io/pointer: re-introduce PassOp

A previous change merged PassOp with AreaOp under the assumption that
the pass mode would be set on a particular area. That assumption turns
out not to hold, so this change brings back PassOp as an independent
stack operation.

This is an API change: replace AreaOp{Pass: true} with a separate
pointer.PassOp operation.

Fixes gio#288

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

internal/ops/ops.go

@@ -23,7 +23,7 @@ type Ops struct {
 	nextStateID int
 
 	macroStack stack
-	stacks     [3]stack
+	stacks     [4]stack
 }
 
 type OpType byte
@@ -45,6 +45,8 @@ const (
 	TypeLinearGradient
 	TypeArea
 	TypePopArea
+	TypePass
+	TypePopPass
 	TypePointerInput
 	TypeClipboardRead
 	TypeClipboardWrite
@@ -88,6 +90,7 @@ const (
 	ClipStack StackKind = iota
 	AreaStack
 	TransStack
+	PassStack
 )
 
 const (
@@ -102,8 +105,10 @@ const (
 	TypePaintLen           = 1
 	TypeColorLen           = 1 + 4
 	TypeLinearGradientLen  = 1 + 8*2 + 4*2
-	TypeAreaLen            = 1 + 1 + 1 + 4*4
+	TypeAreaLen            = 1 + 1 + 4*4
 	TypePopAreaLen         = 1
+	TypePassLen            = 1
+	TypePopPassLen         = 1
 	TypePointerInputLen    = 1 + 1 + 1 + 2*4 + 2*4
 	TypeClipboardReadLen   = 1
 	TypeClipboardWriteLen  = 1
@@ -313,6 +318,8 @@ func (t OpType) Size() int {
 		TypeLinearGradientLen,
 		TypeAreaLen,
 		TypePopAreaLen,
+		TypePassLen,
+		TypePopPassLen,
 		TypePointerInputLen,
 		TypeClipboardReadLen,
 		TypeClipboardWriteLen,
@@ -370,6 +377,10 @@ func (t OpType) String() string {
 		return "Area"
 	case TypePopArea:
 		return "PopArea"
+	case TypePass:
+		return "Pass"
+	case TypePopPass:
+		return "PopPass"
 	case TypePointerInput:
 		return "PointerInput"
 	case TypeClipboardRead:

io/pointer/pointer.go

@@ -42,14 +42,9 @@ type Event struct {
 	Modifiers key.Modifiers
 }
 
-// AreaOp updates the hit area to the intersection of the current
-// hit area and the area. The area is transformed before applying
-// it.
+// AreaOp pushes the current hit area to the stack and updates it to the
+// intersection of the current hit area and the transformed area.
 type AreaOp struct {
-	// PassThrough areas and their children don't block events to siblings
-	// them.
-	PassThrough bool
-
 	kind areaKind
 	rect image.Rectangle
 }
@@ -61,6 +56,18 @@ type AreaStack struct {
 	macroID int
 }
 
+// PassOp sets the pass-through mode. AreaOps added while the pass-through
+// mode is set don't block events to siblings.
+type PassOp struct {
+}
+
+// PassStack represents a PassOp on the pass stack.
+type PassStack struct {
+	ops     *ops.Ops
+	id      ops.StackID
+	macroID int
+}
+
 // CursorNameOp sets the cursor for the current area.
 type CursorNameOp struct {
 	Name CursorName
@@ -204,14 +211,11 @@ func (a AreaOp) add(o *op.Ops, push bool) {
 	data := o.Internal.Write(ops.TypeAreaLen)
 	data[0] = byte(ops.TypeArea)
 	data[1] = byte(a.kind)
-	if a.PassThrough {
-		data[2] = 1
-	}
 	bo := binary.LittleEndian
-	bo.PutUint32(data[3:], uint32(a.rect.Min.X))
-	bo.PutUint32(data[7:], uint32(a.rect.Min.Y))
-	bo.PutUint32(data[11:], uint32(a.rect.Max.X))
-	bo.PutUint32(data[15:], uint32(a.rect.Max.Y))
+	bo.PutUint32(data[2:], uint32(a.rect.Min.X))
+	bo.PutUint32(data[6:], uint32(a.rect.Min.Y))
+	bo.PutUint32(data[10:], uint32(a.rect.Max.X))
+	bo.PutUint32(data[14:], uint32(a.rect.Max.Y))
 }
 
 func (o AreaStack) Pop() {
@@ -220,6 +224,20 @@ func (o AreaStack) Pop() {
 	data[0] = byte(ops.TypePopArea)
 }
 
+// Push the current pass mode to the pass stack and set the pass mode.
+func (p PassOp) Push(o *op.Ops) PassStack {
+	id, mid := o.Internal.PushOp(ops.PassStack)
+	data := o.Internal.Write(ops.TypePassLen)
+	data[0] = byte(ops.TypePass)
+	return PassStack{ops: &o.Internal, id: id, macroID: mid}
+}
+
+func (p PassStack) Pop() {
+	p.ops.PopOp(ops.PassStack, p.id, p.macroID)
+	data := p.ops.Write(ops.TypePopPassLen)
+	data[0] = byte(ops.TypePopPass)
+}
+
 func (op CursorNameOp) Add(o *op.Ops) {
 	data := o.Internal.Write1(ops.TypeCursorLen, op.Name)
 	data[0] = byte(ops.TypeCursor)

io/router/pointer.go

@@ -64,7 +64,6 @@ type pointerHandler struct {
 }
 
 type areaOp struct {
-	pass bool
 	kind areaKind
 	rect f32.Rectangle
 }
@@ -82,7 +81,7 @@ type areaKind uint8
 type collectState struct {
 	t    f32.Affine2D
 	node int
-	pass bool
+	pass int
 }
 
 const (
@@ -122,7 +121,7 @@ func (q *pointerQueue) collectHandlers(r *ops.Reader, events *handlerEvents) {
 				n := q.hitTree[i]
 				area = n.area
 			}
-			q.areas = append(q.areas, areaNode{trans: state.t, next: area, area: op, pass: op.pass})
+			q.areas = append(q.areas, areaNode{trans: state.t, next: area, area: op, pass: state.pass > 0})
 			q.nodeStack = append(q.nodeStack, state.node)
 			q.hitTree = append(q.hitTree, hitNode{
 				next: state.node,
@@ -133,6 +132,10 @@ func (q *pointerQueue) collectHandlers(r *ops.Reader, events *handlerEvents) {
 			n := len(q.nodeStack)
 			state.node = q.nodeStack[n-1]
 			q.nodeStack = q.nodeStack[:n-1]
+		case ops.TypePass:
+			state.pass++
+		case ops.TypePopPass:
+			state.pass--
 		case ops.TypeTransform:
 			dop, push := ops.DecodeTransform(encOp.Data)
 			if push {
@@ -480,18 +483,17 @@ func (op *areaOp) Decode(d []byte) {
 	}
 	rect := f32.Rectangle{
 		Min: f32.Point{
-			X: opDecodeFloat32(d[3:]),
-			Y: opDecodeFloat32(d[7:]),
+			X: opDecodeFloat32(d[2:]),
+			Y: opDecodeFloat32(d[6:]),
 		},
 		Max: f32.Point{
-			X: opDecodeFloat32(d[11:]),
-			Y: opDecodeFloat32(d[15:]),
+			X: opDecodeFloat32(d[10:]),
+			Y: opDecodeFloat32(d[14:]),
 		},
 	}
 	*op = areaOp{
 		kind: areaKind(d[1]),
 		rect: rect,
-		pass: d[2] != 0,
 	}
 }
 

widget/example_test.go

@@ -29,11 +29,9 @@ func ExampleClickable_passthrough() {
 	// widget lays out two buttons on top of each other.
 	widget := func() {
 		button1.Layout(gtx)
-		area := pointer.Rect(image.Rectangle{Max: gtx.Constraints.Max})
 		// button2 completely covers button1, but pass-through allows pointer
 		// events to pass through to button1.
-		area.PassThrough = true
-		defer area.Push(gtx.Ops).Pop()
+		defer pointer.PassOp{}.Push(gtx.Ops).Pop()
 		button2.Layout(gtx)
 	}
 

widget/material/list.go

@@ -161,7 +161,7 @@ func (s ScrollbarStyle) layout(gtx layout.Context, axis layout.Axis, viewportSta
 
 			// Stack a normal clickable area on top of the draggable area
 			// to capture non-dragging clicks.
-			pointerArea.PassThrough = true
+			defer pointer.PassOp{}.Push(gtx.Ops).Pop()
 			defer pointerArea.Push(gtx.Ops).Pop()
 			s.Scrollbar.AddTrack(gtx.Ops)
 
@@ -206,7 +206,7 @@ func (s ScrollbarStyle) layout(gtx layout.Context, axis layout.Axis, viewportSta
 
 				// Add the indicator pointer hit area.
 				area := pointer.Rect(image.Rectangle{Max: indicatorDims})
-				area.PassThrough = true
+				defer pointer.PassOp{}.Push(gtx.Ops).Pop()
 				defer area.Push(gtx.Ops).Pop()
 				s.Scrollbar.AddIndicator(gtx.Ops)