Remove dependency on DOM classes

[vorg]

Currently createTexture2D checks if provided texture object is some kind of image data by doing following checks

if(obj instanceof HTMLCanvasElement ||
       obj instanceof HTMLImageElement ||
       obj instanceof HTMLVideoElement ||
       obj instanceof ImageData) {

that prevents us from suppling valid texture object in non browser environment like Plask.

I've run into this issue while trying to use gl-sprite-text in pex and even though i have texture wrapper passing this test:

if(obj.shape && obj.data && obj.stride) {

it breaks because of the DOM classes.

[mikolalysenko]

Yeah, this is a good idea. Maybe another option could be to use Object.toString() or perhaps we could add a test to skip that whole conditional if HTMLCanvasElement etc. are not defined in the current environment?

@hughsk @mattdesl any ideas?

[hughsk]

👍

It's not pretty but this would work without changing the existing behaviour at all:

if (('undefined' != typeof HTMLCanvasElement && obj instanceof HTMLCanvasElement) ||
    ('undefined' != typeof HTMLImageElement && obj instanceof HTMLImageElement) ||
    ('undefined' != typeof HTMLVideoElement && obj instanceof HTMLVideoElement) ||
    ('undefined' != typeof ImageData && obj instanceof ImageData)) {

[mattdesl]

👍 to @hughsk's solution.

also @vorg, see my thoughts on text rendering here. Feel free to add any thoughts:
stackgl/contributing#26

[gre]

I've provided a PR that implement @hughsk suggested solution.