[meld/windows-font-fixes: 2/2] Default Pango backend to fontconfig on Windows (#445, #453)

[Kai Willadsen <kaiw src gnome org>]

commit 02afad4918b7d8c98ac157bbf3fa258d64fe890b
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 25 08:55:22 2020 +1000

    Default Pango backend to fontconfig on Windows (#445, #453)
    
    The Pango win32 font backend has some long-standing issues with fallback
    fonts (#445) and also has a current problem with line heights for empty
    lines (#453). While there have been problems in the past with fontconfig
    on Windows, it looks like it's currently a better option for us.
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=785313 for an old bug
    related to slowness with fontconfig. The fix there was to switch to the
    native win32 fonts backend, but since that has issues, we're explicitly
    switching the other direction for the moment.
    
    This uses the environment variable method of switching backends rather
    than manually setting the font map, partially for ease and partially
    because it's something the user can then manually override.

 bin/meld | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/bin/meld b/bin/meld
index e193367d..1c769000 100755
--- a/bin/meld
+++ b/bin/meld
@@ -434,6 +434,10 @@ def environment_hacks():
         except KeyError:
             pass
 
+    # Force the fontconfig backend for font fallback and metric handling
+    if sys.platform == 'win32' and 'PANGOCAIRO_BACKEND' not in os.environ:
+        os.environ['PANGOCAIRO_BACKEND'] = 'fontconfig'
+
 
 def run_application():
     from meld.meldapp import MeldApp