Should RRGetCrtcInfo return panning bounds?

Keith Packard keithp at
Fri Jan 9 11:38:48 PST 2009

On Fri, 2009-01-09 at 10:59 -0800, Andy Ritger wrote:
> Probably both the physical region currently scanned out by the CRTC,
> as well as the panning region, are useful things for an RandR client
> to query.  I'm not sure how best to make both pieces of information
> available.

I'm thinking that if we ever send the physical region scanned by the
CRTC, we should provide events that update it when panning occurs.

Clients need to know about monitor geometry for two reasons:

 1) Full-screen presentation mode. In this case, we want to
    fill the monitor, not the panning region. As such, we should
    report the monitor rectangle.

 2) Full-screen web page mode. In this case, the user presumably
    specified a larger panning region precisely because some web
    page could not fit on the monitor. Reporting the monitor size
    will not help as the window manager will set the application size
    to fill that, and not fill the panning region.

 3) Avoiding black holes in window placement. The window manager
    needs to make sure every window can be seen. In this case,
    we want to expose the panning region, not the monitor region.

Given that the usage model for panning requires that applications be
allowed to fill the panning region, I'd say we should report that
rectangle in the CrtcInfo (and Xinerama too). If the user wants a
presentation that fills a monitor, they should set the panning region to
match the monitor anyway.

Should this also extend to the meaning of the X/Y values in the
RRSetCrtcConfig request?

keith.packard at
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