Class GraphicsContext

src/main/java/field/graphics/GraphicsContext.java:35–227

Our main representation for an OpenGL graphics context. The key complexity in doing graphics is that we wish to defer execution of drawing code to a particular time and place in the internalScene graph and that this internalScene graph drawing can only take place inside an OpenGL graphics contex

 * enterContext() and exitContext().
 */
public class GraphicsContext {

    public final ReentrantLock lock = new ReentrantLock(true);

    static protected final ThreadLocal<GraphicsContext> currentGraphicsContext = new ThreadLocal<>();
    static List<GraphicsContext> allGraphicsContexts = new ArrayList<GraphicsContext>();

    public final StateTracker stateTracker = new StateTracker();
    public final UniformCache uniformCache = new UniformCache();

    protected WeakHashMap<Object, Object> context = new WeakHashMap<>();

    static public GraphicsContext getContext() {
        return currentGraphicsContext.get();
    }

    static public boolean isResizing = false;

    /** the preQueue is a list of things that run every time that the context is entered */
    public final BlockingQueue<Runnable> preQueue = new LinkedBlockingQueue<>();

    /** the postQueue is a list of things that run _once_ when the context is exited --- it is cleared every exit (although it is safe to add additional items to this during the exit) */
    public final BlockingQueue<Runnable> postQueue = new LinkedBlockingQueue<>();

    static public GraphicsContext newContext() {
        GraphicsContext c = new GraphicsContext();
        allGraphicsContexts.add(c);
        currentGraphicsContext.set(c);
        return c;
    }

    static public void enterContext(GraphicsContext c) {
        Log.log("graphics.trace", () -> ">> graphics context begin ");
        currentGraphicsContext.set(c);

        ArrayList<Runnable> q = new ArrayList<>(currentGraphicsContext.get().preQueue);
//        currentGraphicsContext.get().preQueue.clear();

        for (Runnable r : q)
            r.run();
    }

    static public void exitContext(GraphicsContext c) {
        if (currentGraphicsContext.get() != c) throw new Error();
        ArrayList<Runnable> q = new ArrayList<>(currentGraphicsContext.get().postQueue);
        currentGraphicsContext.get().postQueue.clear();

        for (Runnable r : q)
            r.run();

        currentGraphicsContext.set(null);
        Log.log("graphics.trace", () -> "<< graphics context end");
    }

    static public <T> T get(Object o) {
        return (T) currentGraphicsContext.get().context.get(o);
    }