Implement seamless glyph cache

draw2dgl/gc.go

@@ -197,10 +197,16 @@ func (gc *GraphicContext) CreateStringPath(s string, x, y float64) float64 {
 	return x - startx
 }
 
+func (gc *GraphicContext) FillString(text string) (cursor float64) {
+	return gc.FillStringAt(text, 0, 0)
+}
+
 func (gc *GraphicContext) FillStringAt(text string, x, y float64) (width float64) {
-	width = gc.CreateStringPath(text, x, y)
-	gc.Fill()
-	return width
+	xorig := x
+	for _, r := range text {
+		x += draw2dbase.FillGlyph(gc, x, y, r)
+	}
+	return x - xorig
 }
 
 // GetStringBounds returns the approximate pixel bounds of the string s at x, y.
@@ -247,9 +253,11 @@ func (gc *GraphicContext) StrokeString(text string) (width float64) {
 }
 
 func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (width float64) {
-	width = gc.CreateStringPath(text, x, y)
-	gc.Stroke()
-	return width
+	xorig := x
+	for _, r := range text {
+		x += draw2dbase.StrokeGlyph(gc, x, y, r)
+	}
+	return x - xorig
 }
 
 // recalc recalculates scale and bounds values from the font size, screen
@@ -293,10 +301,6 @@ func (gc *GraphicContext) DrawImage(img image.Image) {
 	panic("not implemented")
 }
 
-func (gc *GraphicContext) FillString(text string) (cursor float64) {
-	return gc.FillStringAt(text, 0, 0)
-}
-
 func (gc *GraphicContext) paint(rasterizer *raster.Rasterizer, color color.Color) {
 	gc.painter.SetColor(color)
 	rasterizer.Rasterize(gc.painter)

draw2dgl/text.go

@@ -1,12 +1,83 @@
 package draw2dgl
 
 import (
+	"fmt"
+
 	"github.com/golang/freetype/truetype"
 	"github.com/llgcode/draw2d"
 
 	"golang.org/x/image/math/fixed"
 )
 
+var glyphCache map[string]map[rune]*glyph
+
+func init() {
+	glyphCache = make(map[string]map[rune]*glyph)
+}
+
+// FillGlyph copies a glyph from the cache, copies it to the gc, and fills it
+func FillGlyph(gc draw2d.GraphicContext, x, y float64, chr rune) float64 {
+	g := fetchGlyph(gc, chr)
+	gc.Save()
+	gc.BeginPath()
+	gc.Translate(x, y)
+	gc.Fill(g.Path)
+	gc.Restore()
+	return g.Width
+}
+
+// StrokeGlyph fetches a glyph from the cache, copies it to the gc, and strokes it
+func StrokeGlyph(gc draw2d.GraphicContext, x, y float64, chr rune) float64 {
+	g := fetchGlyph(gc, chr)
+	gc.Save()
+	gc.BeginPath()
+	gc.Translate(x, y)
+	gc.Stroke(g.Path)
+	gc.Restore()
+	return g.Width
+}
+
+// fetchGlyph fetches a glyph from the cache, calling renderGlyph first if it doesn't already exist
+func fetchGlyph(gc draw2d.GraphicContext, chr rune) *glyph {
+	fontData := gc.GetFontData()
+	fontName := fmt.Sprintf("%s:%d:%d:%d", fontData.Name, fontData.Family, fontData.Style, gc.GetFontSize())
+	if glyphCache[fontName] == nil {
+		glyphCache[fontName] = make(map[rune]*glyph, 60)
+	}
+	if glyphCache[fontName][chr] == nil {
+		glyphCache[fontName][chr] = renderGlyph(gc, fontName, chr)
+	}
+	return glyphCache[fontName][chr].Copy()
+}
+
+// renderGlyph renders a Glyph then caches and returns it
+func renderGlyph(gc draw2d.GraphicContext, fontName string, chr rune) *glyph {
+	gc.Save()
+	defer gc.Restore()
+	gc.BeginPath()
+	width := gc.CreateStringPath(string(chr), 0, 0)
+	path := gc.GetPath()
+	return &glyph{
+		Path:  &path,
+		Width: width,
+	}
+}
+
+// glyph represents a rune which has been converted to a Path and width
+type glyph struct {
+	// Path represents a glyph, it is always at (0, 0)
+	Path *draw2d.Path
+	// Width of the glyph
+	Width float64
+}
+
+func (g *glyph) Copy() *glyph {
+	return &glyph{
+		Path:  g.Path.Copy(),
+		Width: g.Width,
+	}
+}
+
 // DrawContour draws the given closed contour at the given sub-pixel offset.
 func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) {
 	if len(ps) == 0 {

draw2dimg/ftgc.go

@@ -117,27 +117,31 @@ func (gc *GraphicContext) DrawImage(img image.Image) {
 }
 
 // FillString draws the text at point (0, 0)
-func (gc *GraphicContext) FillString(text string) (cursor float64) {
+func (gc *GraphicContext) FillString(text string) (width float64) {
 	return gc.FillStringAt(text, 0, 0)
 }
 
 // FillStringAt draws the text at the specified point (x, y)
-func (gc *GraphicContext) FillStringAt(text string, x, y float64) (cursor float64) {
-	width := gc.CreateStringPath(text, x, y)
-	gc.Fill()
-	return width
+func (gc *GraphicContext) FillStringAt(text string, x, y float64) (width float64) {
+	xorig := x
+	for _, r := range text {
+		x += draw2dbase.FillGlyph(gc, x, y, r)
+	}
+	return x - xorig
 }
 
 // StrokeString draws the contour of the text at point (0, 0)
-func (gc *GraphicContext) StrokeString(text string) (cursor float64) {
+func (gc *GraphicContext) StrokeString(text string) (width float64) {
 	return gc.StrokeStringAt(text, 0, 0)
 }
 
 // StrokeStringAt draws the contour of the text at point (x, y)
-func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64) {
-	width := gc.CreateStringPath(text, x, y)
-	gc.Stroke()
-	return width
+func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (width float64) {
+	xorig := x
+	for _, r := range text {
+		x += draw2dbase.StrokeGlyph(gc, x, y, r)
+	}
+	return x - xorig
 }
 
 func (gc *GraphicContext) loadCurrentFont() (*truetype.Font, error) {