Added the show system menu method to window

[YouKnow-sys]

This PR add support for showing system menu with calling show_system_menu method on Window.
this can be useful when we are drawing our custom titlebar and want to keep the system menu as well.
currently only supported on windows.

related to: #3108

• Tested on all platforms changed
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[notgull]

This function might be a better fit for menubar.

[YouKnow-sys]

This function might be a better fit for menubar.

well the name of this crate suggest that its for adding menu bar to programs, how can system menu relate to it?
I mean this mainly will be used alongside things like drag_window and drag_resize_window for window that have custom titlbar and can't access the original system menu...
I also tried to run examples of this project, but compile failed...

[kchibisov]

This function might be a better fit for menubar.

This has nothing to do with the menubars, this is a system menu on the right click on decorations, which is used to show a compositor menu. Winit already shows such a thing, it just, we don't expose the API winit uses for it, which is required for the
user defined client side decorations.

[kchibisov]

Given that there was a mention of the mouse or similar happening, I'd say that wayland wants that action to be associated with some input event, like in reaction to mouse click, keyboard button press, touch press, etc.

We should say that the compositor is free to ignore such request though.

[YouKnow-sys]

I think now its mostly done?
I update the code based on recent suggestions and also changed the doc as best as I could.

[daxpedda]

I think now its mostly done?

Couple of nits on the documentation, otherwise LGTM from me.
I'm not familiar with the Windows backend, so somebody else has to review that.

[YouKnow-sys]

Couple of nits on the documentation, otherwise LGTM from me. I'm not familiar with the Windows backend, so somebody else has to review that.

I applied your suggestions, thanks.
sounds good to me.

[daxpedda]

Could you rebase for CI to run?

[YouKnow-sys]

Could you rebase for CI to run?

sure, tests are now running

[msiglreith]

Windows implementation lgtm

[kchibisov]

looks mostly good.

[YouKnow-sys]

had to add another extra unsafe block inside the handle_showing_window_menu method...
to be honest unsafe_op_in_unsafe_fn doesn't make much sense on functions that are actually unsafe, but here we are.