Web support

[hecrj]

Depends on #62 and #60.

This PR allows Coffee to compile to Wasm! 🎉

Examples

I would greatly appreciate it if you report any issues you find!

• Particles
• User Interface
• Mesh
• Fourier (thanks to @PvdBerg1998 🎉) | Source

Known issues

• Text does not render on some environments.

Implementation details

The changes basically use the new gl backend coming to wgpu to run graphics on the web using WebGL2.

The PR uses my own forks of:

• winit – implements a new web platform with support for web-sys and stdweb. Coffee uses the web-sys backend on web.
• gfx-backend-gl – fixes some issues I have detected when dealing with WebGL. More specifically, it implements the CopyImageToSurface command and it fixes a big memory leak.
• wgpu-native – implements new wiring to support the new winit features.
• wgpu-rs – adapts to the changes in wgpu-native.
• wgpu_glyph – fixes an issue with drawArraysInstanced in WebGL2 on Firefox.
• instant – fixes an Illegal invocation error when calling performance.now(). A fix should be merged soon (sebcrozet/instant#5).

This PR does not contain any additional breaking changes to the ones found in #62. The API remains unchanged, meaning web support will be mostly free for projects that are already using Coffee.

Pending work

• Contribute winit Wasm support
  • rust-windowing/winit#797
  • rust-windowing/winit#1038
  • rust-windowing/winit#1040
  • rust-windowing/winit#1089
  • rust-windowing/winit#1072
• Contribute gfx-backend-gl fixes
  • gfx-rs/gfx#2887
  • gfx-rs/gfx#2891
  • gfx-rs/gfx#2892
  • gfx-rs/gfx#2893
  • gfx-rs/gfx#2895
• Contribute wgpu-native and wgpu-rs wiring code
• Improve and merge wgpu_glyph fixes
• Wait for instant fix (sebcrozet/instant#5)
• Wait for gfx backends to integrate with the new winit (and maybe contribute!)
• Wait for rustwasm/wasm-bindgen#1513 to reach the stable toolchain
• Investigate why BGRA* texture formats do not seem to work
• Implement gamma correction
• Remove single-layered texture arrays dirtyfix (if possible)
• Investigate why twox-hash has so many collisions on Wasm
• Investigate and fix text issues on some environments
• Swap File::open with an alternative on Wasm
• Test all backends with the new event loop (#62)
• Merge #60
• Merge #62