[meld/ui-next] chunkmap: Draw a background with theme colours and update handle

[Kai Willadsen <kaiw src gnome org>]

commit 7d80fe319ecb152ebdf139b42b0a41f156adde07
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Sat Apr 13 09:55:02 2019 +1000

    chunkmap: Draw a background with theme colours and update handle
    
    On most documents with a normal number of changes, it was very easy to
    for a couple of small changes to be hard to see on the map, because we
    didn't draw a background for the widget. This was initially intentional
    because it makes it feel a bit less cluttered, but in this case the
    lack of clutter makes actual changes stand out less.
    
    This changes the drawing so that we add a map background and outline
    based on the GTK+ theme colours. Because it's closely related code, this
    also bases the handle colours on the theme, so we now only have the
    alpha values as properties (and probably don't even need that).
    
    This theme code *won't* do the right thing if the GtkSourceView scheme
    differs massively from the GTK+ theme, but that's a moderately
    questionable thing to support anyway. It would also tie the ChunkMap
    code more closely to sourceview, which I'd prefer not to do if possible.

 meld/chunkmap.py | 64 +++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 54 insertions(+), 10 deletions(-)
---
diff --git a/meld/chunkmap.py b/meld/chunkmap.py
index 4a038872..4f489a82 100644
--- a/meld/chunkmap.py
+++ b/meld/chunkmap.py
@@ -42,16 +42,16 @@ class ChunkMap(Gtk.DrawingArea):
         ),
     )
 
-    handle_overdraw = GObject.Property(
-        type=Gdk.RGBA,
-        nick='Color of the document handle overdraw',
-        default=Gdk.RGBA(0.0, 0.0, 0.0, 0.2)
+    handle_overdraw_alpha = GObject.Property(
+        type=float,
+        nick='Alpha of the document handle overdraw',
+        default=0.2,
     )
 
-    handle_outline = GObject.Property(
-        type=Gdk.RGBA,
-        nick='Color of the document handle outline',
-        default=Gdk.RGBA(0.0, 0.0, 0.0, 0.4)
+    handle_outline_alpha = GObject.Property(
+        type=float,
+        nick='Alpha of the document handle outline',
+        default=0.4,
     )
 
     @GObject.Property(
@@ -107,6 +107,33 @@ class ChunkMap(Gtk.DrawingArea):
     def get_height_scale(self) -> float:
         return 1.0
 
+    def get_map_base_colors(
+            self) -> Tuple[Gdk.RGBA, Gdk.RGBA, Gdk.RGBA, Gdk.RGBA]:
+        raise NotImplementedError()
+
+    def _make_map_base_colors(
+            self, widget) -> Tuple[Gdk.RGBA, Gdk.RGBA, Gdk.RGBA, Gdk.RGBA]:
+        stylecontext = widget.get_style_context()
+        base_set, base = (
+            stylecontext.lookup_color('theme_base_color'))
+        if not base_set:
+            base = Gdk.RGBA(1.0, 1.0, 1.0, 1.0)
+        text_set, text = (
+            stylecontext.lookup_color('theme_text_color'))
+        if not text_set:
+            base = Gdk.RGBA(0.0, 0.0, 0.0, 1.0)
+        border_set, border = (
+            stylecontext.lookup_color('borders'))
+        if not border_set:
+            base = Gdk.RGBA(0.95, 0.95, 0.95, 1.0)
+
+        handle_overdraw = text.copy()
+        handle_overdraw.alpha = self.handle_overdraw_alpha
+        handle_outline = text.copy()
+        handle_outline.alpha = self.handle_outline_alpha
+
+        return base, border, handle_overdraw, handle_outline
+
     def chunk_coords_by_tag(self) -> Mapping[str, List[Tuple[float, float]]]:
         """Map chunks to buffer offsets for drawing, ordered by tag"""
         raise NotImplementedError()
@@ -121,6 +148,9 @@ class ChunkMap(Gtk.DrawingArea):
         if width <= 0 or height <= 0:
             return False
 
+        base_bg, base_outline, handle_overdraw, handle_outline = (
+            self.get_map_base_colors())
+
         x0 = self.overdraw_padding + 0.5
         x1 = width - 2 * x0
         height_scale = height * self.get_height_scale()
@@ -131,6 +161,10 @@ class ChunkMap(Gtk.DrawingArea):
             cache_ctx = cairo.Context(surface)
             cache_ctx.set_line_width(1)
 
+            cache_ctx.rectangle(x0, -0.5, x1, height_scale + 0.5)
+            cache_ctx.set_source_rgba(*base_bg)
+            cache_ctx.fill()
+
             # We get drawing coordinates by tag to minimise our source
             # colour setting, and make this loop slightly cleaner.
             tagged_diffs = self.chunk_coords_by_tag()
@@ -145,6 +179,10 @@ class ChunkMap(Gtk.DrawingArea):
                 cache_ctx.set_source_rgba(*self.line_colors[tag])
                 cache_ctx.stroke()
 
+            cache_ctx.rectangle(x0, -0.5, x1, height_scale + 0.5)
+            cache_ctx.set_source_rgba(*base_outline)
+            cache_ctx.stroke()
+
             self._cached_map = surface
 
         context.set_source_surface(self._cached_map, 0, 0)
@@ -152,7 +190,7 @@ class ChunkMap(Gtk.DrawingArea):
 
         # Draw our scroll position indicator
         context.set_line_width(1)
-        Gdk.cairo_set_source_rgba(context, self.handle_overdraw)
+        context.set_source_rgba(*handle_overdraw)
         adj_y = self.adjustment.get_value() / self.adjustment.get_upper()
         adj_h = self.adjustment.get_page_size() / self.adjustment.get_upper()
         context.rectangle(
@@ -160,7 +198,7 @@ class ChunkMap(Gtk.DrawingArea):
             x1 + 2 * self.overdraw_padding, round(height_scale * adj_h) - 1,
         )
         context.fill_preserve()
-        Gdk.cairo_set_source_rgba(context, self.handle_outline)
+        context.set_source_rgba(*handle_outline)
         context.stroke()
 
         return True
@@ -253,6 +291,9 @@ class TextViewChunkMap(ChunkMap):
         ]
         return self.props.adjustment.get_upper() / max(heights)
 
+    def get_map_base_colors(self):
+        return self._make_map_base_colors(self.textview)
+
     def chunk_coords_by_tag(self):
 
         buf = self.textview.get_buffer()
@@ -344,6 +385,9 @@ class TreeViewChunkMap(ChunkMap):
     def clear_cached_map(self, *args):
         self._cached_map = None
 
+    def get_map_base_colors(self):
+        return self._make_map_base_colors(self.treeview)
+
     def chunk_coords_by_tag(self):
         def recurse_tree_states(rowiter):
             row_states.append(