Patches to fix fullscreen games viewport issues with recent Xorg versions

[Hans de Goede]

Hi,

On 11/12/2009 03:37 AM, Peter De Wachter wrote:
> Op Wed, 11 Nov 2009 12:04:39 +0100
> schreef Hans de Goede<hdegoede at redhat.com>:
>
>> Hi,
>>
>> With recent Xorg versions XF86VidModeSetViewPort() does not seem to
>> do anything. So fullscreen games which place an undecorated window
>> at 0,0 and then do XF86VidModeSetViewPort(.., 0, 0) no may end up with
>> the viewport wrong (showing part of the game and part of the
>> desktop).
>>
>> This can be workedaround by doing a XWarpPointer() call to 0, 0
>> before XF86VidModeSwitchToMode().
>>
>> SDL is already doing this, attached are patches for:
>> allegro
>> ClanLib-0.8 / 1.0 (0.6 and 2.x are not affected)
>> xgalaxy
>
> Are these the only ones you checked or the only ones that needed
> patches?

These were the ones of which I know they use XF86VidMode, I've not done
an extensive search, so I may have missed some.

> Debian has many more packages that use XF86VidModeSetViewPort:
> http://source.debian.net/source/search?q=XF86VidModeSetViewPort
> (and that search doesn't even include the stuff in non-free).
>

Hmm, that is a nice feature! Very handy, yes definitely looks like some
other things will need fixing too (or xorg should be fixed)

> I spent way too much time googling, and the problem seems to be this:
> - XF86VidModeSwitchMode centers the viewport around the pointer
> - X11 clients can request a different viewport by calling
>    XF86VidModeSetViewPort
> - Except that some video drivers no longer implement that function
>

I think that is a spot on analysis.

> Your work-around moves the pointer to the top-left corner, so that the
> viewport will be located there, in the hope that's what the application
> will request later. Unfortunately, some applications (I found
> dvr, netrek-client-cow, zapping, vice, and I probably missed some) want
> their viewport elsewhere. So they will need a different work-around.
>

Or they need to move their window to position 0,0 that should be easy.

> I really feel the X server should be fixed instead. This functionality
> is definitely in use in the wild.

I won't disagree, but I don't have the skills, and those who do have
the skills (the driver authors), I don't think will give this high priority,
but I may be wrong. So go and file bugs and please but me in the CC.

Regards,

Hans