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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.
//
using MS.Internal;
namespace System.Windows.Media
{
/// <summary>
/// This is the class for specifying parameters hit testing with a geometry.
/// </summary>
public class GeometryHitTestParameters : HitTestParameters
{
private PathGeometry _hitGeometryInternal; // The internal geometry we use for hit testing
private Geometry _hitGeometryCache = null; // Cached frozen copy we hand out from HitGeometry property.
private Rect _origBounds;
private Rect _bounds;
private MatrixStack _matrixStack;
/// <summary>
/// The constructor takes the geometry to hit test with.
/// </summary>
public GeometryHitTestParameters(Geometry geometry) : base()
{
// This ctor guarantees that we are initialized in the following way:
//
// 1. The geometry provided by the user is unmodified
// 2. _hitGeometryInternal is a PathGeometry equivilent to the supplied geometry
// 3. _hitGeometryInternal.Tranform is a MatrixTransform equivilent to the supplied
// geometry.Transform
// 4. _origBounds is the untransformed bounds of the _hitGeometryInternal (inner space).
// 5. _bounds is the transformed bounds of the _hitGeometryInternal (outer space).
// 6. _matrixStack is an empty stack.
ArgumentNullException.ThrowIfNull(geometry);
// Convert the Geometry to an equivilent PathGeometry up front to prevent
// conversion on every call to DoesContainWithDetail. If the geometry is
// animate this also has the side effect of eliminating animation interplay.
_hitGeometryInternal = geometry.GetAsPathGeometry();
// If GetAsPathGeometry was a no-op, force the copy because we do not
// went to modify the user's Geometry.
if (object.ReferenceEquals(_hitGeometryInternal, geometry))
{
_hitGeometryInternal = _hitGeometryInternal.Clone();
}
// Convert _hitGeometryInternal.Transform to an equivilent MatrixTransform
// so that we can aggregate in PushMatrix/PopMatrix without building a
// TransformCollection.
Transform origTransform = _hitGeometryInternal.Transform;
MatrixTransform newTransform = new MatrixTransform();
_hitGeometryInternal.Transform = newTransform;
// Before we initialize MatrixTransform.Matrix, cache the bounds of this
// geometry without any transforms.
_origBounds = _hitGeometryInternal.Bounds;
// If we had a non-Identity transform, update our MatrixTransform.Matrix
// with its Value. (Note that when GetAsPathGeometry *isn't* a no-op
// it applies the transform to the figures and returns with a Geometry
// with an identity Transform.)
if (origTransform != null && !origTransform.IsIdentity)
{
newTransform.Matrix = origTransform.Value;
}
// Initialize the current transformed bounds of this Geometry
_bounds = _hitGeometryInternal.Bounds;
_matrixStack = new MatrixStack();
}
/// <summary>
/// The geometry to hit test against. This will be a frozen copy of the
/// hit geometry transformed into the local space of the Visual being hit
/// tested.
/// </summary>
public Geometry HitGeometry
{
get
{
if (_hitGeometryCache == null)
{
_hitGeometryCache = (Geometry) _hitGeometryInternal.GetAsFrozen();
}
Debug.Assert(_hitGeometryInternal.Transform.Value == _hitGeometryCache.Transform.Value,
"HitGeometry has a different transform than HitGeometryInternal. Did we forget to invalidate the cache?");
return _hitGeometryCache;
}
}
// Use this property when retrieving the hit geometry internally. Right now it avoids a
// a cast. In the future it will avoid a copy as well.
// There is a bug that allows the HitGeometry returned from GeometryHitTestParamaters
// to be unintentially mutable, allowing users to modify the hit geometry or attach
// changed handlers after the GeometryHitTestParamaters is constructed.
// The value from this property should never be exposed to the user (e.g., do not use it to return
// hit test results.)
internal PathGeometry InternalHitGeometry
{
get
{
return _hitGeometryInternal;
}
}
internal Rect Bounds
{
get
{
return _bounds;
}
}
internal void PushMatrix(ref Matrix newMatrix)
{
MatrixTransform matrixTransform = (MatrixTransform) _hitGeometryInternal.Transform;
// Grab the old composedMatrix from our MatrixTransform and save
// it on our MatrixStack.
Matrix composedMatrix = matrixTransform.Value;
_matrixStack.Push(ref composedMatrix, false);
// Compose the new matrix into our MatrixTransform
MatrixUtil.MultiplyMatrix(ref composedMatrix, ref newMatrix);
matrixTransform.Matrix = composedMatrix;
// Update active bounds based on new tranform.
_bounds = Rect.Transform(_origBounds, composedMatrix);
ClearHitGeometryCache();
}
internal void PopMatrix()
{
Matrix matrix = _matrixStack.Peek();
// Restore saved transform.
((MatrixTransform) (_hitGeometryInternal.Transform)).Matrix = matrix;
// Update active bounds based on new X-form.
_bounds = Rect.Transform(_origBounds, matrix);
_matrixStack.Pop();
ClearHitGeometryCache();
}
// This method is called to restore the _hitGeometryInternal's transform to its original state
// in the event that a user's delegate threw an exception during the hit test walk.
internal void EmergencyRestoreOriginalTransform()
{
// Replace the current transform with the first matrix pushed onto the stack.
Matrix matrix = ((MatrixTransform) (_hitGeometryInternal.Transform)).Matrix;
while (!_matrixStack.IsEmpty)
{
matrix = _matrixStack.Peek();
_matrixStack.Pop();
}
((MatrixTransform) (_hitGeometryInternal.Transform)).Matrix = matrix;
ClearHitGeometryCache();
}
// This clears the
private void ClearHitGeometryCache()
{
_hitGeometryCache = null;
}
}
}
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