fix: remove nav bar back icon, use symbol/path for non-win/non-mobile

doc/controls/NavigationBar.md

@@ -307,6 +307,10 @@ If no `MainCommand` is provided in the XAML, the `NavigationBar` will render the
 
 On **Android**, only icons are supported (`AppBarButton.Icon`). This is due to a platform limitation, which can be explained by the fact that `NavigationBar.Content` is left-aligned.
 
+> [!WARNING]
+> Due to [platform limitations](https://github.com/microsoft/microsoft-ui-xaml/issues/1494) on Windows only, a default back button icon is not provided out of the box. You will need to provide your own icon on each instance of the `NavigationBar` where you want to display a back button. On Android and iOS, the native default back button icon is used. On all other platforms, a back button icon is bundled in the default styles for the `NavigationBar`.
+
+
 ### MainCommand Properties
 
 ### Label
@@ -390,7 +394,7 @@ Gets or sets the back button icon for the `MainCommand`.
 
 Remarks:
 
-Only supports `BitmapImage`
+Only supports `BitmapImage` on iOS/Android
 
 ## Lightweight Styling
 

src/Uno.Toolkit.UI/Controls/NavigationBar/NavigationBar.xaml

@@ -13,11 +13,12 @@
 					xmlns:ios="http://uno.ui/ios"
 					xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
 					xmlns:mobile="http://uno.ui/mobile"
+					xmlns:not_win="http://uno.ui/not_win"
 					xmlns:not_mobile="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 					xmlns:toolkit="using:Uno.UI.Toolkit"
 					xmlns:utu="using:Uno.Toolkit.UI"
 					xmlns:win="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-					mc:Ignorable="android ios mobile">
+					mc:Ignorable="android ios mobile not_win">
 
 	<ResourceDictionary.ThemeDictionaries>
 		<ResourceDictionary x:Key="Default">
@@ -40,10 +41,11 @@
 
 	<Style x:Key="DefaultMainCommandStyle"
 		   TargetType="AppBarButton">
-		<not_mobile:Setter Property="Icon">
-			<not_mobile:Setter.Value>
-				<BitmapIcon UriSource="{StaticResource BackButtonUriSource}" />
-			</not_mobile:Setter.Value>
+		<!-- Native back icons are used on mobile platforms -->
+		<not_mobile:Setter Property="Icon" win:Value="{x:Null}">
+			<not_win:Setter.Value>
+				<SymbolIcon Symbol="Back" />
+			</not_win:Setter.Value>
 		</not_mobile:Setter>
 	</Style>
 

src/Uno.Toolkit.UI/Uno.Toolkit.UI.csproj

@@ -48,7 +48,6 @@
 
 	<ItemGroup>
 		<UpToDateCheckInput Include="**\*.xaml" Exclude="bin\**\*.xaml;obj\**\*.xaml" />
-		<Content Include="Assets\**\*.png" />
 	</ItemGroup>
 
 	<ItemGroup>

src/Uno.Toolkit.UI/xamlmerge-toolkit.props

@@ -6,7 +6,6 @@
 	<ItemGroup>
 		<XamlMergeInput Include="Controls\**\*.xaml" />
 		<XamlMergeInput Include="Behaviors\**\*.xaml" />
-		<XamlMergeInput Include="Resources\AssetCatalog.$(FrameworkLineage).xaml" />
 	</ItemGroup>
 
 	<Import Project="..\xamlmerge.props" />

src/library/Uno.Toolkit.Material/Styles/Controls/v2/NavigationBar.xaml

@@ -18,6 +18,7 @@
 					xmlns:toolkit="using:Uno.UI.Toolkit"
 					xmlns:um="using:Uno.Material"
 					xmlns:utu="using:Uno.Toolkit.UI"
+					xmlns:win="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 					mc:Ignorable="android ios not_win mobile">
 
 	<ResourceDictionary.ThemeDictionaries>
@@ -81,6 +82,7 @@
 			<x:Double x:Key="NavBarAppBarThemeCompactHeight">56</x:Double>
 			<Thickness x:Key="NavBarAppBarButtonPadding">12,16,12,16</Thickness>
 			<Visibility x:Key="NavBarAppBarButtonHasFlyoutChevronVisibility">Collapsed</Visibility>
+			<x:String x:Key="NavigationBarBackIconData">M20 11H7.83L13.42 5.41L12 4L4 12L12 20L13.41 18.59L7.83 13H20V11Z</x:String>
 		</ResourceDictionary>
 		<ResourceDictionary x:Key="Light">
 			<StaticResource x:Key="NavigationBarCommandBarEllipsisIconForegroundDisabled" ResourceKey="CommandBarEllipsisIconForegroundDisabled" />
@@ -137,6 +139,7 @@
 			<x:Double x:Key="NavBarAppBarThemeCompactHeight">56</x:Double>
 			<Thickness x:Key="NavBarAppBarButtonPadding">12,16,12,16</Thickness>
 			<Visibility x:Key="NavBarAppBarButtonHasFlyoutChevronVisibility">Collapsed</Visibility>
+			<x:String x:Key="NavigationBarBackIconData">M20 11H7.83L13.42 5.41L12 4L4 12L12 20L13.41 18.59L7.83 13H20V11Z</x:String>
 		</ResourceDictionary>
 	</ResourceDictionary.ThemeDictionaries>
 
@@ -178,10 +181,11 @@
 		   BasedOn="{StaticResource MaterialAppBarButtonStyle}"
 		   TargetType="AppBarButton">
 		<Setter Property="Foreground" Value="{ThemeResource NavigationBarMainCommandForeground}" />
-		<not_mobile:Setter Property="Icon">
-			<not_mobile:Setter.Value>
-				<BitmapIcon UriSource="{StaticResource MaterialBackButtonUriSource}" />
-			</not_mobile:Setter.Value>
+		<!-- Native back icons are used on mobile platforms -->
+		<not_mobile:Setter Property="Icon" win:Value="{x:Null}">
+			<not_win:Setter.Value>
+				<PathIcon Data="{ThemeResource NavigationBarBackIconData}" />
+			</not_win:Setter.Value>
 		</not_mobile:Setter>
 	</Style>
 

src/library/Uno.Toolkit.Material/Uno.Toolkit.UI.Material.csproj

@@ -30,7 +30,6 @@
 
 	<ItemGroup>
 		<UpToDateCheckInput Include="**\*.xaml" Exclude="bin\**\*.xaml;obj\**\*.xaml" />
-		<Content Include="Assets\**\*.png" />
 	</ItemGroup>
 
 	<ItemGroup Condition="$(IsXamarinIOS) or $(IsMonoAndroid) or $(IsXamarinMac)">

src/library/Uno.Toolkit.Material/xamlmerge-material.props

@@ -6,7 +6,6 @@
 
 		<XamlMergeInput Include="Styles\Controls\v1\**\*.xaml" MergeFile="mergedpages.$(FrameworkLineage).v1.xaml" />
 		<XamlMergeInput Include="Styles\Controls\v2\**\*.xaml" MergeFile="mergedpages.$(FrameworkLineage).v2.xaml" />
-		<XamlMergeInput Include="Resources\AssetCatalog.$(FrameworkLineage).xaml" MergeFile="mergedpages.$(FrameworkLineage).v2.xaml" />
 	</ItemGroup>
 	<Import Project="..\..\xamlmerge.props" />
 </Project>