Add drawTruncatedText for single-pass layout, measure, and render

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

internal/ui/render.go

@@ -95,23 +95,27 @@ func (r *Renderer) drawStatusBar(gtx layout.Context, sb StatusBar) {
 	// Truncate filename only if it doesn't fit
 	displayFilename := sb.Filename
 	availableWidth := int(reg.W - unit.Dp(8) - unit.Dp(40)) // left margin + right icons in DP
-	ellipsisWidths := charWidths(gtx, th.Shaper, "...", r.theme.FontSize)
+
+	// Layout ellipsis once and get its width
+	th.Shaper.LayoutString(text.Parameters{PxPerEm: fixed.I(gtx.Sp(r.theme.FontSize))}, "...")
+	var ellipsisWidths []int
+	for {
+		g, ok := th.Shaper.NextGlyph()
+		if !ok {
+			break
+		}
+		if len(ellipsisWidths) == 0 {
+			ellipsisWidths = append(ellipsisWidths, int(g.Advance>>6))
+		} else {
+			ellipsisWidths = append(ellipsisWidths, ellipsisWidths[len(ellipsisWidths)-1]+int(g.Advance>>6))
+		}
+	}
 	ellipsisWidth := ellipsisWidths[len(ellipsisWidths)-1]
 	// Measure how wide "..." is, then find how many chars fit in availableWidth - ellipsisWidth
 	spaceForText := availableWidth - ellipsisWidth
-	widths := charWidths(gtx, th.Shaper, displayFilename, r.theme.FontSize)
-	if len(widths) > 0 && widths[len(widths)-1] > availableWidth {
-		// Find the largest index where the width fits
-		for i := len(widths)-1; i >= 0; i-- {
-			if widths[i] <= spaceForText {
-				displayFilename = displayFilename[:i] + "..."
-				break
-			}
-		}
-	}
 
-	// Position filename at (reg.X + 8, filenameLineY) - draw using shaper to avoid double-shaping
+	// Layout filename, measure widths, and draw in a single pass
-	r.drawText(gtx, th.Shaper, displayFilename, r.theme.FontSize, reg.X+unit.Dp(8), filenameLineY, color.NRGBA{R: 0, G: 0, B: 0, A: 255})
+	r.drawTruncatedText(gtx, th.Shaper, displayFilename, r.theme.FontSize, reg.X+unit.Dp(8), filenameLineY, availableWidth, spaceForText, color.NRGBA{R: 0, G: 0, B: 0, A: 255})
 
 	// Line 2: Icons
 	iconsLineY := filenameLineY + filenameLineH
@@ -196,6 +200,41 @@ func boolToString(b bool) string {
 	return "Off"
 }
 
+// drawTruncatedText layouts text, measures widths, truncates if needed, and draws in a single pass.
+func (r *Renderer) drawTruncatedText(gtx layout.Context, shp *text.Shaper, str string, size unit.Sp, x, y unit.Dp, availableWidth, spaceForText int, col color.NRGBA) {
+	// Layout text
+	shp.LayoutString(text.Parameters{PxPerEm: fixed.I(gtx.Sp(size))}, str)
+
+	// Measure widths and find truncation point
+	var widths []int
+	var cumWidth fixed.Int26_6
+	fullStr := str
+	for {
+		g, ok := shp.NextGlyph()
+		if !ok {
+			break
+		}
+		cumWidth += g.Advance
+		w := int(cumWidth >> 6)
+		widths = append(widths, w)
+	}
+
+	// Truncate if needed
+	if len(widths) > 0 && widths[len(widths)-1] > availableWidth {
+		// Find truncation point (from longest to shortest)
+		for i := len(widths)-1; i >= 0; i-- {
+			if widths[i] <= spaceForText {
+				fullStr = str[:i] + "..."
+				break
+			}
+		}
+	}
+
+	// Re-layout truncated text and draw
+	shp.LayoutString(text.Parameters{PxPerEm: fixed.I(gtx.Sp(size))}, fullStr)
+	r.drawText(gtx, shp, fullStr, size, x, y, col)
+}
+
 // drawText draws text using the same approach as Gio's textView:
 // layout text, iterate glyphs, buffer into lines, and draw using shaper.Shape().
 func (r *Renderer) drawText(gtx layout.Context, shp *text.Shaper, str string, size unit.Sp, x, y unit.Dp, col color.NRGBA) {