[meld/ui-next] chunkmap: Invalidate the pre-drawn cached map on theme change

[Kai Willadsen <kaiw src gnome org>]

commit fd3343cf89aee96bf22df00b68c96fd8ea3ee9ac
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 6 08:39:58 2019 +1000

    chunkmap: Invalidate the pre-drawn cached map on theme change

 meld/chunkmap.py | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meld/chunkmap.py b/meld/chunkmap.py
index a037b88b..14bdc3af 100644
--- a/meld/chunkmap.py
+++ b/meld/chunkmap.py
@@ -109,6 +109,7 @@ class ChunkMap(Gtk.DrawingArea):
     def on_setting_changed(self, meldsettings, key):
         if key == 'style-scheme':
             self.fill_colors, self.line_colors = get_common_theme()
+            self._cached_map = None
 
     def chunk_coords_by_tag(self) -> Mapping[str, List[Tuple[float, float]]]:
         """Map chunks to buffer offsets for drawing, ordered by tag"""