D26185: Fix font rendering when compiled against Qt >= 5.14

[Andrew Cooligan]

acooligan added a comment.


  I think you may leave ifdef here but set:
  
    qputenv("QT_ENABLE_HIGHDPI_SCALING", "0");
  
  if it's false as `QT_AUTO_SCREEN_SCALE_FACTOR` is deprecated since qt 5.14.
  
  In D26185#582742 <https://phabricator.kde.org/D26185#582742>, @davidedmundson wrote:
  
  > After 900f2cb6f7070 in QtBase auto dpi changed it's meaning somewhat. The comment written no longer applies and #ifdef'ing is the correct thing to get the consistent behaviour.
  >
  > With QT_AUTO_SCREEN_SCALE_FACTOR=0 set, we no longer scale the logical DPI by the screen scale factor which is something we need to deliver high DPI correctly. 
  >  i.e on a low res screen with a physical of 96, running QT_SCREEN_SCALE_FACTORS=2 should double the fonts. This patch breaks that which means we've broken the config UI.
  
  
  On my system, when `QT_AUTO_SCREEN_SCALE_FACTOR/QT_ENABLE_HIGHDPI_SCALING` isn't disabled and both display scaling & font dpi scaling is enabled it results in double scaling - all qt apps are unproportionately huge which **makes ui broken without this patch**.

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D26185

To: ahartmetz, #plasma, apol, davidedmundson
Cc: acooligan, fvogt, asturmlechner, dfaure, davidedmundson, anthonyfieroni, plasma-devel, LeGast00n, The-Feren-OS-Dev, jraleigh, zachus, fbampaloukas, GB_2, ragreen, ZrenBot, ngraham, alexeymin, himcesjf, lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, ahiemstra, mart
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.kde.org/pipermail/plasma-devel/attachments/20200111/277664cb/attachment-0001.html>