op/paint: return ClipOp from Path.End

Instead of adding an implicit ClipOp, return a ClipOp ready to use, freeing the
caller from recording a macro.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

op/op.go

@@ -210,17 +210,22 @@ func (o *Ops) Write(op []byte, refs ...interface{}) {
 		}
 		o.auxLen += len(op)
 	default:
-		if o.inAux {
-			o.inAux = false
-			bo := binary.LittleEndian
-			bo.PutUint32(o.data[o.auxOff+1:], uint32(o.auxLen))
-		}
+		o.endAux()
 	}
 	o.write(op, refs...)
 }
 
-func (d *Ops) pc() pc {
-	return pc{data: len(d.data), refs: len(d.refs)}
+func (o *Ops) endAux() {
+	if !o.inAux {
+		return
+	}
+	o.inAux = false
+	bo := binary.LittleEndian
+	bo.PutUint32(o.data[o.auxOff+1:], uint32(o.auxLen))
+}
+
+func (o *Ops) pc() pc {
+	return pc{data: len(o.data), refs: len(o.refs)}
 }
 
 // Record a macro of operations.
@@ -242,6 +247,7 @@ func (m *MacroOp) Stop() {
 	if !m.recording {
 		panic("not recording")
 	}
+	m.ops.endAux()
 	m.ops.macroDepth--
 	m.recording = false
 	m.fill()

op/paint/path.go

@@ -25,14 +25,17 @@ type Path struct {
 	pen       f32.Point
 	bounds    f32.Rectangle
 	hasBounds bool
+	macro     op.MacroOp
 }
 
 // ClipOp sets the current clip path.
 type ClipOp struct {
+	macro  op.MacroOp
 	bounds f32.Rectangle
 }
 
 func (p ClipOp) Add(o *op.Ops) {
+	p.macro.Add(o)
 	data := make([]byte, opconst.TypeClipLen)
 	data[0] = byte(opconst.TypeClip)
 	bo := binary.LittleEndian
@@ -46,6 +49,7 @@ func (p ClipOp) Add(o *op.Ops) {
 // Begin the path, storing the path data and final ClipOp into ops.
 func (p *Path) Begin(ops *op.Ops) {
 	p.ops = ops
+	p.macro.Record(ops)
 }
 
 // MoveTo moves the pen to the given position.
@@ -280,11 +284,12 @@ func (p *Path) simpleQuadTo(ctrl, to f32.Point) {
 	p.pen = to
 }
 
-// End the path and add the resulting ClipOp to
-// the operation list passed to Init.
-func (p *Path) End() {
+// End the path and return the resulting ClipOp.
+func (p *Path) End() ClipOp {
 	p.end()
-	ClipOp{
+	p.macro.Stop()
+	return ClipOp{
+		macro:  p.macro,
 		bounds: p.bounds,
-	}.Add(p.ops)
+	}
 }