Layout Transform values don't match Render Transform

[michael-hawker]

I'm submitting a...

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

Current behavior

I did notice that with similar values in Skew though that at some point the layout transform seems to start behaving differently...

    <Grid Background="{StaticResource Brush-Grey-01}" Grid.Row="1"
          HorizontalAlignment="Center" VerticalAlignment="Center"
          RenderTransformOrigin="0.5,0.5">
        <Grid.RenderTransform>
          <TransformGroup>
            <RotateTransform Angle="-2.25" />
            <ScaleTransform ScaleX="2.21"
                          ScaleY="2.2" />
            <SkewTransform AngleX="-120"
                           AngleY="180" />
          </TransformGroup>
        </Grid.RenderTransform>
      <Grid HorizontalAlignment="Center" VerticalAlignment="Center" Margin="10">
        <TextBlock Foreground="White" Text="This is a test message." />
      </Grid>
    </Grid>

Compared to when there are less large values:

Expected behavior

Providing same values to Render and Layout transforms should produce similar effects.

Minimal reproduction of the problem with instructions

Copy above XAML into sample app page for layout transform (see PR #1817)

Environment

Nuget Package(s): 

Package Version(s): 

Windows 10 Build Number:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [x] Fall Creators Update (16299)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [x] Fall Creators Update (16299)
- [ ] Insider Build (xxxxx)

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

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

Comparing to reference source for .net, our matrix transform here does seem different. We actually probably want to provide Matrix method extensions for performing these operations like System.Windows.Media.Matrix had.

[Odonno]

@michael-hawker From what I saw, it's the SkewTransform which does not behave as it should (as RenderTransform). The AngleX and AngleY seems to be inverted.

[michael-hawker]

@Odonno yeah, I think it'd be useful to add extensions for the Matrix helpers missing in UWP that the .NET matrix class had (Rotate, Translate, Scale, Skew). Then we can use those in the Layout Transform control instead and should get the better behavior hopefully.