ui/app: (macOS) redraw when NSOpenGLView update is called

When moving a window to another monitor, update is called when the
opengl backing store updates its internal size.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/app/gl_macos.m

@@ -67,6 +67,10 @@ CVDisplayLinkRef displayLink;
 - (BOOL)isFlipped {
 	return YES;
 }
+- (void)update {
+	[super update];
+	gio_onDraw((__bridge CFTypeRef)self);
+}
 - (void)drawRect:(NSRect)r {
 	gio_onDraw((__bridge CFTypeRef)self);
 }