How to perform an undo action on AudioProcessorValueTreeState AudioProcessorParameters?

General JUCE discussion
1

Hi,

Is it possible to undo AudioProcessorParameter changes via the UndoManager in the
AudioProcessorValueTreeState? Or for what takes the AudioProcessorValueTreeState the UndoManager?

    AudioProcessor&processor = ...;
    UndoManager*undoManager = ...;
    AudioProcessorValueTreeState* state 
        = new AudioProcessorValueTreeState(processor,undoManager);

    AudioProcessorParameter* param = state->createAndAddParameter(...);
    param->setValue( x );

    // this does not work
    bool success = undoManager->undo();

Cheers

2

You need to call startTransaction so it knows which batch of actions to undo.

3

Like this? (startTransaction I could not find.)

    AudioProcessor&processor = ...;
    UndoManager*undoManager = ...;
    AudioProcessorValueTreeState* state 
        = new AudioProcessorValueTreeState(processor,undoManager);

    AudioProcessorParameter* param = state->createAndAddParameter(...);
    undoManager->beginNewTransaction();
    param->setValue( x );
    undoManager->beginNewTransaction();
    param->setValue( y );

    // this does not work
    bool success = undoManager->undo();
4

Hi, back to this.

The ValueTree (state) in AudioProcessorValueTreeState is not valid by default - is this right? Have I to initialize the tree with a valid one? Otherwise the AudioProcessorValueTreeState constructor should look like this:

AudioProcessorValueTreeState::AudioProcessorValueTreeState (AudioProcessor& p, UndoManager* um)
    :  ...,
      state("state") // I miss this initialisation
{ 
   // ...
}

Or do I understand the concept wrong?

Thanks!

5

That’s what I missed at first. Add your parameters with createAndAddParameters(). And then create a ValueTree with processorState.state = ValueTree(“FilterParameters”);

6

Achder is right, you have to set it to a valid one. This is because if you serialize it (e.g. to XML) the root node needs to have a valid tag name. This is also the same thing that makes a ValueTree valid or invalid.

I think you get an assert if you set the state before the createParameters IIRC, so I usually add at the end of the constructor:

myAPValueTreeState.state = ValueTree ("MyPluginName");

HTH