Fix offset calculation: derive from first glyph position like Gio's textView

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

internal/ui/render.go

@@ -250,24 +250,33 @@ func (r *Renderer) drawLineText(gtx layout.Context, shp *text.Shaper, x, y unit.
 	m := op.Record(gtx.Ops)
 	var glyphs [32]text.Glyph
 	line := glyphs[:0]
+	var firstGlyph text.Glyph
+	first := true
 	for g, ok := shp.NextGlyph(); ok; g, ok = shp.NextGlyph() {
+		if first {
+			firstGlyph = g
+			first = false
+		}
 		line = append(line, g)
 		if g.Flags&text.FlagLineBreak != 0 || cap(line)-len(line) == 0 {
-			r.drawLine(gtx, shp, line, x, y, col)
+			r.drawLine(gtx, shp, line, firstGlyph, x, y, col)
 			line = line[:0]
 		}
 	}
 	if len(line) > 0 {
-		r.drawLine(gtx, shp, line, x, y, col)
+		r.drawLine(gtx, shp, line, firstGlyph, x, y, col)
 	}
 	call := m.Stop()
 	call.Add(gtx.Ops)
 }
 
 // drawLine draws a line of glyphs using shaper.Shape() and shaper.Bitmaps().
-func (r *Renderer) drawLine(gtx layout.Context, shp *text.Shaper, line []text.Glyph, x, y unit.Dp, col color.NRGBA) {
+func (r *Renderer) drawLine(gtx layout.Context, shp *text.Shaper, line []text.Glyph, firstGlyph text.Glyph, x, y unit.Dp, col color.NRGBA) {
-	// Apply offset transform
+	// Derive offset from first glyph position + desired position
-	off := f32.Point{X: float32(x), Y: float32(y)}
+	// Gio's textView: lineOff = glyphPos - viewportMin
+	// We want: offset = (x, y) - firstGlyphPos
+	firstPos := f32.Point{X: float32(firstGlyph.X) / 64.0, Y: float32(firstGlyph.Y)}
+	off := f32.Point{X: float32(x), Y: float32(y)}.Sub(firstPos)
 	t := op.Affine(f32.Affine2D{}.Offset(off)).Push(gtx.Ops)
 
 	// Draw vector glyphs