This allows to install it as an app, and provide offline support (after
the first run).
Practically, this boils down to adding a JSON file as a manifest, an
offline page to be displayed when the cached files are not avaialble,
and a JS file to cache resources and return them.
The reason for the "first run requirements" is that some browsers, will
emit an "install" by just visiting the page (to see if the JS code is
compatibile), and we do not want to force casual visitors to just
download the 10 MiB+ compressed editor WebAssembly file without pressing
the start button.
Special thanks to Hugo Locurcio (Calinou) for the initial work.
The API is implemented in javascript, and generates C functions that can
be called from godot.
This allows much cleaner code replacing all `EM_ASM` calls in our C++
code with plain C function calls.
This also gets rid of few hacks and comes with few optimizations (e.g.
custom cursor shapes should be much faster now).
No longer parse emscripten/emsdk config to detect emcc/node paths.
Use WhereIs to find "emcc" and "node", look for "node_modules" in "emcc"
path.
(cherry picked from commit 7998745237)
- Refactored the Engine code, splitted across files.
- Use MODULARIZE option to build emscripten code into it's own closure.
- Optional closure compiler run for JS and generated code.
- Enable lto support (saves ~2MiB in release).
- Can now build with tools=yes (not much to see yet).
- Dropped some deprecated code for older toolchains.
- Add onExit, and onExecute JS function.
- Add files drag and drop support.
- Add support for low precessor usage mode (via offscreen render, swap).
