[RegistryPreview]Better theme support for caption bar (#25535)

src/modules/registrypreview/RegistryPreviewUI/App.xaml

@@ -9,6 +9,9 @@
                 <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                 <!-- Other merged dictionaries here -->
             </ResourceDictionary.MergedDictionaries>
+            <!-- Need to set these to transparent to allow the custom title bar to be its real color -->
+            <SolidColorBrush x:Key="WindowCaptionBackground">Transparent</SolidColorBrush>
+            <SolidColorBrush x:Key="WindowCaptionBackgroundDisabled">Transparent</SolidColorBrush>
             <!-- Other app resources here -->
         </ResourceDictionary>
     </Application.Resources>

src/modules/registrypreview/RegistryPreviewUI/MainWindow.Utilities.cs

@@ -513,12 +513,15 @@ namespace RegistryPreview
             string[] file = filename.Split('\\');
             if (file.Length > 0)
             {
-                appWindow.Title = file[file.Length - 1] + " - " + APPNAME;
+                titleBarText.Text = file[file.Length - 1] + " - " + APPNAME;
             }
             else
             {
-                appWindow.Title = filename + " - " + APPNAME;
+                titleBarText.Text = filename + " - " + APPNAME;
             }
+
+            // Continue to update the window's title, after updating the custom title bar
+            appWindow.Title = titleBarText.Text;
         }
 
         /// <summary>
@@ -526,6 +529,7 @@ namespace RegistryPreview
         /// </summary>
         private void UpdateWindowTitle()
         {
+            titleBarText.Text = APPNAME;
             appWindow.Title = APPNAME;
         }
 

src/modules/registrypreview/RegistryPreviewUI/MainWindow.xaml

@@ -11,7 +11,31 @@
     <winuiex:WindowEx.Backdrop>
         <winuiex:MicaSystemBackdrop />
     </winuiex:WindowEx.Backdrop>
+    <Grid>
+        <Grid.RowDefinitions>
+            <RowDefinition Height="32" />
+            <RowDefinition Height="*" />
+        </Grid.RowDefinitions>
         <Grid 
+            x:Name="titleBar" 
+            Grid.Row="0"
+            IsHitTestVisible="True">
+            <StackPanel
+                Margin="8,8,8,8"
+                VerticalAlignment="Bottom"
+                Orientation="Horizontal">
+                <Image Source="app.ico"/>
+                <TextBlock
+                    x:Name="titleBarText"
+                    Margin="8,0,0,0"
+                    FontSize="12"
+                    Style="{StaticResource CaptionTextBlockStyle}"
+                    Text="{Binding ApplicationTitle}" />
+            </StackPanel>
+        </Grid>
+
+        <Grid
+            Grid.Row="1"
             x:Name="gridPreview"
             Width="Auto"
             Height="Auto"
@@ -45,7 +69,7 @@
                 Grid.Row="0"
                 Grid.Column="0"
                 Grid.ColumnSpan="3"
-            Margin="8,8,8,8"
+                Margin="8,0,8,8"
                 CornerRadius="{StaticResource OverlayCornerRadius}"
                 Style="{StaticResource GridCardStyle}">
                 <CommandBar
@@ -320,4 +344,5 @@
                 GripperCursor="SizeNorthSouth"
                 IsTabStop="False" />
         </Grid>
+    </Grid>
 </winuiex:WindowEx>

src/modules/registrypreview/RegistryPreviewUI/MainWindow.xaml.cs

@@ -6,7 +6,6 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using Microsoft.UI;
-using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using Windows.ApplicationModel.Resources;
 using Windows.Data.Json;
@@ -54,6 +53,10 @@ namespace RegistryPreview
             appWindow.SetIcon("app.ico");
             appWindow.Closing += AppWindow_Closing;
 
+            // Extend the canvas to include the title bar so the app can support theming
+            ExtendsContentIntoTitleBar = true;
+            SetTitleBar(titleBar);
+
             // if have settings, update the location of the window
             if (jsonSettings != null)
             {

src/modules/registrypreview/RegistryPreviewUI/Strings/en-US/Resources.resw

@@ -189,6 +189,9 @@
   <data name="textBox.PlaceholderText" xml:space="preserve">
     <value>Registry file text will appear here...</value>
   </data>
+  <data name="titleBarText.ApplicationTitle" xml:space="preserve">
+    <value>Registry Preview</value>
+  </data>
   <data name="ToolTipAddedKey" xml:space="preserve">
     <value>Key will be added, if needed</value>
   </data>