We were previously emitting the signal on the thread parsing the
glyph, but signals can only be trigger from the MapThread
because the observers are living there.
For now, keep a pointer so we can subscribe/unsubscribe to events. In
the future, we should move this object completely to ResourceLoader, but
we can't do it now because we delete the ResourceLoader when changing
the style.
This is the first concrete step to remove promises from the parsing
pipeline. Buckets depending on the Sprite (i.e. SymbolBucket) won't
be created if the Sprite is not loaded yet. When the Sprite finally gets
loaded, it will fire a signal that will ultimately trigger a reparse.
We still have to expose the Sprite to the Map object as it is needed
for getting offset pixels for annotation symbols, but we can probably
improve that.
This pattern, in contrast with callbacks, allows us to clearly see
the dependency and hierarchy between the objects. It will also help
on writing unit tests as we can count how many times a notification
was triggered.
ResourceLoader will handle all the tile changes and notifications
through the Source object owned by the Style. This object lives
entirely on the Map thread and should be only accessed by it.
The observer will receive notifications every time the tile data changes
and this will probably trigger a new rendering operation.
This first patch will delegate Source loading to the ResourceLoader.
This ensures that the worker threads associated with the
style are joined before new worker threads are launched.
I don't know exactly why, but it seems to fix#1384.
Both Android and iOS now use pause/resume. The map thread is
always running, and be able to receive messages. When paused,
it will just refuse to render.
* Provide a callback so MapContext can re-render when it loads.
* Cancel in-progress loading rather than relying on keeping it
alive with a shared_ptr.
* Remove / privatize as much as possible.
