MapHilight v1.4.0 broken on Firefox when using SVG image (naturalWidth === 0)

[Kadigan]

I traced the issue down to the canvas context, this bit:

if(typeof img.naturalWidth != "undefined" && img.naturalWidth === 0) {

Unfortunately, as per Mozilla Bug ID #700533 (funnily enough - opened 9 years ago, and still open...), Firefox returns a 0 on both naturalWidth and naturalHeight when using an SVG image.

As such, on Firefox and when using SVG, it's locked in a permanent "waiting for the image to load" loop. The image is, of course, loaded.

If I return true from there, everything else works as exepcted.

[Kadigan]

For now, I've fixed my local version by adding a check against SVG + Mozilla combo, and then returning true. I'm using Promises to load up the image, I'm pretty sure it's loaded by that point.

Perhaps it could be something I can switch off in the params? Something like

assumeImageLoaded: true /* skips testing whether the map image is loaded or not */

to add to my defaults on configuration.