bugGNU Octave - Bugs: bug #37187, fix font width subpixel rendering...

 
 

bug #37187: fix font width subpixel rendering in the GUI command window

Submitted by:  Mike Miller <mtmiller>
Submitted on:  Sat 25 Aug 2012 12:04:28 AM UTC  
 
Category: GUISeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: FixedAssigned to: None
Originator Name: Open/Closed: Closed
Release: devOperating System: GNU/Linux

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Sat 19 Apr 2014 04:04:26 PM UTC, comment #5:

Looks good to me, compared against 3.8.1 and against gui-release (which does not have this merged yet).

Mike Miller <mtmiller>
Project Member
Fri 18 Apr 2014 12:42:19 PM UTC, comment #4:

I have pushed the fix from Konsole with changeset
http://hg.savannah.gnu.org/hgweb/octave/rev/5fb180e37d7c

Torsten <ttl>
Project Member
Wed 26 Mar 2014 09:16:18 PM UTC, comment #3:

http://quickgit.kde.org/?p=konsole.git&a=commitdiff&h=de5ef9484a253795002d0e6accc86cc3cb1b5c71

Michael Goffioul <goffioul>
Project Member
Wed 26 Mar 2014 09:11:04 PM UTC, comment #2:

Was anything ever done about this problem? The link to the KDE patch doesn't work now. Does anyone know where to find that change?

I agree with ttl that we should implement the first solution now and fix the sub-pixel rendering problem later.

John W. Eaton <jwe>
Project Administrator
Sun 03 Feb 2013 12:33:07 PM UTC, comment #1:

I suggest to implement solution 1 for now but leaving the bug open (maybe with reduced severity).

Torsten <ttl>
Project Member
Sat 25 Aug 2012 12:04:28 AM UTC, original submission:

As discussed at length in this thread

https://mailman.cae.wisc.edu/pipermail/octave-maintainers/2012-July/029014.html

the rendering for fixed width fonts in the GUI command window is still not correct. I can submit screenshots for reference if requested. To reproduce this, one must be using Qt on a system with a font rendering engine that has subpixel rendering (SPR) enabled. In my case, Qt is using the FreeType library with SPR enabled, which is the default for Debian and Ubuntu systems, but not Fedora or Red Hat. With SPR, a character can have a width that is a non-integer number of pixels.

A fix was made to qterminal for this problem

https://code.google.com/p/qterminal/source/detail?r=f91e00f96bc29f7f6395f08c828e09599f945511

but this change only reduces the effect so that it is not cumulative over long strings of characters, now only one character at a time is offset by some fraction of the character width. The larger the font size, the larger the offset.

I can see two possible solutions:

1. Tell Qt to force integer metrics and ignore SPR even if available. This is the approach taken by Konsole, the project that qterminal is derived from. The patch applied to Konsole is shown here:

https://projects.kde.org/projects/kde/kde-baseapps/konsole/repository/revisions/de5ef9484a253795002d0e6accc86cc3cb1b5c71/diff

2. Fix qterminal to compute font and cursor widths and offsets in floating point, which has already started, so there is no round-off error.

With the first solution, this can be fixed immediately. Pursuing the second solution will take time and more investigation, require more floating point arithmetic to be done in the GUI, but will result in improved appearance on systems that support subpixel rendering.

Mike Miller <mtmiller>
Project Member

 

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  • -unavailable- added by goffioul (Posted a comment)
  • -unavailable- added by jwe (Posted a comment)
  • -unavailable- added by ttl (Posted a comment)
  • -unavailable- added by mtmiller (Submitted the item)
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    Follow 2 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sat 19 Apr 2014 04:04:26 PM UTCmtmillerStatusNone=>Fixed
      Open/ClosedOpen=>Closed

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