[WIP] Be able to control when we cancel events.

[iangilman]

As part of our event processing in MouseTracker, we cancel events sometimes. In some cases, we need to be able to turn that off and let the events go through to the browser. This patch is a work in progress to explore how to do that; it's specifically focused around being able to let the touch drag events through to the browser so it does its normal scrolling. I think something similar is needed to allow the browser to do its normal zooming for #1534.

@msalsbery Any thoughts?

[msalsbery]

@iangilman

I have a lot of thoughts on this! When I did the Mousetracker overhaul I left the behavior the way it was, which is certainly not ideal, and continues to frustrate me. The OpenSeadragonViewrInputHook plugin helps to at least get a crack at events before the viewer, but those are OpenSeadragon events, and to mess with the original DOM events, when it’s even possible, still gets tricky and requires a lot of internal knowledge.

I haven’t looked at this WIP patch yet, and letting browsers do default actions brings another level of complexity, but Mousetracker at least at its core needs to have the capability of letting events flow through the DOM layers when needed. That’s something I’m very much interested in doing. With that in place, then viewr features/options could be added to allow default browser behavior when desired...functionality that brings an entirely new level of painful complexity.

Anyway, I’ve been looking into this out of necessity, and I’ll have more to come...

[iangilman]

Great! I look forward to seeing what you find! Let me know if you need any explanation about what I was trying to do here.