Bug 1374989 - Qt 5 uses wrong fontconfig defaults at least for subpixel antialiasing
Summary: Qt 5 uses wrong fontconfig defaults at least for subpixel antialiasing
Keywords:
Status: CLOSED EOL
Alias: None
Product: Fedora
Classification: Fedora
Component: qt5-qtbase
Version: 24
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Than Ngo
QA Contact: Fedora Extras Quality Assurance
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-09-11 13:02 UTC by Kevin Kofler
Modified: 2017-08-08 17:16 UTC (History)
6 users (show)

Fixed In Version:
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Clone Of:
Environment:
Last Closed: 2017-08-08 17:16:59 UTC
Type: Bug


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Description Kevin Kofler 2016-09-11 13:02:10 UTC
Description of problem:
Qt 5 appears to not enable subpixel antialiasing by default when freetype-freeworld is installed, whereas Qt 3 and 4 do. Only when I explicitly enable subpixel antialiasing in KDE System Settings, Qt 5 picks it up.

Version-Release number of selected component (if applicable):
qt5-qtbase-5.6.1-3.fc24

How reproducible:
Always? Feedback wanted…

Steps to Reproduce:
1. Install freetype-freeworld.
2. Restart your session.
3. Look at the antialiasing of various Qt applications. Use KMag to make sure you can see the effect.

Actual results:
While Qt 3 and 4 applications use subpixel antialiasing (i.e., you can see colors in KMag), Qt 5 applications do not (i.e., you see only grayscale).

Only if you explicitly enable subpixel antialiasing in KDE System Settings (rather than keeping it at the default "System default" setting) and then restart your session again (or at least the applications you are checking), you will see the wanted effect in Qt 5 applications.

Expected results:
Qt 5 applications should automatically be subpixel-antialiased if freetype-freeworld is installed, as Qt 3 and 4 applications are.

Additional info:
There is a point&click workaround (explicitly enable subpixel antialiasing in KDE System Settings), thus the low severity and priority.

Comment 1 Rex Dieter 2016-09-11 13:37:31 UTC
It may depend on the fontconfig default for subpixel rendering (I *believe* it is disabled by default).

For example, if you link/copy:
/usr/share/fontconfig/conf.avail/10-sub-pixel-bgr.conf
to
/etc/fonts/fonts.conf.d/

does that help?

Comment 2 Rex Dieter 2016-09-11 13:38:16 UTC
Or use one of:
/usr/share/fontconfig/conf.avail/10-sub-pixel-rgb.conf   /usr/share/fontconfig/conf.avail/10-sub-pixel-vrgb.conf
/usr/share/fontconfig/conf.avail/10-sub-pixel-bgr.conf  /usr/share/fontconfig/conf.avail/10-sub-pixel-vbgr.conf

depending on what you want, of course.

Comment 3 Kevin Kofler 2016-09-11 20:30:57 UTC
But why does it work out of the box in Qt 3 and 4 then? Are they the ones not honoring the system defaults?

Comment 4 Fedora End Of Life 2017-07-25 22:58:10 UTC
This message is a reminder that Fedora 24 is nearing its end of life.
Approximately 2 (two) weeks from now Fedora will stop maintaining
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Comment 5 Fedora End Of Life 2017-08-08 17:16:59 UTC
Fedora 24 changed to end-of-life (EOL) status on 2017-08-08. Fedora 24 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

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