subject:"\[Desktop\-packages\] \[Bug 1547077\] Re\: Some glyphs drawn consistently wrong, bug comes and go"

[Desktop-packages] [Bug 1547077] Re: Some glyphs drawn consistently wrong, bug comes and go

2016-05-18 Thread gouri

The bug is still triggered (not always) by suspend-to-ram then wake-up.

This make a frustrating user experience since the most affordable
workaround is to close the session the reopen it when bug occurs. Since
many applications are defaced (see screenshots), the user cannot
properly check if their work is saved.

Thank you for your attention.

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https://bugs.launchpad.net/bugs/1547077

Title:
Some glyphs drawn consistently wrong, bug comes and go

Status in xorg package in Ubuntu:
Triaged

Bug description:
# Summary
* Some glyphs badly drawn at some moments.
* When happens, same glyph drawn on various windows shows same corruption.
* Problem comes and go.

Cannot use nvidia proprietary driver as a workaround (does not work at
all).

# Context
Laptop, using "intel" (or "nouveau" ?) driver.
Expected: all glyphs rendered correctly.
Observed: some glyphs not rendered correctly

* reproducible: sometimes, eventually. Problem comes and go, severity
varies from one glyph (see
2016y02m17d_18h08m27s_0100Z_x_bug_glyph_firefox_gnome_org.png ) to all
text on screen fully unreadable (see
2016y02m10d_18h42m18s_0100Z_wow_screen_flickers_and_most_glyphs_wrong_01.png
)

* *some* glyphs are affected. For example, letter 'a' of a certain
size will be replaced by colored garbage at many places where it
appears (see
2016y02m18d_16h05m35s_0100Z_same_corruption_on_different_windows.png
), but other 'a' with different size, italic, bold, etc will be
unaffected.

* in some applications (e.g. xfce whisker menu), some glyphs are
rendered correctly or not depending on the direction of mouse
hovering. See video
2016y02m16d_21h41m14s_0100Z_whisker_menu_missing_glyphs.mp4 .

* in menu of gtk application, some glyphs are "fixed" by opening the
menu, but not all. For example, in xfce4-terminal, letter A of
"Affichage" and its menu content as well as "Aide" is affected.
Opening "Affichage" menu does not fix anything. Opening "Aide" menu
fixes the "A" of "Aide". Changing window size reactivates the bug on
"A" or "Aide". See video 2016y02m18d_16h14m25s_0100Z_glyph-redrawn-
bug.mp4 .

* text under icons on desktop is affected, but shadows are not. See

2016y02m16d_21h32m11s_0100Z_x_bug_reenabling_antialias_reactivates_problem_shadow_unaffected.png

# Affected applications
* xfce whisker menu,
* xfce4-terminal (nealy all screenshots)
* firefox (see 2016y02m17d_18h08m27s_0100Z_x_bug_glyph_firefox_gnome_org.png
2016y02m16d_21h32m11s_0100Z_x_bug_reenabling_antialias_reactivates_problem_shadow_unaffected.png
),
* thunderbird (see
2016y02m16d_21h28m35s_0100Z_x_bug_affects_thunderbird_terminal.png ),
* emacs (see
2016y02m10d_18h41m49s_0100Z_wow_screen_flickers_and_most_glyphs_wrong_00.png
and subsequent ),
* superswitcher ( a gtk/gdk app)
* *NOT* affected: xterm, xmessage. Perhaps only gtk/gdk/pango/cairo apps are
affected.

# Additional information
This looks like a cache corruption somewhere.
On IRC #pango, someone suggested a bug in Intel driver.
Running `xfce4-appearance-settings` and there changing any of:
* antialiasing enable/disable,
* hinting strength,
* subpixel alignment
* or dpi
immediately cures the bug (see
2016y02m16d_21h31m52s_0100Z_x_bug_disabling_antialias_immediately_cures_problem.png
)

Setting back the exact same parameters immediately reactivates the bug
(see

2016y02m16d_21h32m11s_0100Z_x_bug_reenabling_antialias_reactivates_problem_shadow_unaffected.png).

It is believed that keeping any new settings for a while will have the
bug reoccur.

It is not like bug 1536751. That one affects rendering quality of
*all* glyphs, at all times, depending on dpi. This is not the case
here: *some* glyphs (randomly chosen) are drawn corrupted (replaced by
garbage or absent), not always.

---
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
CompizPlugins: No value set for
`/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: XFCE
DistUpgraded: Fresh install
DistroCodename: xenial
DistroRelease: Ubuntu 16.04
DistroVariant: ubuntu
DkmsStatus: virtualbox, 5.0.14, 4.4.0-8-generic, x86_64: installed
ExtraDebuggingInterest: Yes, including running git bisection searches
GraphicsCard:
Intel Corporation 4th Gen Core Processor Integrated Graphics Controller
[8086:0416] (rev 06) (prog-if 00 [VGA controller])
Subsystem: ASUSTeK Computer Inc. 4th Gen Core Processor Integrated
Graphics Controller [1043:177d]
Subsystem: ASUSTeK Computer Inc. GM107M [GeForce GTX 850M] [1043:177d]
InstallationDate: Installed on 2016-02-03 (26 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160203)
MachineType: ASUSTeK COMPUTER INC. N551JK
Package: xorg 1:7.7+13ubuntu1
PackageArchitecture:

[Desktop-packages] [Bug 1547077] Re: Some glyphs drawn consistently wrong, bug comes and go

2016-03-18 Thread gouri

Unfortunately, the bug occurred again a few minutes ago.

This means that uninstalling light-locker and using xscreensaver instead
is not enough to prevent the bug from occurring.

AFAIK, doing so avoids light-locker creating possibly short-lived X
servers (for the purpose of asking password for unlocking screen while
allowing to open a new session).

Thus I believe that the bug is not triggered by running several X
servers.

Still, I've noticed that the bug is not active for the whole machine at
a time, but can be active on an X server (for example, while typing
password to unlock) and inactive on another (main session) or vice
versa.

All in all, this and bug
https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1558236 make (for our
usage pattern at least) two important regressions that 16.04 introduces.