Question about redo/undo - Diagramming Components - Windows Forms

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Question about redo/undo (Read 3406 times)

CanadaProgrammer Full Member Offline I love YaBB 1G - SP1! Posts: 113 Joined: Jun 30^th, 2011	Question about redo/undo Jul 11^th, 2011 at 8:15am	Print Post
	I do action A1, A2, then undo, undo, redo, redo,... that can work fine. But if I do action A1, A2, undo , do action A3, then I could not redo A2. So I think when a action was recorded then the redo buffer will be cleared. Is it true ?


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Stoyo God Member Offline MindFusion support Posts: 13230 Joined: Jul 20^th, 2005	Re: Question about redo/undo Reply #1 - Jul 11^th, 2011 at 9:11am	Print Post
	It's true. Any new action you do could modify the diagram in a way that makes the commands ahead in the buffer invalid, so they are purged. For example, if the new action is removing a node, you can't redo a modify command recorded for it, or a create-link command that connects it to another node.


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CanadaProgrammer Full Member Offline I love YaBB 1G - SP1! Posts: 113 Joined: Jun 30^th, 2011	Re: Question about redo/undo Reply #2 - Jul 12^th, 2011 at 1:59am	Print Post
	It's not a good news for me. There is a action to move a shape(or a node). Diagram object can redo and undo it fine. That means the orignal position and current position of a shape must be saved in a command object. But I can not find these data in a modify command. If I can get these data then it's much easier for me to handle redo/undo by myself. Is there any helpful idea ?


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Stoyo God Member Offline MindFusion support Posts: 13230 Joined: Jul 20^th, 2005	Re: Question about redo/undo Reply #3 - Jul 12^th, 2011 at 6:15am	Print Post
	I don't think that's safe even for move operations. For example if there are containers, groups or auto-routed links involved, you can easily get incorrect results if you undo some action, move a node and redo. Now if all that your application does is letting the user move existing nodes around, you can handle NodeStartModifying and NodeModified to record the node positions and keep them in your own undo/redo list.


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CanadaProgrammer Full Member Offline I love YaBB 1G - SP1! Posts: 113 Joined: Jun 30^th, 2011	Re: Question about redo/undo Reply #4 - Jul 13^th, 2011 at 2:36am	Print Post
	Yes I already handled event NodeStartModify but, this event will be lauched only one node selected. If I choose (nodes) or (node and links) then the event does not work.


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Stoyo God Member Offline MindFusion support Posts: 13230 Joined: Jul 20^th, 2005	Re: Question about redo/undo Reply #5 - Jul 13^th, 2011 at 7:43am	Print Post
	You can record initial positions from one of the multiple-selection related events then, such as SelectionChanged or SelectionMoving.


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