text/v2: add a non-image glyphs for index info

examples/text/main.go

@@ -125,6 +125,9 @@ func (g *Game) Draw(screen *ebiten.Image) {
 		// You can customize how to render each glyph.
 		// In this example, multiple colors are used to render glyphs.
 		for i, gl := range g.glyphs {
+			if gl.Image == nil {
+				continue
+			}
 			op.GeoM.Reset()
 			op.GeoM.Translate(x, y)
 			op.GeoM.Translate(gl.X, gl.Y)

text/v2/gotext.go

@@ -300,7 +300,8 @@ func (g *GoTextFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffse
 	_, gs := g.Source.shape(line, g)
 	for _, glyph := range gs {
 		img, imgX, imgY := g.glyphImage(glyph, origin)
-		if img != nil {
+		// Append a glyph even if img is nil.
+		// This is necessary to return index information for control characters.
 		glyphs = append(glyphs, Glyph{
 			StartIndexInBytes: indexOffset + glyph.startIndex,
 			EndIndexInBytes:   indexOffset + glyph.endIndex,
@@ -309,7 +310,6 @@ func (g *GoTextFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffse
 			X:                 float64(imgX),
 			Y:                 float64(imgY),
 		})
-		}
 		origin = origin.Add(fixed.Point26_6{
 			X: glyph.shapingGlyph.XAdvance,
 			Y: -glyph.shapingGlyph.YAdvance,

text/v2/layout.go

@@ -106,6 +106,9 @@ func Draw(dst *ebiten.Image, text string, face Face, options *DrawOptions) {
 
 	geoM := options.GeoM
 	for _, g := range AppendGlyphs(nil, text, face, &options.LayoutOptions) {
+		if g.Image == nil {
+			continue
+		}
 		op := &options.DrawImageOptions
 		op.GeoM.Reset()
 		op.GeoM.Translate(g.X, g.Y)

text/v2/std.go

@@ -108,10 +108,13 @@ func (s *StdFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffset i
 			origin.X += s.f.Kern(prevR, r)
 		}
 		img, imgX, imgY, a := s.glyphImage(r, origin)
-		if img != nil {
+
 		// Adjust the position to the integers.
 		// The current glyph images assume that they are rendered on integer positions so far.
 		_, size := utf8.DecodeRuneInString(line[i:])
+
+		// Append a glyph even if img is nil.
+		// This is necessary to return index information for control characters.
 		glyphs = append(glyphs, Glyph{
 			StartIndexInBytes: indexOffset + i,
 			EndIndexInBytes:   indexOffset + i + size,
@@ -119,7 +122,6 @@ func (s *StdFace) appendGlyphsForLine(glyphs []Glyph, line string, indexOffset i
 			X:                 float64(imgX),
 			Y:                 float64(imgY),
 		})
-		}
 		origin.X += a
 		prevR = r
 	}