Copied font functions from draw2dimg to draw2dgl

cursor -> width for certain functions for clarity
Some panics added, some TODOs added

draw2dgl/gc.go

@@ -1,16 +1,23 @@
 package draw2dgl
 
 import (
+	"errors"
 	"image"
 	"image/color"
 	"image/draw"
+	"log"
+	"math"
 	"runtime"
 
 	"github.com/go-gl/gl/v2.1/gl"
 	"github.com/golang/freetype/raster"
+	"github.com/golang/freetype/truetype"
 	"github.com/llgcode/draw2d"
 	"github.com/llgcode/draw2d/draw2dbase"
 	"github.com/llgcode/draw2d/draw2dimg"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
 )
 
 func init() {
@@ -118,6 +125,8 @@ type GraphicContext struct {
 	painter          *Painter
 	fillRasterizer   *raster.Rasterizer
 	strokeRasterizer *raster.Rasterizer
+	glyphBuf         *truetype.GlyphBuf
+	DPI		int
 }
 
 // NewGraphicContext creates a new Graphic context from an image.
@@ -127,54 +136,170 @@ func NewGraphicContext(width, height int) *GraphicContext {
 		NewPainter(),
 		raster.NewRasterizer(width, height),
 		raster.NewRasterizer(width, height),
+		&truetype.GlyphBuf{},
+		92,
 	}
 	return gc
 }
 
+//FIXME copied from ../draw2dimg
+func (gc *GraphicContext) loadCurrentFont() (*truetype.Font, error) {
+	font := draw2d.GetFont(gc.Current.FontData)
+	if font == nil {
+		font = draw2d.GetFont(draw2dbase.DefaultFontData)
+	}
+	if font == nil {
+		return nil, errors.New("No font set, and no default font available.")
+	}
+	gc.SetFont(font)
+	gc.SetFontSize(gc.Current.FontSize)
+	return font, nil
+}
+
+//FIXME copied from ../draw2dimg
+func (gc *GraphicContext) drawGlyph(glyph truetype.Index, dx, dy float64) error {
+	if err := gc.glyphBuf.Load(gc.Current.Font, fixed.Int26_6(gc.Current.Scale), glyph, font.HintingNone); err != nil {
+		return err
+	}
+	e0 := 0
+	for _, e1 := range gc.glyphBuf.Ends {
+		DrawContour(gc, gc.glyphBuf.Points[e0:e1], dx, dy)
+		e0 = e1
+	}
+	return nil
+}
+
+//FIXME copied from ../draw2dimg
+// CreateStringPath creates a path from the string s at x, y, and returns the string width.
+// The text is placed so that the left edge of the em square of the first character of s
+// and the baseline intersect at x, y. The majority of the affected pixels will be
+// above and to the right of the point, but some may be below or to the left.
+// For example, drawing a string that starts with a 'J' in an italic font may
+// affect pixels below and left of the point.
 func (gc *GraphicContext) CreateStringPath(s string, x, y float64) float64 {
-	panic("not implemented")
+	f, err := gc.loadCurrentFont()
+	if err != nil {
+		log.Println(err)
+		return 0.0
+	}
+	startx := x
+	prev, hasPrev := truetype.Index(0), false
+	for _, rune := range s {
+		index := f.Index(rune)
+		if hasPrev {
+			x += fUnitsToFloat64(f.Kern(fixed.Int26_6(gc.Current.Scale), prev, index))
+		}
+		err := gc.drawGlyph(index, x, y)
+		if err != nil {
+			log.Println(err)
+			return startx - x
+		}
+		x += fUnitsToFloat64(f.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth)
+		prev, hasPrev = index, true
+	}
+	return x - startx
 }
 
-func (gc *GraphicContext) FillStringAt(text string, x, y float64) (cursor float64) {
+func (gc *GraphicContext) FillStringAt(text string, x, y float64) (width float64) {
-	panic("not implemented")
+	width = gc.CreateStringPath(text, x, y)
+	gc.Fill()
+	return width
 }
 
+//FIXME copied from ../draw2dimg
+// GetStringBounds returns the approximate pixel bounds of the string s at x, y.
+// The the left edge of the em square of the first character of s
+// and the baseline intersect at 0, 0 in the returned coordinates.
+// Therefore the top and left coordinates may well be negative.
 func (gc *GraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
-	panic("not implemented")
+	f, err := gc.loadCurrentFont()
+	if err != nil {
+		log.Println(err)
+		return 0, 0, 0, 0
+	}
+	top, left, bottom, right = 10e6, 10e6, -10e6, -10e6
+	cursor := 0.0
+	prev, hasPrev := truetype.Index(0), false
+	for _, rune := range s {
+		index := f.Index(rune)
+		if hasPrev {
+			cursor += fUnitsToFloat64(f.Kern(fixed.Int26_6(gc.Current.Scale), prev, index))
+		}
+		if err := gc.glyphBuf.Load(gc.Current.Font, fixed.Int26_6(gc.Current.Scale), index, font.HintingNone); err != nil {
+			log.Println(err)
+			return 0, 0, 0, 0
+		}
+		e0 := 0
+		for _, e1 := range gc.glyphBuf.Ends {
+			ps := gc.glyphBuf.Points[e0:e1]
+			for _, p := range ps {
+				x, y := pointToF64Point(p)
+				top = math.Min(top, y)
+				bottom = math.Max(bottom, y)
+				left = math.Min(left, x+cursor)
+				right = math.Max(right, x+cursor)
+			}
+		}
+		cursor += fUnitsToFloat64(f.HMetric(fixed.Int26_6(gc.Current.Scale), index).AdvanceWidth)
+		prev, hasPrev = index, true
+	}
+	return left, top, right, bottom
 }
 
-func (gc *GraphicContext) StrokeString(text string) (cursor float64) {
+func (gc *GraphicContext) StrokeString(text string) (width float64) {
 	return gc.StrokeStringAt(text, 0, 0)
 }
 
-func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64) {
+func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (width float64) {
-	width := gc.CreateStringPath(text, x, y)
+	width = gc.CreateStringPath(text, x, y)
 	gc.Stroke()
 	return width
 }
 
-func (gc *GraphicContext) SetDPI(dpi int) {
+//FIXME copied from ../draw2dimg
+// recalc recalculates scale and bounds values from the font size, screen
+// resolution and font metrics, and invalidates the glyph cache.
+func (gc *GraphicContext) recalc() {
+	gc.Current.Scale = gc.Current.FontSize * float64(gc.DPI) * (64.0 / 72.0)
+}
 
+func (gc *GraphicContext) SetDPI(dpi int) {
+	gc.DPI = dpi
+	gc.recalc()
+}
+
+// SetFont sets the font used to draw text.
+func (gc *GraphicContext) SetFont(font *truetype.Font) {
+	gc.Current.Font = font
+}
+
+// SetFontSize sets the font size in points (as in ``a 12 point font'').
+func (gc *GraphicContext) SetFontSize(fontSize float64) {
+	gc.Current.FontSize = fontSize
+	gc.recalc()
 }
 
 func (gc *GraphicContext) GetDPI() int {
-	return -1
+	return gc.DPI
 }
 
+//TODO
 func (gc *GraphicContext) Clear() {
-
+	panic("not implemented")
 }
 
+//TODO
 func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
-
+	panic("not implemented")
 }
 
+//TODO
 func (gc *GraphicContext) DrawImage(img image.Image) {
-
+	panic("not implemented")
 }
 
 func (gc *GraphicContext) FillString(text string) (cursor float64) {
-	return 0
+	return gc.FillStringAt(text, 0, 0)
 }
 
 func (gc *GraphicContext) paint(rasterizer *raster.Rasterizer, color color.Color) {

draw2dgl/text.go

@@ -0,0 +1,83 @@
+package draw2dgl
+//Copied from ../draw2dimg
+
+import (
+	"github.com/golang/freetype/truetype"
+	"github.com/llgcode/draw2d"
+
+	"golang.org/x/image/math/fixed"
+)
+
+// 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 {
+		return
+	}
+	startX, startY := pointToF64Point(ps[0])
+	path.MoveTo(startX+dx, startY+dy)
+	q0X, q0Y, on0 := startX, startY, true
+	for _, p := range ps[1:] {
+		qX, qY := pointToF64Point(p)
+		on := p.Flags&0x01 != 0
+		if on {
+			if on0 {
+				path.LineTo(qX+dx, qY+dy)
+			} else {
+				path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
+			}
+		} else {
+			if on0 {
+				// No-op.
+			} else {
+				midX := (q0X + qX) / 2
+				midY := (q0Y + qY) / 2
+				path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
+			}
+		}
+		q0X, q0Y, on0 = qX, qY, on
+	}
+	// Close the curve.
+	if on0 {
+		path.LineTo(startX+dx, startY+dy)
+	} else {
+		path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
+	}
+}
+
+func pointToF64Point(p truetype.Point) (x, y float64) {
+	return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y)
+}
+
+func fUnitsToFloat64(x fixed.Int26_6) float64 {
+	scaled := x << 2
+	return float64(scaled/256) + float64(scaled%256)/256.0
+}
+
+// FontExtents contains font metric information.
+type FontExtents struct {
+	// Ascent is the distance that the text
+	// extends above the baseline.
+	Ascent float64
+
+	// Descent is the distance that the text
+	// extends below the baseline.  The descent
+	// is given as a negative value.
+	Descent float64
+
+	// Height is the distance from the lowest
+	// descending point to the highest ascending
+	// point.
+	Height float64
+}
+
+// Extents returns the FontExtents for a font.
+// TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro
+func Extents(font *truetype.Font, size float64) FontExtents {
+	bounds := font.Bounds(fixed.Int26_6(font.FUnitsPerEm()))
+	scale := size / float64(font.FUnitsPerEm())
+	return FontExtents{
+		Ascent:  float64(bounds.Max.Y) * scale,
+		Descent: float64(bounds.Min.Y) * scale,
+		Height:  float64(bounds.Max.Y-bounds.Min.Y) * scale,
+	}
+}