Bug 233187 - Antialiasing causes font corruption
Summary: Antialiasing causes font corruption
Status: RESOLVED UPSTREAM
Alias: None
Product: kwin
Classification: Plasma
Component: general (show other bugs)
Version: unspecified
Platform: Ubuntu Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2010-04-03 19:36 UTC by Gary Tang / Dolphinaura
Modified: 2010-04-03 20:35 UTC (History)
0 users

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Description Gary Tang / Dolphinaura 2010-04-03 19:36:13 UTC
Version:            (using KDE 4.4.2)
OS:                Linux
Installed from:    Ubuntu Packages

The Antialiasing settings in System Settings-> Appearance -> Fonts
occasionally can cause font corruption, depending on the settings.

It occurs randomly, only for that particular character on that screen.
By character, I mean that for example, all "Y"s that are in the application are corrupted.

This occurs if the antialiasing settings are set to "enbled" and with the following combinations of settings


SubPixel Rendering: RGB      | Hinting Style: None
SubPixel Rendering: RGB      | Hinting Style: Slight
SubPixel Rendering: RGB      | Hinting Style: Medium
SubPixel Rendering: RGB      | Hinting Style: Full
SubPixel Rendering: Disabled | Hinting Style: Medium
SubPixel Rendering: Disabled | Hinting Style: Full

and does not occur with

SubPixel Rendering: Disabled | Hinting Style: None
SubPixel Rendering: Disabled | Hinting Style: Slight

Ive taken a screenshot, so please take a look -> http://img52.imageshack.us/img52/7463/snapshot1x.png
Comment 1 Martin Flöser 2010-04-03 19:42:46 UTC
It is definately not a kwin bug (not responsible for window content) and I doubt it is a KDE bug, but for that I have some questions:
 * Does it happen with other applications than Synaptics?
 * Does it only happen for applications using GTK+ (as Synaptics is a GTK+ application)?
 * Does it happen for applications not run as system user (as Synaptics is run as root and should use it's own font settings)?
 * Does changing the fonts settings for GTK+ applications in systemsettings change the behaviour?
Comment 2 Thomas Lübking 2010-04-03 20:25:36 UTC
if this occurs for one particular combination of font/glyph/hinting it could be a fontconfig bug, otherwise (randomly hits glyphs across all fonts and hintings) it's the glyph cache on the server.

for nvidia use "nvidia-settings -a GlyphCache=0" to turn it off, otherwise i don't know. you'll have to gg for your gpu/driver.

notce that _not_ caching glyphs makes text rendering slow.
Comment 3 Gary Tang / Dolphinaura 2010-04-03 20:35:58 UTC
*Yes, this happens for all applications
*Nope. Happens for KDE applications as well
*Exists for both root & non root users
*Ive tried 20+ fonts with no effect.