Modularize emscripten build.

[prestomation]

By default, emscripten's generated javascript modules lives in the global object "Module'.

This makes it impossible to load multiple emscripten modules on the same page if they are all built using this default.

In attempt to avoid namespace collision, this change modularizes the emscripten build so the Module is instead called 'BASIS'. See the emscripten FAQ for more info: https://emscripten.org/docs/getting_started/FAQ.html

Many of the target applications for Basis are possibly using other emscripten modules, so this change will reduce friction of adding Basis(assuming any of their existing modules are not modularized)

This will require existing consumers of this package to change how they load Basis when they next upgrade their Basis build.

Testing:

The existing webgl/(texture|gltf) pages have been updated to use the new name and seem to operate as before

(Built/tested on OS X with emscripten sdk-1.38.29-64bit)

[zeux]

How was basis_transcoder.wasm rebuilt? It looks like in this build the settings from CMakeLists.txt from #7 aren't picked up, so the transcoder is back to being large.

[prestomation]

Hmm, I'm not sure why this is.
I built using the instructions in the README(pretty much just emcmake ../ && make) and this change is off HEAD.

I noticed my version of emscripten is behind latest. I've upgraded to sdk-1.38.31-64bit but I'm not seeing any change to the output size.

Checking out origin/master and rebuilding also gives me the larger size so possibly something else is going on.

I'll continue investigating, thanks!

[zeux]

Ok this is my fault; my change in #7 didn't update CMakeLists correctly :( I'll make a patch for this.

[zeux]

Added #27, sorry about that!

[prestomation]

No worries! I will rebase and update this PR once #27 is merged

[prestomation]

This PR has been rebased with HEAD after #27's merge

[zeux]

Just want to make sure everything is fine with #27 - was the .wasm file rebuilt after rebase? GH seems to say that the .wasm file in this PR is still very large, but when I locally do this on a fresh Linux box:

$ git clone https://github.com/emscripten-core/emsdk
$ cd emsdk
$ ./emsdk install latest
$ ./emsdk activate latest
$ source ./emsdk_env.sh
$ cd ..
$ git clone https://github.com/prestomation/basis_universal
$ cd basis_universal/webgl/transcoder/build
$ emcmake cmake ..
$ make

I get this:

$ ls -la
-rw-rw-rw- 1 zeux zeux  61521 Jun 11 17:53 basis_transcoder.js
-rw-rw-rw- 1 zeux zeux 219388 Jun 11 17:53 basis_transcoder.wasm
$ cat basis_transcoder.js | head -n 2

var BASIS = (function() {

(the 200-ish KB .wasm file is what I'd expect, whereas this PR still has a ~750 KB file)

[prestomation]

Sorry! I'm not used to checking in binaries. I had rebuilt, confirmed the size change,but did not checkin updated binaries. Will do so early tomorrow.

[prestomation]

third time is the charm: updated binary now included

[kenrussell]

Could we please review and merge this? It's important for modularity of Basis Universal's WebAssembly build. Thanks!

[richgel999]

Got it, thanks!