io/system: add ActionInputOp to register window move gesture areas

The app.Window.Perform(ActionMove) is the wrong abstraction for
initiating a move gesture: Windows needs to know the move gesture
area at pointer move, and macOS needs to know the pointer button
down event that triggers the move gesture. This change replaces
Perform(ActionMove) with a new system.ActionInputOp that marks an
area movable.

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

app/internal/windows/windows.go

@@ -113,6 +113,7 @@ const (
 
 	HWND_TOPMOST = ^(uint32(1) - 1) // -1
 
+	HTCAPTION     = 2
 	HTCLIENT      = 1
 	HTLEFT        = 10
 	HTRIGHT       = 11

app/os_macos.go

@@ -232,9 +232,8 @@ type window struct {
 	displayLink *displayLink
 	// redraw is a single entry channel for making sure only one
 	// display link redraw request is in flight.
-	redraw    chan struct{}
+	redraw chan struct{}
-	cursor    pointer.Cursor
+	cursor pointer.Cursor
-	lastPress C.CFTypeRef
 
 	scale  float32
 	config Config
@@ -413,12 +412,6 @@ func (w *window) Perform(acts system.Action) {
 			C.setScreenFrame(w.window, C.CGFloat(x), C.CGFloat(y), C.CGFloat(sz.X), C.CGFloat(sz.Y))
 		case system.ActionRaise:
 			C.raiseWindow(w.window)
-		case system.ActionMove:
-			if w.lastPress != 0 {
-				C.performWindowDragWithEvent(w.window, w.lastPress)
-				C.CFRelease(w.lastPress)
-				w.lastPress = 0
-			}
 		}
 	})
 	if acts&system.ActionClose != 0 {
@@ -500,6 +493,10 @@ func gio_onText(view, cstr C.CFTypeRef) {
 //export gio_onMouse
 func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtns C.NSUInteger, x, y, dx, dy C.CGFloat, ti C.double, mods C.NSUInteger) {
 	w := mustView(view)
+	t := time.Duration(float64(ti)*float64(time.Second) + .5)
+	xf, yf := float32(x)*w.scale, float32(y)*w.scale
+	dxf, dyf := float32(dx)*w.scale, float32(dy)*w.scale
+	pos := f32.Point{X: xf, Y: yf}
 	var typ pointer.Type
 	switch cdir {
 	case C.MOUSE_MOVE:
@@ -508,11 +505,14 @@ func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtns C.NSUInteger, x, y, dx
 		typ = pointer.Release
 	case C.MOUSE_DOWN:
 		typ = pointer.Press
-		if w.lastPress != 0 {
+		act, ok := w.w.ActionAt(pos)
-			C.CFRelease(w.lastPress)
+		if ok && w.config.Mode != Fullscreen {
-			w.lastPress = 0
+			switch act {
+			case system.ActionMove:
+				C.performWindowDragWithEvent(w.window, evt)
+				return
+			}
 		}
-		w.lastPress = C.CFRetain(evt)
 	case C.MOUSE_SCROLL:
 		typ = pointer.Scroll
 	default:
@@ -528,15 +528,12 @@ func gio_onMouse(view, evt C.CFTypeRef, cdir C.int, cbtns C.NSUInteger, x, y, dx
 	if cbtns&(1<<2) != 0 {
 		btns |= pointer.ButtonTertiary
 	}
-	t := time.Duration(float64(ti)*float64(time.Second) + .5)
-	xf, yf := float32(x)*w.scale, float32(y)*w.scale
-	dxf, dyf := float32(dx)*w.scale, float32(dy)*w.scale
 	w.w.Event(pointer.Event{
 		Type:      typ,
 		Source:    pointer.Mouse,
 		Time:      t,
 		Buttons:   btns,
-		Position:  f32.Point{X: xf, Y: yf},
+		Position:  pos,
 		Scroll:    f32.Point{X: dxf, Y: dyf},
 		Modifiers: convertMods(mods),
 	})
@@ -768,10 +765,6 @@ func gio_onClose(view C.CFTypeRef) {
 	w.w.Event(ViewEvent{})
 	deleteView(view)
 	w.w.Event(system.DestroyEvent{})
-	if w.lastPress != 0 {
-		C.CFRelease(w.lastPress)
-		w.lastPress = 0
-	}
 	w.displayLink.Close()
 	C.CFRelease(w.view)
 	C.CFRelease(w.window)

app/os_wayland.go

@@ -879,6 +879,14 @@ func gio_onPointerButton(data unsafe.Pointer, p *C.struct_wl_pointer, serial, t,
 			w.resize(serial, edge)
 			return
 		}
+		act, ok := w.w.ActionAt(w.lastPos)
+		if ok && w.config.Mode == Windowed {
+			switch act {
+			case system.ActionMove:
+				w.move(serial)
+				return
+			}
+		}
 	case BTN_RIGHT:
 		btn = pointer.ButtonSecondary
 	case BTN_MIDDLE:
@@ -1073,19 +1081,17 @@ func (w *window) Perform(actions system.Action) {
 	// https://wayland.app/protocols/xdg-shell#xdg_toplevel:request:set_minimized
 	walkActions(actions, func(action system.Action) {
 		switch action {
-		case system.ActionMove:
-			w.move()
 		case system.ActionClose:
 			w.dead = true
 		}
 	})
 }
 
-func (w *window) move() {
+func (w *window) move(serial C.uint32_t) {
-	if !w.inCompositor && w.seat != nil {
+	s := w.seat
+	if !w.inCompositor && s != nil {
 		w.inCompositor = true
-		s := w.seat
+		C.xdg_toplevel_move(w.topLvl, s.seat, serial)
-		C.xdg_toplevel_move(w.topLvl, s.seat, s.serial)
 	}
 }
 

app/os_windows.go

@@ -437,6 +437,11 @@ func (w *window) hitTest(x, y int) uintptr {
 	default:
 		fallthrough
 	case !top && !bottom && !left && !right:
+		p := f32.Pt(float32(x), float32(y))
+		switch a, _ := w.w.ActionAt(p); a {
+		case system.ActionMove:
+			return windows.HTCAPTION
+		}
 		return windows.HTCLIENT
 	case top && left:
 		return windows.HTTOPLEFT

app/window.go

@@ -567,6 +567,10 @@ func (c *callbacks) ClickFocus() {
 	c.w.updateAnimation(c.d)
 }
 
+func (c *callbacks) ActionAt(p f32.Point) (system.Action, bool) {
+	return c.w.queue.q.ActionAt(p)
+}
+
 func (e *editorState) Replace(r key.Range, text string) {
 	if r.Start > r.End {
 		r.Start, r.End = r.End, r.Start

internal/ops/ops.go

@@ -75,6 +75,7 @@ const (
 	TypeSemanticDisabled
 	TypeSnippet
 	TypeSelection
+	TypeActionInput
 )
 
 type StackID struct {
@@ -158,6 +159,7 @@ const (
 	TypeSemanticDisabledLen = 2
 	TypeSnippetLen          = 1 + 4 + 4
 	TypeSelectionLen        = 1 + 2*4 + 2*4 + 4 + 4
+	TypeActionInputLen      = 1 + 1
 )
 
 func (op *ClipOp) Decode(data []byte) {
@@ -418,6 +420,7 @@ func (t OpType) Size() int {
 		TypeSemanticDisabledLen,
 		TypeSnippetLen,
 		TypeSelectionLen,
+		TypeActionInputLen,
 	}[t-firstOpIndex]
 }
 

io/router/pointer.go

@@ -13,6 +13,7 @@ import (
 	"gioui.org/io/key"
 	"gioui.org/io/pointer"
 	"gioui.org/io/semantic"
+	"gioui.org/io/system"
 	"gioui.org/io/transfer"
 )
 
@@ -97,6 +98,7 @@ type areaNode struct {
 		id      SemanticID
 		content semanticContent
 	}
+	action system.Action
 }
 
 type areaKind uint8
@@ -256,6 +258,12 @@ func (c *pointerCollector) keyInputOp(op key.InputOp) {
 	})
 }
 
+func (c *pointerCollector) actionInputOp(act system.Action) {
+	areaID := c.currentArea()
+	area := &c.q.areas[areaID]
+	area.action = act
+}
+
 func (c *pointerCollector) inputOp(op pointer.InputOp, events *handlerEvents) {
 	areaID := c.currentArea()
 	area := &c.q.areas[areaID]
@@ -424,6 +432,19 @@ func (q *pointerQueue) semanticIDFor(content semanticContent) SemanticID {
 	return id.id
 }
 
+func (q *pointerQueue) ActionAt(pos f32.Point) (system.Action, bool) {
+	for i := len(q.hitTree) - 1; i >= 0; i-- {
+		n := &q.hitTree[i]
+		hit, _ := q.hit(n.area, pos)
+		if !hit {
+			continue
+		}
+		area := q.areas[n.area]
+		return area.action, area.action != 0
+	}
+	return 0, false
+}
+
 func (q *pointerQueue) SemanticAt(pos f32.Point) (SemanticID, bool) {
 	q.assignSemIDs()
 	for i := len(q.hitTree) - 1; i >= 0; i-- {

io/router/router.go

@@ -27,6 +27,7 @@ import (
 	"gioui.org/io/pointer"
 	"gioui.org/io/profile"
 	"gioui.org/io/semantic"
+	"gioui.org/io/system"
 	"gioui.org/io/transfer"
 	"gioui.org/op"
 )
@@ -276,6 +277,10 @@ func min(p1, p2 image.Point) image.Point {
 	return m
 }
 
+func (q *Router) ActionAt(p f32.Point) (system.Action, bool) {
+	return q.pointer.queue.ActionAt(p)
+}
+
 func (q *Router) ClickFocus() {
 	focus := q.key.queue.focus
 	if focus == nil {
@@ -444,6 +449,9 @@ func (q *Router) collect() {
 				Data: encOp.Refs[2].(io.ReadCloser),
 			}
 			pc.offerOp(op, &q.handlers)
+		case ops.TypeActionInput:
+			act := system.Action(encOp.Data[1])
+			pc.actionInputOp(act)
 
 		// Key ops.
 		case ops.TypeKeyFocus:

io/system/decoration.go

@@ -2,8 +2,17 @@ package system
 
 import (
 	"strings"
+
+	"gioui.org/internal/ops"
+	"gioui.org/op"
 )
 
+// ActionAreaOp makes the current clip area available for
+// system gestures.
+//
+// Note: only ActionMove is supported.
+type ActionInputOp Action
+
 // Action is a set of window decoration actions.
 type Action uint
 
@@ -31,6 +40,12 @@ const (
 	ActionMove
 )
 
+func (op ActionInputOp) Add(o *op.Ops) {
+	data := ops.Write(&o.Internal, ops.TypeActionInputLen)
+	data[0] = byte(ops.TypeActionInput)
+	data[1] = byte(op)
+}
+
 func (a Action) String() string {
 	var buf strings.Builder
 	for b := Action(1); a != 0; b <<= 1 {

widget/decorations.go

@@ -12,7 +12,6 @@ import (
 
 // Decorations handles the states of window decorations.
 type Decorations struct {
-	move   gesture.Drag
 	clicks []Clickable
 	resize [8]struct {
 		gesture.Hover
@@ -25,13 +24,8 @@ type Decorations struct {
 // LayoutMove lays out the widget that makes a window movable.
 func (d *Decorations) LayoutMove(gtx layout.Context, w layout.Widget) layout.Dimensions {
 	dims := w(gtx)
-	d.move.Events(gtx.Metric, gtx, gesture.Both)
+	defer clip.Rect{Max: dims.Size}.Push(gtx.Ops).Pop()
-	st := clip.Rect{Max: dims.Size}.Push(gtx.Ops)
+	system.ActionInputOp(system.ActionMove).Add(gtx.Ops)
-	d.move.Add(gtx.Ops)
-	if d.move.Pressed() {
-		d.actions |= system.ActionMove
-	}
-	st.Pop()
 	return dims
 }