feat(ui): add splitter to resize caption panes

Both caption rows now share available height equally by default, and a
GridSplitter between them lets the user drag the boundary, e.g. to give
the original caption several lines. Previously the original caption row
was always sized to content (effectively one line) and only the
translated row could grow.

The splitter is hidden when caption log cards are enabled, where rows
are content-sized.

Author: jrkasprzyk

src/pages/CaptionPage.xaml

@@ -13,6 +13,7 @@
     <Grid Margin="5,5,15,5">
         <Grid.RowDefinitions>
             <RowDefinition x:Name="OriginalCaption_Row" Height="Auto" />
+            <RowDefinition Height="Auto" />
             <RowDefinition x:Name="TranslatedCaption_Row" Height="Auto" />
             <RowDefinition x:Name="CaptionLogCard_Row" Height="Auto" />
         </Grid.RowDefinitions>
@@ -38,10 +39,20 @@
                 ToolTip="Click To Copy" />
         </ui:Card>
 
-        <ui:Card
+        <GridSplitter
+            x:Name="CaptionSplitter"
             Grid.Row="1"
+            Height="6"
+            HorizontalAlignment="Stretch"
+            Background="Transparent"
+            Cursor="SizeNS"
+            ResizeBehavior="PreviousAndNext"
+            ResizeDirection="Rows"
+            ToolTip="Drag to Resize" />
+
+        <ui:Card
+            Grid.Row="2"
             MinHeight="43"
-            Margin="0,3,0,0"
             Padding="8"
             VerticalAlignment="Stretch">
             <TextBlock
@@ -57,7 +68,7 @@
 
         <ui:Card
             x:Name="LogCards"
-            Grid.Row="2"
+            Grid.Row="3"
             Margin="0,0,0,5"
             Padding="8"
             VerticalAlignment="Top"

src/pages/CaptionPage.xaml.cs

@@ -80,12 +80,16 @@ public void CollapseTranslatedCaption(bool isCollapsed)
 
             if (isCollapsed)
             {
+                OriginalCaption_Row.Height = (GridLength)converter.ConvertFromString("Auto");
                 TranslatedCaption_Row.Height = (GridLength)converter.ConvertFromString("Auto");
+                CaptionSplitter.Visibility = Visibility.Collapsed;
                 LogCards.Visibility = Visibility.Visible;
             }
             else
             {
+                OriginalCaption_Row.Height = (GridLength)converter.ConvertFromString("*");
                 TranslatedCaption_Row.Height = (GridLength)converter.ConvertFromString("*");
+                CaptionSplitter.Visibility = Visibility.Visible;
                 LogCards.Visibility = Visibility.Collapsed;
             }
         }