WP7 ScrollViewer Bug When Content Height > 2000px

Question

In my project, I use ScrollViewer to show some long height infomation.

I use like this:

Answer 1

If it just a text, you could use this custom control: scrollable textblock. Otherwise, divide your content into blocks with size < 2048.

UPD:

2048px is a limit for GPU cached graphics. You can use a lot of controls (< 2048) inside a scrollviewer (total > 2048). In some cases all is fine, but in some it doesn't

For example:

<ScrollViewer Background="#4FFF6060">
    <Grid Background="#FFFF8A8A" Width="240" HorizontalAlignment="Left" d:LayoutOverrides="Height">
        <Rectangle Fill="Blue" Height="4000" VerticalAlignment="Top" Width="120" HorizontalAlignment="Left"/>
        <Rectangle Fill="Red" Height="2000" VerticalAlignment="Top" Width="120" HorizontalAlignment="Right"/>
        <Rectangle Fill="Red" Height="2000" VerticalAlignment="Top" Width="120" HorizontalAlignment="Right" Margin="0,2000,0,0"/>
    </Grid>
</ScrollViewer>

In this case blue rectangle cropped at 2048px, but two rectangles with 2000px height placed one above the other looks fine.

The second example uses StackPanel to show 4000px area and it works too

<StackPanel Background="#FFFF8A8A" HorizontalAlignment="Right" Width="240" d:LayoutOverrides="Height">
    <Rectangle Fill="#FF88FF00" Height="2000" Width="240" HorizontalAlignment="Right"/>
    <Rectangle Fill="#FF88FF00" Height="2000" VerticalAlignment="Top" Width="240" HorizontalAlignment="Right"/>
</StackPanel>

Answer 2

Max. texture size on WP7 is 2048x2048. The rectangle height exceeds this limit. Once you decrease it below this limit, it starts working.

This code is better suited to experiments as you can identify bottom border:

<Grid Grid.Row="1" Height="630">
  <ScrollViewer Background="Red" Grid.Row="1">
    <Grid>
      <Border Height="2048" BorderBrush="Blue" BorderThickness="5">
        <Rectangle Height="2000" Fill="LightBlue" Width="440"/>
      </Border>
    </Grid>
  </ScrollViewer>
</Grid>

Once you increase the Border height, the bottom part will disappear.

On the other hand, I have to say that this behavior surprises me, too. I would expect that system decomposes large objects into smaller textures, but apparently WP7 designers decided not to do so, but rather manifest UI bug.