Collecting rendering statistics in Libvob
There are several reasons to want rendering statistics: to adjust complexity parameters at run-time, or (currently most importantly) to load high-resolution mipmap levels of the currently most prominent textures.
The requirements for the latter application are more stringent; specifically, the statistics have to be pushed from the activated collectors on the C++ side to the Java side to avoid having to explicitly poll each collector.
Requirements
When statistics get collected, a way to 1) ignore (zero) them, and 2) call callbacks for them.
We only need one central (static) handling point for now, but implementing more in the future should be trivial..
General
Referencing
The main difficulty in implementing the push of data is to ensure that the Java objects will be garbage corrected. Because the Java garbage collector cannot know that a global reference inside the C++ arena depends only on a given Java object (i.e. when the Java proxy of a C++ renderable is deleted, the C++ renderable gets deleted).
Thus, there must be a weak reference in the chain from the C++ object to the callback. It's probably easiest to do this on the java side.
Collection point
In order to make the pushing of triggered statistics possible after the rendering has finished, there needs to be a C++ queue containing pointers to all activated statistics.
When statistics are inserted into a statistics-collecting object, the object should check if it has been inserted to the activated statistics queue. If not, it should insert itself.
