Bug 190307 - no compositing effects when using dual screen in non-clone mode
Summary: no compositing effects when using dual screen in non-clone mode
Status: RESOLVED NOT A BUG
Alias: None
Product: kwin
Classification: Plasma
Component: general (show other bugs)
Version: unspecified
Platform: Debian testing Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2009-04-21 23:54 UTC by Sten Heinze
Modified: 2011-01-16 10:28 UTC (History)
0 users

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Description Sten Heinze 2009-04-21 23:54:57 UTC
Version:            (using KDE 4.2.2)
Compiler:          gcc 4:4.3.3-2 (version from Debian testing) 
OS:                Linux
Installed from:    Debian testing/unstable Packages

I tried to set up an external monitor connected to my laptop in non-clone mode. Since I couldn't figure out how to do this using krandr, I used:
Comment 1 Sten Heinze 2009-04-22 00:19:30 UTC
Apparently something got screwed up and the bug report got submitted half way. The rest of the bug report should have been:

xrandr --output VGA --auto --above LVDS

(I have to use --above instead of --right-of or --left-of, because the maximal supported screen size for use with compositing is 2048x2048 on my 855GM. I'm using UXA, so the virtual screen size is set automatically.)

Upon running above command, no effects work anymore, although they are still shown as enabled in systemsettings. Effects are not working again after turning the external monitor off. They work again after logout && login.

Expected behaviour:
Enabled effects should work even in a dual screen environment, independent of the arrangement of monitors/screens.

Unfortunately title and type of the report are also incorrect, but I don't know how to change it:
Title: no compositing effects when using dual screen in non-clone mode
Type: Bug report, no crash
Comment 2 Dario Andres 2009-04-22 15:36:46 UTC
Fixing report fields.
Comment 3 Martin Flöser 2009-04-22 16:51:18 UTC
When you changed the screens did you see any notification like compositing was suspended?

Could you try after setting up the second screen to use alt+shift+f12 to resume compositing if it has been suspended?

And if I remeber correctly some Intel GPUs are not able to handle larger screen sizes with compositing.
Comment 4 Sten Heinze 2009-04-22 18:05:16 UTC
I didn't see any notification upon setting up the screens. But to be sure I tried again and it worked successful, I got compositing with both screens. 

But the screens seemed to be used inconsistently. Some effects, like the window gallery, are shown on the screen which had the last active window, other, like the desktop overview, are always shown on both.

Upon switching back to a single screen (the built-in LVDS in this case), kwin crashed and plasma disappeared. I ended up having a black screen with mouse cursor on top, and I only could tell where windows are by moving the mouse and seeing the cursor change, e.g. over window borders or edit fields. Not sure what was causing this. I'll try to reproduce and get more information tonight.

(Btw. Intel GPU can generally handle up to 2048x2048, 965 and newer can handle larger sizes. That is the reason I have the extenal screen w/ 1280x1024 above the internal one w/ 1024x768, making the virtual screen size 1280x1792 and thus smaller than 2048x2048.)
Comment 5 Martin Flöser 2011-01-16 10:28:44 UTC
(In reply to comment #4)
> I didn't see any notification upon setting up the screens. But to be sure I
> tried again and it worked successful, I got compositing with both screens. 
Given this information the original problem seems to be resolved. The other issues mentioned in comment #4 are either intended (e.g. CoverSwitch) or other bugs. Especially for crashes we need the backtrace.

for Intel GPUs it is sometimes required to modify the xorg.conf to get compositing in a dual screen setup.