Is there a way to know when another hwnd has closed?

Question

Is there a method for setting up a listener/watcher to know when an unrelated application window is closed?

I can check to see if the window is still open, but that seems silly to continually do.

Answer 1

The Accessibility API's SetWinEventHook filtering for EVENT_OBJECT_DESTROY.

This is notification based so no polling and unlike a CBT hook does not require injection.

Answer 2

You can:

1. poll for HWND validity (esp. if you don't need timing precision)
2. subclass the window to intercept its WM_DESTROY and then forward the notification to your app
3. install a window message hook to be able to intercept the message otherwise
4. create a hidden child window to get it destroyed with the parent destruction, to also have your message handler called on time for you