How are opengl menus that go outside of the window implemented?

Question

I was looking at how sometimes when you right click, the menu goes outside of the window.

Is this implemented with a separate window? If so, how can I get this functionality. I am trying to use GLFW, but I understand if it isn't possible.

Currently I am on windows, but I like keeping my options open, which is why GLFW would be preferable.

I noticed that GLUT has such a feature. If you are confused to what I am looking at then look at that.

Thanks for any help!!

Answer 1

Overlapping menus (in MS Windows) have to be implemented as a new top-level window, you would have a new OpenGL rendering context and draw the menu in that space - yes, it's a fair bit of work all for the edge-case of a menu overspilling the parent window,

However this isn't often a problem in OpenGL programming because if you're working on a full-screen game then the menu will always be displayed within the main window, and even if it isn't a full-screen a game your users really won't notice them as games tend to use different UI concepts like radial-menus which wouldn't overspill the parent window.

Or if you're working on a non-game title, chances are it isn't full-screen and is going to be an OpenGL rendering area within a larger application that is rendered using a native UI toolkit (e.g. 3ds Max, AutoCAD, etc), in which case no problem: just use native menus.

You can, of course, use native menus in an OpenGL application anyway, provided you do the necessary plumbing for native window messages.