/// <summary>
/// Provides the behavior for the "Arrange" pass of layout.
/// </summary>
/// <param name="finalSize">The final area within the parent that this element should use to arrange itself and its children.</param>
/// <returns>The actual size used.</returns>
/// <remarks>
/// Using the WPF paramater name finalSize instead of Silverlight's finalSize for clarity
/// </remarks>
protected override Size ArrangeOverride(Size finalSize)
{
FrameworkElement child = Child;
if ((null == _transformRoot) || (null == child))
{
// No child, use whatever was given
return(finalSize);
}
DiagnosticWriteLine("ArrangeOverride < " + finalSize);
// Determine the largest available size after the transformation
Size finalSizeTransformed = ComputeLargestTransformedSize(finalSize);
if (IsSizeSmaller(finalSizeTransformed, _transformRoot.DesiredSize))
{
// Some elements do not like being given less space than they asked for (ex: TextBlock)
// Bump the working size up to do the right thing by them
DiagnosticWriteLine(" Replacing finalSizeTransformed with larger _transformRoot.DesiredSize");
finalSizeTransformed = _transformRoot.DesiredSize;
}
DiagnosticWriteLine(" finalSizeTransformed = " + finalSizeTransformed);
// Transform the working size to find its width/height
Rect transformedRect = RectTransform(new Rect(0, 0, finalSizeTransformed.Width, finalSizeTransformed.Height), _transformation);
// Create the Arrange rect to center the transformed content
Rect finalRect = new Rect(
-transformedRect.Left + ((finalSize.Width - transformedRect.Width) / 2),
-transformedRect.Top + ((finalSize.Height - transformedRect.Height) / 2),
finalSizeTransformed.Width,
finalSizeTransformed.Height);
// Perform an Arrange on _transformRoot (containing Child)
DiagnosticWriteLine(" _transformRoot.Arrange < " + finalRect);
_transformRoot.Arrange(finalRect);
DiagnosticWriteLine(" Child.RenderSize = " + child.RenderSize);
// This is the first opportunity under Silverlight to find out the Child's true DesiredSize
if (IsSizeSmaller(finalSizeTransformed, child.RenderSize) && (Size.Empty == _childActualSize))
{
// Unfortunately, all the work so far is invalid because the wrong DesiredSize was used
DiagnosticWriteLine(" finalSizeTransformed smaller than Child.RenderSize");
// Make a note of the actual DesiredSize
_childActualSize = new Size(child.ActualWidth, child.ActualHeight);
DiagnosticWriteLine(" _childActualSize = " + _childActualSize);
// Force a new measure/arrange pass
InvalidateMeasure();
}
else
{
// Clear the "need to measure/arrange again" flag
_childActualSize = Size.Empty;
}
DiagnosticWriteLine(" _transformRoot.RenderSize = " + _transformRoot.RenderSize);
// Return result to perform the transformation
DiagnosticWriteLine("ArrangeOverride > " + finalSize);
return(finalSize);
}
