[meld] gutterrendererchunk: Use built-in background drawing support

[Kai Willadsen <kaiw src gnome org>]

commit af5ad58a6787c01fe8f96cae6bf61ab989af5d47
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sun Sep 25 10:29:42 2016 +1000

    gutterrendererchunk: Use built-in background drawing support
    
    This is good for a ~3x performance improvement when drawing chunk
    backgrounds, just because we don't have to individually draw the
    background for each gutter line with nothing going on.

 meld/gutterrendererchunk.py |   18 ++++++++----------
 1 files changed, 8 insertions(+), 10 deletions(-)
---
diff --git a/meld/gutterrendererchunk.py b/meld/gutterrendererchunk.py
index a8b961f..4ba672b 100644
--- a/meld/gutterrendererchunk.py
+++ b/meld/gutterrendererchunk.py
@@ -45,22 +45,12 @@ class MeldGutterRenderer(object):
     def draw_chunks(
             self, context, background_area, cell_area, start, end, state):
 
-        stylecontext = self.props.view.get_style_context()
-        background_set, background_rgba = (
-            stylecontext.lookup_color('theme_bg_color'))
-
         line = start.get_line()
         chunk_index = self.linediffer.locate_chunk(self.from_pane, line)[0]
 
         context.save()
         context.set_line_width(1.0)
 
-        context.rectangle(
-            background_area.x, background_area.y,
-            background_area.width, background_area.height)
-        context.set_source_rgba(*background_rgba)
-        context.fill()
-
         if chunk_index is not None:
             chunk = self.linediffer.get_chunk(
                 chunk_index, self.from_pane, self.to_pane)
@@ -201,6 +191,14 @@ class GutterRendererChunkAction(
             if chunk and chunk[1] == line:
                 action = self._classify_change_actions(chunk)
                 pixbuf = self.action_map.get(action)
+            self.set_background(None)
+        else:
+            # TODO: Remove when fixed in upstream GTK+
+            stylecontext = self.props.view.get_style_context()
+            background_set, background_rgba = (
+                stylecontext.lookup_color('theme_bg_color'))
+            self.set_background(background_rgba)
+
         if pixbuf:
             self.set_pixbuf(pixbuf)
         else: