As discussed in email, I believe that this “mock” backend is a good idea, but should be extended to implement the file effect and haptic effect interfaces, as well as the theme effect interface.

This looks fantastic.

Just a couple of comments: firstly, in ::setEffectState(), put some qDebug()s similar to the one in ::play(), so that the user gets some visual indication that the effect has been started/paused/stopped. Second, it might be nice to have dummy variables to store intensity/duration/attackTime/attackIntensity/fadeTime/fadeIntensity, and allow setting properties other than enabled (and when setting them, also qDebug() what the value of that property has been set to) in ::updateEffectProperty().

Adding more debug prints is a great idea. I did just that. Is there a point to storing values set in updateEffectProperty though? QFeedbackHapticsInterface does not offer ways to read this data(?).

I think the only thing that remains is to queue this up for a legal scan, and then we should be able to merge it in. Thanks for your patience!