Hey,

I'm wanting to build in undo and redo functionality into my MindFusion project but i'm having a few issues that i need some guidance with.

In my software, the user doesn't just create a single node like with most MF examples but one operation may create a few nodes all linked together so in order to do undo/redo i've found that i must use composite commands.

Undoing a single command works absolutely fine; the nextUndo parameter of the UndoManager is populated with the compositeCommand and pressing my undo button does exactly what you'd expect. My first issue is that subsequent presses of the button don't seem to do anything, as though it's run out of history... Does the Capacity field refer to how many composite commands it holds? Or how many individual commands (I.e if ONE composite command has TWENTY individual commands, how many places in history capacity does this take up).

My second problem is that Redo doesn't seem to work at all, no matter what happens the nextRedo method of the UndoManager always remains at Nothing. Am i missing something?

Any help will be great!

Thanks,
Cass

Hi Stoyan,

Cheers for the reply.

I'm enabling undo in the UndoManager and then using the following code to create a command

        Dim composite As CompositeCmd = doc.UndoManager.StartComposite("Create")
       'Do things here
        composite.Execute() 

Hi,

The idea of my program is very similar to the Workflow Designer MF example where you drag a control onto any link on the diagram. The difference being, some controls might be a single node whereas others could be any number of nodes and links... The code i sent is done in the dragDrop method... So the "StartComposite" line is at the beginning of the sub, and then the actual creation is done, and the Execute method is at the end.

The title does stay at "Create", and in the example i've just tried the subCommands list in composite contains 28 commands.

I have just noticed though - some of those 28 commands are actually OTHER compositeCmd records where it does something else as part of the dragDrop. Could that be a problem??

Cass

Hi,

The actual CompositeCmds inside it are internally created and have a title of "Route".

The other commands in there are AddItemCmd and RemoveItemCmd records and these are coded by me using the StartComposite command in separate methods so i'll try and change these for CompositeCommands first of all!

Thanks for your help so far!

Cass

Hi,

Could you trace it with a debugger to verify if execution ever reaches the composite.Execute() call? There could be some exception thrown before that, and you might never notice it because .NET catches all exceptions thrown from OLE drag-and-drop handlers.

Stoyan

Hi,

I have tried this both with and without FlowchartLayout but couldn't see any problems. Here is my test project, let me know what I should change to reproduce:
https://mindfusion.eu/_samples/WorkflowDesignerUndoTest.zip

Stoyan

Hi,

Doing anything that modifies the diagram structure or item positions will clear all redo-able commands in the queue since they would not be consistent with the new diagram state in the general case. That would explain why there's nothing to redo. If your LayoutDiagram method creates a composite command as well, perhaps it was the one left open - check if it is executed at the end.

I hope that helps,
Stoyan