Question

I need to host my window upon a window of another application.
How to enumerate windows of another Cocoa application? Is it possible to control
them?
If no: how can I draw upon a window of another application?
Thanks!

Answer 1

How to enumerate windows of another Cocoa application?

You can enumerate the windows of another application using the Accessibility API. It doesn’t matter whether that application is Cocoa or not.

Is it possible to control them?

Here, it does matter, indirectly, whether the application is Cocoa (or Carbon using standard controls). More precisely, it matters whether the application is accessible.

It usually is possible to move another window, resize it, or do simple things with controls in it (such as press buttons).

It is not possible to tape one of your windows to a window in another application. You will have to observe its location and move your window when the other moves. Following a live drag this way is not possible.

If no: how can I draw upon a window of another application?

You can’t. You can only draw in your own windows.

You can make a transparent overlay window and draw on that, but that gets you back to the problem of taping one of your windows to a window in another application.

You should probably ask a broader question about whatever it is you hope to achieve by taping one of your windows to a window in another application or by drawing into a window in another application.