Too hard to change resource values.

[sjb-sjb]

I'll illustrate this with a specific example, but it is a broad problem.

I tried to change the SizerBaseBackgroundPointerOver brush that is used in the SizerBase control template, and found it to be almost impossible to do.

The only way to do it seems to be to make a copy of the DefaultSizerBaseStyle, rename it and rename the ThemeResources that it uses, such as SizerBaseBackgroundPointerOver. Obviously this is bad from a maintenance point of view.

Notably, it is not sufficient to just merge <ResourceDictionary Source="ms-appx:///CommunityToolkit.WinUI.Controls.Sizers/SizerBase.xaml" /> into your ResourceDictionary and redefine the SizerBaseBackgroundPointerOver brush, even if you then copy in the DefaultSizerBaseStyle -- you have to also change the name of the SizerBaseBackgroundPointerOver brush within that style. It seems that resource resolution is scoped to the dictionary that defines the template (the CommunityToolkit dictionary), not to the dictionary where the style is redefined.

There really should be an easier way to do it. It is very surprising that one cannot change the default colors or other style constants anywhere in the Toolkit!

[lgztx96]

If you only want to override the brush value, copying DefaultSizerBaseStyle may not be necessary.

For example, overriding the resource locally on the control works:

<Grid>
    <!-- This also works if placed in Grid.Resources -->
    <!--<Grid.Resources>
        <StaticResource x:Key="SizerBaseBackgroundPointerOver"
                        ResourceKey="AccentAAFillColorDefaultBrush" />
    </Grid.Resources>-->
    
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>

    <controls:GridSplitter HorizontalAlignment="Right">
        <controls:GridSplitter.Resources>
            <StaticResource x:Key="SizerBaseBackgroundPointerOver"
                            ResourceKey="AccentAAFillColorDefaultBrush" />
        </controls:GridSplitter.Resources>
    </controls:GridSplitter>
</Grid>

In my testing, this correctly overrides SizerBaseBackgroundPointerOver without copying the default style or renaming any resource keys.

[sjb-sjb]

@lgztx96 I like this, but what I am trying to do is define a style that applies the color, rather than have to do this on each instance of the control. Any suggestions for that?

@olga-io-92 I think that what you suggest is what @lgztx96 demonstrates, correct?

[darlcydney26]

It seems like the scoping issue with resource resolution in the SizerBase template is indeed a significant hurdle. Have you considered using a custom style selector that targets the SizerBase control specifically? This way, you can define a style that sets the SizerBaseBackgroundPointerOver brush while keeping the rest of the default styles intact. Implementing a new style in your application resources with a higher precedence could allow for more flexibility without duplicating the entire DefaultSizerBaseStyle.

[chalynseattle]

Have you checked if overriding the DefaultSizerBaseStyle directly in your application's ResourceDictionary, while ensuring that your new brush definition for SizerBaseBackgroundPointerOver is defined before the style application, resolves the scoping issue?

[sjb-sjb]

@darlcydney26 I don't really understand what you are describing, can you show an example?

@chalynseattle Would that mean redefining the DefaultSizerBaseStyle in my resource dictionary? If so then that's what I'm trying to avoid.