Update the UI when an APVTS parameter changes

General JUCE discussion
1

I have a UI display with setBufferedToImage(true) and I would like to only repaint when actually necessary. It’s a filter response display that should react whenever one of my EQ parameters changes. My editor is a listener to all of these parameters and sets a flag “eqDisplayChanged” when one of them changes. Then in the timer callback, the display is repainted.

The problem is that the parameter changes are not reflected in this callback. I sort of expected this because the documentation does mention that I’m supposed to use the “newValue” to see the updated value. But I thought that in the Timer thread I could expect the updated value. I’m kind of at a loss how I could update the display properly if I have no way of knowing when the parameter has actually been updated. I could manually keep track of every EQ parameter but that’s a really ugly solution. I could blindly repaint every Timer tick but I’d like to avoid that.

2

If you query the value from the APVTS itself at the time your update the UI, they should be updated. Not sure when/where you’re getting those values.

3

Are you sure? For getRawParamter value the docs say

Returns a pointer to a floating point representation of a particular parameter which a realtime process can read to find out its current value.

Note that calling this method from within AudioProcessorValueTreeState::Listener::parameterChanged() is not guaranteed to return an up-to-date value for the parameter.

Right now, I’m trying to just store separate variables in the Component that reflect the more up to date value, but it’s really not such a nice solution…

4

I tried to use Value::Listener directly but for some reason the valueChanged is not called at all…

5

Not using getRawParameter. Get the parameter by ID from the APVTS, and get its value directly from the parameter itself.

6

Same result for me unfortunately. apvts.getParameterAsValue().getValue() was not returning the same thing as the newValue passed into parameterChanged. Either way, do they not use the same underlying logic?

7

IIRC, I used the same method in a wave-shapper and it did work. I am not sure why it does not work in your case. According to the documentation, getRawParameterValue() should return the up-to-date value outside the parameterChanged().
By the way, why not using juce::AsyncUpdater to trigger the repaint()? Since you only need to repaint when the filter changes, it is more intuitive.

8

I have it working with the solution I mentioned but still not sure why getRawParameterValue isn’t working… I’ll look into it if I run into the problem again on another component.

I suppose I could use AsyncUpdater but doesn’t repaint just notify the UI thread (or whatever handles it) anyways?