The problem:
I've searched and searched, but I can't find information on how to get a touch event to trigger through an overlay element. I've solved the problem for mouse click events by using the following:
pointer-events: none;
That was simple enough, but it doesn't work on touch events. I know there are some mobile native things that can solve this, but this is purely for browsers--both mobile and non-mobile.
The project:
Here's my basic project, Croppy. I've got some rudimentary touch zoom and good dragging, but it's hampered by my crop div being on top of the canvas (this is visually necessary, unfortunately). There is an example included, if you wish to tinker with it directly. I'm trying to do it all without any external libraries as an exercise.
Any help or pointers would be greatly appreciated!