desktop-packages team mailing list archive

[Fumihito YOSHIDA <hito@xxxxxxxxxxx>]

** Attachment added: "expected result of font rendering."
   https://bugs.launchpad.net/ubuntu/+source/language-selector/+bug/884645/+attachment/2581421/+files/expected-qt.png

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https://bugs.launchpad.net/bugs/884645

Title:
  Improvement for ja-jp conf (69-language-selector-ja-jp.conf): measure
  for ttf-unfonts-core side-effects

Status in “language-selector” package in Ubuntu:
  New

Bug description:
  Improvement for ja-jp conf(69-language-selector-ja-jp.conf),

  Dear language-support/selector maintainers,

  [Problem description]
  In Japanese language environments, ttf-unfonts-core breaks Qt apps/web browsers font selection. 

  - If  ttf-unfonts-core is installed, their application will neglect the 69-language-selector-ja-jp.conf. 
  - 'ttf-unfonts-core' is installed by task dependency(ubuntu-desktop,kubuntu-desktop,xubuntu-desktop and so on).

  Root problem is fontconfig or Unicode specification("CJK overlapping"), but fontconfig-configuration could mitigate that.
  So, 69-language-selector-ja-jp.conf patch is here.

  [Background]
  ttf-unfonts-core package's fontconfig has higher priority than 69-language-selector-ja-jp.conf's, but that is not root-problem. By historical reason, unicode specification has overlapped CJK range, but 69-language-selector-ja-jp is not robust for CJK overlapping.  So, CJK fontconfig is nonpredictable minefield, any CJK related configuration has potential risk like that. ttf-unfonts-core is not guilty.

  Mechanism:
  1) 69-(snip)-ja-jp.conf is constrained by { <test name="lang" compare="contains"><string>ja</string></test> } COND. That COND limit the CJK settings. That mean: "this font use for CJK at lang=ja is provided".

  2) ttf-unfonts-core(and some font packages, microhei may include) has
  not these COND, this configuration mean "this font use  for CJK at
  anytime".

  3) Qt apps are not use lang contains (Notes: That contains are
  optional, not Qt bug).

  These configuration mean: "In Qt apps(and any apps with similar
  implementation), you have to use ttf-unfonts-core".

  So, our measures are:

  a) Fix Qt and any others : Unrealistic...

  b) Fix ttf-unfonts-core and any others : Unrealistic, better than a).

  c) Fix 69-language-selector-ja-jp.conf : Reasonable.

  Yes, c) is not fundamental solution, real solution is fontconfig
  refactoring. But that is too difficult to fix:(

  And,
  - This approach had included at many CJK settings, that COND use at only ja-jp. 
  - This fix is widely well-tested. In "Ubuntu Japanese Remix 11.10"(released at Oct 16) include the lang-deleted config, and not reported any side-effects.

  <test name="lang">.. COND deletion is only extrication at the moment.

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