Added frame identification support.

backends/gdx-backend-android/src/com/badlogic/gdx/backends/android/AndroidGraphics.java

@@ -69,6 +69,7 @@
 	protected long lastFrameTime = System.nanoTime();
 	protected float deltaTime = 0;
 	protected long frameStart = System.nanoTime();
+	protected long frameId = -1;
 	protected int frames = 0;
 	protected int fps;
 	protected WindowedMean mean = new WindowedMean(5);
@@ -411,6 +412,7 @@ public void onDrawFrame (javax.microedition.khronos.opengles.GL10 gl) {
 				}
 			}
 			app.getInput().processEvents();
+			frameId++;
 			app.getApplicationListener().render();
 		}
 
@@ -444,6 +446,11 @@ public void onDrawFrame (javax.microedition.khronos.opengles.GL10 gl) {
 		frames++;
 	}
 
+	@Override
+	public long getFrameId () {
+		return frameId;
+	}
+
 	/** {@inheritDoc} */
 	@Override
 	public float getDeltaTime () {

backends/gdx-backend-android/src/com/badlogic/gdx/backends/android/AndroidGraphicsLiveWallpaper.java

@@ -217,6 +217,7 @@ public void onDrawFrame (javax.microedition.khronos.opengles.GL10 gl) {
 			 */
 
 			app.getInput().processEvents();
+			frameId++;
 			app.getApplicationListener().render();
 		}
 

backends/gdx-backend-headless/src/com/badlogic/gdx/backends/headless/HeadlessApplication.java

@@ -120,6 +120,7 @@ void mainLoop () {
 					t = n + renderInterval;
 
 				executeRunnables();
+				graphics.incrementFrameId();
 				listener.render();
 				graphics.updateTime();
 

backends/gdx-backend-headless/src/com/badlogic/gdx/backends/headless/mock/graphics/MockGraphics.java

@@ -24,6 +24,7 @@
  * server and client as simple as possible.
  */
 public class MockGraphics implements Graphics {
+	long frameId = -1;
 	float deltaTime = 0;
 	long frameStart = 0;
 	int frames = 0;
@@ -55,6 +56,11 @@ public int getHeight() {
 		return 0;
 	}
 
+	@Override
+	public long getFrameId() {
+		return frameId;
+	}
+
 	@Override
 	public float getDeltaTime() {
 		return deltaTime;
@@ -178,4 +184,8 @@ public void updateTime () {
 		frames++;
 	}
 
+	public void incrementFrameId () {
+		frameId++;
+	}
+
 }

backends/gdx-backend-jglfw/src/com/badlogic/gdx/backends/jglfw/JglfwGraphics.java

@@ -53,6 +53,7 @@
 	private volatile boolean isContinuous = true, renderRequested;
 	volatile boolean foreground, minimized;
 
+	private long frameId = -1;
 	private float deltaTime;
 	private long frameStart, lastTime = -1;
 	private int frames, fps;
@@ -155,6 +156,7 @@ void frameStart (long time) {
 			frameStart = time;
 		}
 		frames++;
+		frameId++;
 	}
 
 	void sizeChanged (int width, int height) {
@@ -192,6 +194,10 @@ public int getHeight () {
 		return height;
 	}
 
+	public long getFrameId () {
+		return frameId;
+	}
+
 	public float getDeltaTime () {
 		return deltaTime;
 	}

backends/gdx-backend-lwjgl/src/com/badlogic/gdx/backends/lwjgl/LwjglAWTCanvas.java

@@ -256,6 +256,7 @@ void render () {
 
 		input.processEvents();
 		if (running) {
+			graphics.frameId++;
 			listener.render();
 			if (audio != null) {
 				audio.update();

backends/gdx-backend-lwjgl/src/com/badlogic/gdx/backends/lwjgl/LwjglApplication.java

@@ -203,6 +203,7 @@ void mainLoop () {
 			int frameRate = isActive ? graphics.config.foregroundFPS : graphics.config.backgroundFPS;
 			if (shouldRender) {
 				graphics.updateTime();
+				graphics.frameId++;
 				listener.render();
 				Display.update(false);
 			} else {

backends/gdx-backend-lwjgl/src/com/badlogic/gdx/backends/lwjgl/LwjglCanvas.java

@@ -222,6 +222,7 @@ public void run () {
 
 					input.update();
 					input.processEvents();
+					graphics.frameId++;
 					listener.render();
 					if (audio != null) audio.update();
 					Display.update();

backends/gdx-backend-lwjgl/src/com/badlogic/gdx/backends/lwjgl/LwjglGraphics.java

@@ -41,6 +41,7 @@
 
 	GL20 gl20;
 	GL30 gl30;
+	long frameId = -1;
 	float deltaTime = 0;
 	long frameStart = 0;
 	int frames = 0;
@@ -94,6 +95,10 @@ public boolean isGL20Available () {
 		return gl20 != null;
 	}
 
+	public long getFrameId () {
+		return frameId;
+	}
+
 	public float getDeltaTime () {
 		return deltaTime;
 	}

backends/gdx-backends-gwt/src/com/badlogic/gdx/backends/gwt/GwtApplication.java

@@ -216,6 +216,7 @@ void mainLoop() {
 			runnablesHelper.get(i).run();
 		}
 		runnablesHelper.clear();
+		graphics.frameId++;
 		listener.render();
 		input.reset();
 	}

backends/gdx-backends-gwt/src/com/badlogic/gdx/backends/gwt/GwtGraphics.java

@@ -34,6 +34,7 @@
 	String extensions;
 	float fps = 0;
 	long lastTimeStamp = System.currentTimeMillis();
+	long frameId = -1;
 	float deltaTime = 0;
 	float time = 0;
 	int frames;
@@ -80,6 +81,11 @@ public int getHeight () {
 		return canvas.getHeight();
 	}
 
+	@Override
+	public long getFrameId () {
+		return frameId;
+	}
+
 	@Override
 	public float getDeltaTime () {
 		return deltaTime;

gdx/src/com/badlogic/gdx/Graphics.java

@@ -116,6 +116,13 @@ public String toString () {
 	/** @return the height in pixels of the display surface */
 	public int getHeight ();
 
+	/** Returns the id of the current frame. The general contract of this method is that the id is incremented only when the
+	 * application is in the running state right before calling the {@link ApplicationListener#render()} method. Also, the id of
+	 * the first frame is 0; the id of subsequent frames is guaranteed to take increasing values for 2<sup>63</sup>-1 rendering
+	 * cycles.
+	 * @return the id of the current frame */
+	public long getFrameId ();
+
 	/** @return the time span between the current frame and the last frame in seconds. Might be smoothed over n frames. */
 	public float getDeltaTime ();