/// <summary>
/// This is called by AddUndo, so that primitives are always in a fully merged state as we go.
/// </summary>
protected void MergeMostRecentUndoPrimitive()
{
// no merging unless there are at least two items
if (_primitives.Count < 2)
{
return;
}
ITextUndoPrimitive top = _primitives[_primitives.Count - 1];
ITextUndoPrimitive victim = null;
int victimIndex = -1;
for (int i = _primitives.Count - 2; i >= 0; --i)
{
if (top.GetType() == _primitives[i].GetType() && top.CanMerge(_primitives[i]))
{
victim = _primitives[i];
victimIndex = i;
break;
}
}
if (victim != null)
{
ITextUndoPrimitive newPrimitive = top.Merge(victim);
_primitives.RemoveRange(_primitives.Count - 1, 1);
_primitives.RemoveRange(victimIndex, 1);
_primitives.Add(newPrimitive);
}
}
public bool CanMerge(ITextUndoTransaction newTransaction, ITextUndoTransaction oldTransaction)
{
MergeUndoActionPolicy oldPolicy = oldTransaction.MergePolicy as MergeUndoActionPolicy;
MergeUndoActionPolicy newPolicy = newTransaction.MergePolicy as MergeUndoActionPolicy;
if (oldPolicy != null && oldPolicy._mergeNext &&
newPolicy != null && newPolicy._mergePrevious &&
oldPolicy._actionName == newPolicy._actionName)
{
// If one of the transactions is empty, than it is safe to merge
if (newTransaction.UndoPrimitives.Count == 0 ||
oldTransaction.UndoPrimitives.Count == 0)
{
return(true);
}
// Make sure that we only merge consecutive edits
ITextUndoPrimitive newPrimitive = newTransaction.UndoPrimitives[0];
ITextUndoPrimitive oldPrimitive = oldTransaction.UndoPrimitives[oldTransaction.UndoPrimitives.Count - 1];
return(newPrimitive.CanMerge(oldPrimitive));
}
return(false);
}
public bool CanMerge(ITextUndoTransaction newTransaction, ITextUndoTransaction oldTransaction)
{
// Validate
if (newTransaction == null)
{
throw new ArgumentNullException(nameof(newTransaction));
}
if (oldTransaction == null)
{
throw new ArgumentNullException(nameof(oldTransaction));
}
TextTransactionMergePolicy oldPolicy = oldTransaction.MergePolicy as TextTransactionMergePolicy;
TextTransactionMergePolicy newPolicy = newTransaction.MergePolicy as TextTransactionMergePolicy;
if (oldPolicy == null || newPolicy == null)
{
throw new InvalidOperationException("The MergePolicy for both transactions should be a TextTransactionMergePolicy.");
}
// Make sure the merge policy directions permit merging these two transactions.
if ((oldPolicy._allowableMergeDirections & TextTransactionMergeDirections.Forward) == 0 ||
(newPolicy._allowableMergeDirections & TextTransactionMergeDirections.Backward) == 0)
{
return(false);
}
// Only merge text transactions that have the same description
if (!string.Equals(newTransaction.Description, oldTransaction.Description, StringComparison.Ordinal))
{
return(false);
}
// If one of the transactions is empty, than it is safe to merge
if ((newTransaction.UndoPrimitives.Count == 0) || (oldTransaction.UndoPrimitives.Count == 0))
{
return(true);
}
// Make sure that we only merge consecutive edits
ITextUndoPrimitive newerBeforeTextChangePrimitive = newTransaction.UndoPrimitives[0];
ITextUndoPrimitive olderAfterTextChangePrimitive = oldTransaction.UndoPrimitives[oldTransaction.UndoPrimitives.Count - 1];
return(newerBeforeTextChangePrimitive.CanMerge(olderAfterTextChangePrimitive));
}