DockablePane & font size != 100%

[FRFR1426]

I've made a dockable pane which hosts a WPF user control. It works OK, but if I go to Control Panel > Appearance and Personalization > Display and I change the size of the font for the entire system to 150%:

The WPF user control children do not resize themselves properly. I've got this result:

Note that the Textbox is truncated on the right. The width of the root grid is not correctly computed.

At 100%, it's OK.

There is a similar problem described here: https://bimdev.blogspot.fr/2014/11/revit-dockable-pane-failures-with.html but the solution presented does not work for me on Windows 10 - Revit 2016/2017

[FRFR1426 · Accepted solution]

I've found a solution. We can compensate by adding a margin to the root grid (grMain):

void UserControl_OnSizeChanged(object sender, SizeChangedEventArgs e)
{
    HandleTextScaling();
}

void HandleTextScaling()
{
    PresentationSource source = PresentationSource.FromVisual(this);
    Debug.Assert(source != null, "source != null");
    CompositionTarget target = source.CompositionTarget;
    Debug.Assert(target != null, "target != null");
    Matrix m = target.TransformToDevice;
    double scale1 = m.M11;
    double scale2 = scale1 - 1;
    grMain.Margin = new Thickness(0, 0, scale2 * ActualWidth / scale1, scale2 * ActualHeight / scale1);
}