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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: Text highlights associated with a TextContainer.
//
using System.Collections;
using System.Collections.ObjectModel;
using MS.Internal;
namespace System.Windows.Documents
{
/// <summary>
/// Text highlights associated with a TextContainer.
/// </summary>
internal class Highlights
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
// Constructor.
internal Highlights(ITextContainer textContainer)
{
_textContainer = textContainer;
}
#endregion Constructors
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
/// <summary>
/// Returns the value of a property stored on scoping highlight, if any.
/// </summary>
/// <param name="textPosition">
/// Position to query.
/// </param>
/// <param name="direction">
/// Direction of content to query.
/// </param>
/// <param name="highlightLayerOwnerType">
/// Type of the matching highlight layer owner.
/// </param>
/// <returns>
/// The highlight value if set on any scoping highlight. If no property
/// value is set, returns DependencyProperty.UnsetValue.
/// </returns>
internal virtual object GetHighlightValue(StaticTextPointer textPosition, LogicalDirection direction, Type highlightLayerOwnerType)
{
int layerIndex;
object value;
HighlightLayer layer;
value = DependencyProperty.UnsetValue;
// Take the value on the closest layer. "Closest" == added first.
for (layerIndex = 0; layerIndex < this.LayerCount; layerIndex++)
{
layer = GetLayer(layerIndex);
if (layer.OwnerType == highlightLayerOwnerType)
{
value = layer.GetHighlightValue(textPosition, direction);
if (value != DependencyProperty.UnsetValue)
break;
}
}
return value;
}
/// <summary>
/// Returns true iff the indicated content has scoping highlights.
/// </summary>
/// <param name="textPosition">
/// Position to query.
/// </param>
/// <param name="direction">
/// Direction of content to query.
/// </param>
internal virtual bool IsContentHighlighted(StaticTextPointer textPosition, LogicalDirection direction)
{
int i;
for (i = 0; i < this.LayerCount; i++)
{
if (GetLayer(i).IsContentHighlighted(textPosition, direction))
{
break;
}
}
return (i < this.LayerCount);
}
/// <summary>
/// Returns the position of the next highlight start or end in an
/// indicated direction, or null if there is no such position.
/// </summary>
/// <param name="textPosition">
/// Position to query.
/// </param>
/// <param name="direction">
/// Direction of content to query.
/// </param>
internal virtual StaticTextPointer GetNextHighlightChangePosition(StaticTextPointer textPosition, LogicalDirection direction)
{
StaticTextPointer changePosition;
StaticTextPointer closestChangePosition;
int i;
closestChangePosition = StaticTextPointer.Null;
// Calculate the min of the layers' transitions.
for (i = 0; i < this.LayerCount; i++)
{
changePosition = GetLayer(i).GetNextChangePosition(textPosition, direction);
if (!changePosition.IsNull)
{
if (closestChangePosition.IsNull)
{
closestChangePosition = changePosition;
}
else if (direction == LogicalDirection.Forward)
{
closestChangePosition = StaticTextPointer.Min(closestChangePosition, changePosition);
}
else
{
closestChangePosition = StaticTextPointer.Max(closestChangePosition, changePosition);
}
}
}
return closestChangePosition;
}
/// <summary>
/// Returns the closest neighboring TextPointer in an indicated
/// direction where a property value calculated from an embedded
/// object, scoping text element, or scoping highlight could
/// change.
/// </summary>
/// <param name="textPosition">
/// Position to query.
/// </param>
/// <param name="direction">
/// Direction of content to query.
/// </param>
/// <returns>
/// If the following symbol is TextPointerContext.EmbeddedElement,
/// TextPointerContext.ElementBegin, or TextPointerContext.ElementEnd, returns
/// a TextPointer exactly one symbol distant.
///
/// If the following symbol is TextPointerContext.Text, the distance
/// of the returned TextPointer is the minimum of the value returned
/// by textPosition.GetTextLength and the distance to any highlight
/// start or end edge.
///
/// If the following symbol is TextPointerContext.None, returns null.
/// </returns>
internal virtual StaticTextPointer GetNextPropertyChangePosition(StaticTextPointer textPosition, LogicalDirection direction)
{
StaticTextPointer changePosition;
StaticTextPointer characterRunEndPosition;
switch (textPosition.GetPointerContext(direction))
{
case TextPointerContext.None:
changePosition = StaticTextPointer.Null;
break;
case TextPointerContext.Text:
changePosition = GetNextHighlightChangePosition(textPosition, direction);
characterRunEndPosition = textPosition.GetNextContextPosition(LogicalDirection.Forward);
if (changePosition.IsNull ||
characterRunEndPosition.CompareTo(changePosition) < 0)
{
changePosition = characterRunEndPosition;
}
break;
case TextPointerContext.EmbeddedElement:
case TextPointerContext.ElementStart:
case TextPointerContext.ElementEnd:
default:
changePosition = textPosition.CreatePointer(+1);
break;
}
return changePosition;
}
/// <summary>
/// Adds a HighlightLayer to this collection.
/// </summary>
/// <param name="highlightLayer">
/// HighlightLayer to add.
/// </param>
internal void AddLayer(HighlightLayer highlightLayer)
{
// Delay alloc the layers store.
if (_layers == null)
{
_layers = new ArrayList(1);
}
Invariant.Assert(!_layers.Contains(highlightLayer));
_layers.Add(highlightLayer);
highlightLayer.Changed += new HighlightChangedEventHandler(OnLayerChanged);
// Raise initial change event to cover existing content.
RaiseChangedEventForLayerContent(highlightLayer);
}
/// <summary>
/// Removes a HighlightLayer to this collection.
/// </summary>
/// <param name="highlightLayer">
/// HighlightLayer to add.
/// </param>
internal void RemoveLayer(HighlightLayer highlightLayer)
{
Invariant.Assert(_layers != null && _layers.Contains(highlightLayer));
// Raise final change event to cover existing content.
RaiseChangedEventForLayerContent(highlightLayer);
highlightLayer.Changed -= new HighlightChangedEventHandler(OnLayerChanged);
_layers.Remove(highlightLayer);
}
/// <summary>
/// Retrieve a HighlightLayer from this collection
/// </summary>
/// <param name="highlightLayerType">
/// </param>
/// <returns>
/// The first added HighlightLayer owned by the type.
/// null if no such HighlightLayer can be found.
/// </returns>
internal HighlightLayer GetLayer(Type highlightLayerType)
{
int i;
for (i = 0; i < this.LayerCount; i++)
{
if (highlightLayerType == GetLayer(i).OwnerType)
{
return GetLayer(i);
}
}
return null;
}
#endregion Internal Methods
//------------------------------------------------------
//
// Protected Properties
//
//------------------------------------------------------
#region Protected Properties
protected ITextContainer TextContainer
{
get
{
return _textContainer;
}
}
#endregion Protected Properties
//------------------------------------------------------
//
// Internal Events
//
//------------------------------------------------------
#region Internal Events
/// <summary>
/// Event raised when a highlight is inserted, removed, moved, or
/// has a local property value change.
/// </summary>
internal event HighlightChangedEventHandler Changed;
#endregion Internal Events
//------------------------------------------------------
//
// Private Methods
//
//------------------------------------------------------
#region Private Methods
// Returns a contained HighlightLayer.
private HighlightLayer GetLayer(int index)
{
return (HighlightLayer)_layers[index];
}
// Callback for changes on a single layer.
private void OnLayerChanged(object sender, HighlightChangedEventArgs args)
{
// Forward on the event to any listeners.
if (this.Changed != null)
{
Changed(this, args);
}
}
// Raises initial or final change event for added/removed layers.
private void RaiseChangedEventForLayerContent(HighlightLayer highlightLayer)
{
List<TextSegment> ranges;
StaticTextPointer highlightTransitionPosition;
StaticTextPointer highlightRangeStart;
if (this.Changed != null)
{
// Build a list of all highlights in this layer -- they're all
// going to "change" as the layer is added/removed.
ranges = new List<TextSegment>();
highlightTransitionPosition = _textContainer.CreateStaticPointerAtOffset(0);
while (true)
{
// Move to the next highlight start.
if (!highlightLayer.IsContentHighlighted(highlightTransitionPosition, LogicalDirection.Forward))
{
highlightTransitionPosition = highlightLayer.GetNextChangePosition(highlightTransitionPosition, LogicalDirection.Forward);
// No more highlights?
if (highlightTransitionPosition.IsNull)
break;
}
highlightRangeStart = highlightTransitionPosition;
highlightTransitionPosition = highlightLayer.GetNextChangePosition(highlightTransitionPosition, LogicalDirection.Forward);
Invariant.Assert(!highlightTransitionPosition.IsNull, "Highlight start not followed by highlight end!");
ranges.Add(new TextSegment(highlightRangeStart.CreateDynamicTextPointer(LogicalDirection.Forward), highlightTransitionPosition.CreateDynamicTextPointer(LogicalDirection.Forward)));
}
if (ranges.Count > 0)
{
Changed(this, new LayerHighlightChangedEventArgs(new ReadOnlyCollection<TextSegment>(ranges), highlightLayer.OwnerType));
}
}
}
#endregion Private Methods
//------------------------------------------------------
//
// Private Properties
//
//------------------------------------------------------
#region Private Properties
// Count of contained HighlightLayers.
private int LayerCount
{
get
{
return (_layers == null) ? 0 : _layers.Count;
}
}
#endregion Private Properties
//------------------------------------------------------
//
// Private Types
//
//------------------------------------------------------
#region Private Types
// EventArgs for the Changed event.
private class LayerHighlightChangedEventArgs : HighlightChangedEventArgs
{
// Constructor.
internal LayerHighlightChangedEventArgs(ReadOnlyCollection<TextSegment> ranges, Type ownerType)
{
_ranges = ranges;
_ownerType = ownerType;
}
// List of changed ranges.
internal override IList Ranges
{
get
{
return _ranges;
}
}
// Type identifying the owner of the changed layer.
internal override Type OwnerType
{
get
{
return _ownerType;
}
}
// List of changed ranges.
private readonly ReadOnlyCollection<TextSegment> _ranges;
// Type identifying the owner of the changed layer.
private readonly Type _ownerType;
}
#endregion Private Types
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
// Associated TextContainer.
private readonly ITextContainer _textContainer;
// List of contained HighlightLayers.
private ArrayList _layers;
#endregion Private Fields
}
}
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