io/pointer,io/router: replace AreaOp with clip.Op

Pointer hit areas and paint clip areas are separate concepts, but
similar enough to warrant merging. This change replaces pointer hit
areas with clip areas, so Gio is left with just one area concept (in
package op/clip).

The reason for separating the concepts in the original Gio release was
because of my being unsure general path/stroke hit areas would ever be
implemented, let alone efficient.

This change represents a change of mind, in the sense that it's better
to have an incomplete API than two separate area concepts.

Leave the deprecated pointer.Rect, pointer.Ellipse for temporary
backwards compatibility.

This is an API change. Most existing programs should continue to build
with this change, but may have to adjust to having all clip.Ops participate
in InputOp hit areas.

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

internal/ops/ops.go

@@ -29,6 +29,8 @@ type Ops struct {
 
 type OpType byte
 
+type Shape byte
+
 // Start at a high number for easier debugging.
 const firstOpIndex = 200
 
@@ -44,8 +46,6 @@ const (
 	TypePaint
 	TypeColor
 	TypeLinearGradient
-	TypeArea
-	TypePopArea
 	TypePass
 	TypePopPass
 	TypePointerInput
@@ -91,15 +91,21 @@ type StackKind uint8
 type ClipOp struct {
 	Bounds  image.Rectangle
 	Outline bool
+	Shape   Shape
 }
 
 const (
 	ClipStack StackKind = iota
-	AreaStack
 	TransStack
 	PassStack
 )
 
+const (
+	Path Shape = iota
+	Ellipse
+	Rect
+)
+
 const (
 	TypeMacroLen           = 1 + 4 + 4
 	TypeCallLen            = 1 + 4 + 4
@@ -112,8 +118,6 @@ const (
 	TypePaintLen           = 1
 	TypeColorLen           = 1 + 4
 	TypeLinearGradientLen  = 1 + 8*2 + 4*2
-	TypeAreaLen            = 1 + 1 + 4*4
-	TypePopAreaLen         = 1
 	TypePassLen            = 1
 	TypePopPassLen         = 1
 	TypePointerInputLen    = 1 + 1 + 1*2 + 2*4 + 2*4
@@ -125,7 +129,7 @@ const (
 	TypeSaveLen            = 1 + 4
 	TypeLoadLen            = 1 + 4
 	TypeAuxLen             = 1
-	TypeClipLen            = 1 + 4*4 + 1
+	TypeClipLen            = 1 + 4*4 + 1 + 1
 	TypePopClipLen         = 1
 	TypeProfileLen         = 1
 	TypeCursorLen          = 1 + 1
@@ -151,6 +155,7 @@ func (op *ClipOp) Decode(data []byte) {
 	*op = ClipOp{
 		Bounds:  r,
 		Outline: data[17] == 1,
+		Shape:   Shape(data[18]),
 	}
 }
 
@@ -332,8 +337,6 @@ func (t OpType) Size() int {
 		TypePaintLen,
 		TypeColorLen,
 		TypeLinearGradientLen,
-		TypeAreaLen,
-		TypePopAreaLen,
 		TypePassLen,
 		TypePopPassLen,
 		TypePointerInputLen,
@@ -389,10 +392,6 @@ func (t OpType) String() string {
 		return "Color"
 	case TypeLinearGradient:
 		return "LinearGradient"
-	case TypeArea:
-		return "Area"
-	case TypePopArea:
-		return "PopArea"
 	case TypePass:
 		return "Pass"
 	case TypePopPass: