SpriteBatch, FilterMode and src/offset

[maciejhirsz]

Added couple of things:

• SpriteBatch compatible with ggez. It's working, although it's actually not batching anything, so room for improvement here!
• FilterMode for Image via set_filter. Works as intended, although I'm not particularly fond of having to use a dirty boolean flag, so this also can be done better.
• The src on DrawParam actually works now. I'd appreciate if someone actually looked at what I did here as this was first time in my life I touched GLSL :P.
• Fixed scale and offset on DrawParam.

I hope I haven't broken anything in Zemeroth with this 😅. I've uploaded a demo video of what I'm building, all sprite animations and font rendering is done via atlases, so src not working broke things horribly.

[not-fl3]

Wow, happy to see good-web-game actually used in another project!
And thank you very much for the great PR!

Can confirm that it did not break Zemeroth 👍

I don't have any quick fixes to avoid the dirty flag right now. I think it should should be possible to use webgl's set_filter just in the image's set_filter immediately. I see the texture binding problem leaded to the dirty flag, but I am considering this as a good-web-game's issue that should be fixed somehow.
Going to try a few things soon - maybe introduce some internal dirty flag to force rebind cached uniforms? Not sure yet.

[maciejhirsz]

Caching uniforms would help a bit, though for me biggest win in FPS would definitely come form sprite batching, I'll make an issue for that.