Cannot handle ApplicationShouldTerminate in application without window

[PaulBol]

Some observations related to #2

When the application currently does not display any form ApplicationShouldTerminate in MonoApplicationDelegate.cs obviously cannot notify any window. It will return NSApplicationTerminateReply.Cancel to allow termination but the application has no chance to clean up before terminating.

I came up with this added code as a workaround

Message m = Message.Create(IntPtr.Zero, (int)Msg.WM_QUIT, IntPtr.Zero, IntPtr.Zero);
if (Application.FilterMessage(ref m))
	return NSApplicationTerminateReply.Cancel;

This way an application without a main form may install a message filter and handle ApplicationShouldTerminate.

The next observation is that with a dynamically top-level window ApplicationShouldTerminate is not received. I figured out that the behavior is caused by the SetModal call for the top-level window. Though I'm not sure why. The following change resolves the issue. But since I haven't really understood modal sessions I'm wondering if it might break anything else.

internal override void SetModal (IntPtr handle, bool Modal)
{
	NSView vuWrap = handle.ToNSView();
	NSWindow winWrap = vuWrap.Window;
	IntPtr session;
	if (Modal)
	{
		if (winWrap.ParentWindow == null)
		{
			winWrap.Center();
			ModalSessions.Push(IntPtr.Zero);
		}
		else
		{
			session = NSApplication.SharedApplication.BeginModalSession(winWrap);
			ModalSessions.Push(session);
		}
	}
	else if ((session = ModalSessions.Pop()) != IntPtr.Zero)
		NSApplication.SharedApplication.EndModalSession(session);
}

Are the suggested changes good enough for a pull request or do they not make sense?

[filipnavara]

How do you handle this situation on Windows?

ApplicationShouldTerminate should probably call XplatUI.PostQuitMessage, which handles the case of sending WM_QUIT to a thread message queue. I am not sure if it's correctly wired up everywhere to do the right thing though. More importantly it will only help if there is some message loop and it's not immediately obvious if that's the case for you.

[PaulBol]

My understanding is that this case does on not exist on Windows. I can only choose "Close window" from the task bar for windows that are shown. Having an application run temporarily without a window seems like an unnatural approach not following the Windows look&feel.

But it's not so uncommon on Mac. E.g. if I close the last window in TextEdit or Terminal the application is still running and can be accessed from the dock and its main menu.

I have such an application. When it's not showing a window I'm continuously calling DoEvents to pump messages. I came up with the above mentioned workaround to handle "Quit" from the dock. Maybe there's a better way to achieve the behavior?