all: use a single tag per widget for event handling

With the introduction of filters, it is now possible to have one tag per
widget by convention. Note that gestures still have their own tags, for
disambiguation.

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

widget/button.go

@@ -21,7 +21,6 @@ type Clickable struct {
 	click   gesture.Click
 	history []Press
 
-	keyTag        struct{}
 	requestClicks int
 	focused       bool
 	pressedKey    key.Name
@@ -69,7 +68,7 @@ func (b *Clickable) Pressed() bool {
 
 // Focus requests the input focus for the element.
 func (b *Clickable) Focus(gtx layout.Context) {
-	gtx.Execute(key.FocusCmd{Tag: &b.keyTag})
+	gtx.Execute(key.FocusCmd{Tag: b})
 }
 
 // Focused reports whether b has focus.
@@ -97,7 +96,7 @@ func (b *Clickable) Layout(gtx layout.Context, w layout.Widget) layout.Dimension
 	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()
 	semantic.EnabledOp(gtx.Enabled()).Add(gtx.Ops)
 	b.click.Add(gtx.Ops)
-	event.InputOp(gtx.Ops, &b.keyTag)
+	event.InputOp(gtx.Ops, b)
 	c.Add(gtx.Ops)
 	return dims
 }
@@ -141,7 +140,7 @@ func (b *Clickable) Update(gtx layout.Context) (Click, bool) {
 			}
 		case gesture.KindPress:
 			if e.Source == pointer.Mouse {
-				gtx.Execute(key.FocusCmd{Tag: &b.keyTag})
+				gtx.Execute(key.FocusCmd{Tag: b})
 			}
 			b.history = append(b.history, Press{
 				Position: e.Position,
@@ -156,7 +155,7 @@ func (b *Clickable) Update(gtx layout.Context) (Click, bool) {
 		filters = append(filters, key.Filter{Name: key.NameReturn}, key.Filter{Name: key.NameSpace})
 	}
 	for {
-		e, ok := gtx.Event(&b.keyTag, filters...)
+		e, ok := gtx.Event(b, filters...)
 		if !ok {
 			break
 		}

widget/dnd.go

@@ -18,10 +18,9 @@ type Draggable struct {
 	// Type contains the MIME type and matches transfer.SourceOp.
 	Type string
 
-	handle struct{}
-	drag   gesture.Drag
-	click  f32.Point
-	pos    f32.Point
+	drag  gesture.Drag
+	click f32.Point
+	pos   f32.Point
 }
 
 func (d *Draggable) Layout(gtx layout.Context, w, drag layout.Widget) layout.Dimensions {
@@ -32,7 +31,7 @@ func (d *Draggable) Layout(gtx layout.Context, w, drag layout.Widget) layout.Dim
 
 	stack := clip.Rect{Max: dims.Size}.Push(gtx.Ops)
 	d.drag.Add(gtx.Ops)
-	event.InputOp(gtx.Ops, &d.handle)
+	event.InputOp(gtx.Ops, d)
 	stack.Pop()
 
 	if drag != nil && d.drag.Pressed() {
@@ -66,7 +65,7 @@ func (d *Draggable) Update(gtx layout.Context) (mime string, requested bool) {
 	d.pos = pos
 
 	for {
-		e, ok := gtx.Event(&d.handle, transfer.SourceFilter{Type: d.Type})
+		e, ok := gtx.Event(d, transfer.SourceFilter{Type: d.Type})
 		if !ok {
 			break
 		}
@@ -80,7 +79,7 @@ func (d *Draggable) Update(gtx layout.Context) (mime string, requested bool) {
 // Offer the data ready for a drop. Must be called after being Requested.
 // The mime must be one in the requested list.
 func (d *Draggable) Offer(gtx layout.Context, mime string, data io.ReadCloser) {
-	gtx.Execute(transfer.OfferCmd{Tag: &d.handle, Type: mime, Data: data})
+	gtx.Execute(transfer.OfferCmd{Tag: d, Type: mime, Data: data})
 }
 
 // Pos returns the drag position relative to its initial click position.

widget/dnd_test.go

@@ -25,16 +25,17 @@ func TestDraggable(t *testing.T) {
 	drag := &Draggable{
 		Type: "file",
 	}
+	tgt := new(int)
 	defer pointer.PassOp{}.Push(gtx.Ops).Pop()
 	dims := drag.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 		return layout.Dimensions{Size: gtx.Constraints.Min}
 	}, nil)
 	stack := clip.Rect{Max: dims.Size}.Push(gtx.Ops)
-	event.InputOp(gtx.Ops, drag)
+	event.InputOp(gtx.Ops, tgt)
 	stack.Pop()
 
 	drag.Update(gtx)
-	r.Event(drag, transfer.TargetFilter{Type: drag.Type})
+	r.Event(tgt, transfer.TargetFilter{Type: drag.Type})
 	r.Frame(gtx.Ops)
 	r.Queue(
 		pointer.Event{
@@ -52,10 +53,10 @@ func TestDraggable(t *testing.T) {
 	)
 	ofr := &offer{data: "hello"}
 	drag.Update(gtx)
-	r.Event(drag, transfer.TargetFilter{Type: drag.Type})
+	r.Event(tgt, transfer.TargetFilter{Type: drag.Type})
 	drag.Offer(gtx, "file", ofr)
 
-	e, ok := r.Event(drag, transfer.TargetFilter{Type: drag.Type})
+	e, ok := r.Event(tgt, transfer.TargetFilter{Type: drag.Type})
 	if !ok {
 		t.Fatalf("expected event")
 	}
@@ -66,7 +67,7 @@ func TestDraggable(t *testing.T) {
 	if ofr.closed {
 		t.Error("offer closed prematurely")
 	}
-	e, ok = r.Event(drag, transfer.TargetFilter{Type: drag.Type})
+	e, ok = r.Event(tgt, transfer.TargetFilter{Type: drag.Type})
 	if !ok {
 		t.Fatalf("expected event")
 	}

widget/editor.go

@@ -71,7 +71,6 @@ type Editor struct {
 	// scratch is a byte buffer that is reused to efficiently read portions of text
 	// from the textView.
 	scratch    []byte
-	eventKey   int
 	blinkStart time.Time
 	focused    bool
 
@@ -381,7 +380,7 @@ func (e *Editor) processKey(gtx layout.Context) {
 	// adjust keeps track of runes dropped because of MaxLen.
 	var adjust int
 	for {
-		ke, ok := gtx.Event(&e.eventKey, filters...)
+		ke, ok := gtx.Event(e, filters...)
 		if !ok {
 			break
 		}
@@ -479,7 +478,7 @@ func (e *Editor) command(gtx layout.Context, k key.Event) {
 		// half is in Editor.processKey() under clipboard.Event.
 		case "V":
 			if !e.ReadOnly {
-				gtx.Execute(clipboard.ReadCmd{Tag: &e.eventKey})
+				gtx.Execute(clipboard.ReadCmd{Tag: e})
 			}
 		// Copy or Cut selection -- ignored if nothing selected.
 		case "C", "X":
@@ -560,7 +559,7 @@ func (e *Editor) command(gtx layout.Context, k key.Event) {
 
 // Focus requests the input focus for the Editor.
 func (e *Editor) Focus(gtx layout.Context) {
-	gtx.Execute(key.FocusCmd{Tag: &e.eventKey})
+	gtx.Execute(key.FocusCmd{Tag: e})
 	gtx.Execute(key.SoftKeyboardCmd{Show: true})
 }
 
@@ -605,7 +604,7 @@ func (e *Editor) Update(gtx layout.Context) {
 		}
 		if newSel != e.ime.selection {
 			e.ime.selection = newSel
-			gtx.Execute(key.SelectionCmd{Tag: &e.eventKey, Range: newSel.rng, Caret: newSel.caret})
+			gtx.Execute(key.SelectionCmd{Tag: e, Range: newSel.rng, Caret: newSel.caret})
 		}
 
 		e.updateSnippet(gtx, e.ime.start, e.ime.end)
@@ -662,7 +661,7 @@ func (e *Editor) updateSnippet(gtx layout.Context, start, end int) {
 		return
 	}
 	e.ime.snippet = newSnip
-	gtx.Execute(key.SnippetCmd{Tag: &e.eventKey, Snippet: newSnip})
+	gtx.Execute(key.SnippetCmd{Tag: e, Snippet: newSnip})
 }
 
 func (e *Editor) layout(gtx layout.Context, textMaterial, selectMaterial op.CallOp) layout.Dimensions {
@@ -677,8 +676,8 @@ func (e *Editor) layout(gtx layout.Context, textMaterial, selectMaterial op.Call
 
 	defer clip.Rect(image.Rectangle{Max: visibleDims.Size}).Push(gtx.Ops).Pop()
 	pointer.CursorText.Add(gtx.Ops)
-	event.InputOp(gtx.Ops, &e.eventKey)
-	key.InputHintOp{Tag: &e.eventKey, Hint: e.InputHint}.Add(gtx.Ops)
+	event.InputOp(gtx.Ops, e)
+	key.InputHintOp{Tag: e, Hint: e.InputHint}.Add(gtx.Ops)
 
 	e.scroller.Add(gtx.Ops)