loading of assets after ready()

[oberhamsi]

currently only one set of assets can be preloaded before ready() is executed. for large games it would be useful to be able to load additional resources after the game is already initialized (e.g. for loading the next map assets).

API RFC

calling preload() after initialization triggers another async preloader. Once all assets were loaded, an event PRELOAD_SUCCESS or PRELOAD_ERROR is triggered.

the preloadId returned by preload() and in the resulting event is there, in case the game triggers multiple preload()s and needs to differantiate which one was finished:

// in game code:
var preloadId = gamejs.preload(['./images/foo.png']);

// in event handler:
if (event.type === gamejs.event.PRELOAD_SUCCESS) {
       gamejs.log('Loaded assets ', event.preloadId);
}

[systemstart]

sounds good.

maybe let preload return an object which can be queried for progress and which emits success/error event.