VectorDraw使用教程：清空重做堆棧

最近一直有網友在問，在使用VectorDraw的過程中如何在用戶執行一個新的動作之后清空重做棧。有兩種方法可以實現這一點。

方案一

vdFramedControl1.BaseControl.ActiveDocument.UndoHistory.OnStoreValue += new VectorDraw.Professional.UndoRedo.ModificationHistory.StoreValueEventHandler(UndoHistory_OnStoreValue);

Add this function as the event handler:
bool whileRedo = false;
void UndoHistory_OnStoreValue(object sender, bool isRedo, object propObject, string propName, object value, ref bool Cancel)
{
//We use this check to make sure that the new Undo value stored is not coming from a Redo command.
if (!isRedo && !whileRedo)
vdFramedControl1.BaseControl.ActiveDocument.UndoHistory.ClearRedoStack();
}
Also get this event in order to override the functionality of Redo:
vdFramedControl1.CommandLine.CommandExecute += new VectorDraw.Professional.vdCommandLine.CommandExecuteEventHandler(CommandLine_CommandExecute);
Add this function to handle the above event:
void CommandLine_CommandExecute(string commandname, bool isDefaultImplemented, ref bool success)
{
//Here we override the Redo command in order to set the whileRedo function to true. That way we will know if the OnStoreValue event mentioned above is called due to a Redo function.
if (string.Compare(commandname, "redo", true) == 0 || string.Compare(commandname, "r", true) == 0)
{
success = true; doc.CommandAction.Prompt("\r\n" + commandname); doc.CommandAction.Prompt(null);

whileRedo = true;
doc.UndoHistory.Redo();
whileRedo = false;

doc.Update();
doc.Invalidate();
}
}

使用上述代碼后，每次修改對象屬性，或添加一個創建undo值的新對象，重做堆棧將被清除。這樣的話，在用戶新增一個項目或修改一個屬性后，無需 Redoing 選項。

方案二

vdFramedControl1.CommandLine.CommandExecute += new VectorDraw.Professional.vdCommandLine.CommandExecuteEventHandler(CommandLine_CommandExecute);
Add this function to handle the above event:
void CommandLine_CommandExecute(string commandname, bool isDefaultImplemented, ref bool success)
{
//Here we override every command after which we want the Redo stack cleared
if (string.Compare(commandname, "line", true) == 0 || string.Compare(commandname, "l", true) == 0
|| string.Compare(commandname, "rect", true) == 0 || string.Compare(commandname, "move", true) == 0)
{
//Don't set success to true, so that the execution of already implemented commands won't stop after this function!

vdFramedControl1.BaseControl.ActiveDocument.UndoHistory.ClearRedoStack();

doc.Update();
doc.Invalidate();
}
}

使用上述代碼后，每次使用的矩形或移動命令時，重做堆棧都將被清除。