This calculation is not abstract enough. A highlight is not always a DOM element. So expecting the ```x = hl.getTop() - wrapper.offset().top - defaultView.pageYOffset``` formula is not always working.

I.e. for image annotations (sorry, it is js not coffee): https://github.com/gergely-ujvari/annotorious/blob/hypo-plugin/src/hypo/hypo_image_plugin.js#L214

The correct way to do this, imho, that the highlights should have ```getX()``` and ```getH()``` calls.