Improve toSvgPathDesc

some toArcs paths still does not work correctly

draw2dsvg/gc.go

@@ -4,22 +4,22 @@
 package draw2dsvg
 
 import (
-	"fmt"
-	"image"
-	"image/color"
-	"strings"
 	"bytes"
+	"fmt"
 	"github.com/llgcode/draw2d"
 	"github.com/llgcode/draw2d/draw2dbase"
+	"image"
+	"image/color"
+	"math"
+	"strings"
 )
 
-const (
+const ()
-)
 
-var (
+var ()
-)
 
 type drawType int
+
 const (
 	filled drawType = 1 << iota
 	stroked
@@ -47,7 +47,7 @@ func NewGraphicContext(svg *Svg) *GraphicContext {
 func (gc *GraphicContext) Clear() {
 	gc.svg.Groups = nil
 	gc.svg.Groups = append(gc.svg.Groups, Group{
-		// TODO add background color?
+	// TODO add background color?
 	})
 }
 
@@ -56,25 +56,27 @@ func (gc *GraphicContext) Stroke(paths ...*draw2d.Path) {
 	gc.drawPaths(stroked, paths...)
 	gc.Current.Path.Clear()
 }
+
 // Fill fills the paths with the color specified by SetFillColor
 func (gc *GraphicContext) Fill(paths ...*draw2d.Path) {
 	gc.drawPaths(filled, paths...)
 	gc.Current.Path.Clear()
 }
+
 // FillStroke first fills the paths and than strokes them
 func (gc *GraphicContext) FillStroke(paths ...*draw2d.Path) {
-	gc.drawPaths(filled | stroked, paths...)
+	gc.drawPaths(filled|stroked, paths...)
 	gc.Current.Path.Clear()
 }
 
-func (gc *GraphicContext) drawPaths (drawType drawType, paths ...*draw2d.Path) {
+func (gc *GraphicContext) drawPaths(drawType drawType, paths ...*draw2d.Path) {
 	paths = append(paths, gc.Current.Path)
 
 	svgPaths := make([]Path, len(paths))
 
 	for i, path := range paths {
 		svgPaths[i].Desc = toSvgPathDesc(path)
-		if drawType & stroked == stroked {
+		if drawType&stroked == stroked {
 			svgPaths[i].Stroke = toSvgRGBA(gc.Current.StrokeColor)
 			svgPaths[i].StrokeWidth = toSvgLength(gc.Current.LineWidth)
 			svgPaths[i].StrokeLinecap = gc.Current.Cap.String()
@@ -82,7 +84,7 @@ func (gc *GraphicContext) drawPaths (drawType drawType, paths ...*draw2d.Path) {
 		} else {
 			svgPaths[i].Stroke = "none"
 		}
-		if drawType & filled == filled {
+		if drawType&filled == filled {
 			svgPaths[i].Fill = toSvgRGBA(gc.Current.FillColor)
 		} else {
 			svgPaths[i].Fill = "none"
@@ -94,57 +96,70 @@ func (gc *GraphicContext) drawPaths (drawType drawType, paths ...*draw2d.Path) {
 	})
 }
 
-func toSvgRGBA (c color.Color) string { // TODO move elsewhere
+func toSvgRGBA(c color.Color) string { // TODO move elsewhere
 	r, g, b, a := c.RGBA()
 	return fmt.Sprintf("rgba(%v, %v, %v, %.3f)", r>>8, g>>8, b>>8, float64(a>>8)/255)
 }
 
-func toSvgLength (l float64) string {
+func toSvgLength(l float64) string {
 	return fmt.Sprintf("%.4f", l)
 }
 
-func toSvgPathDesc (p *draw2d.Path) string { // TODO move elsewhere
+func toSvgPathDesc(p *draw2d.Path) string { // TODO move elsewhere
 	parts := make([]string, len(p.Components))
-	i := 0
+	ps := p.Points
-	for j, cmp := range p.Components {
+	for i, cmp := range p.Components {
 		switch cmp {
 		case draw2d.MoveToCmp:
-			parts[j] = fmt.Sprintf("M %v %v", p.Points[i], p.Points[i+1])
+			parts[i] = fmt.Sprintf("M %.4f,%.4f", ps[0], ps[1])
-			i += 2
+			ps = ps[2:]
 		case draw2d.LineToCmp:
-			parts[j] = fmt.Sprintf("L %v %v", p.Points[i], p.Points[i+1])
+			parts[i] = fmt.Sprintf("L %.4f,%.4f", ps[0], ps[1])
-			i += 2
+			ps = ps[2:]
 		case draw2d.QuadCurveToCmp:
-			parts[j] = fmt.Sprintf("Q %v %v %v %v", p.Points[i], p.Points[i+1], p.Points[i+2], p.Points[i+3])
+			parts[i] = fmt.Sprintf("Q %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3])
-			i += 4
+			ps = ps[4:]
 		case draw2d.CubicCurveToCmp:
-			parts[j] = fmt.Sprintf("C %v %v %v %v %v %v", p.Points[i], p.Points[i+1], p.Points[i+2], p.Points[i+3], p.Points[i+4], p.Points[i+5])
+			parts[i] = fmt.Sprintf("C %.4f,%.4f %.4f,%.4f %.4f,%.4f", ps[0], ps[1], ps[2], ps[3], ps[4], ps[5])
-			i += 6
+			ps = ps[6:]
 		case draw2d.ArcToCmp:
+			cx, cy := ps[0], ps[1] // center
+			rx, ry := ps[2], ps[3] // radii
+			fi := ps[4] + ps[5]    // startAngle + angle
+
+			// compute endpoint
+			sinfi, cosfi := math.Sincos(fi)
+			nom := math.Hypot(ry*cosfi, rx*sinfi)
+			x := cx + (rx*ry*cosfi)/nom
+			y := cy + (rx*ry*sinfi)/nom
+			x += 0.001 // dirty hack to ensure whole arc is drawn if start point equals endpoint
+			y += 0.001
+
+			// compute large and sweep flags
 			large := 0
 			sweep := 0
-			if p.Points[i+4] - p.Points[i+5] > 0 { // TODO this is probably not correct
+			if math.Abs(ps[5]) > math.Pi {
 				large = 1
+			}
+			if !math.Signbit(ps[5]) {
 				sweep = 1
 			}
+
 			// rx ry x-axis-rotation large-arc-flag sweep-flag x y
-			parts[j] = fmt.Sprintf("A %v %v %v %v %v %v %v",
+			parts[i] = fmt.Sprintf("A %.4f %.4f %v %v %v %.4f %.4f",
-				p.Points[i+2], // rx
+				rx, ry,
-				p.Points[i+3], // ry
+				0,
-				0, // x-axis-rotation
+				large, sweep,
-				large, // large-arc-flag
+				x, y,
-				sweep, // // sweep-flag
-				p.Points[i], // x // TODO this is center of arc not an endpont
-				p.Points[i+1], // y // TODO -//-
 			)
-			i += 6
+			ps = ps[6:]
 		case draw2d.CloseCmp:
-			parts[j] = "Z"
+			parts[i] = "Z"
 		}
 	}
-	println("parts", parts)
 	return strings.Join(parts, " ")
 }
+
 ///////////////////////////////////////
 // TODO implement following methods (or remove if not neccesary)
 
@@ -152,58 +167,72 @@ func toSvgPathDesc (p *draw2d.Path) string { // TODO move elsewhere
 func (gc *GraphicContext) SetFontData(fontData draw2d.FontData) {
 
 }
+
 // GetFontData gets the current FontData
 func (gc *GraphicContext) GetFontData() draw2d.FontData {
 	return draw2d.FontData{}
 }
+
 // GetFontName gets the current FontData as a string
 func (gc *GraphicContext) GetFontName() string {
 	return ""
 }
+
 // DrawImage draws the raster image in the current canvas
 func (gc *GraphicContext) DrawImage(image image.Image) {
 
 }
+
 // Save the context and push it to the context stack
 func (gc *GraphicContext) Save() {
 
 }
+
 // Restore remove the current context and restore the last one
 func (gc *GraphicContext) Restore() {
 
 }
+
 // ClearRect fills the specified rectangle with a default transparent color
 func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
 
 }
+
 // SetDPI sets the current DPI
 func (gc *GraphicContext) SetDPI(dpi int) {
 
 }
+
 // GetDPI gets the current DPI
 func (gc *GraphicContext) GetDPI() int {
 	return 0
 }
+
 // GetStringBounds gets pixel bounds(dimensions) of given string
 func (gc *GraphicContext) GetStringBounds(s string) (left, top, right, bottom float64) {
 	return 0, 0, 0, 0
 }
+
 // CreateStringPath creates a path from the string s at x, y
 func (gc *GraphicContext) CreateStringPath(text string, x, y float64) (cursor float64) {
 	return 0
 }
+
 // FillString draws the text at point (0, 0)
 func (gc *GraphicContext) FillString(text string) (cursor float64) {
 	return 0
 }
+
 // FillStringAt draws the text at the specified point (x, y)
 func (gc *GraphicContext) FillStringAt(text string, x, y float64) (cursor float64) {
 	return 0
 }
+
 // StrokeString draws the contour of the text at point (0, 0)
 func (gc *GraphicContext) StrokeString(text string) (cursor float64) {
 	return 0
 }
+
 // StrokeStringAt draws the contour of the text at point (x, y)
 func (gc *GraphicContext) StrokeStringAt(text string, x, y float64) (cursor float64) {
 	return 0