app: add Window.Maximize and Center, add Windows implementation

Signed-off-by: Jan Kare Vatne <jkvatne@online.no>

app/internal/windows/windows.go

@@ -200,6 +200,7 @@ const (
 
 	WS_CLIPCHILDREN     = 0x00010000
 	WS_CLIPSIBLINGS     = 0x04000000
+	WS_MAXIMIZE         = 0x01000000
 	WS_VISIBLE          = 0x10000000
 	WS_OVERLAPPED       = 0x00000000
 	WS_OVERLAPPEDWINDOW = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME |

app/os.go

@@ -149,6 +149,11 @@ type driver interface {
 	Close()
 	// Wakeup wakes up the event loop and sends a WakeupEvent.
 	Wakeup()
+
+	// Maximize will make the window as large as possible, but keep the frame decorations.
+	Maximize()
+	// Center will place the window at monitor center.
+	Center()
 }
 
 type windowRendezvous struct {

app/os_android.go

@@ -922,6 +922,12 @@ func setNavigationColor(env *C.JNIEnv, view C.jobject, color color.NRGBA) {
 // Close the window. Not implemented for Android.
 func (w *window) Close() {}
 
+// Maximize maximizes the window. Not implemented for Android.
+func (w *window) Maximize() {}
+
+// Center the window. Not implemented for Android.
+func (w *window) Center() {}
+
 // runOnMain runs a function on the Java main thread.
 func runOnMain(f func(env *C.JNIEnv)) {
 	go func() {

app/os_ios.go

@@ -331,6 +331,12 @@ func (w *window) SetInputHint(_ key.InputHint) {}
 // Close the window. Not implemented for iOS.
 func (w *window) Close() {}
 
+// Maximize the window. Not implemented for iOS.
+func (w *window) Maximize() {}
+
+// Center the window. Not implemented for iOS.
+func (w *window) Center() {}
+
 func newWindow(win *callbacks, options []Option) error {
 	mainWindow.in <- windowAndConfig{win, options}
 	return <-mainWindow.errs

app/os_js.go

@@ -566,6 +566,12 @@ func (w *window) SetInputHint(mode key.InputHint) {
 // Close the window. Not implemented for js.
 func (w *window) Close() {}
 
+// Maximize the window. Not implemented for js.
+func (w *window) Maximize() {}
+
+// Center the window. Not implemented for js.
+func (w *window) Center() {}
+
 func (w *window) resize() {
 	w.scale = float32(w.window.Get("devicePixelRatio").Float())
 

app/os_macos.go

@@ -291,6 +291,12 @@ func (w *window) Close() {
 	C.closeWindow(w.window)
 }
 
+// Maximize the window. Not implemented for macos.
+func (w *window) Maximize() {}
+
+// Center the window. Not implemented for macos.
+func (w *window) Center() {}
+
 func (w *window) setStage(stage system.Stage) {
 	if stage == w.stage {
 		return

app/os_wayland.go

@@ -1481,6 +1481,12 @@ func (w *window) SetInputHint(_ key.InputHint) {}
 // Close the window. Not implemented for Wayland.
 func (w *window) Close() {}
 
+// Maximize the window. Not implemented for Wayland.
+func (w *window) Maximize() {}
+
+// Center the window. Not implemented for Wayland.
+func (w *window) Center() {}
+
 func (w *window) NewContext() (context, error) {
 	var firstErr error
 	if f := newWaylandVulkanContext; f != nil {

app/os_windows.go

@@ -539,6 +539,46 @@ func (w *window) Configure(options []Option) {
 	}
 }
 
+// Maximize the window. It will have no effect when in fullscreen mode.
+func (w *window) Maximize() {
+	if w.config.Mode == Fullscreen {
+		return
+	}
+	style := windows.GetWindowLong(w.hwnd)
+	windows.SetWindowLong(w.hwnd, windows.GWL_STYLE, style|windows.WS_OVERLAPPEDWINDOW|windows.WS_MAXIMIZE)
+	mi := windows.GetMonitorInfo(w.hwnd)
+	windows.SetWindowPos(w.hwnd, 0,
+		mi.Monitor.Left, mi.Monitor.Top,
+		mi.Monitor.Right-mi.Monitor.Left,
+		mi.Monitor.Bottom-mi.Monitor.Top,
+		windows.SWP_NOOWNERZORDER|windows.SWP_FRAMECHANGED,
+	)
+}
+
+// Center will place window at monitor center.
+func (w *window) Center() {
+	// Make sure that the window is sizeable
+	style := windows.GetWindowLong(w.hwnd) & (^uintptr(windows.WS_MAXIMIZE))
+	windows.SetWindowLong(w.hwnd, windows.GWL_STYLE, style|windows.WS_OVERLAPPEDWINDOW)
+
+	// Find with/height including the window decorations.
+	wr := windows.Rect{
+		Right:  int32(w.config.Size.X),
+		Bottom: int32(w.config.Size.Y),
+	}
+	dwStyle := uint32(windows.WS_OVERLAPPEDWINDOW)
+	dwExStyle := uint32(windows.WS_EX_APPWINDOW | windows.WS_EX_WINDOWEDGE)
+	windows.AdjustWindowRectEx(&wr, dwStyle, 0, dwExStyle)
+	width := wr.Right - wr.Left
+	height := wr.Bottom - wr.Top
+
+	// Move to center of current monitor
+	mi := windows.GetMonitorInfo(w.hwnd).Monitor
+	x := mi.Left + (mi.Right-mi.Left-width)/2
+	y := mi.Top + (mi.Bottom-mi.Top-height)/2
+	windows.MoveWindow(w.hwnd, x, y, width, height, true)
+}
+
 func (w *window) SetWindowMode(mode WindowMode) {
 	// https://devblogs.microsoft.com/oldnewthing/20100412-00/?p=14353
 	switch mode {

app/os_x11.go

@@ -295,6 +295,12 @@ func (w *x11Window) Close() {
 	C.XSendEvent(w.x, w.xw, C.False, C.NoEventMask, &xev)
 }
 
+// Maximize the window. Not implemented for x11.
+func (w *x11Window) Maximize() {}
+
+// Center the window. Not implemented for x11.
+func (w *x11Window) Center() {}
+
 var x11OneByte = make([]byte, 1)
 
 func (w *x11Window) Wakeup() {

app/window.go

@@ -311,6 +311,22 @@ func (w *Window) Close() {
 	})
 }
 
+// Maximize the window.
+// Note: only implemented on Windows.
+func (w *Window) Maximize() {
+	w.driverDefer(func(d driver) {
+		d.Maximize()
+	})
+}
+
+// Center the window.
+// Note: only implemented on Windows.
+func (w *Window) Center() {
+	w.driverDefer(func(d driver) {
+		d.Center()
+	})
+}
+
 // Run f in the same thread as the native window event loop, and wait for f to
 // return or the window to close. Run is guaranteed not to deadlock if it is
 // invoked during the handling of a ViewEvent, system.FrameEvent,