I have a possible culprit.
The composite extension requires premultiplied alpha data when
compositing images with alpha. So (0, 0, 0, 0) means fully transparent
and (0, 0, 0, 1) means solid black. This is consistent with what I am
seeing with the login window.
I found some example code with walks through the proposed matching GLX
FB configs and uses the Render exentsion to check for the alpha mask of
that framebuffer. This is used by code that explicitly wants an alpha
channel for compositing.
Something along the lines of
for (i = 0; i < numfbconfigs; i++) {
visinfo = glXGetVisualFromFBConfig(dpy, fbconfigs[i]);
if (!visinfo) continue;
pictFormat = XRenderFindVisualFormat(dpy, visinfo->visual);
if (!pictFormat) continue;
printf("%d %d %d\n", numfbconfigs, i,
pictFormat->direct.alphaMask);
}
When playing around with attributes and looking for matching FB visuals,
there are usually one or more matches and only the last one listed has
an alphaMask of 255, all others are 0.
Now it appears that on my system the only FB config available matching
Minecraft's requested attributes is the one with alphaMask of 255, i.e.
its alpha value *is* passed to the compositor.
Now my guess is that Minecraft simply isn't expecting that, so the alpha
bit contains a random value (typically 0) which is then accidentally
used by the compositor.
So, to support my theory one would need to check if the issue is simply
Minecraft/LWJGL now selecting an RGBA visual with the alpha channel
interpreted by the compositor whereas before that was not the case.
I'll try to hack Minecraft to set the alpha value to 1 in the meantime
to see if it helps. I am just wondering whether this is standard or
nonstandard and Minecraft/LWJGL is supposed to handle this correclty or
not.
--
You received this bug notification because you are a member of Desktop
Packages, which is subscribed to xserver-xorg-video-intel in Ubuntu.
https://bugs.launchpad.net/bugs/1277905
Title:
Game windows (minecraft, titan attacks, maybe others) on Intel are
transparent and no longer playable
Status in “xserver-xorg-video-intel” package in Ubuntu:
Confirmed
Bug description:
Fully up to date Trusty.
Open Minecraft, notice that the window is transparent - you can see through
to the desktop wallpaper, making the game unplayable.
Also tested with Titan Attacks which is also a lwjgl based game - dunno if
that's coincidence
This worked a few days ago. Probably before the most recent xorg
update.
See screenshots.
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xserver-xorg-video-intel 2:2.99.909-0ubuntu2
ProcVersionSignature: Ubuntu 3.13.0-7.25-generic 3.13.1
Uname: Linux 3.13.0-7-generic x86_64
.tmp.unity.support.test.0:
ApportVersion: 2.13.2-0ubuntu2
Architecture: amd64
CompizPlugins:
[core,composite,opengl,compiztoolbox,decor,grid,imgpng,gnomecompat,scale,workarounds,mousepoll,regex,wall,move,place,vpswitch,resize,unitymtgrabhandles,snap,session,expo,ezoom,unityshell]
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Sat Feb 8 10:54:09 2014
DistUpgraded: 2014-01-20 08:54:25,315 DEBUG enabling apt cron job
DistroCodename: trusty
DistroVariant: ubuntu
EcryptfsInUse: Yes
ExtraDebuggingInterest: Yes
GraphicsCard:
Intel Corporation 2nd Generation Core Processor Family Integrated Graphics
Controller [8086:0126] (rev 09) (prog-if 00 [VGA controller])
Subsystem: Lenovo Device [17aa:21da]
InstallationDate: Installed on 2012-06-29 (588 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64
(20120425)
MachineType: LENOVO 4287CTO
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-7-generic
root=UUID=6088859e-4fc3-4ec8-903f-5b52cdc1d0eb ro quiet splash vt.handoff=7
SourcePackage: xserver-xorg-video-intel
UpgradeStatus: Upgraded to trusty on 2014-01-20 (19 days ago)
dmi.bios.date: 12/05/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET67WW (1.37 )
dmi.board.asset.tag: Not Available
dmi.board.name: 4287CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias:
dmi:bvnLENOVO:bvr8DET67WW(1.37):bd12/05/2012:svnLENOVO:pn4287CTO:pvrThinkPadX220:rvnLENOVO:rn4287CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 4287CTO
dmi.product.version: ThinkPad X220
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.10+13.10.20131011-0ubuntu4
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.52-1
version.libgl1-mesa-dri: libgl1-mesa-dri 10.0.1-1ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.0.1-1ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.15.0-1ubuntu3
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.909-0ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau
1:1.0.10-1ubuntu2
xserver.bootTime: Sat Feb 8 10:50:45 2014
xserver.configfile: default
xserver.errors:
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
product id 728
vendor LGD
xserver.version: 2:1.15.0-1ubuntu3
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