[ubuntu-x] [Gutsy] Should Xinerama be active when only a single monitor is connected?

Dan Munckton lists at munckfish.net
Tue Nov 27 11:08:22 GMT 2007


I'm new to this list and I've been brought here because I'm trying to
find a solution for the following Java/Xinerama issue:


Basically Java uses Xrandr for its Fullscreen Exclusive Mode. However it
rightly avoids using Xrandr if Xinerama is active.

I've tested it across 3 Gutsy installed machines
(xorg-server_1.3.0.0.dfsg-12ubuntu8) with only a single monitor attached
to each and Xinerama appears to be active in all. This is a change in
behaviour from Feisty (xorg-server_1.2.0-3ubuntu8) where Xinerama isn't
active by default.

By active I mean that XQueryExtension() and XineramaIsActive() both
return TRUE and XineramaQueryScreens() returns non-NULL and reports 1

So I've been searching through the xorg-server source and I've noticed
that the PanoramiXExtensionInit() function in Xext/panoramiX.c checks
that there is not only 1 screen attached, and if there is only 1 it
returns without initialising. However, on my machines this appears to
not be working. I applied all the Ubuntu patches and the code there
remains the same.

Also, in the xorg.conf man page I see there is a "Xinerama" option in
the "ServerFlags" section which should enable or disable Xinerama.
However, setting this to "off" doesn't seem to be having any effect. I
can see from the source that this should result in the global variable
noPanoramiXExtension being set to FALSE which should also cause
PanoramiXExtensionInit() to return without initialising.

Now I'm just about to start adding debug statements to explore this but
first I wanted to ask: 

Should Xinerama really be active for only 1 screen by default in Gutsy?
Is this the correct behaviour or have I found a bug?

If this is correct what would the consequences be of disabling it? Are
there any applications that now rely on this e.g. DisplayConfigGTK?


Dan Munckton

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