Uno.XamlMerge.Task 0.1.0-dev.44

Uno.XamlMerge.Task

An msbuild task which enables the merging of WinUI XAML resource dictionaries into a single flat ResourceDictionary.

This code is derived from WinUI's BatchMergeXaml class, to be reused in any WinUI and Uno Platform Controls library.

Why merge ResourceDictionary instances ?

This task is generally used to allow for separate resource dictionary authoring (which makes them easier to load and read) to avoid impacting resources lookup runtime performance. In WinUI, ResourceDictionary resolution is performed through a graph traversal of MergedDictionaries, which generally implies that a worse case resolution can require as many lookups as there are dictionaries.

To limit the impact of the traversal, this task task takes all resource dictionaries found in a specific MSBuild item group, and merges them into a single file. This file is then generally either named Themes\Generic.xaml or referenced as a merged dictionary from another Themes\Generic.xaml file.

Using the task

Include the following block:

<PropertyGroup>
    <_Uno_XamlMerge_Task_Version></_Uno_XamlMerge_Task_Version>
</PropertyGroup>
<ItemGroup>
    <PackageReference Include="Uno.XamlMerge.Task" Version="$(_Uno_XamlMerge_Task_Version)" />
</ItemGroup>

Then select the resource dictionaries to be merged:

<ItemGroup>
    <XamlMergeInput Include="Styles\**\*.xaml" />
</ItemGroup>

Then add the following block at the end your project library:

<Import Project="$(NuGetPackageRoot)uno.xamlmerge.task\$(_Uno_XamlMerge_Task_Version)\build\Uno.XamlMerge.Task.targets"
        Condition="'$(TargetFramework)' == ''" />

The generated file is called Generated\mergedpages.xaml by default, but can be overriden as follows:

<PropertyGroup>
    <XamlMergeOutputFile>Themes\Generic.xaml</XamlMergeOutputFile>
</PropertyGroup>

Otherwise, the generated file can be referenced as follows:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:TestLibrary">

	<ResourceDictionary.MergedDictionaries>
		<ResourceDictionary Source="ms-appx:///REPLACE_ME/Generated/mergedpages.xaml" />
	</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>