Description

When using a BitmapCacheBrush whose Target is a ProgressBar with Indeterminate="True", the rendered control does not animate.

Reproduction Steps

Create a new WPF project that targets either .NET 7 (net7.0-windows) or .NET 8 (net8.0-windows).

Add the following code to MainWindow.xaml:

<Window x:Class="BlankWpf.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:BlankWpf"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Window.Resources>
        <ProgressBar x:Key="CachedProgressBar" Width="200" Height="10" IsIndeterminate="True" >
            <ProgressBar.CacheMode>
                <BitmapCache SnapsToDevicePixels="True" />
            </ProgressBar.CacheMode>
        </ProgressBar>

        <BitmapCacheBrush x:Key="CachedProgressBarBrush" Target="{StaticResource CachedProgressBar}" />
    </Window.Resources>

    <Grid>
        <Rectangle Fill="{StaticResource CachedProgressBarBrush}" Width="200" Height="10" />
    </Grid>
</Window>

Run the application.

Expected behavior

An animated, indeterminate progress bar should be rendered. This is the behavior on .NET 6.

Actual behavior

A static, completely filled progress bar is rendered:

Regression?

This is a regression; it used to work in .NET 6.

Known Workarounds

Instead of using a BitmapCacheBrush, you can use a VisualBrush and assign its Visual property to the progress bar (instead of the BitmapCacheBrush.Target property). This fixes the UI, but obviously is less ideal than using a BitmapCacheBrush.

Impact

My application uses many progress bars that we synchronize and reduce their overhead with by using the bitmap cache. This bug breaks all of those bars.

Configuration

No response

Other information

No response