/// <summary>
/// Provides the behavior for the "Measure" pass of layout.
/// </summary>
/// <param name="availableSize">The available size that this element can
/// give to child elements. Infinity can be specified as a value to
/// indicate that the element will size to whatever content is available.</param>
/// <returns>The size that this element determines it needs during
/// layout, based on its calculations of child element sizes.</returns>
protected override Size MeasureOverride(Size availableSize)
{
FrameworkElement child = Child;
if (_layoutRoot == null || child == null)
{
// No content, no size
return Size.Empty;
}
Size measureSize;
if (_childActualSize == Size.Empty)
{
// Determine the largest size after the transformation
measureSize = ComputeLargestTransformedSize(availableSize);
}
else
{
// Previous measure/arrange pass determined that Child.DesiredSize was larger than believed.
measureSize = _childActualSize;
}
// Perform a mesaure on the _layoutRoot (containing Child)
_layoutRoot.Measure(measureSize);
// Transform DesiredSize to find its width/height
Rect transformedDesiredRect = MatrixHelperEx.RectTransform(new Rect(0, 0, _layoutRoot.DesiredSize.Width, _layoutRoot.DesiredSize.Height), _transformation);
Size transformedDesiredSize = new Size(transformedDesiredRect.Width, transformedDesiredRect.Height);
// Return result to allocate enough space for the transformation
return transformedDesiredSize;
}
/// <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>
protected override Size ArrangeOverride(Size finalSize)
{
FrameworkElement child = Child;
if (_layoutRoot == null || child == null)
{
// No child, use whatever was given
return(finalSize);
}
// Determine the largest available size after the transformation
Size finalSizeTransformed = ComputeLargestTransformedSize(finalSize);
if (IsSizeSmaller(finalSizeTransformed, _layoutRoot.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
finalSizeTransformed = _layoutRoot.DesiredSize;
}
// Transform the working size to find its width/height
Rect transformedRect = MatrixHelperEx.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 _layoutRoot (containing Child)
_layoutRoot.Arrange(finalRect);
// This is the first opportunity 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
// Make a note of the actual DesiredSize
_childActualSize = new Size(child.ActualWidth, child.ActualHeight);
// Force a new measure/arrange pass
InvalidateMeasure();
}
else
{
// Clear the "need to measure/arrange again" flag
_childActualSize = Size.Empty;
}
// Return result to perform the transformation
return(finalSize);
}