app: ignore Invalidate for Windows not yet created

While here, don't overflow the Windows event queue.

Fixes: https://todo.sr.ht/~eliasnaur/gio/596
Signed-off-by: Elias Naur <mail@eliasnaur.com>

Author: eliasnaur

app/os.go

@@ -173,19 +173,13 @@ type context interface {
 	Unlock()
 }
 
-// basicDriver is the subset of [driver] that may be called even after
-// a window is destroyed.
-type basicDriver interface {
+// driver is the interface for the platform implementation
+// of a window.
+type driver interface {
 	// Event blocks until an event is available and returns it.
 	Event() event.Event
 	// Invalidate requests a FrameEvent.
 	Invalidate()
-}
-
-// driver is the interface for the platform implementation
-// of a window.
-type driver interface {
-	basicDriver
 	// SetAnimating sets the animation flag. When the window is animating,
 	// FrameEvents are delivered as fast as the display can handle them.
 	SetAnimating(anim bool)

app/os_unix.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"unsafe"
 
-	"gioui.org/io/event"
 	"gioui.org/io/pointer"
 )
 
@@ -57,35 +56,12 @@ func newWindow(window *callbacks, options []Option) {
 			errFirst = err
 		}
 	}
-	window.SetDriver(&dummyDriver{
-		win:     window,
-		wakeups: make(chan event.Event, 1),
-	})
 	if errFirst == nil {
 		errFirst = errors.New("app: no window driver available")
 	}
 	window.ProcessEvent(DestroyEvent{Err: errFirst})
 }
 
-type dummyDriver struct {
-	win     *callbacks
-	wakeups chan event.Event
-}
-
-func (d *dummyDriver) Event() event.Event {
-	if e, ok := d.win.nextEvent(); ok {
-		return e
-	}
-	return <-d.wakeups
-}
-
-func (d *dummyDriver) Invalidate() {
-	select {
-	case d.wakeups <- wakeupEvent{}:
-	default:
-	}
-}
-
 // xCursor contains mapping from pointer.Cursor to XCursor.
 var xCursor = [...]string{
 	pointer.CursorDefault:                  "left_ptr",

app/os_wayland.go

@@ -217,10 +217,6 @@ type window struct {
 	wakeups chan struct{}
 
 	closing bool
-
-	// invMu avoids the race between the destruction of disp and
-	// Invalidate waking it up.
-	invMu sync.Mutex
 }
 
 type poller struct {
@@ -1369,10 +1365,8 @@ func (w *window) close(err error) {
 	w.ProcessEvent(WaylandViewEvent{})
 	w.ProcessEvent(DestroyEvent{Err: err})
 	w.destroy()
-	w.invMu.Lock()
 	w.disp.destroy()
 	w.disp = nil
-	w.invMu.Unlock()
 }
 
 func (w *window) dispatch() {
@@ -1416,11 +1410,7 @@ func (w *window) Invalidate() {
 	default:
 		return
 	}
-	w.invMu.Lock()
-	defer w.invMu.Unlock()
-	if w.disp != nil {
-		w.disp.wakeup()
-	}
+	w.disp.wakeup()
 }
 
 func (w *window) Run(f func()) {

app/os_windows.go

@@ -54,9 +54,6 @@ type window struct {
 	borderSize image.Point
 	config     Config
 	loop       *eventLoop
-
-	// invMu avoids the race between destroying the window and Invalidate.
-	invMu sync.Mutex
 }
 
 const _WM_WAKEUP = windows.WM_USER + iota
@@ -304,10 +301,8 @@ func windowProc(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) uintptr
 			windows.ReleaseDC(w.hdc)
 			w.hdc = 0
 		}
-		w.invMu.Lock()
 		// The system destroys the HWND for us.
 		w.hwnd = 0
-		w.invMu.Unlock()
 		windows.PostQuitMessage(0)
 	case windows.WM_NCCALCSIZE:
 		if w.config.Decorated {
@@ -620,13 +615,6 @@ func (w *window) Frame(frame *op.Ops) {
 }
 
 func (w *window) wakeup() {
-	w.invMu.Lock()
-	defer w.invMu.Unlock()
-	if w.hwnd == 0 {
-		w.loop.Wakeup()
-		w.loop.FlushEvents()
-		return
-	}
 	if err := windows.PostMessage(w.hwnd, _WM_WAKEUP, 0, 0); err != nil {
 		panic(err)
 	}

app/os_x11.go

@@ -113,9 +113,6 @@ type x11Window struct {
 	wakeups chan struct{}
 	handler x11EventHandler
 	buf     [100]byte
-
-	// invMy avoids the race between destroy and Invalidate.
-	invMu sync.Mutex
 }
 
 var (
@@ -416,11 +413,6 @@ func (w *x11Window) Invalidate() {
 	case w.wakeups <- struct{}{}:
 	default:
 	}
-	w.invMu.Lock()
-	defer w.invMu.Unlock()
-	if w.x == nil {
-		return
-	}
 	if _, err := syscall.Write(w.notify.write, x11OneByte); err != nil && err != syscall.EAGAIN {
 		panic(fmt.Errorf("failed to write to pipe: %v", err))
 	}
@@ -509,8 +501,6 @@ func (w *x11Window) dispatch() {
 }
 
 func (w *x11Window) destroy() {
-	w.invMu.Lock()
-	defer w.invMu.Unlock()
 	if w.notify.write != 0 {
 		syscall.Close(w.notify.write)
 		w.notify.write = 0

app/window.go

@@ -9,6 +9,7 @@ import (
 	"image/color"
 	"reflect"
 	"runtime"
+	"sync"
 	"time"
 	"unicode/utf8"
 
@@ -89,8 +90,11 @@ type Window struct {
 	}
 	imeState editorState
 	driver   driver
-	// basic is the driver interface that is needed even after the window is gone.
-	basic basicDriver
+
+	// invMu protects mayInvalidate.
+	invMu         sync.Mutex
+	mayInvalidate bool
+
 	// coalesced tracks the most recent events waiting to be delivered
 	// to the client.
 	coalesced eventSummary
@@ -272,8 +276,11 @@ func (w *Window) updateState() {
 //
 // Invalidate is safe for concurrent use.
 func (w *Window) Invalidate() {
-	if w.basic != nil {
-		w.basic.Invalidate()
+	w.invMu.Lock()
+	defer w.invMu.Unlock()
+	if w.mayInvalidate {
+		w.mayInvalidate = false
+		w.driver.Invalidate()
 	}
 }
 
@@ -283,7 +290,7 @@ func (w *Window) Option(opts ...Option) {
 	if len(opts) == 0 {
 		return
 	}
-	if w.basic == nil {
+	if w.driver == nil {
 		w.initialOpts = append(w.initialOpts, opts...)
 		return
 	}
@@ -378,11 +385,8 @@ func (w *Window) setNextFrame(at time.Time) {
 	}
 }
 
-func (c *callbacks) SetDriver(d basicDriver) {
-	c.w.basic = d
-	if d, ok := d.(driver); ok {
-		c.w.driver = d
-	}
+func (c *callbacks) SetDriver(d driver) {
+	c.w.driver = d
 }
 
 func (c *callbacks) ProcessFrame(frame *op.Ops, ack chan<- struct{}) {
@@ -549,9 +553,19 @@ func (c *callbacks) Invalidate() {
 }
 
 func (c *callbacks) nextEvent() (event.Event, bool) {
-	s := &c.w.coalesced
-	// Every event counts as a wakeup.
-	defer func() { s.wakeup = false }()
+	return c.w.nextEvent()
+}
+
+func (w *Window) nextEvent() (event.Event, bool) {
+	s := &w.coalesced
+	mayInvalidate := true
+	defer func() {
+		// Every event counts as a wakeup.
+		s.wakeup = false
+		w.invMu.Lock()
+		defer w.invMu.Unlock()
+		w.mayInvalidate = mayInvalidate
+	}()
 	switch {
 	case s.view != nil:
 		e := *s.view
@@ -561,6 +575,7 @@ func (c *callbacks) nextEvent() (event.Event, bool) {
 		e := *s.destroy
 		// Clear pending events after DestroyEvent is delivered.
 		*s = eventSummary{}
+		mayInvalidate = false
 		return e, true
 	case s.cfg != nil:
 		e := *s.cfg
@@ -573,6 +588,7 @@ func (c *callbacks) nextEvent() (event.Event, bool) {
 	case s.wakeup:
 		return wakeupEvent{}, true
 	}
+	mayInvalidate = false
 	return nil, false
 }
 
@@ -616,8 +632,10 @@ func (w *Window) processEvent(e event.Event) bool {
 		w.coalesced.frame = &e2
 	case DestroyEvent:
 		w.destroyGPU()
+		w.invMu.Lock()
+		w.mayInvalidate = false
+		w.invMu.Unlock()
 		w.driver = nil
-		w.basic = nil
 		if q := w.timer.quit; q != nil {
 			q <- struct{}{}
 			<-q
@@ -688,10 +706,17 @@ func (w *Window) processEvent(e event.Event) bool {
 // [FrameEvent], or until [Invalidate] is called. The window is created
 // and shown the first time Event is called.
 func (w *Window) Event() event.Event {
-	if w.basic == nil {
+	if w.driver == nil {
 		w.init()
 	}
-	return w.basic.Event()
+	if w.driver == nil {
+		e, ok := w.nextEvent()
+		if !ok {
+			panic("window initializion failed without a DestroyEvent")
+		}
+		return e
+	}
+	return w.driver.Event()
 }
 
 func (w *Window) init() {
@@ -832,7 +857,7 @@ func (w *Window) Perform(actions system.Action) {
 	if acts == 0 {
 		return
 	}
-	if w.basic == nil {
+	if w.driver == nil {
 		w.initialActions = append(w.initialActions, acts)
 		return
 	}