app: support changing Window options at runtime

A Window can now be requested to change its options after
it has been started via its Option method.

All options are supported on macOS, Windows and X11.
On Wayland, only the Size and Title options can be changed
at runtime.

Signed-off-by: pierre <pierre.curto@gmail.com>

app/internal/wm/os_x11.go

@@ -89,6 +89,7 @@ type x11Window struct {
 
 	mu        sync.Mutex
 	animating bool
+	opts      *Options
 
 	pointerBtns pointer.Buttons
 
@@ -98,6 +99,7 @@ type x11Window struct {
 		content []byte
 	}
 	cursor pointer.CursorName
+	mode   WindowMode
 }
 
 func (w *x11Window) SetAnimating(anim bool) {
@@ -124,22 +126,33 @@ func (w *x11Window) WriteClipboard(s string) {
 }
 
 func (w *x11Window) Option(opts *Options) {
-	dpy := w.x
-	win := w.xw
-	cfg := w.cfg
+	w.mu.Lock()
+	w.opts = opts
+	w.mu.Unlock()
+	w.wakeup()
+}
+
+func (w *x11Window) setOptions() {
+	w.mu.Lock()
+	opts := w.opts
+	w.opts = nil
+	w.mu.Unlock()
+	if opts == nil {
+		return
+	}
 	var shints C.XSizeHints
 	if o := opts.MinSize; o != nil {
-		shints.min_width = C.int(cfg.Px(o.Width))
-		shints.min_height = C.int(cfg.Px(o.Height))
+		shints.min_width = C.int(w.cfg.Px(o.Width))
+		shints.min_height = C.int(w.cfg.Px(o.Height))
 		shints.flags = C.PMinSize
 	}
 	if o := opts.MaxSize; o != nil {
-		shints.max_width = C.int(cfg.Px(o.Width))
-		shints.max_height = C.int(cfg.Px(o.Height))
+		shints.max_width = C.int(w.cfg.Px(o.Width))
+		shints.max_height = C.int(w.cfg.Px(o.Height))
 		shints.flags = shints.flags | C.PMaxSize
 	}
 	if shints.flags != 0 {
-		C.XSetWMNormalHints(dpy, win, &shints)
+		C.XSetWMNormalHints(w.x, w.xw, &shints)
 	}
 
 	var title string
@@ -148,9 +161,9 @@ func (w *x11Window) Option(opts *Options) {
 	}
 	ctitle := C.CString(title)
 	defer C.free(unsafe.Pointer(ctitle))
-	C.XStoreName(dpy, win, ctitle)
+	C.XStoreName(w.x, w.xw, ctitle)
 	// set _NET_WM_NAME as well for UTF-8 support in window title.
-	C.XSetTextProperty(dpy, win,
+	C.XSetTextProperty(w.x, w.xw,
 		&C.XTextProperty{
 			value:    (*C.uchar)(unsafe.Pointer(ctitle)),
 			encoding: w.atoms.utf8string,
@@ -190,6 +203,8 @@ func (w *x11Window) SetCursor(name pointer.CursorName) {
 
 func (w *x11Window) SetWindowMode(mode WindowMode) {
 	switch mode {
+	case w.mode:
+		return
 	case Windowed:
 		C.XDeleteProperty(w.x, w.xw, w.atoms.wmStateFullscreen)
 	case Fullscreen:
@@ -197,7 +212,34 @@ func (w *x11Window) SetWindowMode(mode WindowMode) {
 			32, C.PropModeReplace,
 			(*C.uchar)(unsafe.Pointer(&w.atoms.wmStateFullscreen)), 1,
 		)
+	default:
+		return
 	}
+	w.mode = mode
+	// "A Client wishing to change the state of a window MUST send
+	//  a _NET_WM_STATE client message to the root window (see below)."
+	var xev C.XEvent
+	ev := (*C.XClientMessageEvent)(unsafe.Pointer(&xev))
+	*ev = C.XClientMessageEvent{
+		_type:        C.ClientMessage,
+		display:      w.x,
+		window:       w.xw,
+		message_type: w.atoms.wmState,
+		format:       32,
+	}
+	arr := (*[5]C.long)(unsafe.Pointer(&ev.data))
+	arr[0] = 2 // _NET_WM_STATE_TOGGLE
+	arr[1] = C.long(w.atoms.wmStateFullscreen)
+	arr[2] = 0
+	arr[3] = 1 // application
+	arr[4] = 0
+	C.XSendEvent(
+		w.x,
+		C.XDefaultRootWindow(w.x), // MUST be the root window
+		C.False,
+		C.SubstructureNotifyMask|C.SubstructureRedirectMask,
+		&xev,
+	)
 }
 
 func (w *x11Window) ShowTextInput(show bool) {}
@@ -287,6 +329,7 @@ loop:
 				}
 			}
 		}
+		w.setOptions()
 		// Clear notifications.
 		for {
 			_, err := syscall.Read(w.notify.read, buf)