When scrolling within an HTML widget, you’re going to be sending your scroll X / Y events to that window, which is a different level from your main Hype scene. So if there’s a way to instantiate the ‘canvas’ object within a regular rectangle that would help you workaround this. You would need to run a function ‘On Layout Load’ that inserts the Processing element within that rectangle.
Alternatively, you would need to setup cross-frame communication so a scroll in one frame can be ‘heard’ by the parent frame: Control a timeline from an external HTML ( communicating between iframes )