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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
// Spec: LayoutInformation class.doc
using System.Windows.Media;
using System.Windows.Threading;
namespace System.Windows.Controls.Primitives
{
/// <summary>
/// This interface exposes additional layout information not exposed otherwise on FrameworkElement.
/// This information is mostly used by the designer programs to produce additional visual clues for the user
/// during interactive editing of the elements and layout properties.
/// </summary>
public static class LayoutInformation
{
private static void CheckArgument(FrameworkElement element)
{
ArgumentNullException.ThrowIfNull(element);
}
/// <summary>
/// Returns the rectangle that represents Layout Slot - the layout partition reserved for the
/// child by the layout parent. This info is in the coordinte system of the layout parent.
/// </summary>
public static Rect GetLayoutSlot(FrameworkElement element)
{
CheckArgument(element);
return element.PreviousArrangeRect;
}
/// <summary>
/// Returns a geometry which was computed by layout for the child. This is generally a visible region of the child.
/// Layout can compute automatic clip region when the child is larger then layout constraints or has ClipToBounds
/// property set. Note that because of LayoutTransform, this could be a non-rectangular geometry. While general geometry is somewhat
/// complex to operate with, it is possible to check if the Geometry returned is RectangularGeometry or, if not - use Geometry.Bounds
/// property to get bounding box of the visible portion of the element.
/// </summary>
public static Geometry GetLayoutClip(FrameworkElement element)
{
CheckArgument(element);
return element.GetLayoutClipInternal();
}
/// <summary>
/// Returns a UIElement which was being processed by Layout Engine at the moment
/// an unhandled exception casued Layout Engine to abandon the operation and unwind.
/// Returns non-null result only for a period of time before next layout update is
/// initiated. Can be examined from the application exception handler.
/// </summary>
/// <param name="dispatcher">The Dispatcher object that specifies the scope of operation. There is one Layout Engine per Dispatcher.</param>
public static UIElement GetLayoutExceptionElement(Dispatcher dispatcher)
{
ArgumentNullException.ThrowIfNull(dispatcher);
UIElement e = null;
ContextLayoutManager lm = ContextLayoutManager.From(dispatcher);
if(lm != null)
e = lm.GetLastExceptionElement();
return e;
}
}
}
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