Public bug reported:
I'm using xfwm4 with Xubuntu 16.04. With compositing enabled, and when
I cycle through windows with Alt-Tab, xfwm4 draws an opaque rectangle
bordering a candidate window, and it fills that rectangle with a semi-
transparent blue color. When I use the nouveau driver, the filled
rectangle is clipped. The problem does not reproduce with the
proprietary nvidia driver.
It seems as though a drawing command should be issued using a window-
relative coordinate, but sometimes is instead issued using a screen-
relative coordinate.
I extracted relevant bits of xfwm4 into a small test program that
reproduces the problem. The test program creates a transparent XWindow
at (100,100) with size (210,210). It draws six rectangles centered
inside the window of varying parameters. Two of them are drawn at the
wrong place.
xfwm4 should be off-the-hook, I think, unless it's doing something wrong
(e.g. unspecified/undefined behavior).
$ lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04
$ apt-cache policy xserver-xorg-video-nouveau
xserver-xorg-video-nouveau:
Installed: 1:1.0.12-1build2
Candidate: 1:1.0.12-1build2
Version table:
*** 1:1.0.12-1build2 500
500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
100 /var/lib/dpkg/status
$ apt-cache policy xfwm4
xfwm4:
Installed: 4.12.3-1ubuntu2
Candidate: 4.12.3-1ubuntu2
Version table:
*** 4.12.3-1ubuntu2 500
500 http://us.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
100 /var/lib/dpkg/status
I created a video demonstrating the problem in xfwm4:
https://www.youtube.com/watch?v=8dZN80tMA6M. If you look closely, you
can see that the opaque blue border is positioned correctly, while the
semi-transparent overlay isn't.
FWIW, I'm using an NVIDIA GeForce GTX 750 Ti card.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13
Uname: Linux 4.4.0-31-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Mon Jul 25 00:50:21 2016
InstallationDate: Installed on 2016-07-19 (6 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: xorg (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug xenial
** Attachment added: "extracted-from-xfwm4.c"
https://bugs.launchpad.net/bugs/1606122/+attachment/4706853/+files/extracted-from-xfwm4.c
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https://bugs.launchpad.net/bugs/1606122
Title:
Cairo drawing coordinates are broken w/nouveau (affects xfwm4)
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