LayoutTransformControl behaves oddly in UniformGrid

[michael-hawker]

I'm submitting a...

• Bug report (I searched for similar issues and did not find one)

Current behavior

If you have a LayoutTransformControl like so:

<Page
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

  <Grid x:Name="Grid">
    <controls:LayoutTransformControl>
      <controls:LayoutTransformControl.Transform>
        <TransformGroup>
          <RotateTransform Angle="25" />
          <ScaleTransform ScaleX="4.5"
                          ScaleY="1" />
          <SkewTransform AngleX="0"
                         AngleY="0" />
        </TransformGroup>
      </controls:LayoutTransformControl.Transform>

      <Border Background="#FF333333"
              BorderBrush="Red"
              BorderThickness="5">
        <Grid>
          <TextBlock Padding="10" Foreground="White" Text="This is a test message." />
        </Grid>
      </Border>
    </controls:LayoutTransformControl>
  </Grid>
</Page>

You get one result:

But when Grid is a UniformGrid instead, you get a different result:

Expected behavior

As per WPF, these should result in the same behavior.

Minimal reproduction of the problem with instructions

Use provided XAML in sample app for LayoutTransformControl.

Other Info

I have confirmed this behavior was there before change #2149 as well, so that change did not introduce this behavior.

I'm not sure if this is an issue with the UniformGrid or the LayoutTransformControl or the interaction between their two layout algorithms. Since it does work with Grid and UniformGrid does inherit now from Grid it is a bit odd, so leads me to believe it may be the former.

Environment

Nuget Package(s): 

Package Version(s): 

Windows 10 Build Number:
- [ ] Creators Update (15063)
- [ ] Fall Creators Update (16299)
- [x] April 2018 Update (17134)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Creators Update (15063)
- [ ] Fall Creators Update (16299)
- [x] April 2018 Update (17134)
- [ ] Insider Build (xxxxx)

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

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

[michael-hawker]

When I have a chance, I'm going to try with my older UniformGrid branch that used the traditional/reference implementation and see how it behaves there. It might help point to where the issue is.

[lucaasrojas]

I tried to replicate the bug without success, I'm thinking it may have been fixed. Could someone check to confirm?
Grid:

UniformGrid:

[lucaasrojas]

@michael-hawker can you still replicate it?

[michael-hawker]

@lucaasrojas, Yup I can still repro. Once you change to the UniformGrid, use the GridSplitter to change the view size, and you should see it jump at certain points from being the right size to a different size.

[lucaasrojas]

@michael-hawker I tried it again and I could reproduce the problem. Is this what you see?

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