Pad/internal/editor/frame.go

package editor

import (
	"time"

	"pad/internal/ui"
)

// Frame is the unit of handoff from the logic goroutine to the frame
// receiver. Per architecture.md §9, the frame is the ONLY cross-goroutine
// state carrier: the main goroutine must never read *State directly, it
// reads the snapshot stored here by the frame receiver (under the frame
// mutex).
//
// Elems is the computed element tree for the next draw.
// The remaining fields are the view-state snapshot that the main goroutine
// needs to route events and forward input:
//
//   - Scale: current px-per-Dp, so the main goroutine can detect scale
//     changes and pass the scale to the renderer's Draw call.
//   - FocusedElementID: which registered element receives key/edit events.
//   - Query: the search query the logic goroutine is currently filtering
//     with; the main goroutine compares it against the (main-owned) search
//     widget's text and forwards changes via SearchQueryChan.
type Frame struct {
	Elems     []ui.Element
	Scale     float32
	FontScale float32 // user font-size setting the logic bookkeeping used
	// AppFontScale is the app-local pinch font scale (1.0 = default, 0 =
	// not set yet). The renderer multiplies the editor font size by it;
	// FontScale is already folded into gtx.Metric (PxPerSp).
	AppFontScale     float32
	FocusedElementID string
	Query            string
	// FindQuery: the in-file search query the logic goroutine has processed
	// (mirrors EditorState.Find.Query). Main compares it against the
	// "find_bar" widget's text and forwards changes via FindQueryChan — the
	// same contract as Query/searchQueryChan.
	FindQuery string
	// FindClearSeq mirrors EditorState.Find.ClearSeq: main wipes the widget
	// input once per NEW value (the X button cleared the logic-side query).
	FindClearSeq int
	// ScrollOffset is the editor scroll offset this frame's elements laid
	// out at, shipped with the shaped glyph layout (LayoutFeedback) so the
	// logic can express layout positions in content coordinates.
	ScrollOffset ui.Dp
	// WindowStartByte / WindowStartLine / EditSeq: the editor window this
	// frame's elements describe. The main goroutine forwards them with the
	// shaped glyph layout (LayoutFeedback) so the logic goroutine can apply
	// the layout's wrap counts to exactly the lines it was shaped for, and
	// drop them if an edit landed in the meantime.
	WindowStartByte int
	WindowStartLine int    // -1 when the frame has no editor window
	WindowText      string // the editor window this frame's text element holds
	EditSeq         uint64
	// ViewportDegenerate is set when this frame was built before the
	// window's pixel size was known (0x0). Its editor window, if shaped at
	// all, was shaped at zero width: the shaper wraps every line into many
	// visual lines, and feeding those counts back (LayoutFeedback) would
	// poison the WrapIndex for the window's lines. The main goroutine
	// drops the feedback for such frames.
	ViewportDegenerate bool
}

// frameOf wraps a computed element tree with the current view-state
// snapshot. Must be called on the logic goroutine.
func (l *Logic) frameOf(elems []ui.Element) Frame {
	return Frame{
		Elems:              elems,
		Scale:              l.state.scale,
		FontScale:          l.state.fontScale,
		AppFontScale:       l.state.appFontScale,
		FocusedElementID:   l.state.FocusedElementID,
		Query:              l.state.Browser.Query,
		FindQuery:          l.state.Editor.Find.Query,
		FindClearSeq:       l.state.Editor.Find.ClearSeq,
		ScrollOffset:       l.state.ScrollOffset,
		WindowStartByte:    l.state.Editor.IMEWindowStartByte,
		WindowStartLine:    l.state.WindowStartLine,
		WindowText:         l.state.Editor.IMEWindowText,
		EditSeq:            l.state.Editor.EditSeq,
		ViewportDegenerate: l.state.PixelWidth <= 0 || l.state.PixelHeight <= 0,
	}
}

// inspectReq is a test-only request to run fn on the logic goroutine.
// It preserves the single-owner invariant (architecture.md §1): the fn
// executes on the owner, not on the caller. fn must not block on sends to
// logic channels.
type inspectReq struct {
	fn   func(st *State) any
	resp chan any
}

// Inspect runs fn on the logic goroutine and returns its result. It is
// intended for tests; production code must use the regular channels.
func (l *Logic) Inspect(fn func(st *State) any) (any, bool) {
	req := &inspectReq{fn: fn, resp: make(chan any, 1)}
	select {
	case l.inspectChan <- req:
	case <-time.After(5 * time.Second):
		return nil, false
	}
	select {
	case v := <-req.resp:
		return v, true
	case <-time.After(5 * time.Second):
		return nil, false
	}
}