Expose the glyph background color as a dynamic resource

Rather than setting the glyph background color directly, expose it as a dynamic resource with the key `DiffChangeBackground`.

Author: jcansdale

src/GitHub.InlineReviews/Tags/AddInlineCommentGlyph.xaml

@@ -4,8 +4,14 @@
              xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
              mc:Ignorable="d">
-    <Viewbox x:Name="AddViewbox">
-        <Path Stroke="Black"
+    <UserControl.Resources>
+        <SolidColorBrush x:Key="DiffChangeBackground" Color="DarkSlateGray" />
+    </UserControl.Resources>
+
+    <Grid Background="{DynamicResource DiffChangeBackground}">
+        <Viewbox x:Name="AddViewbox">
+            <Path Stroke="Black"
           Data="M13 2H1c-0.55 0-1 0.45-1 1v8c0 0.55 0.45 1 1 1h2v3.5l3.5-3.5h6.5c0.55 0 1-0.45 1-1V3c0-0.55-0.45-1-1-1z m0 9H6L4 13V11H1V3h12v8z M7,5 L7,9 M5,7 L9,7"/>
-    </Viewbox>
+        </Viewbox>
+    </Grid>
 </UserControl>

src/GitHub.InlineReviews/Tags/InlineCommentGlyphFactory.cs

@@ -76,7 +76,7 @@ public UIElement GenerateGlyph(IWpfTextViewLine line, InlineCommentTag tag)
                 if (OpenThreadView(tag)) e.Handled = true;
             };
 
-            glyph.Background = brushesManager.GetBackground(tag.DiffChangeType);
+            glyph.Resources["DiffChangeBackground"] = brushesManager.GetBackground(tag.DiffChangeType);
             return glyph;
         }
 

src/GitHub.InlineReviews/Tags/ShowInlineCommentGlyph.xaml

@@ -5,11 +5,20 @@
              xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
              mc:Ignorable="d"
              ToolTipService.ShowDuration="600000" ToolTipService.HasDropShadow="True">
+
+    <UserControl.Resources>
+        <!-- This will be the color of an added/deleted word in the diff view or the indicator margin color -->
+        <SolidColorBrush x:Key="DiffChangeBackground" Color="DarkSlateGray" />
+    </UserControl.Resources>
+
     <UserControl.ToolTip>
         <ToolTip x:Name="CommentToolTip" />
     </UserControl.ToolTip>
-    <Viewbox>
-        <Path Stroke="Black"
+
+    <Grid Background="{DynamicResource DiffChangeBackground}">
+        <Viewbox>
+            <Path Stroke="Black"
           Data="M13 2H1c-0.55 0-1 0.45-1 1v8c0 0.55 0.45 1 1 1h2v3.5l3.5-3.5h6.5c0.55 0 1-0.45 1-1V3c0-0.55-0.45-1-1-1z m0 9H6L4 13V11H1V3h12v8z"/>
-    </Viewbox>
+        </Viewbox>
+    </Grid>
 </UserControl>