Window change event?

Thomas Lübking thomas.luebking at
Sun Aug 4 08:16:18 PDT 2013

On Sonntag, 4. August 2013 16:08:08 CEST, László Monda wrote:

> I'm writing an application that has to be aware of the current window.
> So far I've extracted the relevant code from xprop and put it into
> .  (I screwed up

> The above solution would work but it'd involve polling the info of the
> current window from time to time which is not very efficient.
> Wondering whether there's a way to register a callback for a "window
> change" event.  That'd be so much more efficient.  Ideally I'm looking
> for a way to do this in a window manager independent manner.

XSelectInput(dpy, root, PropertyChangeMask );

You'll then receive "PropertyNotify" type events (google for "X11 event handler" w/o quotes - you'll find examples for main event loop implementations) from the root window.
Then you've to check whether it's the correct property.

I didn't check what you're actually trying to do, but this is different from selecting input of FocusChangeMask on each interesting window and receive FocusIn/Out events.
Focus and Active window do not necessarily have to go along each other (and also clients grabbing the keyboard might actually receive keyboard events)


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