Bug 68397

Summary: Xephyr: enhance -screen option with window placement feature (WxH+X+Y), for multiseat purposes
Product: xorg Reporter: Laércio de Sousa <lbsousajr>
Component: Server/DDX/XephyrAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: enhancement    
Priority: medium    
Version: 7.7 (2012.06)   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
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Description Flags
Enhance Xephyr -screen option with window placement feature (WxH+X+Y), for multiseat purposes. none

Description Laércio de Sousa 2013-08-21 19:05:40 UTC 
Created attachment 84410 [details]
Enhance Xephyr -screen option with window placement feature (WxH+X+Y), for multiseat purposes.

I know there was a long discussion years ago about adding or not a -geometry option to Xephyr, mainly for multiseat purposes (see https://bugs.freedesktop.org/show_bug.cgi?id=12221). So, I don't expect this patch will be accepted by upstream, but it still may be interesting for multiseat setup maintainers.

I've written a patch, in the same spirit of https://bugs.freedesktop.org/attachment.cgi?id=11331, that extends the -screen option so that Xephyr can process strings like HxW+X+Y and move its window origin to (X, Y).

In my tests, the +X+Y option is completely overriden if Xephyr is handled by a window manager (the typical use for which it's designed for, I guess), but it works if Xephyr is launched directly with no window manager running, which is the case in multiseat setups.

Now that systemd-logind is available in several systems, multiseat configuration becomes less and less painful, so it's time to revival those old Xephyr-based multiseat solutions.
Comment 1 Laércio de Sousa 2014-03-14 16:13:11 UTC 
I'm giving up this bug for now. I've noticed that just enabling window placement within Xephyr is not sufficient to address all issues about single-card multiseat. There's some inconvenients that arise when I don't start Xephyr with -fullscreen or -parent options, namely, modern desktop environments set, by default, my Xephyr screen resolution to the highest available one via RANDR, 1600x1200, despite my monitor native resolutions.

I'm working on a Xephyr wrapper for multiseat (see https://launchpad.net/multi-seat-xephyr). Since Bazaar revision 97, I've implemented something like the seat-parent-window approach from former project Multiseat Display Manager by C3SL/UFPR a.k.a. MDM-C3SL (which code is currently available in my GitHub fork https://github.com/lbssousa/multidm): the wrapper creates an empty window, whose geometry I can set easily, and passes its window id to Xephyr via -parent option. In this case, the only available resolution via RANDR is the size of the Xephyr parent window, so my desktop environment doesn't change it to 1600x1200 anymore.

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