                e.position = crate::api::LogicalPosition::from_euclid(
                    crate::lengths::logical_point_from_api(e.position) + vec,
                );
                None
            }
            MouseEvent::Exit => None,
        };
        if let Some(pos) = pos {
            *pos += vec;
        }
    }

    /// Transform the position by the given item transform.
    pub fn transform(&mut self, transform: ItemTransform) {
        let pos = match self {
            MouseEvent::Pressed { position, .. } => Some(position),
            MouseEvent::Released { position, .. } => Some(position),
            MouseEvent::Moved { position, .. } => Some(position),
            MouseEvent::Wheel { position, .. } => Some(position),
            MouseEvent::PinchGesture { position, .. } => Some(position),
            MouseEvent::RotationGesture { position, .. } => Some(position),
            MouseEvent::DragMove { event: e, .. } | MouseEvent::Drop { event: e, .. } => {
                e.position = crate::api::LogicalPosition::from_euclid(
                    transform
                        .transform_point(crate::lengths::logical_point_from_api(e.position).cast())
                        .cast(),
                );
                None
            }
            MouseEvent::Exit => None,
        };
        if let Some(pos) = pos {
            *pos = transform.transform_point(pos.cast()).cast();
        }
    }

    /// Set the click count of the pressed or released event
    fn set_click_count(&mut self, count: u8) {
        match self {
            MouseEvent::Pressed { click_count, .. } | MouseEvent::Released { click_count, .. } => {
                *click_count = count
            }
            _ => (),
        }
    }
}

/// The mouse events a backend can deliver to the runtime.
#[allow(missing_docs)]
#[repr(C)]
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum BackendMouseEvent {
    /// The mouse or finger was pressed
    Pressed {
        position: LogicalPoint,
        button: PointerEventButton,
        click_count: u8,
        touch_finger_id: i32,
    },
    /// The mouse or finger was released
    Released {
        position: LogicalPoint,
        button: PointerEventButton,
        click_count: u8,
        touch_finger_id: i32,
    },
    /// The position of the pointer has changed
    Moved { position: LogicalPoint, touch_finger_id: i32 },
    /// Wheel was operated.
    Wheel { position: LogicalPoint, delta_x: Coord, delta_y: Coord, phase: TouchPhase },
    /// A platform-recognized pinch gesture (macOS/iOS trackpad, Qt).
    PinchGesture { position: LogicalPoint, delta: f32, phase: TouchPhase },
    /// A platform-recognized rotation gesture (macOS/iOS trackpad, Qt).
    RotationGesture { position: LogicalPoint, delta: f32, phase: TouchPhase },
    /// The mouse exited the item or component
    Exit,
}

impl From<BackendMouseEvent> for MouseEvent {
    fn from(event: BackendMouseEvent) -> Self {
        match event {
            BackendMouseEvent::Pressed { position, button, click_count, touch_finger_id } => {
                Self::Pressed { position, button, click_count, touch_finger_id }
            }
            BackendMouseEvent::Released { position, button, click_count, touch_finger_id } => {
                Self::Released { position, button, click_count, touch_finger_id }
            }
            BackendMouseEvent::Moved { position, touch_finger_id } => {
                Self::Moved { position, touch_finger_id }
            }
            BackendMouseEvent::Wheel { position, delta_x, delta_y, phase } => {
                Self::Wheel { position, delta_x, delta_y, phase }
            }
            BackendMouseEvent::PinchGesture { position, delta, phase } => {
                Self::PinchGesture { position, delta, phase }
            }
            BackendMouseEvent::RotationGesture { position, delta, phase } => {
                Self::RotationGesture { position, delta, phase }
            }
            BackendMouseEvent::Exit => Self::Exit,
        }
    }
}

/// The drag and drop events a backend can deliver, through [`WindowInner::process_drag_event`].
#[allow(missing_docs)]
#[derive(Debug, Clone, PartialEq)]
pub enum BackendDragEvent {
    /// A drag is hovering over the window.
    Move { event: DropEvent, allowed: AllowedDragActions },
    /// A drag was released over the window.
    Drop { event: DropEvent, allowed: AllowedDragActions },
    /// A drag left the window, or was cancelled while hovering over it.
    Leave,
}

impl From<BackendDragEvent> for MouseEvent {
    fn from(event: BackendDragEvent) -> Self {
        match event {
            BackendDragEvent::Move { event, allowed } => Self::DragMove { event, allowed },
            BackendDragEvent::Drop { event, allowed } => Self::Drop { event, allowed },
            // A drag leaving tears down the hover state the same way the pointer leaving does.
            BackendDragEvent::Leave => Self::Exit,
        }
    }
}

/// Phase of a touch, gesture event or wheel event.
/// A touchpad is recognized as wheel event and therefore
/// we need to find out when the touch event starts and ends
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum TouchPhase {
    /// The gesture began (e.g., first finger touched or platform gesture started).
    Started,
    /// The gesture is ongoing (e.g., fingers moved or platform gesture updated).
    Moved,
    /// The gesture completed normally.
    Ended,
    /// The gesture was cancelled (e.g., interrupted by the system) or the mouse wheel was used
    Cancelled,
}

/// This value is returned by the `input_event` function of an Item
/// to notify the run-time about how the event was handled and
/// what the next steps are.
/// See [`crate::items::ItemVTable::input_event`].
#[repr(u8)]
#[derive(Debug, Copy, Clone, Eq, PartialEq, Default)]
pub enum InputEventResult {
    /// The event was accepted. This may result in additional events, for example
    /// accepting a mouse move will result in a MouseExit event later.
    EventAccepted,
    /// The event was ignored.
    #[default]
    EventIgnored,
    /// All further mouse events need to be sent to this item or component
    GrabMouse,
    /// Will start a drag operation. Can only be returned from a [`crate::items::DragArea`] item.
    StartDrag,
}

/// This value is returned by the `input_event_filter_before_children` function, which
/// can specify how to further process the event.
/// See [`crate::items::ItemVTable::input_event_filter_before_children`].
#[repr(C)]
#[derive(Debug, Copy, Clone, PartialEq, Default)]
pub enum InputEventFilterResult {
    /// The event is going to be forwarded to children, then the [`crate::items::ItemVTable::input_event`]
    /// function is called
    #[default]
    ForwardEvent,
    /// The event will be forwarded to the children, but the [`crate::items::ItemVTable::input_event`] is not
    /// going to be called for this item
    ForwardAndIgnore,
    /// Just like `ForwardEvent`, but even in the case that children grabs the mouse, this function
    /// will still be called for further events
    ForwardAndInterceptGrab,
    /// The event will not be forwarded to children, if a child already had the grab, the
    /// grab will be cancelled with a [`MouseEvent::Exit`] event
    Intercept,
    /// The event will be forwarded to the children with a delay (in milliseconds), unless it is
    /// being intercepted.
    /// This is what happens when the flickable wants to delay the event.
    /// This should only be used for Press event, and the event will be sent after the delay, or
    /// if a release event is seen before that delay
    /// If any other component is handling the event it will be not handled by the component returned this result
    //(Can't use core::time::Duration because it is not repr(c))
    DelayForwarding(u64),
    /// Like `ForwardAndIgnore`, but the item still receives a [`MouseEvent::Exit`]
    /// when the pointer leaves, even if a sibling handles the event in between.
    ForwardAndObserve,
}

/// This module contains the constant character code used to represent the keys.
#[allow(missing_docs, non_upper_case_globals)]
pub mod key_codes {
    macro_rules! declare_consts_for_special_keys {
       ($($char:literal # $name:ident # $($shifted:ident)? $(=> $($_muda:ident)? # $($_qt:ident)|* # $($_winit:ident $(($_pos:ident))?)|*    # $($_xkb:ident)|* )? ;)*) => {
            $(pub const $name : char = $char;)*

            #[allow(missing_docs)]
            #[derive(Debug, Copy, Clone, PartialEq)]
            #[non_exhaustive]
            /// The `Key` enum is used to map a specific key by name e.g. `Key::Control` to an
            /// internal used unicode representation. The enum is convertible to [`std::char`] and [`slint::SharedString`](`crate::SharedString`).
            /// Use this with [`slint::platform::WindowEvent`](`crate::platform::WindowEvent`) to supply key events to Slint's platform abstraction.
            ///
            /// # Example
            ///
            /// Send an tab key press event to a window
            ///
            /// ```
            /// use slint::platform::{WindowEvent, Key};
            /// fn send_tab_pressed(window: &slint::Window) {
            ///     window.dispatch_event(WindowEvent::KeyPressed { text: Key::Tab.into() });
            /// }
            /// ```
            pub enum Key {
                $($name,)*
            }

            impl From<Key> for char {
                fn from(k: Key) -> Self {
                    match k {
                        $(Key::$name => $name,)*
                    }
                }
            }

            impl From<Key> for crate::SharedString {
                fn from(k: Key) -> Self {
                    char::from(k).into()
                }
            }
        };
    }

    i_slint_common::for_each_keys!(declare_consts_for_special_keys);
}

/// Internal struct to maintain the pressed/released state of the keys that
/// map to keyboard modifiers.
#[derive(Clone, Copy, Default, Debug)]
pub(crate) struct InternalKeyboardModifierState {
    left_alt: bool,
    right_alt: bool,
    altgr: bool,
    left_control: bool,
    right_control: bool,
    left_meta: bool,
    right_meta: bool,
    left_shift: bool,
    right_shift: bool,
}

impl InternalKeyboardModifierState {
    /// Updates a flag of the modifiers if the key of the given text is pressed.
    /// Returns an updated modifier if detected; None otherwise;
    pub(crate) fn state_update(mut self, pressed: bool, text: &SharedString) -> Option<Self> {
        if let Some(key_code) = text.chars().next() {
            match key_code {
                key_codes::Alt => self.left_alt = pressed,
                key_codes::AltGr => self.altgr = pressed,
                key_codes::Control => self.left_control = pressed,
                key_codes::ControlR => self.right_control = pressed,
                key_codes::Shift => self.left_shift = pressed,
                key_codes::ShiftR => self.right_shift = pressed,
                key_codes::Meta => self.left_meta = pressed,
                key_codes::MetaR => self.right_meta = pressed,
                _ => return None,
            };

            // Encoded keyboard modifiers must appear as individual key events. This could
            // be relaxed by implementing a string split, but right now WindowEvent::KeyPressed
            // holds only a single char.
            debug_assert_eq!(key_code.len_utf8(), text.len());
        }

        Some(self)
    }

    pub fn shift(&self) -> bool {
        self.right_shift || self.left_shift
    }
    pub fn alt(&self) -> bool {
        self.right_alt || self.left_alt
    }
    pub fn meta(&self) -> bool {
        self.right_meta || self.left_meta
    }
    pub fn control(&self) -> bool {
        self.right_control || self.left_control
    }

    pub fn modifiers_for(&self, _event: &InternalKeyEvent) -> KeyboardModifiers {
        #[allow(unused_mut)]
        let mut alt = self.alt();
        #[allow(unused_mut)]
        let mut control = self.control();

        // Windows treats Ctrl+Alt as implying AltGr, but not vice-versa
        // Unfortunately, our different backends produce different key combinations here.
        //
        // ## Qt
        // Qt always sends Ctrl + Alt instead of AltGr, and does not tell us whether this
        // was interpreted as AltGr or not. So with Qt we have no way of telling whether
        // AltGr is pressed, and we have to assume that it is pressed whenever Ctrl + Alt is pressed.
        // In that case the `text_without_modifiers` is also not set.
        //
        // ## Winit
        // Winit sends the actual Ctrl/Alt/AltGr keypress correctly.
        // With winit we can detect whether ctrl+alt actually caused a AltGr conversion or not,
        // by checking whether the text_without_modifiers is different from the event text.
        //
        // ## Wasm
        // Winit on the web for some reasons sends first a Ctrl and then AltGr event when only AltGr
        // is pressed.
        // So there we need to get rid of the additional Ctrl event whenever AltGr is pressed.
        #[cfg(target_os = "windows")]
        {
            // Non-web windows (Usually winit or Qt)
            if !self.altgr && self.control() && self.alt() {
                // AltGr is not pressed, but Ctrl+Alt is pressed.
                // Try to detect if an AltGr conversion occurred.
                // If so, disable Ctrl and Alt
                //
                // On platforms that don't provide text_without_modifiers, fall back to a simple
                // heuristic that assumes A-Z & 0-9 are not produced with AltGr, but all other keys are.
                let implies_altgr = if _event.text_without_modifiers.is_empty() {
                    _event.key_event.text.chars().any(|c| !c.is_ascii_alphanumeric())
                } else {
                    _event.text_without_modifiers.to_lowercase()
                        != _event.key_event.text.to_lowercase()
                };
                if implies_altgr {
                    alt = false;
                    control = false;
                }
            }
        }
        #[cfg(target_family = "wasm")]
        if crate::detect_operating_system() == OperatingSystemType::Windows {
            // Non-native windows (e.g. Winit on the web)
            // This currently injects additional Ctrl events, so remove those if AltGr is
            // pressed.
            let is_altgr = self.altgr
                || (self.control()
                    && self.alt()
                    && _event.key_event.text.chars().any(|c| !c.is_ascii_alphanumeric()));
            if is_altgr {
                alt = false;
                control = false;
            }
        }

        KeyboardModifiers { alt, control, meta: self.meta(), shift: self.shift() }
    }
}

impl From<InternalKeyboardModifierState> for KeyboardModifiers {
    fn from(internal_state: InternalKeyboardModifierState) -> Self {
        Self {
            alt: internal_state.alt(),
            control: internal_state.control(),
            meta: internal_state.meta(),
            shift: internal_state.shift(),
        }
    }
}

#[i_slint_core_macros::slint_doc]
/// The `Keys` type is the Rust representation of Slint's `keys` primitive type.
///
/// It can be created with the `@keys` macro in Slint and defines which key event(s) activate a KeyBinding.
///
/// See also the Slint documentation on [Key Bindings](slint:KeyBindingOverview).
///
/// In `.slint` files, `Keys` values are typically created via the `@keys(...)` macro.
/// From backend code, they can be created from a list of string parts with the similar
/// syntax as the macro:
///
/// ```rust
/// use slint::Keys;
///
/// let save = Keys::from_parts(["Control", "S"])?;
/// let undo = Keys::from_parts(["Control", "Shift?", "Z"])?;
/// let f5 = Keys::from_parts(["F5"])?;
/// let zoom_in = Keys::from_parts(["Control", "Plus"])?;
/// let euro = Keys::from_parts(["Control", "€"])?;
/// let empty = Keys::from_parts([])?;  // same as Keys::default()
/// # Ok::<(), i_slint_core::input::KeysParseError>(())
/// ```
/// ## Parts format
///
/// Each element is either a modifier or a key (case-sensitive, matching the `@keys` macro):
/// - **Modifiers** (optional): `Control`, `Alt`, `Shift`, `Meta`
/// - **Optional modifiers**: `Shift?`, `Alt?` (match regardless of that modifier's state)
/// - **Named key** (required, exactly one): A named key (`Return`, `Tab`, `F1`, `Plus`, `Space`, `A`–`Z`, etc.)
/// - **String literal fallback**: If no named key matches, the part is treated as a string
///   literal — it must be a single lowercase grapheme cluster (e.g., `"€"`, `"é"`)
///
/// Keys with layout-dependent shifted variants (digits `Digit0`–`Digit9`, symbols like
/// `Plus`, `Comma`, etc.) automatically get `Shift?` behavior, just like the `@keys` macro.
#[derive(Clone, Eq, PartialEq, Default)]
#[repr(C)]
pub struct Keys {
    inner: KeysInner,
}

/// Internal representation of key-parse errors. Variants are not part of the public API.
#[derive(Debug, Clone, PartialEq, Eq)]
enum KeysParseErrorInner {
    /// No key was found (only modifiers were specified).
    NoKey,
    /// More than one non-modifier key was found.
    MultipleKeys,
    /// A string literal contains more than one grapheme cluster.
    /// The contained string is the offending key part (e.g. `"ab"` or `"return"`).
    MultipleGraphemeClusters(SharedString),
    /// A string literal is not lowercase.
    /// The contained string is the offending key part (e.g. `"É"`).
    NotLowercase(SharedString),
    /// Incompatible modifiers were specified (e.g. both `Shift` and `Shift?`).
    /// The contained string is a human-readable description of the conflict.
    IncompatibleModifiers(SharedString),
}

/// Error type returned when constructing a [`Keys`] from string parts.
///
/// This is an opaque error type. Use its [`Display`] implementation
/// to obtain a human-readable description of the problem.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct KeysParseError(KeysParseErrorInner);

impl core::fmt::Display for KeysParseError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        match &self.0 {
            KeysParseErrorInner::NoKey => write!(f, "no key found (only modifiers)"),
            KeysParseErrorInner::MultipleKeys => {
                write!(f, "multiple non-modifier keys found")
            }
            KeysParseErrorInner::MultipleGraphemeClusters(s) => {
                write!(f, "key string must be a single grapheme cluster, got: {s}")
            }
            KeysParseErrorInner::NotLowercase(s) => {
                let lower = s.to_lowercase();
                write!(f, "key string must be lowercase, use \"{lower}\" instead")
            }
            KeysParseErrorInner::IncompatibleModifiers(msg) => write!(f, "{msg}"),
        }
    }
}

impl core::error::Error for KeysParseError {}

use i_slint_common::key_codes::{ShiftBehavior, lookup_key_name};

/// Re-exported in private_unstable_api to create a Keys struct.
pub fn make_keys(
    key: SharedString,
    modifiers: KeyboardModifiers,
    ignore_shift: bool,
    ignore_alt: bool,
) -> Keys {
    Keys {
        inner: KeysInner { key: key.to_lowercase().into(), modifiers, ignore_shift, ignore_alt },
    }
}

#[cfg(feature = "ffi")]
#[allow(unsafe_code)]
pub(crate) mod ffi {
    use crate::api::ToSharedString as _;

    use super::*;

    #[unsafe(no_mangle)]
    pub unsafe extern "C" fn slint_keys(
        key: &SharedString,
        alt: bool,
        control: bool,
        shift: bool,
        meta: bool,
        ignore_shift: bool,
        ignore_alt: bool,
        out: &mut Keys,
    ) {
        *out = make_keys(
            key.clone(),
            KeyboardModifiers { alt, control, shift, meta },
            ignore_shift,
            ignore_alt,
        );
    }

    #[unsafe(no_mangle)]
    pub unsafe extern "C" fn slint_keys_debug_string(shortcut: &Keys, out: &mut SharedString) {
        *out = crate::format!("{shortcut:?}");
    }

    #[unsafe(no_mangle)]
    pub unsafe extern "C" fn slint_keys_to_string(shortcut: &Keys, out: &mut SharedString) {
        *out = shortcut.to_shared_string();
    }

    #[unsafe(no_mangle)]
    pub unsafe extern "C" fn slint_keys_from_parts(
        parts: crate::slice::Slice<'_, SharedString>,
        out: &mut Keys,
    ) -> bool {
        match keys_from_parts(parts.as_slice().iter().map(|s| s.as_str())) {
            Ok(keys) => {
                *out = keys;
                true
            }
            Err(_) => false,
        }
    }

    #[unsafe(no_mangle)]
    pub unsafe extern "C" fn slint_keys_to_parts(
        keys: &Keys,
        out: &mut crate::SharedVector<SharedString>,
    ) {
        *out = keys.to_parts().map(SharedString::from).collect();
    }
}

/// Normalize a key string: lowercase and NFC-normalize.
fn normalize_key(key: &str) -> SharedString {
    let lowered = key.to_lowercase();
    cfg_if::cfg_if! {
        if #[cfg(feature = "shared-parley")] {
            let normalizer = icu_normalizer::ComposingNormalizer::new_nfc();
            let normalized = normalizer.normalize(&lowered);
            SharedString::from(normalized.as_ref())
        } else {
            SharedString::from(lowered.as_str())
        }
    }
}

fn keys_from_parts<'a>(parts: impl Iterator<Item = &'a str>) -> Result<Keys, KeysParseError> {
    keys_from_parts_inner(parts).map_err(KeysParseError)
}

fn keys_from_parts_inner<'a>(
    parts: impl Iterator<Item = &'a str>,
) -> Result<Keys, KeysParseErrorInner> {
    use unicode_segmentation::UnicodeSegmentation;

    let mut modifiers = KeyboardModifiers::default();
    let mut ignore_shift = false;
    let mut ignore_alt = false;
    let mut key_part: Option<&str> = None;

    for part in parts {
        // Parts are *not* trimmed: whitespace is significant, so `" "`, `"\t"` and
        // `"\n"` are valid literal spellings of the Space, Tab and Return keys, the
        // same way `@keys(" ")` is valid in Slint. Trimming would silently swallow
        // them and make those keys unreachable through a literal. Empty parts carry
        // no information and are skipped, which keeps `from_parts([""])` equivalent
        // to `from_parts([])`.
        if part.is_empty() {
            continue;
        }
        match part {
            "Control" => modifiers.control = true,
            "Alt" => {
                if ignore_alt {
                    return Err(KeysParseErrorInner::IncompatibleModifiers(
                        "Alt and Alt? cannot be combined".into(),
                    ));
                }
                modifiers.alt = true;
            }
            "Shift" => {
                if ignore_shift {
                    return Err(KeysParseErrorInner::IncompatibleModifiers(
                        "Shift and Shift? cannot be combined".into(),
                    ));
                }
                modifiers.shift = true;
            }
            "Meta" => modifiers.meta = true,
            "Shift?" => {
                if modifiers.shift {
                    return Err(KeysParseErrorInner::IncompatibleModifiers(
                        "Shift and Shift? cannot be combined".into(),
                    ));
                }
                ignore_shift = true;
            }
            "Alt?" => {
                if modifiers.alt {
                    return Err(KeysParseErrorInner::IncompatibleModifiers(
                        "Alt and Alt? cannot be combined".into(),
                    ));
                }
                ignore_alt = true;
            }
            _ => {
                if key_part.is_some() {
                    return Err(KeysParseErrorInner::MultipleKeys);
                }
                key_part = Some(part);
            }
        }
    }

    let key_name = match key_part {
        Some(k) => k,
        None if modifiers == KeyboardModifiers::default() && !ignore_shift && !ignore_alt => {
            // Empty input (or only empty parts) → Keys::default(), same as @keys()
            return Ok(Keys::default());
        }
        None => return Err(KeysParseErrorInner::NoKey),
    };

    // First: try named-key lookup (case-sensitive, like the @keys macro)
    if let Some((key_char, shift_behavior)) = lookup_key_name(key_name) {
        // Auto-set ignore_shift for keys with localized shifted variants
        if matches!(shift_behavior, ShiftBehavior::LocalizedShiftable { .. }) {
            if modifiers.shift {
                return Err(KeysParseErrorInner::IncompatibleModifiers(
                    alloc::format!(
                        "Key bindings involving {key_name} ignore Shift to support different keyboard layouts; remove Shift"
                    ).into(),
                ));
            }
            ignore_shift = true;
        }
        // Key code literals in key_codes.rs are already NFC-normalized, just lowercase.
        let key: SharedString = key_char.to_lowercase().collect::<alloc::string::String>().into();
        return Ok(Keys { inner: KeysInner { key, modifiers, ignore_shift, ignore_alt } });
    }

    // Fallback: treat as a string literal (like @keys("€"))
    // Must be a single grapheme cluster
    let grapheme_count = key_name.graphemes(true).count();
    if grapheme_count > 1 {
        return Err(KeysParseErrorInner::MultipleGraphemeClusters(key_name.into()));
    }

    // Must be lowercase
    let lowered = key_name.to_lowercase();
    if lowered != key_name {
        return Err(KeysParseErrorInner::NotLowercase(key_name.into()));
    }

    let key = normalize_key(key_name);
    Ok(Keys { inner: KeysInner { key, modifiers, ignore_shift, ignore_alt } })
}

/// Internal representation of the `Keys` type.
/// This is semver exempt and is only used to set up the native menu in the backends.
#[derive(PartialEq, Eq, Clone, Default)]
#[repr(C)]
pub struct KeysInner {
    /// The `key` used to trigger the shortcut
    ///
    /// Note: This is currently converted to lowercase when the shortcut is created!
    pub key: SharedString,
    /// `KeyboardModifier`s that need to be pressed for the shortcut to fire
    pub modifiers: KeyboardModifiers,
    /// Whether to ignore shift state when matching the shortcut
    pub ignore_shift: bool,
    /// Whether to ignore alt state when matching the shortcut
    pub ignore_alt: bool,
}

impl KeysInner {
    /// Private access to the KeysInner for a given Keys value.
    pub fn from_pub(keys: &Keys) -> &Self {
        &keys.inner
    }
}

impl Keys {
    #[i_slint_core_macros::slint_doc]
    /// Create a `Keys` from an iterator of string parts (matching `@keys` macro syntax).
    ///
    /// Each element is either a modifier (`Control`, `Shift`, `Alt`, `Meta`, `Shift?`, `Alt?`)
    /// or a key. Keys are first looked up by name (case-sensitive) in the Key namespace;
    /// if not found, treated as a string literal (must be a single lowercase grapheme cluster).
    /// Exactly one non-modifier key must be present.
    ///
    /// Parts are taken verbatim — they are not trimmed — so whitespace is significant:
    /// `" "`, `"\t"` and `"\n"` are literal spellings of the `Space`, `Tab` and `Return`
    /// keys, just as `@keys(" ")` is valid in Slint. A part must therefore match a
    /// modifier or key exactly; `" Control "` is not the `Control` modifier.
    ///
    /// An empty iterator returns `Keys::default()` (same as `@keys()`). Empty parts are
    /// skipped, so `from_parts([""])` is also `Keys::default()`.
    ///
    /// See also the Slint documentation on [Key Bindings](slint:KeyBindingOverview).
    ///
    /// Note: This currently only supports a **single shortcut** (one key + modifiers).
    pub fn from_parts<'a>(
        parts: impl IntoIterator<Item = &'a str>,
    ) -> Result<Keys, KeysParseError> {
        keys_from_parts(parts.into_iter())
    }

    #[i_slint_core_macros::slint_doc]
    /// Decompose this `Keys` value into the string parts that
    /// [`Keys::from_parts`] accepts.
    ///
    /// See also the Slint documentation on [Key Bindings](slint:KeyBindingOverview).
    ///
    /// A `Keys` value that is converted into parts and then re-created from those parts
    /// with [`Keys::from_parts`] will be equal to the input `Keys` value:
    ///
    /// ```
    /// use slint::Keys;
    /// let k = Keys::from_parts(["Control", "Shift?", "Z"])?;
    /// let k_from_parts = Keys::from_parts(k.to_parts())?;
    /// assert_eq!(k_from_parts, k);
    /// # Ok::<(), i_slint_core::input::KeysParseError>(())
    /// ```
    ///
    /// Note that while a round-trip guarantees that the resulting `Keys` instances will
    /// be equal, the parts returned by `to_parts` can be different from the parts used
    /// to construct the `Keys` instance with `from_parts`.
    ///
    /// A part is not necessarily printable, so a text format storing parts has to quote
    /// or escape them. The
    /// [`runtime_key_bindings`](https://github.com/slint-ui/slint/tree/master/examples/runtime_key_bindings)
    /// example shows one way to persist a user-configured shortcut and restore it.
    ///
    /// An empty `Keys` (i.e. [`Keys::default()`]) returns an empty iterator.
    pub fn to_parts(&self) -> impl Iterator<Item = &str> {
        let inner = &self.inner;
        let has_key = !inner.key.is_empty();
        // Order matches the `@keys` macro / Debug impl: Meta, Control, Alt, Shift.
        //
        // The key itself is always emitted as the stored character, never as the
        // name it may have been created from. Names are not reversed back: a
        // `LocalizedShiftable` name auto-applies `ignore_shift` on re-parse, so
        // emitting one would break the round-trip of a literal such as
        // `["Control", "+"]` (which has `ignore_shift = false`). Emitting the raw
        // character lets `ignore_shift` be carried explicitly by `Shift?`, so
        // `@keys(Control + Plus)` comes back as `["Control", "Shift?", "+"]`.
        [
            (has_key && inner.modifiers.meta).then_some("Meta"),
            (has_key && inner.modifiers.control).then_some("Control"),
            (has_key && inner.modifiers.alt).then_some("Alt"),
            (has_key && !inner.modifiers.alt && inner.ignore_alt).then_some("Alt?"),
            (has_key && inner.modifiers.shift).then_some("Shift"),
            (has_key && !inner.modifiers.shift && inner.ignore_shift).then_some("Shift?"),
            has_key.then(|| inner.key.as_str()),
        ]
        .into_iter()
        .flatten()
    }

    /// Check whether a `Keys` can be triggered by the given `KeyEvent`
    pub(crate) fn matches(&self, key_event: &KeyEvent) -> bool {
        let inner = &self.inner;
        // An empty Keys is never triggered, even if the modifiers match.
        if inner.key.is_empty() {
            return false;
        }

        // TODO: Should this check the event_type and only match on KeyReleased?
        let mut expected_modifiers = inner.modifiers;
        if inner.ignore_shift {
            expected_modifiers.shift = key_event.modifiers.shift;
        }
        if inner.ignore_alt {
            expected_modifiers.alt = key_event.modifiers.alt;
        }
        // Note: The shortcut's key is already in lowercase and NFC-normalized
        // (by the compiler and backends respectively), so we only need to
        // lowercase the event text. Backends are expected to NFC-normalize
        // key event text before dispatching.
        //
        // This improves our handling of CapsLock and Shift, as the event text will be in uppercase
        // if caps lock is active, even if shift is not pressed.
        let event_text = key_event.text.chars().flat_map(|character| character.to_lowercase());

        event_text.eq(inner.key.chars()) && key_event.modifiers == expected_modifiers
    }

    fn format_key_for_display(&self) -> crate::SharedString {
        let key_str = self.inner.key.as_str();
        let first_char = key_str.chars().next();

        if let Some(first_char) = first_char {
            macro_rules! check_special_key {
                ($($char:literal # $name:ident # $($shifted:ident)? $(=> $($_muda:ident)? # $($qt:ident)|* # $($winit:ident $(($_pos:ident))?)|* # $($xkb:ident)|*)? ;)*) => {
                    match first_char {
                    $($(
                        // Use $qt as a marker - if it exists, generate the check
                        $char => {
                            let _ = stringify!($($qt)|*); // Use $qt to enable this branch
                            return stringify!($name).into();
                        }
                    )?)*
                        _ => ()
                    }
                };
            }
            i_slint_common::for_each_keys!(check_special_key);
        }

        if key_str.chars().count() == 1 {
            return key_str.to_uppercase().into();
        }

        key_str.into()
    }
}

impl Display for Keys {
    /// Converts the [`Keys`] to a string that looks native on the current platform.
    ///
    /// For example, the shortcut created with `@keys(Meta + Control + A)`
    /// will be converted like this:
    /// - **macOS**: `⌃⌘A`
    /// - **Windows**: `Win+Ctrl+A`
    /// - **Linux**: `Super+Ctrl+A`
    ///
    /// Note that this functions output is best-effort and may be adjusted/improved at any time,
    /// do not rely on this output to be stable!
    //
    // References for implementation
    // - macOS: <https://developer.apple.com/design/human-interface-guidelines/keyboards>
    // - Windows: <https://learn.microsoft.com/en-us/windows/apps/design/input/keyboard-accelerators>
    // - Linux: <https://developer.gnome.org/hig/guidelines/keyboard.html>
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let inner = &self.inner;
        if inner.key.is_empty() {
            return Ok(());
        }

        if crate::is_apple_platform() {
            // Slint remaps modifiers on macOS: control → Command, meta → Control
            // From Apple's documentation:
            //
            // List modifier keys in the correct order.
            // If you use more than one modifier key in a custom shortcut, always list them in this order:
            //  Control, Option, Shift, Command
            if inner.modifiers.meta {
                f.write_str("⌃")?;
            }
            if !inner.ignore_alt && inner.modifiers.alt {
                f.write_str("⌥")?;
            }
            if !inner.ignore_shift && inner.modifiers.shift {
                f.write_str("⇧")?;
            }
            if inner.modifiers.control {
                f.write_str("⌘")?;
            }
        } else {
            let separator = "+";

            // TODO: These should probably be translated, but better to have at least
            // platform-local names than nothing.
            let (ctrl_str, alt_str, shift_str, meta_str) =
                if crate::detect_operating_system() == OperatingSystemType::Windows {
                    ("Ctrl", "Alt", "Shift", "Win")
                } else {
                    ("Ctrl", "Alt", "Shift", "Super")
                };

            if inner.modifiers.meta {
                f.write_str(meta_str)?;
                f.write_str(separator)?;
            }
            if inner.modifiers.control {
                f.write_str(ctrl_str)?;
                f.write_str(separator)?;
            }
            if !inner.ignore_alt && inner.modifiers.alt {
                f.write_str(alt_str)?;
                f.write_str(separator)?;
            }
            if !inner.ignore_shift && inner.modifiers.shift {
                f.write_str(shift_str)?;
                f.write_str(separator)?;
            }
        }
        f.write_str(&self.format_key_for_display())
    }
}

impl core::fmt::Debug for Keys {
    /// Formats the keyboard shortcut so that the output would be accepted by the @keys macro in Slint.
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let inner = &self.inner;
        // Make sure to keep this in sync with the implementation in compiler/langtype.rs
        if inner.key.is_empty() {
            write!(f, "")
        } else {
            let alt = inner
                .ignore_alt
                .then_some("Alt?+")
                .or(inner.modifiers.alt.then_some("Alt+"))
                .unwrap_or_default();
            let ctrl = if inner.modifiers.control { "Control+" } else { "" };
            let meta = if inner.modifiers.meta { "Meta+" } else { "" };
            let shift = inner
                .ignore_shift
                .then_some("Shift?+")
                .or(inner.modifiers.shift.then_some("Shift+"))
                .unwrap_or_default();
            let keycode: SharedString = inner
                .key
                .chars()
                .flat_map(|character| {
                    let mut escaped = alloc::vec![];
                    if character.is_control() {
                        escaped.extend(character.escape_unicode());
                    } else {
                        escaped.push(character);
                    }
                    escaped
                })
                .collect();
            write!(f, "{meta}{ctrl}{alt}{shift}\"{keycode}\"")
        }
    }
}

/// This enum defines the different kinds of key events that can happen.
#[derive(Copy, Clone, Debug, PartialEq, Eq, Default)]
#[repr(u8)]
pub enum KeyEventType {
    /// A key on a keyboard was pressed.
    #[default]
    KeyPressed = 0,
    /// A key on a keyboard was released.
    KeyReleased = 1,
    /// The input method updates the currently composed text. The KeyEvent's text field is the pre-edit text and
    /// composition_selection specifies the placement of the cursor within the pre-edit text.
    UpdateComposition = 2,
    /// The input method replaces the currently composed text with the final result of the composition.
    CommitComposition = 3,
}

#[derive(Default, Debug, Clone, PartialEq)]
/// This struct is used to pass key events to the runtime.
pub struct InternalKeyEvent {
    /// That's the public type with only public fields
    pub key_event: KeyEvent,
    /// Indicates whether the key was pressed or released
    pub event_type: KeyEventType,
    /// The key without any modifiers held
    /// Important on Windows, to distinguish between key presses when Ctrl+Alt was pressed
    /// vs. AltGr.
    /// This is optional, and we will fall back to a heuristic for Ctrl+Alt on Windows if this
    /// isn't provided.
    #[cfg(target_os = "windows")]
    pub text_without_modifiers: SharedString,
    /// If the event type is KeyEventType::UpdateComposition or KeyEventType::CommitComposition,
    /// then this field specifies what part of the current text to replace.
    /// Relative to the offset of the pre-edit text within the text input element's text.
    pub replacement_range: Option<core::ops::Range<i32>>,
    /// If the event type is KeyEventType::UpdateComposition, this is the new pre-edit text
    pub preedit_text: SharedString,
    /// The selection within the preedit_text
    pub preedit_selection: Option<core::ops::Range<i32>>,
    /// The new cursor position, when None, the cursor is put after the text that was just inserted
    pub cursor_position: Option<i32>,
    /// The anchor position, when None, the cursor is put after the text that was just inserted
    pub anchor_position: Option<i32>,
}

impl InternalKeyEvent {
    /// If a shortcut was pressed, this function returns `Some(StandardShortcut)`.
    /// Otherwise it returns None.
    pub fn shortcut(&self) -> Option<StandardShortcut> {
        if self.key_event.modifiers.control && !self.key_event.modifiers.shift {
            match self.key_event.text.as_str() {
                #[cfg(not(target_arch = "wasm32"))]
                "c" => Some(StandardShortcut::Copy),
                #[cfg(not(target_arch = "wasm32"))]
                "x" => Some(StandardShortcut::Cut),
                #[cfg(not(target_arch = "wasm32"))]
                "v" => Some(StandardShortcut::Paste),
                "a" => Some(StandardShortcut::SelectAll),
                "f" => Some(StandardShortcut::Find),
                "s" => Some(StandardShortcut::Save),
                "p" => Some(StandardShortcut::Print),
                "z" => Some(StandardShortcut::Undo),
                #[cfg(target_os = "windows")]
                "y" => Some(StandardShortcut::Redo),
                "r" => Some(StandardShortcut::Refresh),
                _ => None,
            }
        } else if self.key_event.modifiers.control && self.key_event.modifiers.shift {
            match self.key_event.text.as_str() {
                #[cfg(not(target_os = "windows"))]
                "z" | "Z" => Some(StandardShortcut::Redo),
                _ => None,
            }
        } else {
            None
        }
    }

    /// If a shortcut concerning text editing was pressed, this function
    /// returns `Some(TextShortcut)`. Otherwise it returns None.
    pub fn text_shortcut(&self) -> Option<TextShortcut> {
        let ke = &self.key_event;
        let keycode = ke.text.chars().next()?;

        let is_apple = crate::is_apple_platform();

        let move_mod = if is_apple {
            ke.modifiers.alt && !ke.modifiers.control && !ke.modifiers.meta
        } else {
            ke.modifiers.control && !ke.modifiers.alt && !ke.modifiers.meta
        };

        if move_mod {
            match keycode {
                key_codes::LeftArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::BackwardByWord));
                }
                key_codes::RightArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::ForwardByWord));
                }
                key_codes::UpArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::StartOfParagraph));
                }
                key_codes::DownArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::EndOfParagraph));
                }
                key_codes::Backspace => {
                    return Some(TextShortcut::DeleteWordBackward);
                }
                key_codes::Delete => {
                    return Some(TextShortcut::DeleteWordForward);
                }
                _ => (),
            };
        }

        #[cfg(not(target_os = "macos"))]
        {
            if ke.modifiers.control && !ke.modifiers.alt && !ke.modifiers.meta {
                match keycode {
                    key_codes::Home => {
                        return Some(TextShortcut::Move(TextCursorDirection::StartOfText));
                    }
                    key_codes::End => {
                        return Some(TextShortcut::Move(TextCursorDirection::EndOfText));
                    }
                    _ => (),
                };
            }
        }

        if is_apple && ke.modifiers.control {
            match keycode {
                key_codes::LeftArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::StartOfLine));
                }
                key_codes::RightArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::EndOfLine));
                }
                key_codes::UpArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::StartOfText));
                }
                key_codes::DownArrow => {
                    return Some(TextShortcut::Move(TextCursorDirection::EndOfText));
                }
                key_codes::Backspace => {
                    return Some(TextShortcut::DeleteToStartOfLine);
                }
                _ => (),
            };
        }

        if let Ok(direction) = TextCursorDirection::try_from(keycode) {
            Some(TextShortcut::Move(direction))
        } else {
            match keycode {
                key_codes::Backspace => Some(TextShortcut::DeleteBackward),
                key_codes::Delete => Some(TextShortcut::DeleteForward),
                _ => None,
            }
        }
    }
}

/// Represents a non context specific shortcut.
pub enum StandardShortcut {
    /// Copy Something
    Copy,
    /// Cut Something
    Cut,
    /// Paste Something
    Paste,
    /// Select All
    SelectAll,
    /// Find/Search Something
    Find,
    /// Save Something
    Save,
    /// Print Something
    Print,
    /// Undo the last action
    Undo,
    /// Redo the last undone action
    Redo,
    /// Refresh
    Refresh,
}

/// Shortcuts that are used when editing text
pub enum TextShortcut {
    /// Move the cursor
    Move(TextCursorDirection),
    /// Delete the Character to the right of the cursor
    DeleteForward,
    /// Delete the Character to the left of the cursor (aka Backspace).
    DeleteBackward,
    /// Delete the word to the right of the cursor
    DeleteWordForward,
    /// Delete the word to the left of the cursor (aka Ctrl + Backspace).
    DeleteWordBackward,
    /// Delete to the left of the cursor until the start of the line
    DeleteToStartOfLine,
}

/// Represents how an item's key_event handler dealt with a key event.
/// An accepted event results in no further event propagation.
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub enum KeyEventResult {
    /// The event was handled.
    EventAccepted,
    /// The event was not handled and should be sent to other items.
    #[default]
    EventIgnored,
}

/// Represents how an item's focus_event handler dealt with a focus event.
/// An accepted event results in no further event propagation.
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub enum FocusEventResult {
    /// The event was handled.
    FocusAccepted,
    /// The event was not handled and should be sent to other items.
    #[default]
    FocusIgnored,
}

/// This event is sent to a component and items when they receive or lose
/// the keyboard focus.
#[derive(Debug, Clone, Copy, PartialEq)]
#[repr(u8)]
pub enum FocusEvent {
    /// This event is sent when an item receives the focus.
    FocusIn(FocusReason),
    /// This event is sent when an item loses the focus.
    FocusOut(FocusReason),
}

/// This state is used to count the clicks separated by [`crate::platform::Platform::click_interval`]
#[derive(Default)]
pub struct ClickState {
    click_count_time_stamp: Cell<Option<crate::animations::Instant>>,
    click_count: Cell<u8>,
    click_position: Cell<LogicalPoint>,
    click_button: Cell<PointerEventButton>,
}

impl ClickState {
    /// Resets the timer and count.
    fn restart(
        &self,
        position: LogicalPoint,
        button: PointerEventButton,
        now: crate::animations::Instant,
    ) {
        self.click_count.set(0);
        self.click_count_time_stamp.set(Some(now));
        self.click_position.set(position);
        self.click_button.set(button);
    }

    /// Reset to an invalid state
    pub fn reset(&self) {
        self.click_count.set(0);
        self.click_count_time_stamp.replace(None);
    }

    /// Check if the click is repeated.
    /// Takes the context rather than just the interval: the timestamps it compares have to
    /// come from the same clock, which only the context can name.
    pub fn check_repeat(&self, mouse_event: MouseEvent, ctx: &crate::SlintContext) -> MouseEvent {
        let click_interval = ctx.platform().click_interval();
        match mouse_event {
            MouseEvent::Pressed { position, button, touch_finger_id, .. } => {
                let instant_now = crate::animations::Instant::now(ctx);

                if let Some(click_count_time_stamp) = self.click_count_time_stamp.get() {
                    if instant_now - click_count_time_stamp < click_interval
                        && button == self.click_button.get()
                        && (position - self.click_position.get()).square_length() < 100 as _
                    {
                        self.click_count.set(self.click_count.get().wrapping_add(1));
                        self.click_count_time_stamp.set(Some(instant_now));
                    } else {
                        self.restart(position, button, instant_now);
                    }
                } else {
                    self.restart(position, button, instant_now);
                }

                return MouseEvent::Pressed {
                    position,
                    button,
                    click_count: self.click_count.get(),
                    touch_finger_id,
                };
            }
            MouseEvent::Released { position, button, touch_finger_id, .. } => {
                return MouseEvent::Released {
                    position,
                    button,
                    click_count: self.click_count.get(),
                    touch_finger_id,
                };
            }
            _ => {}
        };

        mouse_event
    }
}

/// The data for an in-flight drag-and-drop operation, held while a drag is active.
#[derive(Clone)]
pub(crate) struct DragData {
    /// The dragged payload together with its current position and proposed action.
    /// The `position` is updated on every move.
    pub(crate) event: DropEvent,
    /// The actions the drag source permits, captured at drag start.
    pub(crate) allowed: AllowedDragActions,
}

/// The state which a window should hold for the mouse input
#[derive(Default)]
pub struct MouseInputState {
    /// The stack of item which contain the mouse cursor (or grab),
    /// along with the last result from the input function
    item_stack: Vec<(ItemWeak, InputEventFilterResult)>,
    /// Passive trackers that saw the last event without claiming it (see
    /// [`InputEventResult::ObserveEvent`]). Held outside `item_stack` so the stack
    /// stays a single root-to-leaf path; entries here receive a synthesized
    /// [`MouseEvent::Exit`] when they no longer appear after a new event.
    observers: Vec<ItemWeak>,
    /// Offset to apply to the first item of the stack (used if there is a popup)
    pub(crate) offset: LogicalPoint,
    /// true if the top item of the stack has the mouse grab
    grabbed: bool,
    /// When this is Some, it means we are in the middle of a drag-drop operation and it contains the dragged data.
    /// The `position` field has no signification
    pub(crate) drag_data: Option<DragData>,
    /// The `DragArea` that initiated the in-flight drag.
    /// `None` for drags coming from outside (native cross-window/cross-process DnD).
    pub(crate) drag_source: Option<ItemWeak>,
    /// The DropArea that accepted the most recent DragMove, if any. On release we use
    /// this to decide whether to deliver a Drop — matching OS DnD pipelines, where a
    /// target that didn't previously accept never receives a drop.
    pub(crate) drop_target: Option<ItemWeak>,
    delayed: Option<(crate::timers::Timer, MouseEvent)>,
    delayed_exit_items: Vec<ItemWeak>,
    pub(crate) cursor: MouseCursorInner,
}

impl MouseInputState {
    /// Return the item in the top of the stack
    fn top_item(&self) -> Option<ItemRc> {
        self.item_stack.last().and_then(|x| x.0.upgrade())
    }

    /// Arm the in-window drag: seed `drag_data`/`drag_source` from `drag_area` at `seed_position`
    /// and mark it dragging.
    pub(crate) fn arm_in_window_drag(
        &mut self,
        drag_area: core::pin::Pin<&crate::items::DragArea>,
        source: ItemWeak,
        seed_position: crate::api::LogicalPosition,
    ) {
        let (mut drop_event, allowed) = drag_area.initial_drop_event();
        drop_event.position = seed_position;
        self.drag_data = Some(DragData { event: drop_event, allowed });
        self.drag_source = Some(source);
        drag_area.dragging.set(true);
    }

    /// Returns the item in the top of the stack, if there is a delayed event, this would be the top of the delayed stack
    pub fn top_item_including_delayed(&self) -> Option<ItemRc> {
        self.delayed_exit_items.last().and_then(|x| x.upgrade()).or_else(|| self.top_item())
    }

    /// Returns true if there is a pending delayed event (e.g. from a Flickable)
    pub fn has_delayed_event(&self) -> bool {
        self.delayed.is_some()
    }

    /// The action negotiated with the `DropArea` that accepted the most recent
    /// `DragMove`/`Drop`, or `None` if none accepted.
    pub fn drop_target_action(&self) -> Option<crate::items::DragAction> {
        let action = self
            .drop_target
            .as_ref()
            .and_then(|t| t.upgrade())
            .and_then(|i| i.downcast::<crate::items::DropArea>())
            .map(|d| d.as_pin_ref().current_action())?;
        (action != crate::items::DragAction::None).then_some(action)
    }
}

pub(crate) struct MouseGrabResult {
    /// The event that still needs normal hit-test dispatch. `None` means the grabber
    /// fully handled the original event.
    pub event: Option<MouseEvent>,
    /// Whether the grabber consumed the original event before any follow-up event was
    /// synthesized for hover/grab refresh.
    pub accepted: bool,
}

/// Start a drag from `drag_area`, preferring a native (OS-level) drag and falling back to the
/// in-window drag (armed on `state`) when no backend takes over.
fn offer_native_drag(
    window_adapter: &Rc<dyn WindowAdapter>,
    drag_area: core::pin::Pin<&crate::items::DragArea>,
    source: ItemWeak,
    seed_position: crate::api::LogicalPosition,
    state: &mut MouseInputState,
) {
    let data = drag_area.data();
    if data.has_native_data() {
        let request = crate::window::DragRequest {
            data: data.clone(),
            allowed: drag_area.allowed_actions(),
            drag_image: drag_area.drag_image(),
            drag_image_offset: euclid::vec2(
                drag_area.drag_image_offset_x(),
                drag_area.drag_image_offset_y(),
            ),
        };
        if window_adapter.internal(crate::InternalToken).is_some_and(|i| i.start_drag(&request)) {
            // The backend took over (and defers the actual drag). Stash it so it can report
            // completion or fall back, and so a drop back onto this window restores the data.
            let drag = crate::window::NativePendingDrag { request, source, seed_position };
            crate::window::WindowInner::from_pub(window_adapter.window())
                .set_native_drag(Some(drag));
            drag_area.dragging.set(true);
            return;
        }
    }
    // No backend took over: fall back to the in-window drag.
    state.arm_in_window_drag(drag_area, source, seed_position);
}

/// Try to handle the mouse grabber.
pub(crate) fn handle_mouse_grab(
    mouse_event: &MouseEvent,
    window_adapter: &Rc<dyn WindowAdapter>,
    mouse_input_state: &mut MouseInputState,
) -> MouseGrabResult {
    if !mouse_input_state.grabbed || mouse_input_state.item_stack.is_empty() {
        return MouseGrabResult { event: Some(mouse_event.clone()), accepted: false };
    };

    let mut event = mouse_event.clone();
    let mut intercept = false;
    let mut invalid = false;

    event.translate(-mouse_input_state.offset.to_vector());

    mouse_input_state.item_stack.retain(|it| {
        if invalid {
            return false;
        }
        let item = if let Some(item) = it.0.upgrade() {
            item
        } else {
            invalid = true;
            return false;
        };
        if intercept {
            item.borrow().as_ref().input_event(
                &MouseEvent::Exit,
                window_adapter,
                &item,
                &mut mouse_input_state.cursor,
            );
            return false;
        }
        let g = item.geometry();
        event.translate(-g.origin.to_vector());
        if window_adapter.renderer().supports_transformations()
            && let Some(inverse_transform) = item.inverse_children_transform()
        {
            event.transform(inverse_transform);
        }

        let interested = matches!(
            it.1,
            InputEventFilterResult::ForwardAndInterceptGrab
                | InputEventFilterResult::DelayForwarding(_)
        );

        if interested
            && item.borrow().as_ref().input_event_filter_before_children(
                &event,
                window_adapter,
                &item,
                &mut mouse_input_state.cursor,
            ) == InputEventFilterResult::Intercept
        {
            intercept = true;
        }
        true
    });
    if invalid {
        return MouseGrabResult { event: Some(mouse_event.clone()), accepted: false };
    }

    let grabber = mouse_input_state.top_item().unwrap();
    let input_result = grabber.borrow().as_ref().input_event(
        &event,
        window_adapter,
        &grabber,
        &mut mouse_input_state.cursor,
    );
    match input_result {
        InputEventResult::GrabMouse => MouseGrabResult { event: None, accepted: true },
        InputEventResult::StartDrag => {
            mouse_input_state.grabbed = false;
            let drag_area_item = grabber.downcast::<crate::items::DragArea>().unwrap();
            let drag_area = drag_area_item.as_pin_ref();
            // Seed the drag position from the event that crossed the drag threshold so
            // the renderer can place the drag-image overlay before the first DragMove.
            let seed_position = mouse_event
                .position()
                .map(crate::lengths::logical_position_to_api)
                .unwrap_or_default();
            offer_native_drag(
                window_adapter,
                drag_area,
                grabber.downgrade(),
                seed_position,
                mouse_input_state,
            );
            MouseGrabResult { event: None, accepted: true }
        }
        InputEventResult::EventAccepted | InputEventResult::EventIgnored => {
            mouse_input_state.grabbed = false;
            // Return a move event so that the new position can be registered properly
            MouseGrabResult {
                event: Some(mouse_event.position().map_or(MouseEvent::Exit, |position| {
                    MouseEvent::Moved { position, touch_finger_id: mouse_event.touch_finger_id() }
                })),
                accepted: input_result == InputEventResult::EventAccepted,
            }
        }
    }
}

pub(crate) fn send_exit_events(
    old_input_state: &MouseInputState,
    new_input_state: &mut MouseInputState,
    mut pos: Option<LogicalPoint>,
    window_adapter: &Rc<dyn WindowAdapter>,
) {
    // Note that exit events can't actually change the cursor from default so we'll ignore the result
    let cursor = &mut MouseCursorInner::BuiltIn(BuiltInMouseCursor::Default);

    for it in core::mem::take(&mut new_input_state.delayed_exit_items) {
        let Some(item) = it.upgrade() else { continue };
        item.borrow().as_ref().input_event(&MouseEvent::Exit, window_adapter, &item, cursor);
    }

    let mut clipped = false;
    for (idx, it) in old_input_state.item_stack.iter().enumerate() {
        let Some(item) = it.0.upgrade() else { break };
        let g = item.geometry();
        let contains = pos.is_some_and(|p| g.contains(p));
        if let Some(p) = pos.as_mut() {
            *p -= g.origin.to_vector();
            if window_adapter.renderer().supports_transformations()
                && let Some(inverse_transform) = item.inverse_children_transform()
            {
                *p = inverse_transform.transform_point(p.cast()).cast();
            }
        }
        if !contains || clipped {
            if item.borrow().as_ref().clips_children() {
                clipped = true;
            }
            item.borrow().as_ref().input_event(&MouseEvent::Exit, window_adapter, &item, cursor);
        } else if new_input_state.item_stack.get(idx).is_none_or(|(x, _)| *x != it.0) {
            // The item is still under the mouse, but no longer in the item stack. We should also sent the exit event, unless we delay it
            if new_input_state.delayed.is_some() {
                new_input_state.delayed_exit_items.push(it.0.clone());
            } else {
                item.borrow().as_ref().input_event(
                    &MouseEvent::Exit,
                    window_adapter,
                    &item,
                    cursor,
                );
            }
        }
    }

    // Observers live outside the path-stack and are tracked by identity. Exit fires
    // only when the item is missing from BOTH the new observer set and the new path
    // stack: an item whose ForwardAndObserve filter never ran (because a child aborted
    // before reaching it) is still on the path stack with another filter result, and
    // should not receive Exit.
    for obs in &old_input_state.observers {
        if new_input_state.observers.iter().any(|x| x == obs)
            || new_input_state.item_stack.iter().any(|(x, _)| x == obs)
        {
            continue;
        }
        let Some(item) = obs.upgrade() else { continue };
        item.borrow().as_ref().input_event(&MouseEvent::Exit, window_adapter, &item, cursor);
    }
}

/// Outcome of [`process_mouse_input`].
pub struct MouseInputResult {
    /// The new dispatch state to install in place of the one passed in.
    pub state: MouseInputState,
    /// `true` when an item consumed the event (`EventAccepted`, `GrabMouse`,
    /// `StartDrag`, or a `DropArea` taking a `DragMove`/`Drop`).
    pub accepted: bool,
}

/// Process the `mouse_event` on the `component`. The `mouse_input_state` is the previous
/// dispatch state (grab stack, cursor, in-flight drag); the returned [`MouseInputResult`]
/// carries the state that replaces it and whether the event was consumed.
pub fn process_mouse_input(
    root: ItemRc,
    mouse_event: &MouseEvent,
    window_adapter: &Rc<dyn WindowAdapter>,
    mut mouse_input_state: MouseInputState,
) -> MouseInputResult {
    let mut result = MouseInputState {
        drag_data: mouse_input_state.drag_data.clone(),
        drag_source: mouse_input_state.drag_source.clone(),
        drop_target: mouse_input_state.drop_target.clone(),
        cursor: mouse_input_state.cursor.clone(),
        ..Default::default()
    };
    let r = send_mouse_event_to_item(
        mouse_event,
        root.clone(),
        window_adapter,
        &mut result,
        mouse_input_state.top_item().as_ref(),
        false,
    );
    let accepted = r.has_aborted();
    if matches!(mouse_event, MouseEvent::DragMove { .. }) {
        // Remember the accepting DropArea (or forget if none did) so the subsequent
        // Release knows whether to deliver a Drop.
        result.drop_target =
            accepted.then(|| result.item_stack.last().map(|(w, _)| w.clone())).flatten();
    }
    if mouse_input_state.delayed.is_some()
        && (!accepted
            || Option::zip(result.item_stack.last(), mouse_input_state.item_stack.last())
                .is_none_or(|(a, b)| a.0 != b.0))
    {
        // Keep the delayed event but transfer the just-attempted dispatch's cursor.
        mouse_input_state.cursor = result.cursor;
        return MouseInputResult { state: mouse_input_state, accepted };
    }
    send_exit_events(&mouse_input_state, &mut result, mouse_event.position(), window_adapter);

    if let MouseEvent::Wheel { position, .. } = mouse_event
        && accepted
    {
        // An accepted wheel event might have moved things. Send a synthetic Moved to refresh
        // has-hover. The original wheel's `accepted` (always `true` in this branch) is the
        // outcome the caller sees — the synthetic Moved is an internal implementation detail.
        let moved = process_mouse_input(
            root,
            &MouseEvent::Moved { position: *position, touch_finger_id: 0 },
            window_adapter,
            result,
        );
        return MouseInputResult { state: moved.state, accepted: true };
    }

    MouseInputResult { state: result, accepted }
}

pub(crate) fn process_delayed_event(
    window_adapter: &Rc<dyn WindowAdapter>,
    mut mouse_input_state: MouseInputState,
) -> MouseInputState {
    // the take bellow will also destroy the Timer
    let event = match mouse_input_state.delayed.take() {
        Some(e) => e.1,
        None => return mouse_input_state,
    };

    let top_item = match mouse_input_state.top_item() {
        Some(i) => i,
        None => return MouseInputState::default(),
    };

    // Recover the real previous click target so click_count is preserved across delayed events
    let prev_target = mouse_input_state.delayed_exit_items.last().and_then(|x| x.upgrade());
    let last_top_item = prev_target.as_ref().unwrap_or(&top_item);

    let mut actual_visitor =
        |component: &ItemTreeRc, index: u32, _: Pin<ItemRef>| -> VisitChildrenResult {
            send_mouse_event_to_item(
                &event,
                ItemRc::new(component.clone(), index),
                window_adapter,
                &mut mouse_input_state,
                Some(last_top_item),
                true,
            )
        };
    vtable::new_vref!(let mut actual_visitor : VRefMut<crate::item_tree::ItemVisitorVTable> for crate::item_tree::ItemVisitor = &mut actual_visitor);
    vtable::VRc::borrow_pin(top_item.item_tree()).as_ref().visit_children_item(
        top_item.index() as isize,
        crate::item_tree::TraversalOrder::FrontToBack,
        actual_visitor,
    );
    mouse_input_state
}

fn send_mouse_event_to_item(
    mouse_event: &MouseEvent,
    item_rc: ItemRc,
    window_adapter: &Rc<dyn WindowAdapter>,
    result: &mut MouseInputState,
    last_top_item: Option<&ItemRc>,
    ignore_delays: bool,
) -> VisitChildrenResult {
    let item = item_rc.borrow();
    let geom = item_rc.geometry();
    // translated in our coordinate
    let mut event_for_children = mouse_event.clone();
    // Unapply the translation to go from 'world' space to local space
    event_for_children.translate(-geom.origin.to_vector());
    if window_adapter.renderer().supports_transformations() {
        // Unapply other transforms.
        if let Some(inverse_transform) = item_rc.inverse_children_transform() {
            event_for_children.transform(inverse_transform);
        }
    }

    let filter_result = if mouse_event.position().is_some_and(|p| geom.contains(p))
        || item.as_ref().clips_children()
    {
        item.as_ref().input_event_filter_before_children(
            &event_for_children,
            window_adapter,
            &item_rc,
            &mut result.cursor,
        )
    } else {
        InputEventFilterResult::ForwardAndIgnore
    };

    let (forward_to_children, ignore) = match filter_result {
        InputEventFilterResult::ForwardEvent => (true, false),
        InputEventFilterResult::ForwardAndIgnore => (true, true),
        InputEventFilterResult::ForwardAndInterceptGrab => (true, false),
        InputEventFilterResult::Intercept => (false, false),
        InputEventFilterResult::DelayForwarding(_) if ignore_delays => (true, false),
        InputEventFilterResult::DelayForwarding(duration) => {
            let timer = WindowInner::from_pub(window_adapter.window()).context().new_timer();
            let w = Rc::downgrade(window_adapter);
            timer.start(
                crate::timers::TimerMode::SingleShot,
                Duration::from_millis(duration),
                move || {
                    if let Some(w) = w.upgrade() {
                        WindowInner::from_pub(w.window()).process_delayed_event();
                    }
                },
            );
            result.delayed = Some((timer, event_for_children));
            result
                .item_stack
                .push((item_rc.downgrade(), InputEventFilterResult::DelayForwarding(duration)));
            return VisitChildrenResult::abort(item_rc.index(), 0);
        }
        // Like ForwardAndIgnore: forward to children, skip input_event. The
        // EventIgnored arm below moves our entry from the path stack to the observers
        // side list instead of dropping it.
        InputEventFilterResult::ForwardAndObserve => (true, true),
    };

    result.item_stack.push((item_rc.downgrade(), filter_result));
    if forward_to_children {
        let mut actual_visitor =
            |component: &ItemTreeRc, index: u32, _: Pin<ItemRef>| -> VisitChildrenResult {
                send_mouse_event_to_item(
                    &event_for_children,
                    ItemRc::new(component.clone(), index),
                    window_adapter,
                    result,
                    last_top_item,
                    ignore_delays,
                )
            };
        vtable::new_vref!(let mut actual_visitor : VRefMut<crate::item_tree::ItemVisitorVTable> for crate::item_tree::ItemVisitor = &mut actual_visitor);
        let r = vtable::VRc::borrow_pin(item_rc.item_tree()).as_ref().visit_children_item(
            item_rc.index() as isize,
            crate::item_tree::TraversalOrder::FrontToBack,
            actual_visitor,
        );
        if r.has_aborted() {
            return r;
        }
    };

    let r = if ignore {
        InputEventResult::EventIgnored
    } else {
        let mut event = mouse_event.clone();
        event.translate(-geom.origin.to_vector());
        if last_top_item.is_none_or(|x| *x != item_rc) {
            event.set_click_count(0);
        }
        item.as_ref().input_event(&event, window_adapter, &item_rc, &mut result.cursor)
    };
    match r {
        InputEventResult::EventAccepted => VisitChildrenResult::abort(item_rc.index(), 0),
        InputEventResult::EventIgnored => {
            let popped = result.item_stack.pop();
            debug_assert_eq!(
                popped.as_ref().map(|x| (x.0.upgrade().unwrap().index(), x.1)).unwrap(),
                (item_rc.index(), filter_result)
            );
            // For ForwardAndObserve, migrate the entry to the observers side list (dedup)
            // so a later Exit can still reach it.
            if filter_result == InputEventFilterResult::ForwardAndObserve
                && let Some((weak, _)) = popped
                && !result.observers.contains(&weak)
            {
                result.observers.push(weak);
            }
            VisitChildrenResult::CONTINUE
        }
        InputEventResult::GrabMouse => {
            result.item_stack.last_mut().unwrap().1 =
                InputEventFilterResult::ForwardAndInterceptGrab;
            result.grabbed = true;
            VisitChildrenResult::abort(item_rc.index(), 0)
        }
        InputEventResult::StartDrag => {
            result.item_stack.last_mut().unwrap().1 =
                InputEventFilterResult::ForwardAndInterceptGrab;
            result.grabbed = false;
            let drag_area_item = item_rc.downcast::<crate::items::DragArea>().unwrap();
            let drag_area = drag_area_item.as_pin_ref();
            // `mouse_event` here is in the parent item's coords (this function is called
            // recursively); translate into the DragArea's local coords, then map back to
            // window coords so the drag-image overlay places at the right spot from the start.
            let seed_position = mouse_event
                .position()
                .map(|p| p - geom.origin.to_vector())
                .map(|p| item_rc.map_to_window(p))
                .map(crate::lengths::logical_position_to_api)
                .unwrap_or_default();
            offer_native_drag(
                window_adapter,
                drag_area,
                item_rc.downgrade(),
                seed_position,
                result,
            );
            VisitChildrenResult::abort(item_rc.index(), 0)
        }
    }
}

/// The TextCursorBlinker takes care of providing a toggled boolean property
/// that can be used to animate a blinking cursor. It's typically stored in the
/// Window using a Weak and set_binding() can be used to set up a binding on a given
/// property that'll keep it up-to-date. That binding keeps a strong reference to the
/// blinker. If the underlying item that uses it goes away, the binding goes away and
/// so does the blinker.
#[derive(FieldOffsets)]
#[repr(C)]
#[pin]
pub(crate) struct TextCursorBlinker {
    cursor_visible: Property<bool>,
    cursor_blink_timer: crate::timers::Timer,
}

impl TextCursorBlinker {
    /// Creates a new instance, wrapped in a Pin<Rc<_>> because the boolean property
    /// the blinker properties uses the property system that requires pinning.
    pub fn new() -> Pin<Rc<Self>> {
        Rc::pin(Self {
            cursor_visible: Property::new(true),
            cursor_blink_timer: Default::default(),
        })
    }

    /// Sets a binding on the provided property that will ensure that the property value
    /// is true when the cursor should be shown and false if not.
    pub fn set_binding(
        instance: Pin<Rc<TextCursorBlinker>>,
        prop: &Property<bool>,
        ctx: &crate::SlintContext,
        cycle_duration: Duration,
    ) {
        instance.as_ref().cursor_visible.set(true);
        // Re-start timer, in case.
        Self::start(&instance, ctx, cycle_duration);
        prop.set_binding(move || {
            TextCursorBlinker::FIELD_OFFSETS.cursor_visible().apply_pin(instance.as_ref()).get()
        });
    }

    /// Starts the blinking cursor timer that will toggle the cursor and update all bindings that
    /// were installed on properties with set_binding call.
    pub fn start(self: &Pin<Rc<Self>>, ctx: &crate::SlintContext, cycle_duration: Duration) {
        if self.cursor_blink_timer.running() {
            self.cursor_blink_timer.restart();
        } else {
            let toggle_cursor = {
                let weak_blinker = pin_weak::rc::PinWeak::downgrade(self.clone());
                move || {
                    if let Some(blinker) = weak_blinker.upgrade() {
                        let visible = TextCursorBlinker::FIELD_OFFSETS
                            .cursor_visible()
                            .apply_pin(blinker.as_ref())
                            .get();
                        blinker.cursor_visible.set(!visible);
                    }
                }
            };
            if !cycle_duration.is_zero() {
                self.cursor_blink_timer.start_on(
                    ctx,
                    crate::timers::TimerMode::Repeated,
                    cycle_duration / 2,
                    toggle_cursor,
                );
            }
        }
    }

    /// Stops the blinking cursor timer. This is usually used for example when the window that contains
    /// text editable elements looses the focus or is hidden.
    pub fn stop(&self) {
        self.cursor_blink_timer.stop()
    }
}

/// A single active touch point.
#[derive(Clone, Copy, Default)]
struct TouchPoint {
    id: i32,
    position: LogicalPoint,
}

/// Fixed-capacity map of touch IDs to touch points.
///
/// Touchscreens rarely report more than 5 simultaneous contacts, and gesture
/// recognition only uses the first two. A linear-scan array avoids the heap
/// allocation and pointer-chasing overhead of `BTreeMap` for this tiny collection.
const MAX_TRACKED_TOUCHES: usize = 5;

#[derive(Clone)]
struct TouchMap {
    entries: [TouchPoint; MAX_TRACKED_TOUCHES],
    len: usize,
}

impl Default for TouchMap {
    fn default() -> Self {
        Self { entries: [TouchPoint::default(); MAX_TRACKED_TOUCHES], len: 0 }
    }
}

impl TouchMap {
    fn get(&self, id: i32) -> Option<&TouchPoint> {
        self.entries[..self.len].iter().find(|tp| tp.id == id)
    }

    fn get_mut(&mut self, id: i32) -> Option<&mut TouchPoint> {
        self.entries[..self.len].iter_mut().find(|tp| tp.id == id)
    }

    fn insert(&mut self, point: TouchPoint) {
        if let Some(existing) = self.entries[..self.len].iter_mut().find(|tp| tp.id == point.id) {
            *existing = point;
        } else if self.len < MAX_TRACKED_TOUCHES {
            self.entries[self.len] = point;
            self.len += 1;
        }
    }

    fn remove(&mut self, id: i32) {
        if let Some(idx) = self.entries[..self.len].iter().position(|tp| tp.id == id) {
            self.len -= 1;
            self.entries[idx] = self.entries[self.len];
        }
    }

    fn len(&self) -> usize {
        self.len
    }

    /// Returns the first two distinct IDs, or `None` if fewer than 2 entries.
    fn first_two_ids(&self) -> Option<(i32, i32)> {
        if self.len >= 2 { Some((self.entries[0].id, self.entries[1].id)) } else { None }
    }

    /// Returns the first entry, if any.
    fn first(&self) -> Option<&TouchPoint> {
        if self.len > 0 { Some(&self.entries[0]) } else { None }
    }
}

/// Fixed-capacity buffer for [`MouseEvent`]s produced by the touch state machine.
///
/// No branch in [`TouchState::process`] emits more than 3 events (gesture end
/// produces PinchEnded + RotationEnded + Pressed/Exit). Capacity 4 provides a
/// margin without heap allocation.
const MAX_TOUCH_EVENTS: usize = 4;

#[derive(Clone)]
pub(crate) struct TouchEventBuffer {
    events: [Option<MouseEvent>; MAX_TOUCH_EVENTS],
    len: usize,
}

impl TouchEventBuffer {
    fn new() -> Self {
        Self { events: [None, None, None, None], len: 0 }
    }

    fn push(&mut self, event: MouseEvent) {
        debug_assert!(self.len < MAX_TOUCH_EVENTS, "TouchEventBuffer overflow");
        if self.len < MAX_TOUCH_EVENTS {
            self.events[self.len] = Some(event);
            self.len += 1;
        }
    }

    /// Returns an iterator over the buffered events.
    pub(crate) fn into_iter(self) -> impl Iterator<Item = MouseEvent> {
        let len = self.len;
        self.events.into_iter().take(len).flatten()
    }
}

/// State of the multi-touch gesture recognizer.
#[derive(Default, Debug, Clone, Copy)]
enum GestureRecognitionState {
    /// 0-1 fingers; forwarding as mouse events.
    #[default]
    Idle,
    /// 2 fingers down, waiting for movement to exceed threshold.
    TwoFingersDown { finger_ids: (i32, i32), initial_distance: f32, last_angle: euclid::Angle<f32> },
    /// Actively synthesizing PinchGesture/RotationGesture events.
    Pinching {
        finger_ids: (i32, i32),
        initial_distance: f32,
        last_scale: f32,
        last_angle: euclid::Angle<f32>,
    },
}

/// Tracks all active touch points and recognizes pinch/rotation gestures.
///
/// When only one finger is down, touch events are forwarded as mouse events.
/// When two fingers are down and move beyond a threshold, synthesized
/// `PinchGesture` and `RotationGesture` events are emitted — the same events
/// that platform gesture recognition (e.g. macOS trackpad) produces.
pub(crate) struct TouchState {
    active_touches: TouchMap,
    /// The finger forwarded as mouse events during single-touch.
    primary_touch_id: Option<i32>,
    gesture_state: GestureRecognitionState,
}

impl Default for TouchState {
    fn default() -> Self {
        Self {
            active_touches: TouchMap::default(),
            primary_touch_id: None,
            gesture_state: GestureRecognitionState::Idle,
        }
    }
}

impl TouchState {
    /// Minimum movement (in logical pixels) before two fingers are recognized as a pinch.
    const PINCH_THRESHOLD: f32 = 8.0;

    /// Minimum angular change (in degrees) before two fingers are recognized as a rotation.
    const ROTATION_THRESHOLD: f32 = 5.0;

    /// Returns the finger IDs from the current gesture state, if any.
    fn gesture_finger_ids(&self) -> Option<(i32, i32)> {
        match self.gesture_state {
            GestureRecognitionState::TwoFingersDown { finger_ids, .. }
            | GestureRecognitionState::Pinching { finger_ids, .. } => Some(finger_ids),
            GestureRecognitionState::Idle => None,
        }
    }

    /// Returns (distance, angle) between two specific touch points.
    fn geometry_for(&self, (id_a, id_b): (i32, i32)) -> Option<(f32, euclid::Angle<f32>)> {
        let a = self.active_touches.get(id_a)?;
        let b = self.active_touches.get(id_b)?;
        let delta = (b.position - a.position).cast::<f32>();
        Some((delta.length(), delta.angle_from_x_axis()))
    }

    /// Returns the positions of the two gesture fingers, or `None` if not available.
    fn gesture_finger_positions(&self) -> Option<(&TouchPoint, &TouchPoint)> {
        let (id_a, id_b) = self.gesture_finger_ids()?;
        let a = self.active_touches.get(id_a)?;
        let b = self.active_touches.get(id_b)?;
        Some((a, b))
    }

    /// Returns the midpoint between the two gesture fingers, or `None`.
    fn gesture_midpoint(&self) -> Option<LogicalPoint> {
        let (a, b) = self.gesture_finger_positions()?;
        let mid = a.position.cast::<f32>().lerp(b.position.cast::<f32>(), 0.5);
        Some(mid.cast())
    }

    /// Returns (distance, angle) between the two gesture fingers.
    fn gesture_geometry(&self) -> Option<(f32, euclid::Angle<f32>)> {
        let (a, b) = self.gesture_finger_positions()?;
        let delta = (b.position - a.position).cast::<f32>();
        Some((delta.length(), delta.angle_from_x_axis()))
    }

    /// Returns true if the given touch ID is one of the two gesture fingers.
    fn is_gesture_finger(&self, id: i32) -> bool {
        self.gesture_finger_ids().is_some_and(|(a, b)| id == a || id == b)
    }

    /// Run the touch state machine for a single event and return the
    /// [`MouseEvent`]s to dispatch.
    ///
    /// This is intentionally separated from [`crate::window::WindowInner::process_touch_input`]
    /// so that the `RefCell` borrow can be dropped *once* before dispatching,
    /// rather than requiring a manual `drop` at every branch.
    pub(crate) fn process(
        &mut self,
        id: i32,
        position: LogicalPoint,
        phase: TouchPhase,
    ) -> TouchEventBuffer {
        let mut events = TouchEventBuffer::new();
        match phase {
            TouchPhase::Started => self.process_started(id, position, &mut events),
            TouchPhase::Moved => self.process_moved(id, position, &mut events),
            TouchPhase::Ended => self.process_ended(id, position, false, &mut events),
            TouchPhase::Cancelled => self.process_ended(id, position, true, &mut events),
        }
        events
    }

    fn process_started(&mut self, id: i32, position: LogicalPoint, events: &mut TouchEventBuffer) {
        self.active_touches.insert(TouchPoint { id, position });

        let total = self.active_touches.len();
        if total == 1 {
            // First finger: become primary, forward as mouse press.
            self.primary_touch_id = Some(id);
            self.gesture_state = GestureRecognitionState::Idle;
            events.push(MouseEvent::Pressed {
                position,
                button: PointerEventButton::Left,
                click_count: 0,
                touch_finger_id: id + 1,
            });
        } else if total == 2 {
            // Second finger: transition Idle → TwoFingersDown.
            let finger_ids = self.active_touches.first_two_ids().unwrap_or((0, 0));

            // Synthesize a Release for the primary finger to clear any
            // Flickable grab / delay state.
            let primary_pos = self
                .primary_touch_id
                .and_then(|pid| self.active_touches.get(pid))
                .map(|tp| tp.position)
                .unwrap_or(position);

            // Compute initial geometry for threshold detection.
            let (initial_distance, last_angle) =
                self.geometry_for(finger_ids).unwrap_or((0.0, euclid::Angle::zero()));
            self.gesture_state = GestureRecognitionState::TwoFingersDown {
                finger_ids,
                initial_distance,
                last_angle,
            };

            events.push(MouseEvent::Released {
                position: primary_pos,
                button: PointerEventButton::Left,
                click_count: 0,
                touch_finger_id: id + 1,
            });
        }
        // 3+ fingers: tracked in active_touches but ignored for gesture.
    }

    #[allow(clippy::collapsible_match)]
    fn process_moved(&mut self, id: i32, position: LogicalPoint, events: &mut TouchEventBuffer) {
        if let Some(tp) = self.active_touches.get_mut(id) {
            tp.position = position;
        }

        let is_gesture_finger = self.is_gesture_finger(id);

        match self.gesture_state {
            GestureRecognitionState::Idle => {
                if self.primary_touch_id == Some(id) {
                    events.push(MouseEvent::Moved { position, touch_finger_id: id + 1 });
                }
            }
            GestureRecognitionState::TwoFingersDown {
                finger_ids,
                initial_distance,
                last_angle,
            } if is_gesture_finger => {
                if let Some((dist, angle)) = self.gesture_geometry() {
                    let delta_dist = (dist - initial_distance).abs();
                    let delta_angle = (angle - last_angle).signed().to_degrees().abs();
                    if delta_dist > Self::PINCH_THRESHOLD || delta_angle > Self::ROTATION_THRESHOLD
                    {
                        // Re-snapshot so the first gesture event starts from
                        // the current geometry rather than accumulating the
                        // threshold movement.
                        self.gesture_state = GestureRecognitionState::Pinching {
                            finger_ids,
                            initial_distance: dist,
                            last_scale: 1.0,
                            last_angle: angle,
                        };

                        let midpoint = self.gesture_midpoint().unwrap_or(position);

                        events.push(MouseEvent::PinchGesture {
                            position: midpoint,
                            delta: 0.0,
                            phase: TouchPhase::Started,
                        });
                        events.push(MouseEvent::RotationGesture {
                            position: midpoint,
                            delta: 0.0,
                            phase: TouchPhase::Started,
                        });
                    }
                }
            }
            GestureRecognitionState::Pinching {
                initial_distance, last_scale, last_angle, ..
            } if is_gesture_finger => {
                if let Some((dist, angle)) = self.gesture_geometry() {
                    let midpoint = self.gesture_midpoint().unwrap_or(position);

                    let current_scale =
                        if initial_distance > 0.0 { dist / initial_distance } else { 1.0 };
                    let scale_delta = current_scale - last_scale;

                    // `.signed()` wraps to [-pi, pi] so crossing the ±180°
                    // atan2 boundary doesn't produce a full-revolution jump.
                    let rotation_delta = (angle - last_angle).signed().to_degrees();

                    // Update the mutable state for next frame.
                    if let GestureRecognitionState::Pinching {
                        last_scale: ref mut ls,
                        last_angle: ref mut la,
                        ..
                    } = self.gesture_state
                    {
                        *ls = current_scale;
                        *la = angle;
                    }

                    events.push(MouseEvent::PinchGesture {
                        position: midpoint,
                        delta: scale_delta,
                        phase: TouchPhase::Moved,
                    });
                    events.push(MouseEvent::RotationGesture {
                        position: midpoint,
                        delta: rotation_delta,
                        phase: TouchPhase::Moved,
                    });
                }
            }
            _ => {}
        }
    }

    #[allow(clippy::collapsible_match)]
    fn process_ended(
        &mut self,
        id: i32,
        position: LogicalPoint,
        is_cancelled: bool,
        events: &mut TouchEventBuffer,
    ) {
        // Check gesture membership *before* removing from the map.
        let is_gesture_finger = self.is_gesture_finger(id);
        let midpoint = self.gesture_midpoint().unwrap_or(position);
        self.active_touches.remove(id);

        match self.gesture_state {
            GestureRecognitionState::Idle => {
                if self.primary_touch_id == Some(id) {
                    self.primary_touch_id = None;
                    events.push(MouseEvent::Released {
                        position,
                        button: PointerEventButton::Left,
                        click_count: 0,
                        touch_finger_id: id + 1,
                    });
                    events.push(MouseEvent::Exit);
                }
            }
            GestureRecognitionState::TwoFingersDown { .. } if is_gesture_finger => {
                self.gesture_state = GestureRecognitionState::Idle;
                if !is_cancelled {
                    if let Some(remaining) = self.active_touches.first() {
                        let remaining_pos = remaining.position;
                        self.primary_touch_id = Some(remaining.id);
                        events.push(MouseEvent::Pressed {
                            position: remaining_pos,
                            button: PointerEventButton::Left,
                            click_count: 0,
                            touch_finger_id: remaining.id + 1,
                        });
                    } else {
                        self.primary_touch_id = None;
                        events.push(MouseEvent::Exit);
                    }
                } else {
                    self.primary_touch_id = None;
                    events.push(MouseEvent::Exit);
                }
            }
            GestureRecognitionState::Pinching { .. } if is_gesture_finger => {
                self.gesture_state = GestureRecognitionState::Idle;

                let gesture_phase =
                    if is_cancelled { TouchPhase::Cancelled } else { TouchPhase::Ended };

                let remaining = if !is_cancelled {
                    self.active_touches.first().map(|tp| (tp.id, tp.position))
                } else {
                    None
                };
                if let Some((rid, _)) = remaining {
                    self.primary_touch_id = Some(rid);
                } else {
                    self.primary_touch_id = None;
                }

                events.push(MouseEvent::PinchGesture {
                    position: midpoint,
                    delta: 0.0,
                    phase: gesture_phase,
                });
                events.push(MouseEvent::RotationGesture {
                    position: midpoint,
                    delta: 0.0,
                    phase: gesture_phase,
                });

                if let Some((rid, rpos)) = remaining {
                    events.push(MouseEvent::Pressed {
                        position: rpos,
                        button: PointerEventButton::Left,
                        click_count: 0,
                        touch_finger_id: rid + 1,
                    });
                } else {
                    events.push(MouseEvent::Exit);
                }
            }
            _ => {}
        }
    }
}

#[cfg(test)]
mod touch_tests {
    extern crate alloc;
    use alloc::vec;
    use alloc::vec::Vec;

    use super::*;
    use crate::lengths::LogicalPoint;

    fn pt(x: f32, y: f32) -> LogicalPoint {
        euclid::point2(x, y)
    }

    // -----------------------------------------------------------------------
    // TouchMap tests
    // -----------------------------------------------------------------------

    #[test]
    fn touch_map_insert_and_get() {
        let mut map = TouchMap::default();
        assert_eq!(map.len(), 0);
        map.insert(TouchPoint { id: 1, position: pt(10.0, 20.0) });
        assert_eq!(map.len(), 1);
        assert!(map.get(1).is_some());
        assert!((map.get(1).unwrap().position.x - 10.0).abs() < f32::EPSILON);
        assert!(map.get(2).is_none());
    }

    #[test]
    fn touch_map_update_existing() {
        let mut map = TouchMap::default();
        map.insert(TouchPoint { id: 1, position: pt(10.0, 20.0) });
        map.insert(TouchPoint { id: 1, position: pt(30.0, 40.0) });
        assert_eq!(map.len(), 1);
        assert!((map.get(1).unwrap().position.x - 30.0).abs() < f32::EPSILON);
    }

    #[test]
    fn touch_map_remove() {
        let mut map = TouchMap::default();
        map.insert(TouchPoint { id: 1, position: pt(10.0, 20.0) });
        map.insert(TouchPoint { id: 2, position: pt(30.0, 40.0) });
        assert_eq!(map.len(), 2);
        map.remove(1);
        assert_eq!(map.len(), 1);
        assert!(map.get(1).is_none());
        assert!(map.get(2).is_some());
    }

    #[test]
    fn touch_map_remove_nonexistent() {
        let mut map = TouchMap::default();
        map.insert(TouchPoint { id: 1, position: pt(10.0, 20.0) });
        map.remove(99);
        assert_eq!(map.len(), 1);
    }

    #[test]
    fn touch_map_capacity() {
        let mut map = TouchMap::default();
        for i in 0..MAX_TRACKED_TOUCHES {
            map.insert(TouchPoint { id: i as i32, position: pt(i as f32, 0.0) });
        }
        assert_eq!(map.len(), MAX_TRACKED_TOUCHES);
        // Inserting beyond capacity is silently ignored.
        map.insert(TouchPoint { id: 99, position: pt(99.0, 0.0) });
        assert_eq!(map.len(), MAX_TRACKED_TOUCHES);
        assert!(map.get(99).is_none());
    }

    #[test]
    fn touch_map_first_two_ids() {
        let mut map = TouchMap::default();
        assert!(map.first_two_ids().is_none());
        map.insert(TouchPoint { id: 5, position: pt(0.0, 0.0) });
        assert!(map.first_two_ids().is_none());
        map.insert(TouchPoint { id: 10, position: pt(0.0, 0.0) });
        assert_eq!(map.first_two_ids(), Some((5, 10)));
    }

    #[test]
    fn touch_map_first() {
        let mut map = TouchMap::default();
        assert!(map.first().is_none());
        map.insert(TouchPoint { id: 7, position: pt(1.0, 2.0) });
        let tp = map.first().unwrap();
        assert_eq!(tp.id, 7);
        assert!((tp.position.x - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn touch_map_get_mut() {
        let mut map = TouchMap::default();
        map.insert(TouchPoint { id: 1, position: pt(0.0, 0.0) });
        map.get_mut(1).unwrap().position = pt(5.0, 6.0);
        assert!((map.get(1).unwrap().position.x - 5.0).abs() < f32::EPSILON);
    }

    // -----------------------------------------------------------------------
    // Helper: extract event types for readable assertions
    // -----------------------------------------------------------------------

    #[derive(Debug, PartialEq)]
    enum Ev {
        Pressed(f32, f32),
        Released(f32, f32),
        Moved(f32, f32),
        Exit,
        PinchStarted,
        PinchMoved(f32),
        PinchEnded,
        PinchCancelled,
        RotationStarted,
        RotationMoved(f32),
        RotationEnded,
        RotationCancelled,
    }

    fn classify(events: &TouchEventBuffer) -> Vec<Ev> {
        events
            .clone()
            .into_iter()
            .map(|e| match e {
                MouseEvent::Pressed { position, .. } => Ev::Pressed(position.x, position.y),
                MouseEvent::Released { position, .. } => Ev::Released(position.x, position.y),
                MouseEvent::Moved { position, .. } => Ev::Moved(position.x, position.y),
                MouseEvent::Exit => Ev::Exit,
                MouseEvent::PinchGesture { delta, phase, .. } => match phase {
                    TouchPhase::Started => Ev::PinchStarted,
                    TouchPhase::Moved => Ev::PinchMoved(delta),
                    TouchPhase::Ended => Ev::PinchEnded,
                    TouchPhase::Cancelled => Ev::PinchCancelled,
                },
                MouseEvent::RotationGesture { delta, phase, .. } => match phase {
                    TouchPhase::Started => Ev::RotationStarted,
                    TouchPhase::Moved => Ev::RotationMoved(delta),
                    TouchPhase::Ended => Ev::RotationEnded,
                    TouchPhase::Cancelled => Ev::RotationCancelled,
                },
                _ => panic!("unexpected event: {:?}", e),
            })
            .collect()
    }

    // -----------------------------------------------------------------------
    // TouchState: single-finger forwarding
    // -----------------------------------------------------------------------

    #[test]
    fn single_finger_press_move_release() {
        let mut state = TouchState::default();

        let evs = state.process(1, pt(100.0, 200.0), TouchPhase::Started);
        assert_eq!(classify(&evs), vec![Ev::Pressed(100.0, 200.0)]);

        let evs = state.process(1, pt(110.0, 200.0), TouchPhase::Moved);
        assert_eq!(classify(&evs), vec![Ev::Moved(110.0, 200.0)]);

        let evs = state.process(1, pt(110.0, 200.0), TouchPhase::Ended);
        assert_eq!(classify(&evs), vec![Ev::Released(110.0, 200.0), Ev::Exit]);
    }

    #[test]
    fn single_finger_cancel() {
        let mut state = TouchState::default();

        state.process(1, pt(100.0, 200.0), TouchPhase::Started);

        let evs = state.process(1, pt(100.0, 200.0), TouchPhase::Cancelled);
        assert_eq!(classify(&evs), vec![Ev::Released(100.0, 200.0), Ev::Exit]);
    }

    #[test]
    fn non_primary_move_ignored() {
        let mut state = TouchState::default();
        // Touch 1 is primary.
        state.process(1, pt(100.0, 200.0), TouchPhase::Started);

        // Move for a different ID that was never started (edge case).
        let evs = state.process(99, pt(50.0, 50.0), TouchPhase::Moved);
        assert!(classify(&evs).is_empty());
    }

    // -----------------------------------------------------------------------
    // TouchState: two-finger → gesture transition
    // -----------------------------------------------------------------------

    #[test]
    fn two_fingers_synthesize_release_then_gesture() {
        let mut state = TouchState::default();

        // Finger 1 down.
        let evs = state.process(1, pt(100.0, 200.0), TouchPhase::Started);
        assert_eq!(classify(&evs), vec![Ev::Pressed(100.0, 200.0)]);

        // Finger 2 down → synthesized release for finger 1.
        let evs = state.process(2, pt(200.0, 200.0), TouchPhase::Started);
        assert_eq!(classify(&evs), vec![Ev::Released(100.0, 200.0)]);
        assert!(matches!(state.gesture_state, GestureRecognitionState::TwoFingersDown { .. }));

        // Move finger 2 far enough to trigger pinch (> 8px threshold).
        let evs = state.process(2, pt(220.0, 200.0), TouchPhase::Moved);
        assert_eq!(classify(&evs), vec![Ev::PinchStarted, Ev::RotationStarted]);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Pinching { .. }));
    }

    #[test]
    fn two_fingers_below_threshold_no_gesture() {
        let mut state = TouchState::default();

        state.process(1, pt(100.0, 200.0), TouchPhase::Started);
        state.process(2, pt(200.0, 200.0), TouchPhase::Started);

        // Small movement within threshold.
        let evs = state.process(2, pt(202.0, 200.0), TouchPhase::Moved);
        assert!(classify(&evs).is_empty());
        assert!(matches!(state.gesture_state, GestureRecognitionState::TwoFingersDown { .. }));
    }

    #[test]
    fn pinch_produces_scale_deltas() {
        let mut state = TouchState::default();

        // Set up: finger 1 at (0, 0), finger 2 at (100, 0) → distance = 100.
        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(100.0, 0.0), TouchPhase::Started);

        // Move finger 2 to (120, 0) to exceed threshold and start pinching.
        state.process(2, pt(120.0, 0.0), TouchPhase::Moved);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Pinching { .. }));

        // Now move finger 2 further to (180, 0).
        // New distance = 180, initial distance (re-snapshotted) = 120.
        // Scale = 180/120 = 1.5, delta = 1.5 - 1.0 = 0.5.
        let evs = state.process(2, pt(180.0, 0.0), TouchPhase::Moved);
        let classified = classify(&evs);
        assert_eq!(classified.len(), 2);
        if let Ev::PinchMoved(delta) = classified[0] {
            assert!((delta - 0.5).abs() < 0.01, "expected ~0.5, got {}", delta);
        } else {
            panic!("expected PinchMoved, got {:?}", classified[0]);
        }
    }

    #[test]
    fn rotation_produces_correct_deltas() {
        let mut state = TouchState::default();

        // Finger 1 at origin, finger 2 on the X axis at (100, 0).
        // Initial angle = atan2(0, 100) = 0°.
        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(100.0, 0.0), TouchPhase::Started);

        // Move finger 2 far enough to trigger gesture.
        state.process(2, pt(120.0, 0.0), TouchPhase::Moved);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Pinching { .. }));

        // Rotate ~45° clockwise: move finger 2 from (120, 0) to roughly
        // (70.7, 70.7) which is at 45° from origin.
        // atan2(70.7, 70.7) ≈ 45°. Delta from re-snapshotted 0° = +45°.
        // Slint convention: positive = clockwise → delta ≈ +45°.
        let evs = state.process(2, pt(70.7, 70.7), TouchPhase::Moved);
        let classified = classify(&evs);
        assert_eq!(classified.len(), 2);
        if let Ev::RotationMoved(delta) = classified[1] {
            assert!((delta - 45.0).abs() < 1.0, "expected ~45.0 (clockwise), got {}", delta);
        } else {
            panic!("expected RotationMoved, got {:?}", classified[1]);
        }
    }

    #[test]
    fn rotation_across_180_degree_boundary() {
        let mut state = TouchState::default();

        // Finger 1 at origin, finger 2 at (-100, -10).
        // angle = atan2(-10, -100) ≈ -174.3°.
        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(-100.0, -10.0), TouchPhase::Started);

        // Trigger gesture by moving far enough.
        state.process(2, pt(-120.0, -10.0), TouchPhase::Moved);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Pinching { .. }));

        // Rotate across the ±180° boundary: move finger 2 to (-100, 10).
        // New angle = atan2(10, -100) ≈ 174.3°.
        // Raw angular change crosses ±180°, but per-frame delta should be
        // small (~11.4° which is 2 * 5.7°), NOT a ~349° jump.
        let evs = state.process(2, pt(-100.0, 10.0), TouchPhase::Moved);
        let classified = classify(&evs);
        if let Ev::RotationMoved(delta) = classified[1] {
            assert!(
                delta.abs() < 20.0,
                "rotation should be a small delta (~11°), got {} (discontinuity!)",
                delta
            );
        } else {
            panic!("expected RotationMoved, got {:?}", classified[1]);
        }
    }

    // -----------------------------------------------------------------------
    // TouchState: gesture end transitions
    // -----------------------------------------------------------------------

    #[test]
    fn pinch_end_with_remaining_finger() {
        let mut state = TouchState::default();

        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(100.0, 0.0), TouchPhase::Started);
        // Trigger pinch.
        state.process(2, pt(120.0, 0.0), TouchPhase::Moved);

        // Lift finger 2 → gesture ends, finger 1 gets re-pressed.
        let evs = state.process(2, pt(120.0, 0.0), TouchPhase::Ended);
        let classified = classify(&evs);
        assert_eq!(classified, vec![Ev::PinchEnded, Ev::RotationEnded, Ev::Pressed(0.0, 0.0)]);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Idle));
        assert_eq!(state.primary_touch_id, Some(1));
    }

    #[test]
    fn pinch_cancel_emits_cancelled_and_exit() {
        let mut state = TouchState::default();

        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(100.0, 0.0), TouchPhase::Started);
        state.process(2, pt(120.0, 0.0), TouchPhase::Moved);

        // Cancel finger 2.
        let evs = state.process(2, pt(120.0, 0.0), TouchPhase::Cancelled);
        let classified = classify(&evs);
        assert_eq!(classified, vec![Ev::PinchCancelled, Ev::RotationCancelled, Ev::Exit]);
        assert!(state.primary_touch_id.is_none());
    }

    #[test]
    fn two_fingers_down_lift_before_threshold_returns_to_idle() {
        let mut state = TouchState::default();

        state.process(1, pt(100.0, 200.0), TouchPhase::Started);
        state.process(2, pt(200.0, 200.0), TouchPhase::Started);
        assert!(matches!(state.gesture_state, GestureRecognitionState::TwoFingersDown { .. }));

        // Lift finger 2 without exceeding movement threshold.
        let evs = state.process(2, pt(200.0, 200.0), TouchPhase::Ended);
        let classified = classify(&evs);
        // Remaining finger 1 gets re-pressed.
        assert_eq!(classified, vec![Ev::Pressed(100.0, 200.0)]);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Idle));
        assert_eq!(state.primary_touch_id, Some(1));
    }

    #[test]
    fn two_fingers_down_cancel_both_emits_exit() {
        let mut state = TouchState::default();

        state.process(1, pt(100.0, 200.0), TouchPhase::Started);
        state.process(2, pt(200.0, 200.0), TouchPhase::Started);

        // Cancel finger 2 (gesture finger, no remaining → Exit).
        let evs = state.process(2, pt(200.0, 200.0), TouchPhase::Cancelled);
        assert_eq!(classify(&evs), vec![Ev::Exit]);

        // Cancel finger 1 (now in Idle, but not primary since cancel cleared it).
        let evs = state.process(1, pt(100.0, 200.0), TouchPhase::Cancelled);
        assert!(classify(&evs).is_empty());
    }

    // -----------------------------------------------------------------------
    // TouchState: 3+ fingers
    // -----------------------------------------------------------------------

    #[test]
    fn third_finger_ignored_for_gesture() {
        let mut state = TouchState::default();

        state.process(1, pt(0.0, 0.0), TouchPhase::Started);
        state.process(2, pt(100.0, 0.0), TouchPhase::Started);

        // Third finger: no additional events.
        let evs = state.process(3, pt(50.0, 50.0), TouchPhase::Started);
        assert!(classify(&evs).is_empty());
        assert_eq!(state.active_touches.len(), 3);
    }

    // -----------------------------------------------------------------------
    // Angle wrapping via Euclid
    // -----------------------------------------------------------------------

    #[test]
    fn euclid_angle_signed_wrapping() {
        use euclid::Angle;
        let wrap = |deg: f32| Angle::degrees(deg).signed().to_degrees();
        assert!(wrap(0.0).abs() < f32::EPSILON);
        assert!((wrap(180.0) - 180.0).abs() < 0.01);
        assert!((wrap(181.0) - (-179.0)).abs() < 0.01);
        assert!((wrap(-181.0) - 179.0).abs() < 0.01);
        assert!(wrap(360.0).abs() < 0.01);
    }

    #[test]
    fn zero_distance_fingers_no_division_by_zero() {
        let mut state = TouchState::default();

        // Two fingers at the exact same position → distance = 0.
        state.process(1, pt(100.0, 100.0), TouchPhase::Started);
        state.process(2, pt(100.0, 100.0), TouchPhase::Started);
        assert!(matches!(state.gesture_state, GestureRecognitionState::TwoFingersDown { .. }));

        // Move one finger far enough to trigger gesture.
        let evs = state.process(2, pt(120.0, 100.0), TouchPhase::Moved);
        assert!(matches!(state.gesture_state, GestureRecognitionState::Pinching { .. }));
        let classified = classify(&evs);
        assert_eq!(classified.len(), 2);
        assert_eq!(classified[0], Ev::PinchStarted);

        // Move further — scale should not be inf/NaN despite initial_distance
        // having been 0 (re-snapshotted to 20.0 at threshold crossing).
        let evs = state.process(2, pt(140.0, 100.0), TouchPhase::Moved);
        let classified = classify(&evs);
        if let Ev::PinchMoved(delta) = classified[0] {
            assert!(delta.is_finite(), "scale delta should be finite, got {}", delta);
        } else {
            panic!("expected PinchMoved, got {:?}", classified[0]);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    extern crate alloc;

    #[test]
    fn test_to_string() {
        let test_cases = [
            (
                "a",
                KeyboardModifiers { alt: false, control: true, shift: false, meta: false },
                false,
                false,
                "⌘A",
                "Ctrl+A",
                "Ctrl+A",
            ),
            (
                "a",
                KeyboardModifiers { alt: true, control: true, shift: true, meta: true },
                false,
                false,
                "⌃⌥⇧⌘A",
                "Win+Ctrl+Alt+Shift+A",
                "Super+Ctrl+Alt+Shift+A",
            ),
            (
                "\u{001b}",
                KeyboardModifiers { alt: false, control: true, shift: true, meta: false },
                false,
                false,
                "⇧⌘Escape",
                "Ctrl+Shift+Escape",
                "Ctrl+Shift+Escape",
            ),
            (
                "+",
                KeyboardModifiers { alt: false, control: true, shift: false, meta: false },
                true,
                false,
                "⌘+",
                "Ctrl++",
                "Ctrl++",
            ),
            (
                "a",
                KeyboardModifiers { alt: true, control: true, shift: false, meta: false },
                false,
                true,
                "⌘A",
                "Ctrl+A",
                "Ctrl+A",
            ),
            (
                "",
                KeyboardModifiers { alt: false, control: true, shift: false, meta: false },
                false,
                false,
                "",
                "",
                "",
            ),
            (
                "\u{000a}",
                KeyboardModifiers { alt: false, control: false, shift: false, meta: false },
                false,
                false,
                "Return",
                "Return",
                "Return",
            ),
            (
                "\u{0009}",
                KeyboardModifiers { alt: false, control: false, shift: false, meta: false },
                false,
                false,
                "Tab",
                "Tab",
                "Tab",
            ),
            (
                "\u{0020}",
                KeyboardModifiers { alt: false, control: false, shift: false, meta: false },
                false,
                false,
                "Space",
                "Space",
                "Space",
            ),
            (
                "\u{0008}",
                KeyboardModifiers { alt: false, control: false, shift: false, meta: false },
                false,
                false,
                "Backspace",
                "Backspace",
                "Backspace",
            ),
        ];

        for (
            key,
            modifiers,
            ignore_shift,
            ignore_alt,
            _expected_macos,
            _expected_windows,
            _expected_linux,
        ) in test_cases
        {
            let shortcut = make_keys(key.into(), modifiers, ignore_shift, ignore_alt);

            use crate::alloc::string::ToString;
            let result = shortcut.to_string();

            #[cfg(target_os = "macos")]
            assert_eq!(result.as_str(), _expected_macos, "Failed for key: {:?}", key);

            #[cfg(target_os = "windows")]
            assert_eq!(result.as_str(), _expected_windows, "Failed for key: {:?}", key);

            #[cfg(not(any(target_os = "macos", target_os = "windows")))]
            assert_eq!(result.as_str(), _expected_linux, "Failed for key: {:?}", key);
        }
    }

    #[test]
    fn test_from_parts_valid() {
        let f5_key = alloc::string::String::from(char::from(key_codes::Key::F5));
        let ret_key = alloc::string::String::from(char::from(key_codes::Key::Return));
        let pause_key = alloc::string::String::from(char::from(key_codes::Key::Pause));

        // (description, input parts, expected key, modifiers, ignore_shift, ignore_alt)
        let cases: &[(&str, &[&str], &str, KeyboardModifiers, bool, bool)] = &[
            (
                "Control+A",
                &["Control", "A"],
                "a",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            (
                "Control+Shift+A",
                &["Control", "Shift", "A"],
                "a",
                KeyboardModifiers { control: true, shift: true, ..Default::default() },
                false,
                false,
            ),
            (
                "Control+Shift?+Z (explicit ignore_shift)",
                &["Control", "Shift?", "Z"],
                "z",
                KeyboardModifiers { control: true, ..Default::default() },
                true,
                false,
            ),
            (
                "Control+Alt?+A (ignore_alt)",
                &["Control", "Alt?", "A"],
                "a",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                true,
            ),
            (
                "F5 alone (special key)",
                &["F5"],
                &f5_key,
                KeyboardModifiers::default(),
                false,
                false,
            ),
            ("Return key", &["Return"], &ret_key, KeyboardModifiers::default(), false, false),
            (
                "Control+Plus (LocalizedShiftable → auto ignore_shift)",
                &["Control", "Plus"],
                "+",
                KeyboardModifiers { control: true, ..Default::default() },
                true,
                false,
            ),
            (
                "Control+'+' (literal, no auto ignore_shift)",
                &["Control", "+"],
                "+",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            (
                "Control+Shift+Alt+A (all modifiers)",
                &["Control", "Shift", "Alt", "A"],
                "a",
                KeyboardModifiers { control: true, shift: true, alt: true, ..Default::default() },
                false,
                false,
            ),
            ("empty input → Keys::default()", &[], "", KeyboardModifiers::default(), false, false),
            (
                "Control+€ (unicode literal)",
                &["Control", "€"],
                "€",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            (
                "Control+é (lowercase literal)",
                &["Control", "é"],
                "é",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            ("A alone (named key)", &["A"], "a", KeyboardModifiers::default(), false, false),
            // The special keys are represented by reserved unicode codepoints. Passing
            // one of those characters as a literal must produce the same `Keys` as its
            // name, so `to_parts` output stays acceptable to `from_parts`.
            (
                "F5 codepoint literal",
                &[&f5_key],
                &f5_key,
                KeyboardModifiers::default(),
                false,
                false,
            ),
            (
                "Pause codepoint literal",
                &[&pause_key],
                &pause_key,
                KeyboardModifiers::default(),
                false,
                false,
            ),
            (
                "Control + F5 codepoint literal",
                &["Control", &f5_key],
                &f5_key,
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            // Whitespace is significant: these literals name the Space/Tab/Return keys
            // and must agree with their named spellings (parts are not trimmed).
            ("\" \" literal → Space", &[" "], " ", KeyboardModifiers::default(), false, false),
            ("Space named", &["Space"], " ", KeyboardModifiers::default(), false, false),
            ("\"\\t\" literal → Tab", &["\t"], "\t", KeyboardModifiers::default(), false, false),
            ("Tab named", &["Tab"], "\t", KeyboardModifiers::default(), false, false),
            (
                "\"\\n\" literal → Return",
                &["\n"],
                &ret_key,
                KeyboardModifiers::default(),
                false,
                false,
            ),
            (
                "Control+\" \" (literal space with a modifier)",
                &["Control", " "],
                " ",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
                false,
            ),
            (
                "empty part is skipped → Keys::default()",
                &[""],
                "",
                KeyboardModifiers::default(),
                false,
                false,
            ),
            (
                "a alone (literal fallback, same result as named A)",
                &["a"],
                "a",
                KeyboardModifiers::default(),
                false,
                false,
            ),
        ];

        for (desc, parts, expected_key, mods, is, ia) in cases {
            let result =
                Keys::from_parts(parts.iter().copied()).unwrap_or_else(|e| panic!("{desc}: {e}"));
            assert_eq!(result, make_keys((*expected_key).into(), *mods, *is, *ia), "{desc}");
        }
    }

    #[test]
    fn test_from_parts_invalid() {
        use super::KeysParseErrorInner;
        let cases: &[(&str, &[&str], KeysParseError)] = &[
            // Case-sensitive modifiers: unrecognized modifier parses as a second key
            ("lowercase 'control'", &["control", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            ("uppercase 'CONTROL'", &["CONTROL", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            ("'Ctrl' alias", &["Ctrl", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            ("'ctrl' alias", &["ctrl", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            // Meta aliases not accepted
            ("'Win' alias", &["Win", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            ("'Super' alias", &["Super", "A"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            // No key
            ("modifiers only", &["Control", "Shift"], KeysParseError(KeysParseErrorInner::NoKey)),
            // Multiple keys
            ("two keys", &["A", "B"], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            // Multi-grapheme cluster
            (
                "multi-char unknown",
                &["Control", "Foobar"],
                KeysParseError(KeysParseErrorInner::MultipleGraphemeClusters("Foobar".into())),
            ),
            (
                "two-char literal",
                &["Control", "ab"],
                KeysParseError(KeysParseErrorInner::MultipleGraphemeClusters("ab".into())),
            ),
            // Parts are not trimmed, so a padded modifier is no longer a modifier: it
            // falls through to the key branch and fails as a multi-grapheme literal.
            (
                "padded modifier ' Control ' alone",
                &[" Control "],
                KeysParseError(KeysParseErrorInner::MultipleGraphemeClusters(" Control ".into())),
            ),
            (
                "padded modifier ' Control ' is a key, so 'A' is a second key",
                &[" Control ", "A"],
                KeysParseError(KeysParseErrorInner::MultipleKeys),
            ),
            (
                "padded key ' A '",
                &["Control", " A "],
                KeysParseError(KeysParseErrorInner::MultipleGraphemeClusters(" A ".into())),
            ),
            // Two whitespace literals are two keys, not one trimmed-away key.
            ("two space literals", &[" ", " "], KeysParseError(KeysParseErrorInner::MultipleKeys)),
            (
                "lowercase 'return' (not a named key)",
                &["return"],
                KeysParseError(KeysParseErrorInner::MultipleGraphemeClusters("return".into())),
            ),
            // Not lowercase
            (
                "uppercase literal É",
                &["Control", "É"],
                KeysParseError(KeysParseErrorInner::NotLowercase("É".into())),
            ),
            // Incompatible modifiers
            (
                "Shift + Shift?",
                &["Shift", "Shift?", "A"],
                KeysParseError(KeysParseErrorInner::IncompatibleModifiers("Shift and Shift? cannot be combined".into())),
            ),
            (
                "Alt + Alt?",
                &["Alt", "Alt?", "A"],
                KeysParseError(KeysParseErrorInner::IncompatibleModifiers("Alt and Alt? cannot be combined".into())),
            ),
            (
                "Shift + LocalizedShiftable key (Plus)",
                &["Control", "Shift", "Plus"],
                KeysParseError(KeysParseErrorInner::IncompatibleModifiers(
                    "Key bindings involving Plus ignore Shift to support different keyboard layouts; remove Shift".into(),
                )),
            ),
        ];

        for (desc, parts, expected_err) in cases {
            let result = Keys::from_parts(parts.iter().copied());
            assert!(result.is_err(), "{desc}: expected error, got {result:?}");
            assert_eq!(&result.unwrap_err(), expected_err, "{desc}");
        }
    }

    #[test]
    fn test_to_parts_roundtrip() {
        // Inputs that should round-trip identically through from_parts → to_parts.
        let inputs: &[&[&str]] = &[
            &[],
            &["A"],
            &["Control", "A"],
            &["Control", "Shift", "A"],
            &["Control", "Shift?", "Z"],
            &["Control", "Alt?", "A"],
            &["Control", "Alt", "Shift", "Meta", "A"],
            &["Meta", "Control", "Alt", "Shift", "A"],
            &["F5"],
            &["Return"],
            &["Space"],
            &[" "],  // literal space: to_parts emits the "Space" name
            &["\t"], // literal tab: to_parts emits the "Tab" name
            &["\n"], // literal newline: to_parts emits the "Return" name
            &["Control", " "],
            &["Control", "Plus"], // LocalizedShiftable: desugars to ["Control", "Shift?", "+"]
            &["Control", "+"],    // literal '+': stays ["Control", "+"] (no auto ignore_shift)
            &["Control", "Digit0"],
            &["Control", "€"],
            &["Control", "é"],
        ];
        for parts in inputs {
            let k = Keys::from_parts(parts.iter().copied()).unwrap();
            let out_strs: alloc::vec::Vec<&str> = k.to_parts().collect();
            let k2 = Keys::from_parts(out_strs.iter().copied()).unwrap();
            assert_eq!(k, k2, "round-trip mismatch for {parts:?} → {out_strs:?}");
        }
    }

    #[test]
    fn test_to_parts_canonical_form() {
        // Spot-check the exact strings to lock in the canonical output. Modifiers keep
        // their names; the key is always the stored character, never a key name.
        let f5 = alloc::string::String::from(char::from(key_codes::Key::F5));
        let ret = alloc::string::String::from(char::from(key_codes::Key::Return));
        let pause = alloc::string::String::from(char::from(key_codes::Key::Pause));
        let cases: &[(&[&str], &[&str])] = &[
            (&[], &[]),
            (&["A"], &["a"]), // named key → its stored character
            (&["a"], &["a"]),
            (&["Control", "S"], &["Control", "s"]),
            (&["Control", "Shift?", "Z"], &["Control", "Shift?", "z"]),
            (&["Control", "Alt?", "A"], &["Control", "Alt?", "a"]),
            (&["F5"], &[&f5]),
            (&[&f5], &[&f5]), // reserved codepoint as a literal
            (&["Pause"], &[&pause]),
            (&[&pause], &[&pause]),
            // Whitespace and control characters are emitted raw, which is why a text
            // format storing these has to escape them (see the runtime_key_bindings
            // example). They still round-trip, because from_parts does not trim.
            (&[" "], &[" "]),
            (&["Space"], &[" "]),
            (&["\t"], &["\t"]),
            (&["Tab"], &["\t"]),
            (&["\n"], &[&ret]),
            (&["Return"], &[&ret]),
            (&["Control", " "], &["Control", " "]),
            // LocalizedShiftable: the auto ignore_shift is surfaced as Shift? and the
            // raw character is emitted, so the "Plus" name is not reproduced.
            (&["Control", "Plus"], &["Control", "Shift?", "+"]),
            (&["Control", "+"], &["Control", "+"]), // literal '+': no auto ignore_shift
            (&["Control", "€"], &["Control", "€"]),
            (&["Meta", "Control", "Alt", "Shift", "A"], &["Meta", "Control", "Alt", "Shift", "a"]),
        ];
        for (input, expected) in cases {
            let k = Keys::from_parts(input.iter().copied()).unwrap();
            let out_strs: alloc::vec::Vec<&str> = k.to_parts().collect();
            assert_eq!(&out_strs.as_slice(), expected, "for input {input:?}");
        }
    }

    #[test]
    fn test_from_parts_matching() {
        // (description, input parts, event text, event modifiers, should_match)
        let cases: &[(&str, &[&str], &str, KeyboardModifiers, bool)] = &[
            (
                "Control+A matches",
                &["Control", "A"],
                "a",
                KeyboardModifiers { control: true, ..Default::default() },
                true,
            ),
            (
                "Control+A wrong key",
                &["Control", "A"],
                "b",
                KeyboardModifiers { control: true, ..Default::default() },
                false,
            ),
            (
                "Control+A wrong modifier",
                &["Control", "A"],
                "a",
                KeyboardModifiers { alt: true, ..Default::default() },
                false,
            ),
            (
                "Shift? matches with shift",
                &["Control", "Shift?", "Z"],
                "z",
                KeyboardModifiers { control: true, shift: true, ..Default::default() },
                true,
            ),
            (
                "Shift? matches without shift",
                &["Control", "Shift?", "Z"],
                "z",
                KeyboardModifiers { control: true, ..Default::default() },
                true,
            ),
        ];

        for (desc, parts, text, mods, expected) in cases {
            let k =
                Keys::from_parts(parts.iter().copied()).unwrap_or_else(|e| panic!("{desc}: {e}"));
            let event = KeyEvent { text: (*text).into(), modifiers: *mods, ..Default::default() };
            assert_eq!(k.matches(&event), *expected, "{desc}");
        }

        // Special key matching: Return
        let return_char: char = key_codes::Key::Return.into();
        let k = Keys::from_parts(["Return"]).unwrap();
        let event = KeyEvent {
            text: SharedString::from(alloc::string::String::from(return_char)),
            modifiers: KeyboardModifiers::default(),
            ..Default::default()
        };
        assert!(k.matches(&event), "Return key should match Return event");
    }
}