app: added support for fullscreen mode

The option field WindowMode allows changing the window mode of an application in either Windowed or Fullscreen.
Only macOS, Windows and X11 platforms are currently supported.

Updates gio#89.

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

app/internal/wm/os_macos.go

@@ -41,6 +41,7 @@ __attribute__ ((visibility ("hidden"))) CGFloat gio_getScreenBackingScale(void);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_readClipboard(void);
 __attribute__ ((visibility ("hidden"))) void gio_writeClipboard(unichar *chars, NSUInteger length);
 __attribute__ ((visibility ("hidden"))) void gio_setNeedsDisplay(CFTypeRef viewRef);
+__attribute__ ((visibility ("hidden"))) void gio_toggleFullScreen(CFTypeRef windowRef);
 __attribute__ ((visibility ("hidden"))) CFTypeRef gio_createWindow(CFTypeRef viewRef, const char *title, CGFloat width, CGFloat height, CGFloat minWidth, CGFloat minHeight, CGFloat maxWidth, CGFloat maxHeight);
 __attribute__ ((visibility ("hidden"))) void gio_makeKeyAndOrderFront(CFTypeRef windowRef);
 __attribute__ ((visibility ("hidden"))) NSPoint gio_cascadeTopLeftFromPoint(CFTypeRef windowRef, NSPoint topLeft);
@@ -62,6 +63,7 @@ type window struct {
 	cursor      pointer.CursorName
 
 	scale float32
+	mode  WindowMode
 }
 
 // viewMap is the mapping from Cocoa NSViews to Go windows.
@@ -124,6 +126,16 @@ func (w *window) WriteClipboard(s string) {
 	})
 }
 
+func (w *window) SetWindowMode(mode WindowMode) {
+	switch mode {
+	case w.mode:
+		return
+	case Fullscreen:
+		C.gio_toggleFullScreen(w.window)
+	}
+	w.mode = mode
+}
+
 func (w *window) SetCursor(name pointer.CursorName) {
 	w.cursor = windowSetCursor(w.cursor, name)
 }
@@ -353,6 +365,7 @@ func NewWindow(win Callbacks, opts *Options) error {
 		}
 		nextTopLeft = C.gio_cascadeTopLeftFromPoint(w.window, nextTopLeft)
 		C.gio_makeKeyAndOrderFront(w.window)
+		w.SetWindowMode(opts.WindowMode)
 	})
 	return <-errch
 }