RadialGradientBrush doesn't respond to the change of ThemeResource.

[Berrysoft]

I'm submitting a bug of RadialGradientBrush

I set the Color of the GradientStop of a RadialGradientBrush to a ThemeResource color like SystemAccentColor.

Current behavior

The color doesn't change after I change the system accent color.

Expected behavior

It should change correctly just like LinearGradientBrush.

Minimal reproduction of the problem with instructions

<Page
    x:Class="RadialGradientBrushTest.MainPage"
    ...
    xmlns:media="using:Microsoft.Toolkit.Uwp.UI.Media"
    ...>
    <Page.Resources>
        <media:RadialGradientBrush x:Key="MyRadialGradientBrush">
            <GradientStop Offset="0" Color="{ThemeResource SystemAccentColorLight3}"/>
            <GradientStop Offset="1" Color="{ThemeResource SystemAccentColorDark3}"/>
        </media:RadialGradientBrush>
        <LinearGradientBrush x:Key="MyLinearGradientBrush">
            <GradientStop Offset="0" Color="{ThemeResource SystemAccentColorLight3}"/>
            <GradientStop Offset="1" Color="{ThemeResource SystemAccentColorDark3}"/>
        </LinearGradientBrush>
    </Page.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Ellipse Grid.Column="0" Grid.Row="0" Width="400" Height="400" Fill="{StaticResource MyRadialGradientBrush}"/>
        <Rectangle Grid.Column="1" Grid.Row="0" Width="400" Height="400" Fill="{StaticResource MyLinearGradientBrush}"/>
        <TextBlock Grid.Column="0" Grid.Row="1" Style="{ThemeResource TitleTextBlockStyle}" HorizontalAlignment="Center">RadialGradientBrush</TextBlock>
        <TextBlock Grid.Column="1" Grid.Row="1" Style="{ThemeResource TitleTextBlockStyle}" HorizontalAlignment="Center">LinearGradientBrush</TextBlock>
    </Grid>
</Page>

Run the app and change the system accent color. The rectangle changes correctly while the ellipse doesn't.

Environment

Nuget Package(s): 
Microsoft.Toolkit.Uwp.UI
Package Version(s): 
v5.0.0
Windows 10 Build Number:
- [ ] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [x] October 2018 Update (17763)
- [ ] Insider Build (build number: )

App min and target version:
- [x] Fall Creators Update (16299)
- [ ] April 2018 Update (17134)
- [ ] October 2018 Update (17763)
- [ ] Insider Build (xxxxx)

Device form factor:
- [x] Desktop
- [ ] Mobile
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [ ] 2017 (version: )
- [ ] 2017 Preview (version: )
- [x] 2019 Preview 1.1

[windowstoolkitbot]

No response from the community. ping @nmetulev @Odonno @IbraheemOsama

[windowstoolkitbot]

This issue seems inactive. It will automatically be closed in 14 days if there is no activity.

[Berrysoft]

So maybe I should say something to keep it active?

[windowstoolkitbot]

This issue seems inactive. It will automatically be closed in 14 days if there is no activity.

[michael-hawker]

@Berrysoft the RadialGradientBrush has been added to the most recent release of WinUI. Can you check their implementation out, I believe it should handle these scenarios. If not, can you open an issue on their repo. Thanks!