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//---------------------------------------------------------------------------
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// Description: DrawingGroup represents a collection of Drawing objects, and
// can apply group-operations such as clip and opacity to it's
// collections
//
// History:
//
// 2004/11/17 : timothyc - Created it.
//
//---------------------------------------------------------------------------
using System;
using System.Windows.Threading;
using MS.Win32;
using System.Security;
using System.Security.Permissions;
using System.Windows.Markup;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Media.Animation;
using System.Windows.Media.Composition;
using System.Windows.Media.Effects;
using System.Diagnostics;
using System.Collections;
using System.Collections.Generic;
using MS.Internal;
using MS.Internal.Media;
using System.Resources;
using MS.Utility;
using System.Runtime.InteropServices;
using MS.Internal.PresentationCore;
using System.ComponentModel.Design.Serialization;
using System.ComponentModel;
using SR = MS.Internal.PresentationCore.SR;
using SRID = MS.Internal.PresentationCore.SRID;
namespace System.Windows.Media
{
/// <summary>
/// DrawingGroup represents a collection of Drawing objects, and
/// can apply group-operations such as clip and opacity to it's
/// collections.
/// </summary>
[ContentProperty("Children")]
public sealed partial class DrawingGroup : Drawing
{
#region Constructors
/// <summary>
/// Default DrawingGroup constructor.
/// Constructs an object with all properties set to their default values.
/// </summary>
public DrawingGroup()
{
}
#endregion Constructors
#region Public methods
/// <summary>
/// Opens the DrawingGroup for re-populating it's children, clearing any existing
/// children.
/// </summary>
/// <returns>
/// Returns DrawingContext to populate the DrawingGroup's children.
/// </returns>
public DrawingContext Open()
{
VerifyOpen();
_openedForAppend = false;
return new DrawingGroupDrawingContext(this);
}
/// <summary>
/// Opens the DrawingGroup for populating it's children, appending to
/// any existing children in the collection.
/// </summary>
/// <returns>
/// Returns DrawingContext to populate the DrawingGroup's children.
/// </returns>
public DrawingContext Append()
{
VerifyOpen();
_openedForAppend = true;
return new DrawingGroupDrawingContext(this);
}
#endregion Public methods
#region Internal methods
/// <summary>
/// Called by a DrawingContext returned from Open or Append when the content
/// created by it needs to be committed (because DrawingContext.Close/Dispose
/// was called)
/// </summary>
/// <param name="rootDrawingGroupChildren">
/// Collection containing the Drawing elements created by a DrawingContext
/// returned from Open or Append.
/// </param>
internal void Close(DrawingCollection rootDrawingGroupChildren)
{
WritePreamble();
Debug.Assert(_open);
Debug.Assert(rootDrawingGroupChildren != null);
if (!_openedForAppend)
{
// Clear out the previous contents by replacing the current collection with
// the new collection.
//
// When more than one element exists in rootDrawingGroupChildren, the
// DrawingContext had to create this new collection anyways. To behave
// consistently between the one-element and many-element cases,
// we always set Children to a new DrawingCollection instance during Close().
//
// Doing this also avoids having to protect against exceptions being thrown
// from user-code, which could be executed if a Changed event was fired when
// we tried to add elements to a pre-existing collection.
//
// The collection created by the DrawingContext will no longer be
// used after the DrawingContext is closed, so we can take ownership
// of the reference here to avoid any more unneccesary copies.
Children = rootDrawingGroupChildren;
}
else
{
//
//
// Append the collection to the current Children collection
//
//
DrawingCollection children = Children;
//
// Ensure that we can Append to the Children collection
//
if (children == null)
{
throw new InvalidOperationException(SR.Get(SRID.DrawingGroup_CannotAppendToNullCollection));
}
if (children.IsFrozen)
{
throw new InvalidOperationException(SR.Get(SRID.DrawingGroup_CannotAppendToFrozenCollection));
}
// Append the new collection to our current Children.
//
// TransactionalAppend rolls-back the Append operation in the event
// an exception is thrown from the Changed event.
children.TransactionalAppend(rootDrawingGroupChildren);
}
// This DrawingGroup is no longer open
_open = false;
}
/// <summary>
/// Calls methods on the DrawingContext that are equivalent to the
/// Drawing with the Drawing's current value.
/// </summary>
internal override void WalkCurrentValue(DrawingContextWalker ctx)
{
int popCount = 0;
// We avoid unneccessary ShouldStopWalking checks based on assumptions
// about when ShouldStopWalking is set. Guard that assumption with an
// assertion.
//
// ShouldStopWalking is currently only set during a hit-test walk after
// an object has been hit. Because a DrawingGroup can't be hit until after
// the first Drawing is tested, this method doesn't check ShouldStopWalking
// until after the first child.
//
// We don't need to add this check to other Drawing subclasses for
// the same reason -- if the Drawing being tested isn't a DrawingGroup,
// they are always the 'first child'.
//
// If this assumption is ever broken then the ShouldStopWalking
// check should be done on the first child -- including in the
// WalkCurrentValue method of other Drawing subclasses.
Debug.Assert(!ctx.ShouldStopWalking);
//
// Draw the transform property
//
// Avoid calling PushTransform if the base value is set to the default and
// no animations have been set on the property.
if (!IsBaseValueDefault(DrawingGroup.TransformProperty) ||
(null != AnimationStorage.GetStorage(this, DrawingGroup.TransformProperty)))
{
ctx.PushTransform(Transform);
popCount++;
}
//
// Draw the clip property
//
// Avoid calling PushClip if the base value is set to the default and
// no animations have been set on the property.
if (!IsBaseValueDefault(DrawingGroup.ClipGeometryProperty) ||
(null != AnimationStorage.GetStorage(this, DrawingGroup.ClipGeometryProperty)))
{
ctx.PushClip(ClipGeometry);
popCount++;
}
//
// Draw the opacity property
//
// Avoid calling PushOpacity if the base value is set to the default and
// no animations have been set on the property.
if (!IsBaseValueDefault(DrawingGroup.OpacityProperty) ||
(null != AnimationStorage.GetStorage(this, DrawingGroup.OpacityProperty)))
{
// Push the current value of the opacity property, which
// is what Opacity returns.
ctx.PushOpacity(Opacity);
popCount++;
}
// Draw the opacity mask property
//
if (OpacityMask != null)
{
ctx.PushOpacityMask(OpacityMask);
popCount++;
}
//
// Draw the effect property
//
// Push the current value of the effect property, which
// is what BitmapEffect returns.
if (BitmapEffect != null)
{
// Disable warning about obsolete method. This code must remain active
// until we can remove the public BitmapEffect APIs.
#pragma warning disable 0618
ctx.PushEffect(BitmapEffect, BitmapEffectInput);
#pragma warning restore 0618
popCount++;
}
//
// Draw the Children collection
//
// Get the current value of the children collection
DrawingCollection collection = Children;
// Call Walk on each child
if (collection != null)
{
for (int i = 0; i < collection.Count; i++)
{
Drawing drawing = collection.Internal_GetItem(i);
if (drawing != null)
{
drawing.WalkCurrentValue(ctx);
// Don't visit the remaining children if the previous
// child caused us to stop walking.
if (ctx.ShouldStopWalking)
{
break;
}
}
}
}
//
// Call Pop() for every Push
//
// Avoid placing this logic in a finally block because if an exception is
// thrown, the Walk is simply aborted. There is no requirement to Walk
// through Pop instructions when an exception is thrown.
//
for (int i = 0; i < popCount; i++)
{
ctx.Pop();
}
}
#endregion Internal methods
#region Private Methods
/// <summary>
/// Called by both Open() and Append(), this method verifies the
/// DrawingGroup isn't already open, and set's the open flag.
/// </summary>
private void VerifyOpen()
{
WritePreamble();
// Throw an exception if we are already opened
if (_open)
{
throw new InvalidOperationException(SR.Get(SRID.DrawingGroup_AlreadyOpen));
}
_open = true;
}
#endregion Private Methods
#region Private fields
private bool _openedForAppend;
private bool _open;
#endregion Private fields
}
}
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