/// <summary>
/// Updates DesiredSize of the ClipBorder. Called by parent UIElement. This is the first pass of layout.
/// </summary>
/// <remarks>
/// Border determines its desired size it needs from the specified border the child: its sizing
/// properties, margin, and requested size.
/// </remarks>
/// <param name="constraint">Constraint size is an "upper limit" that the return value should not exceed.</param>
/// <returns>The Decorator's desired size.</returns>
protected override Size MeasureOverride(Size constraint)
{
var child = Child;
var desiredSize = new Size();
var borders = BorderThickness;
// Compute the total size required
var borderSize = borders.CollapseThickness();
var paddingSize = Padding.CollapseThickness();
// Does the ClipBorder have a child?
if (child != null)
{
// Combine into total decorating size
var combined = new Size(borderSize.Width + paddingSize.Width, borderSize.Height + paddingSize.Height);
// Remove size of border only from child's reference size.
var childConstraint = new Size(Math.Max(0.0, constraint.Width - combined.Width),
Math.Max(0.0, constraint.Height - combined.Height));
child.Measure(childConstraint);
var childSize = child.DesiredSize;
// Now use the returned size to drive our size, by adding back the margins, etc.
desiredSize.Width = childSize.Width + combined.Width;
desiredSize.Height = childSize.Height + combined.Height;
}
else
{
// Since there is no child, the border requires only the size occupied by the BorderThickness
// and the Padding
desiredSize = new Size(borderSize.Width + paddingSize.Width, borderSize.Height + paddingSize.Height);
}
return desiredSize;
}
