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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.
//
// Description: The arguments sent when a TextChangedEvent is fired in a TextContainer.
//
using System.Windows.Controls;
namespace System.Windows.Documents
{
/// <summary>
/// The TextContainerChangedEventArgs defines the event arguments sent when a
/// TextContainer is changed.
/// </summary>
internal class TextContainerChangedEventArgs : EventArgs
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
internal TextContainerChangedEventArgs()
{
_changes = new SortedList<int, TextChange>();
}
#endregion Constructors
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
// Called by TextElement when a local property value changes.
// Sets the HasLocalPropertyValueChange property true.
internal void SetLocalPropertyValueChanged()
{
_hasLocalPropertyValueChange = true;
}
// Adds a new change to the Delta list.
internal void AddChange(PrecursorTextChangeType textChange, int offset, int length, bool collectTextChanges)
{
if (textChange == PrecursorTextChangeType.ContentAdded ||
textChange == PrecursorTextChangeType.ElementAdded ||
textChange == PrecursorTextChangeType.ContentRemoved ||
textChange == PrecursorTextChangeType.ElementExtracted)
{
_hasContentAddedOrRemoved = true;
}
if (!collectTextChanges)
{
return;
}
// We only want to add or remove the edges for empty elements (and ElementAdded /
// ElementRemoved are only used with empty elements). Note that since we're making
// two changes instead of one the order matters. We have to treat the two cases differently.
if (textChange == PrecursorTextChangeType.ElementAdded)
{
AddChangeToList(textChange, offset, 1);
AddChangeToList(textChange, offset + length - 1, 1);
}
else if (textChange == PrecursorTextChangeType.ElementExtracted)
{
AddChangeToList(textChange, offset + length - 1, 1);
AddChangeToList(textChange, offset, 1);
}
else if (textChange == PrecursorTextChangeType.PropertyModified)
{
// ignore property changes
return;
}
else
{
AddChangeToList(textChange, offset, length);
}
}
#if PROPERTY_CHANGES
// We don't merge property changes with each other when they're added, so that when an element is removed
// we can remove the property changes associated with it. This method merges all of them at once.
internal void MergePropertyChanges()
{
TextChange leftChange = null;
for (int index = 0; index < Changes.Count; index++)
{
TextChange curChange = Changes.Values[index];
if (leftChange == null || leftChange.Offset + leftChange.PropertyCount < curChange.Offset)
{
leftChange = curChange;
}
else if (leftChange.Offset + leftChange.PropertyCount >= curChange.Offset)
{
if (MergePropertyChange(leftChange, curChange))
{
// Changes merged. If the right-hand change is now empty, remove it.
if (curChange.RemovedLength == 0 && curChange.AddedLength == 0)
{
Changes.RemoveAt(index--); // decrement index since we're removing an element, otherwise we'll skip one
}
}
}
}
}
#endif
#endregion Internal Methods
//------------------------------------------------------
//
// Internal Properties
//
//------------------------------------------------------
#region Internal Properties
/// <summary>
/// Returns true if at least one of the TextChangeSegments in this TextChangeCollection
/// is not of type TextChange.LayoutAffected or TextChange.RenderAffect. This means that
/// content was added or removed -- rather than content only affected by DependencyProperty
/// values changes on scoping elements.
/// </summary>
/// <value></value>
internal bool HasContentAddedOrRemoved
{
get
{
return _hasContentAddedOrRemoved;
}
}
/// <summary>
/// Returns true if the collection contains one or more entries that
/// result from a local property value changing on a TextElement.
/// </summary>
/// <remarks>
/// Note "local property value" does NOT include property changes
/// that arrive via inheritance or styles.
/// </remarks>
internal bool HasLocalPropertyValueChange
{
get
{
return _hasLocalPropertyValueChange;
}
}
/// <summary>
/// List of TextChanges representing the aggregate changes made to the container.
/// </summary>
internal SortedList<int, TextChange> Changes
{
get
{
return _changes;
}
}
#endregion Internal Properties
#region Private Methods
//------------------------------------------------------
//
// Private Methods
//
//------------------------------------------------------
//
// First we discover where the new change goes in the sorted list. If there's already
// a change there, merge the new one with the old one.
//
// Next, if the new change is an insertion or deletion, see if the offset of the change
// is within a range covered by an insertion at a lower offset. If so, merge the change at
// the higher offset into the previous change and delete the change at the higher offset.
//
// Next, if the change is a deletion, see if we delete enough characters to run into a
// change at a higher offset. If so, merge the change at the higher offset into this newer
// change and delete the older, higher-offset change.
//
// Finally, update all offsets higher than the current change to reflect the number of
// characters inserted or deleted.
//
private void AddChangeToList(PrecursorTextChangeType textChange, int offset, int length)
{
int offsetDelta = 0; // Value by which to adjust other offsets in list
int curIndex; // loop counter
TextChange change = null; // initialize to satisfy compiler
bool isDeletion = false;
#if PROPERTY_CHANGES
bool shiftPropertyChanges = false;
#endif
//
// Is there already a change at this offset in our list? If so, use it
//
int keyIndex = Changes.IndexOfKey(offset);
if (keyIndex != -1)
{
change = Changes.Values[keyIndex];
}
else
{
change = new TextChange();
change.Offset = offset;
Changes.Add(offset, change);
keyIndex = Changes.IndexOfKey(offset);
}
//
// Merge values from new change into empty or pre-existing change
//
if (textChange == PrecursorTextChangeType.ContentAdded || textChange == PrecursorTextChangeType.ElementAdded)
{
change.AddedLength += length;
offsetDelta = length;
#if PROPERTY_CHANGES
if (change.PropertyCount > 0)
{
shiftPropertyChanges = true;
}
#endif
}
else if (textChange == PrecursorTextChangeType.ContentRemoved || textChange == PrecursorTextChangeType.ElementExtracted)
{
// Any deletions made after an addition just cancel out the earlier addition
change.RemovedLength += Math.Max(0, length - change.AddedLength);
change.AddedLength = Math.Max(0, change.AddedLength - length);
#if PROPERTY_CHANGES
// If an element was extracted, any property change made on that element should be removed as well
if (textChange == PrecursorTextChangeType.ElementExtracted)
{
change.SetPropertyCount(0);
}
else
{
change.SetPropertyCount(Math.Max(0, change.PropertyCount - length));
}
#endif
offsetDelta = -length;
isDeletion = true;
}
#if PROPERTY_CHANGES
else
{
// Property change
if (change.PropertyCount < length)
{
change.SetPropertyCount(length);
}
}
#endif
//
// Done with simple case. Now look for changes that intersect.
// There are two possible (non-exclusive) merge conditions:
// 1. A positionally preceding change spans this offset (this change is inserting
// into or deleting from the middle or right edge of previous inserted text)
// 2. On deletion, the change spans one or more positionally later changes
//
if (keyIndex > 0 && textChange != PrecursorTextChangeType.PropertyModified)
{
curIndex = keyIndex - 1;
// Since we don't merge property changes, there could be an arbitrary number of
// them between the new change and an overlapping insertion or overlapping property
// change. In fact, there could be multiple property changes that overlap this
// change. We need to adjust ALL of them. There can be only one overlapping
// insertion, but there's no way to leverage that fact.
TextChange mergedChange = null;
while (curIndex >= 0)
{
TextChange prevChange = Changes.Values[curIndex];
#if PROPERTY_CHANGES
if (prevChange.Offset + prevChange.AddedLength >= offset || prevChange.Offset + prevChange.PropertyCount >= offset)
#else
if (prevChange.Offset + prevChange.AddedLength >= offset)
#endif
{
if (MergeTextChangeLeft(prevChange, change, isDeletion, length))
{
mergedChange = prevChange;
}
}
curIndex--;
}
if (mergedChange != null)
{
// the change got merged. Use the merged change as the basis for righthand merging.
change = mergedChange;
}
// changes may have been deleted, so update the index of the change we're working with
keyIndex = Changes.IndexOfKey(change.Offset);
}
curIndex = keyIndex + 1;
if (isDeletion && curIndex < Changes.Count)
{
while (curIndex < Changes.Count && Changes.Values[curIndex].Offset <= offset + length)
{
// offset and length must be passed because if we've also merged left, we haven't yet adjusted indices.
// Note that MergeTextChangeRight() always removes Changes.Values[curIndex] from the list, so
// we don't need to increment curIndex.
MergeTextChangeRight(Changes.Values[curIndex], change, offset, length);
}
// changes may have been deleted, so update the index of the change we're working with
keyIndex = Changes.IndexOfKey(change.Offset);
}
// Update all changes to reflect new offsets.
// If offsetDelta is positive, go right to left; otherwise, go left to right.
// The order of the offsets will never change, so we can use an indexer safely.
// To avoid nasty N-squared perf, create a new list instead of moving things within
// the old one.
// Change the implementation of Changes to a more efficient structure.
if (offsetDelta != 0)
{
SortedList<int, TextChange> newChanges = new SortedList<int, TextChange>(Changes.Count);
for (curIndex = 0; curIndex < Changes.Count; curIndex++)
{
TextChange curChange = Changes.Values[curIndex];
if (curIndex > keyIndex)
{
curChange.Offset += offsetDelta;
}
newChanges.Add(curChange.Offset, curChange);
}
_changes = newChanges;
}
DeleteChangeIfEmpty(change);
#if PROPERTY_CHANGES
// Finally, if the change was an insertion and there are property changes starting
// at this location, the insertion is not part of the property changes. Shift the
// property changes forward by the length of the insertion.
if (shiftPropertyChanges)
{
int propertyCount = change.PropertyCount;
change.SetPropertyCount(0);
AddChangeToList(PrecursorTextChangeType.PropertyModified, offset + offsetDelta, propertyCount);
}
#endif
}
private void DeleteChangeIfEmpty(TextChange change)
{
#if PROPERTY_CHANGES
if (change.AddedLength == 0 && change.RemovedLength == 0 && change.PropertyCount == 0)
#else
if (change.AddedLength == 0 && change.RemovedLength == 0)
#endif
{
Changes.Remove(change.Offset);
}
}
// returns true if the change merged into an earlier insertion
private bool MergeTextChangeLeft(TextChange oldChange, TextChange newChange, bool isDeletion, int length)
{
// newChange is inserting or deleting text inside oldChange.
int overlap;
#if PROPERTY_CHANGES
// Check for a property change in the old change that overlaps the new change
if (oldChange.Offset + oldChange.PropertyCount >= newChange.Offset)
{
if (isDeletion)
{
overlap = oldChange.PropertyCount - (newChange.Offset - oldChange.Offset);
oldChange.SetPropertyCount(oldChange.PropertyCount - Math.Min(overlap, length));
DeleteChangeIfEmpty(oldChange);
}
else
{
oldChange.SetPropertyCount(oldChange.PropertyCount + length);
}
}
#endif
if (oldChange.Offset + oldChange.AddedLength >= newChange.Offset)
{
// If any text was deleted in the new change, adjust the added count of the
// previous change accordingly. The removed count of the new change must be
// adjusted by the same amount.
if (isDeletion)
{
overlap = oldChange.AddedLength - (newChange.Offset - oldChange.Offset);
int cancelledCount = Math.Min(overlap, newChange.RemovedLength);
oldChange.AddedLength -= cancelledCount;
oldChange.RemovedLength += (length - cancelledCount);
}
else
{
oldChange.AddedLength += length;
}
#if PROPERTY_CHANGES
if (newChange.PropertyCount == 0)
{
// We've merged the data from the new change into an older one, so we can
// delete the change from the list.
Changes.Remove(newChange.Offset);
}
else
{
// Can't delete the change, since there's pre-existing property change data, so
// just clear the data instead.
newChange.AddedLength = 0;
newChange.RemovedLength = 0;
}
#else
// We've merged the data from the new change into an older one, so we can
// delete the change from the list.
Changes.Remove(newChange.Offset);
#endif
return true;
}
return false;
}
private void MergeTextChangeRight(TextChange oldChange, TextChange newChange, int offset, int length)
{
// If the old change is an addition, find the length of the overlap
// and adjust the addition and new deletion counts accordingly
int addedLengthOverlap = oldChange.AddedLength > 0 ? offset + length - oldChange.Offset : 0;
#if PROPERTY_CHANGES
// Check for a property change in the new change that overlaps the old change
int propertyOverlap = newChange.Offset + newChange.PropertyCount - oldChange.Offset;
if (propertyOverlap > 0)
{
int delta = Math.Min(propertyOverlap, addedLengthOverlap);
newChange.SetPropertyCount(newChange.PropertyCount - delta);
// Don't need to adjust oldChange.PropertyCount, since oldChange is about to be removed
}
#endif
// adjust removed count
if (addedLengthOverlap >= oldChange.AddedLength)
{
// old change is entirely within new one
newChange.RemovedLength += (oldChange.RemovedLength - oldChange.AddedLength);
Changes.Remove(oldChange.Offset);
}
else
{
newChange.RemovedLength += (oldChange.RemovedLength - addedLengthOverlap);
newChange.AddedLength += (oldChange.AddedLength - addedLengthOverlap);
Changes.Remove(oldChange.Offset);
}
}
#if PROPERTY_CHANGES
private bool MergePropertyChange(TextChange leftChange, TextChange rightChange)
{
if (leftChange.Offset + leftChange.PropertyCount >= rightChange.Offset)
{
if (leftChange.Offset + leftChange.PropertyCount < rightChange.Offset + rightChange.PropertyCount)
{
// right change is partially inside left, but not completely.
int overlap = leftChange.Offset + leftChange.PropertyCount - rightChange.Offset;
int delta = rightChange.PropertyCount - overlap;
leftChange.SetPropertyCount(leftChange.PropertyCount + delta);
}
rightChange.SetPropertyCount(0);
return true;
}
return false;
}
#endif
#endregion Private Methods
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
// true if at least one of the changes in this TextChangeCollection
// is not of type TextChange.LayoutAffected or TextChange.RenderAffect.
private bool _hasContentAddedOrRemoved;
// True if the collection contains one or more entries that
// result from a local property value changing on a TextElement.
private bool _hasLocalPropertyValueChange;
private SortedList<int, TextChange> _changes;
#endregion Private Fields
}
}
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