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 void PerformTransactionMerge(ITextUndoTransaction oldTransaction, ITextUndoTransaction newTransaction)
{
MergeUndoActionPolicy oldPolicy = (MergeUndoActionPolicy)oldTransaction.MergePolicy;
MergeUndoActionPolicy newPolicy = (MergeUndoActionPolicy)newTransaction.MergePolicy;
// Remove trailing AfterTextBufferChangeUndoPrimitive from previous transaction and skip copying
// initial BeforeTextBufferChangeUndoPrimitive from newTransaction, as they are unnecessary.
if (oldTransaction.UndoPrimitives.Count > 0 && oldPolicy._addedTextChangePrimitives)
{
oldTransaction.UndoPrimitives.RemoveAt(oldTransaction.UndoPrimitives.Count - 1);
}
int copyStartIndex = newPolicy._addedTextChangePrimitives ? 1 : 0;
for (int i = copyStartIndex; i < newTransaction.UndoPrimitives.Count; i++)
{
oldTransaction.UndoPrimitives.Add(newTransaction.UndoPrimitives[i]);
}
}
