uidriver/glfw: Reduce mutex to avoid potential deadlock

internal/uidriver/glfw/input.go

@@ -47,7 +47,6 @@ type Input struct {
 	touches            map[int]pos // This is not updated until GLFW 3.3 is available (#417)
 	runeBuffer         []rune
 	ui                 *UserInterface
-	m                  sync.RWMutex
 }
 
 type pos struct {
@@ -56,14 +55,15 @@ type pos struct {
 }
 
 func (i *Input) CursorPosition() (x, y int) {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	cx, cy := i.cursorX, i.cursorY
-	return i.ui.adjustPosition(i.cursorX, i.cursorY)
+	i.ui.m.RUnlock()
+	return i.ui.adjustPosition(cx, cy)
 }
 
 func (i *Input) GamepadIDs() []int {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if len(i.gamepads) == 0 {
 		return nil
 	}
@@ -77,8 +77,8 @@ func (i *Input) GamepadIDs() []int {
 }
 
 func (i *Input) GamepadAxisNum(id int) int {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if len(i.gamepads) <= id {
 		return 0
 	}
@@ -86,8 +86,8 @@ func (i *Input) GamepadAxisNum(id int) int {
 }
 
 func (i *Input) GamepadAxis(id int, axis int) float64 {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if len(i.gamepads) <= id {
 		return 0
 	}
@@ -95,8 +95,8 @@ func (i *Input) GamepadAxis(id int, axis int) float64 {
 }
 
 func (i *Input) GamepadButtonNum(id int) int {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if len(i.gamepads) <= id {
 		return 0
 	}
@@ -104,8 +104,8 @@ func (i *Input) GamepadButtonNum(id int) int {
 }
 
 func (i *Input) IsGamepadButtonPressed(id int, button driver.GamepadButton) bool {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if len(i.gamepads) <= id {
 		return false
 	}
@@ -113,8 +113,8 @@ func (i *Input) IsGamepadButtonPressed(id int, button driver.GamepadButton) bool
 }
 
 func (i *Input) TouchIDs() []int {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 
 	if len(i.touches) == 0 {
 		return nil
@@ -128,33 +128,40 @@ func (i *Input) TouchIDs() []int {
 }
 
 func (i *Input) TouchPosition(id int) (x, y int) {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	found := false
-
+	var p pos
 	for tid, pos := range i.touches {
 		if id == tid {
-			return i.ui.adjustPosition(pos.X, pos.Y)
+			p = pos
+			found = true
+			break
 		}
 	}
+	i.ui.m.RUnlock()
+
+	if !found {
 		return 0, 0
+	}
+	return i.ui.adjustPosition(p.X, p.Y)
 }
 
 func (i *Input) RuneBuffer() []rune {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	return i.runeBuffer
 }
 
 func (i *Input) ResetForFrame() {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	i.runeBuffer = i.runeBuffer[:0]
 	i.scrollX, i.scrollY = 0, 0
 }
 
 func (i *Input) IsKeyPressed(key driver.Key) bool {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if i.keyPressed == nil {
 		i.keyPressed = map[glfw.Key]bool{}
 	}
@@ -170,8 +177,8 @@ func (i *Input) IsKeyPressed(key driver.Key) bool {
 }
 
 func (i *Input) IsMouseButtonPressed(button driver.MouseButton) bool {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	if i.mouseButtonPressed == nil {
 		i.mouseButtonPressed = map[glfw.MouseButton]bool{}
 	}
@@ -187,8 +194,8 @@ func (i *Input) IsMouseButtonPressed(button driver.MouseButton) bool {
 }
 
 func (i *Input) Wheel() (xoff, yoff float64) {
-	i.m.RLock()
+	i.ui.m.RLock()
-	defer i.m.RUnlock()
+	defer i.ui.m.RUnlock()
 	return i.scrollX, i.scrollY
 }
 
@@ -202,21 +209,21 @@ func (i *Input) appendRuneBuffer(char rune) {
 	if !unicode.IsPrint(char) {
 		return
 	}
-	i.m.Lock()
+	i.ui.m.Lock()
 	i.runeBuffer = append(i.runeBuffer, char)
-	i.m.Unlock()
+	i.ui.m.Unlock()
 }
 
 func (i *Input) setWheel(xoff, yoff float64) {
-	i.m.Lock()
+	i.ui.m.Lock()
 	i.scrollX = xoff
 	i.scrollY = yoff
-	i.m.Unlock()
+	i.ui.m.Unlock()
 }
 
 func (i *Input) update(window *glfw.Window, scale float64) {
-	i.m.Lock()
+	i.ui.m.Lock()
-	defer i.m.Unlock()
+	defer i.ui.m.Unlock()
 
 	i.onceCallback.Do(func() {
 		window.SetCharModsCallback(func(w *glfw.Window, char rune, mods glfw.ModifierKey) {

internal/uidriver/glfw/ui.go

@@ -68,7 +68,7 @@ type UserInterface struct {
 	input    Input
 
 	t *thread.Thread
-	m sync.Mutex
+	m sync.RWMutex
 }
 
 const (
@@ -178,9 +178,9 @@ func getCachedMonitor(wx, wy int) (*cachedMonitor, bool) {
 }
 
 func (u *UserInterface) isRunning() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.running
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -191,9 +191,9 @@ func (u *UserInterface) setRunning(running bool) {
 }
 
 func (u *UserInterface) isInitFullscreen() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.initFullscreen
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -204,9 +204,9 @@ func (u *UserInterface) setInitFullscreen(initFullscreen bool) {
 }
 
 func (u *UserInterface) isInitCursorVisible() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.initCursorVisible
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -217,9 +217,9 @@ func (u *UserInterface) setInitCursorVisible(visible bool) {
 }
 
 func (u *UserInterface) isInitWindowDecorated() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.initWindowDecorated
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -230,9 +230,9 @@ func (u *UserInterface) setInitWindowDecorated(decorated bool) {
 }
 
 func (u *UserInterface) isRunnableInBackground() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.runnableInBackground
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -243,9 +243,9 @@ func (u *UserInterface) setRunnableInBackground(runnableInBackground bool) {
 }
 
 func (u *UserInterface) isInitWindowResizable() bool {
-	u.m.Lock()
+	u.m.RLock()
 	v := u.initWindowResizable
-	u.m.Unlock()
+	u.m.RUnlock()
 	return v
 }
 
@@ -256,9 +256,9 @@ func (u *UserInterface) setInitWindowResizable(resizable bool) {
 }
 
 func (u *UserInterface) getInitIconImages() []image.Image {
-	u.m.Lock()
+	u.m.RLock()
 	i := u.initIconImages
-	u.m.Unlock()
+	u.m.RUnlock()
 	return i
 }
 
@@ -362,9 +362,9 @@ func (u *UserInterface) SetVsyncEnabled(enabled bool) {
 		// m is not used for updating vsync in setScreenSize so far, but
 		// it should be OK since any goroutines can't reach here when
 		// the game already starts and setScreenSize can be called.
-		u.m.Lock()
+		u.m.RLock()
 		u.vsync = enabled
-		u.m.Unlock()
+		u.m.RUnlock()
 		return
 	}
 	_ = u.t.Call(func() error {
@@ -374,9 +374,9 @@ func (u *UserInterface) SetVsyncEnabled(enabled bool) {
 }
 
 func (u *UserInterface) IsVsyncEnabled() bool {
-	u.m.Lock()
+	u.m.RLock()
 	r := u.vsync
-	u.m.Unlock()
+	u.m.RUnlock()
 	return r
 }
 
@@ -822,9 +822,9 @@ func (u *UserInterface) loop(context driver.UIContext) error {
 			return err
 		}
 
-		u.m.Lock()
+		u.m.RLock()
 		vsync := u.vsync
-		u.m.Unlock()
+		u.m.RUnlock()
 
 		_ = u.t.Call(func() error {
 			if !vsync {