Merge c6bc44d31e into dcbfbe505d

draw2dbase/stack_gc.go

@@ -165,6 +165,10 @@ func (gc *StackGraphicContext) ArcTo(cx, cy, rx, ry, startAngle, angle float64)
 	gc.Current.Path.ArcTo(cx, cy, rx, ry, startAngle, angle)
 }
 
+func (gc *StackGraphicContext) Shift(x, y float64) {
+	gc.Current.Path.Shift(x, y)
+}
+
 func (gc *StackGraphicContext) Close() {
 	gc.Current.Path.Close()
 }

path.go

@@ -22,6 +22,8 @@ type PathBuilder interface {
 	CubicCurveTo(cx1, cy1, cx2, cy2, x, y float64)
 	// ArcTo adds an arc to the current subpath
 	ArcTo(cx, cy, rx, ry, startAngle, angle float64)
+	// Shift moves every point in the path by x and y
+	Shift(x, y float64)
 	// Close creates a line from the current point to the last MoveTo
 	// point (if not the same) and mark the path as closed so the
 	// first and last lines join nicely.
@@ -163,6 +165,35 @@ func (p *Path) IsEmpty() bool {
 	return len(p.Components) == 0
 }
 
+// Shift moves every point in the path by x and y
+func (p *Path) Shift(x, y float64) {
+	j := 0
+	for _, cmd := range p.Components {
+		if cmd == CloseCmp {
+			continue
+		}
+		p.Points[j] += x
+		p.Points[j+1] += y
+		j += 2
+		switch cmd {
+		case QuadCurveToCmp:
+			p.Points[j] += x
+			p.Points[j+1] += y
+			j += 2
+		case CubicCurveToCmp:
+			p.Points[j] += x
+			p.Points[j+1] += y
+			p.Points[j+2] += x
+			p.Points[j+3] += y
+			j += 4
+		case ArcToCmp:
+			p.Points[j] += x
+			p.Points[j+1] += y
+			j += 4
+		}
+	}
+}
+
 // String returns a debug text view of the path
 func (p *Path) String() string {
 	s := ""