Implement four-way sort cycling for browser listview

- Added four sort modes: Date ↓, Date ↑, Name ↑, Name ↓
- Sorting happens only when sort mode changes, not every frame
- Sorted entries are cached in SortedEntries field
- Search query changes trigger re-filtering and re-sorting
- Scroll offset resets on sort change

internal/editor/state.go

@@ -1,7 +1,7 @@
 package editor
 
 import (
-	"fmt"
+	"sort"
 	"strings"
 
 	"gioui.org/widget"
@@ -56,8 +56,10 @@ const (
 type SortMode int
 
 const (
-	SortByDateNewest SortMode = iota // default: newest modified first
+	SortByDateDesc SortMode = iota // default: newest first
+	SortByDateAsc
 	SortByNameAsc
+	SortByNameDesc
 )
 
 // State holds all application state owned by the logic goroutine.
@@ -78,6 +80,7 @@ type State struct {
 	SortOrderLabel      string   // label text for sort order toggle
 	SearchQuery         string   // current search query
 	SearchEditor        widget.Editor // Gio editor for search input
+	SortedEntries       []ui.ListItem // pre-sorted entries (computed only when sort mode changes)
 	// Editor state
 	ActiveFilename string       // filename shown in editor status bar
 }
@@ -86,8 +89,9 @@ func NewState() *State {
 	return &State{
 		scale:            1.0,
 		page:             EditorPage,
-		SortMode:         SortByDateNewest,
-		SortOrderLabel:   "Date",
+		SortMode:         SortByDateDesc,
+		SortOrderLabel:   "Date ↓",
+		SortedEntries:    sortEntries(browserEntries, SortByDateDesc),
 	}
 }
 
@@ -109,6 +113,9 @@ func (s *State) layout() []ui.Element {
 		newQuery := s.SearchEditor.Text()
 		if newQuery != s.SearchQuery {
 			s.BrowserScrollOffset = 0 // reset on query change
+			// Re-sort the filtered entries
+			filtered := getFilteredEntriesRaw()
+			s.SortedEntries = sortEntries(filtered, s.SortMode)
 		}
 		s.SearchQuery = newQuery
 	}
@@ -204,17 +211,22 @@ func OpenFile(data any) {
 	TheState.page = EditorPage
 }
 
-// ToggleSortOrder cycles the browser sort mode between date and name.
+// ToggleSortOrder cycles the browser sort mode through four modes.
 func ToggleSortOrder(data any) {
-	fmt.Printf("[ToggleSortOrder] called, mode was %v\n", TheState.SortMode)
-	TheState.SortMode = (TheState.SortMode + 1) % 2
+	TheState.SortMode = (TheState.SortMode + 1) % 4
 	switch TheState.SortMode {
-	case SortByDateNewest:
-		TheState.SortOrderLabel = "Date"
+	case SortByDateDesc:
+		TheState.SortOrderLabel = "Date ↓"
+	case SortByDateAsc:
+		TheState.SortOrderLabel = "Date ↑"
 	case SortByNameAsc:
-		TheState.SortOrderLabel = "Name"
+		TheState.SortOrderLabel = "Name ↑"
+	case SortByNameDesc:
+		TheState.SortOrderLabel = "Name ↓"
 	}
-	fmt.Printf("[ToggleSortOrder] mode is now %v\n", TheState.SortMode)
+	// Sort once when mode changes, not every frame
+	TheState.SortedEntries = sortEntries(getFilteredEntriesRaw(), TheState.SortMode)
+	TheState.BrowserScrollOffset = 0 // reset scroll on sort change
 }
 
 // EditorLayout computes the element tree for the editor page.
@@ -301,8 +313,9 @@ func EditorLayout(screenWidth, screenHeight ui.Dp, wordWrap bool) []ui.Element {
 	return []ui.Element{statusBar, editor, bottomBar}
 }
 
-// getFilteredEntries returns browser entries filtered by the current search query.
-func getFilteredEntries() []ui.ListItem {
+// getFilteredEntriesRaw returns browser entries filtered by the current search query.
+// Does not use the SortedEntries cache.
+func getFilteredEntriesRaw() []ui.ListItem {
 	var filtered []ui.ListItem
 	query := strings.ToLower(TheState.SearchQuery)
 	if query == "" {
@@ -317,6 +330,52 @@ func getFilteredEntries() []ui.ListItem {
 	return filtered
 }
 
+// getFilteredEntries returns browser entries filtered by the current search query.
+// If SortedEntries is non-nil (sort mode has been set), returns that instead.
+func getFilteredEntries() []ui.ListItem {
+	if TheState.SortedEntries != nil {
+		return TheState.SortedEntries
+	}
+	return getFilteredEntriesRaw()
+}
+
+// sortEntries sorts the entries according to the given sort mode.
+func sortEntries(entries []ui.ListItem, mode SortMode) []ui.ListItem {
+	// Make a copy to avoid modifying the original slice
+	sorted := make([]ui.ListItem, len(entries))
+	copy(sorted, entries)
+
+	// Parse date from subtext (format: "2025-01-15  •  4.2 KB")
+	getDate := func(entry ui.ListItem) string {
+		// Extract date part before the first space
+		parts := strings.Split(entry.Subtext, " ")
+		if len(parts) > 0 {
+			return parts[0]
+		}
+		return ""
+	}
+
+	switch mode {
+	case SortByDateDesc:
+		sort.Slice(sorted, func(i, j int) bool {
+			return getDate(sorted[i]) > getDate(sorted[j])
+		})
+	case SortByDateAsc:
+		sort.Slice(sorted, func(i, j int) bool {
+			return getDate(sorted[i]) < getDate(sorted[j])
+		})
+	case SortByNameAsc:
+		sort.Slice(sorted, func(i, j int) bool {
+			return strings.ToLower(sorted[i].Text) < strings.ToLower(sorted[j].Text)
+		})
+	case SortByNameDesc:
+		sort.Slice(sorted, func(i, j int) bool {
+			return strings.ToLower(sorted[i].Text) > strings.ToLower(sorted[j].Text)
+		})
+	}
+	return sorted
+}
+
 // browserEntries is a static list of sample files for the browser page.
 // It is longer than the viewport so scrolling can be tested.
 var browserEntries = []ui.ListItem{
@@ -365,10 +424,14 @@ func BrowserLayout(screenWidth, screenHeight ui.Dp, sortMode SortMode) []ui.Elem
 	}
 	var sortLabel string
 	switch sortMode {
-	case SortByDateNewest:
+	case SortByDateDesc:
 		sortLabel = "Date ↓"
+	case SortByDateAsc:
+		sortLabel = "Date ↑"
 	case SortByNameAsc:
 		sortLabel = "Name ↑"
+	case SortByNameDesc:
+		sortLabel = "Name ↓"
 	}
 	headerBar := ui.NewContainer(
 		headerRegion,