doodle/wasm
Noah Petherbridge 48fc40ade4 Texture Caching for WASM Canvas Engine
* Add RGBA color blending support in WASM build.
* Initial texture caching API for Canvas renderer engine. The WASM build
  writes the chunk caches as a "data:image/png" base64 URL on the
  browser's sessionStorage, for access to copy into the Canvas.
* Separated the ClickEvent from the MouseEvent (motion) in the WASM
  event queue system, to allow clicking and dragging.
* Added the EscapeKey handler, which will abruptly terminate the WASM
  application, same as it kills the window in the desktop build.
* Optimization fix: I discovered that if the user clicks and holds over
  a single pixel when drawing a level, repeated Set() operations were
  firing meaning multiple cache invalidations. Not noticeable on PC but
  on WebAssembly it crippled the browser. Now if the cursor isn't moving
  it doesn't do anything.
2019-06-26 22:44:08 -07:00
..
index.html Initial WebAssembly Build Target 2019-06-26 18:40:40 -07:00
main_wasm.go Texture Caching for WASM Canvas Engine 2019-06-26 22:44:08 -07:00
Makefile Initial WebAssembly Build Target 2019-06-26 18:40:40 -07:00
README.md Initial WebAssembly Build Target 2019-06-26 18:40:40 -07:00
server.go Initial WebAssembly Build Target 2019-06-26 18:40:40 -07:00
wasm_exec.js Initial WebAssembly Build Target 2019-06-26 18:40:40 -07:00

WebAssembly Port

Build and Test

Change to the wasm/ folder and type make to build doodle.wasm

To test it with a local Go server, cd to the wasm/ folder and run go run server.go and visit http://localhost:8080/

Copy the fonts and assets folders from the project root to the wasm/ directory so they're available over HTTP.

wasm_exec.js

To update the wasm_exec.js to match your version of Go:

# Fedora: install golang-misc
sudo dnf install golang-misc

# Copy the wasm_exec.js
cp $(go env GOROOT)/misc/wasm/wasm_exec.js ./

Font Support

Fonts are implemented as CSS embedded fonts configured in wasm/index.html

The font family name should match the filename, sans .ttf extension, for example "DejaVuSans-Bold". Doodle's internal logic converts a FontFilename string like "./fonts/DejaVuSans.ttf" into the base name to use as the font family. It also has fallbacks for sans-serif and serif in case of any problems.

Known Bugs and Limitations

  • github.com/kirsle/golog
    • The detection of an interactive terminal is broken in WASM.
    • terminal.IsTerminal(int(os.Stdout.Fd()))
    • As a workaround, comment it out and hardcode to false
  • Userdir
    • For WASM we'll want to use localStorage to store user drawings instead of the userdir.
  • Wallpaper support
    • WASM can't use os.Open to read the wallpaper image, so will need another method to load the image.
    • Texture caching support isn't implemented yet to hold the four corner textures of a wallpaper.
    • As a workaround, added a wallpaper.ready boolean and relevant functions exit early for WASM so wallpapers don't render at all.