The Tor Browser: mobile/android/base/gfx/LayerRenderer.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/LayerRenderer.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/LayerRenderer.java

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.gfx;
 import org.mozilla.gecko.GeckoAppShell;
 import org.mozilla.gecko.R;
 import org.mozilla.gecko.Tab;
 import org.mozilla.gecko.Tabs;
 import org.mozilla.gecko.gfx.Layer.RenderContext;
 import org.mozilla.gecko.gfx.RenderTask;
 import org.mozilla.gecko.mozglue.DirectBufferAllocator;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.res.Resources;
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Matrix;
 import android.graphics.PointF;
 import android.graphics.Rect;
 import android.graphics.RectF;
 import android.opengl.GLES20;
 import android.os.SystemClock;
 import android.util.Log;
 import org.mozilla.gecko.mozglue.JNITarget;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.FloatBuffer;
 import java.nio.IntBuffer;
 import java.util.concurrent.CopyOnWriteArrayList;
 import javax.microedition.khronos.egl.EGLConfig;
 /**
  * The layer renderer implements the rendering logic for a layer view.
  */
 public class LayerRenderer implements Tabs.OnTabsChangedListener {
     private static final String LOGTAG = "GeckoLayerRenderer";
     private static final String PROFTAG = "GeckoLayerRendererProf";
     /*
      * The amount of time a frame is allowed to take to render before we declare it a dropped
      * frame.
      */
     private static final int MAX_FRAME_TIME = 16;   /* 1000 ms / 60 FPS */
     private static final int FRAME_RATE_METER_WIDTH = 128;
     private static final int FRAME_RATE_METER_HEIGHT = 32;
     private static final long NANOS_PER_MS = 1000000;
     private static final int NANOS_PER_SECOND = 1000000000;
     private final LayerView mView;
     private TextLayer mFrameRateLayer;
     private final ScrollbarLayer mHorizScrollLayer;
     private final ScrollbarLayer mVertScrollLayer;
     private final FadeRunnable mFadeRunnable;
     private ByteBuffer mCoordByteBuffer;
     private FloatBuffer mCoordBuffer;
     private RenderContext mLastPageContext;
     private int mMaxTextureSize;
     private int mBackgroundColor;
     private int mOverscrollColor;
     private long mLastFrameTime;
     private final CopyOnWriteArrayList<RenderTask> mTasks;
     private CopyOnWriteArrayList<Layer> mExtraLayers = new CopyOnWriteArrayList<Layer>();
     // Dropped frames display
     private int[] mFrameTimings;
     private int mCurrentFrame, mFrameTimingsSum, mDroppedFrames;
     // Render profiling output
     private int mFramesRendered;
     private float mCompleteFramesRendered;
     private boolean mProfileRender;
     private long mProfileOutputTime;
     private IntBuffer mPixelBuffer;
     // Used by GLES 2.0
     private int mProgram;
     private int mPositionHandle;
     private int mTextureHandle;
     private int mSampleHandle;
     private int mTMatrixHandle;
     // column-major matrix applied to each vertex to shift the viewport from
     // one ranging from (-1, -1),(1,1) to (0,0),(1,1) and to scale all sizes by
     // a factor of 2 to fill up the screen
     public static final float[] DEFAULT_TEXTURE_MATRIX = {
 .0f, 0.0f, 0.0f, 0.0f,
 .0f, 2.0f, 0.0f, 0.0f,
 .0f, 0.0f, 2.0f, 0.0f,
         -1.0f, -1.0f, 0.0f, 1.0f
     };
     private static final int COORD_BUFFER_SIZE = 20;
     // The shaders run on the GPU directly, the vertex shader is only applying the
     // matrix transform detailed above
     // Note we flip the y-coordinate in the vertex shader from a
     // coordinate system with (0,0) in the top left to one with (0,0) in
     // the bottom left.
     public static final String DEFAULT_VERTEX_SHADER =
         "uniform mat4 uTMatrix;\n" +
         "attribute vec4 vPosition;\n" +
         "attribute vec2 aTexCoord;\n" +
         "varying vec2 vTexCoord;\n" +
         "void main() {\n" +
         "    gl_Position = uTMatrix * vPosition;\n" +
         "    vTexCoord.x = aTexCoord.x;\n" +
         "    vTexCoord.y = 1.0 - aTexCoord.y;\n" +
         "}\n";
     // We use highp because the screenshot textures
     // we use are large and we stretch them alot
     // so we need all the precision we can get.
     // Unfortunately, highp is not required by ES 2.0
     // so on GPU's like Mali we end up getting mediump
     public static final String DEFAULT_FRAGMENT_SHADER =
         "precision highp float;\n" +
         "varying vec2 vTexCoord;\n" +
         "uniform sampler2D sTexture;\n" +
         "void main() {\n" +
         "    gl_FragColor = texture2D(sTexture, vTexCoord);\n" +
         "}\n";
     public LayerRenderer(LayerView view) {
         mView = view;
         try {
             mOverscrollColor = view.getContext().getResources().getColor(R.color.background_normal);
         } catch (Resources.NotFoundException nfe) { mOverscrollColor = Color.BLACK; }
         Bitmap scrollbarImage = view.getScrollbarImage();
         IntSize size = new IntSize(scrollbarImage.getWidth(), scrollbarImage.getHeight());
         scrollbarImage = expandCanvasToPowerOfTwo(scrollbarImage, size);
         mTasks = new CopyOnWriteArrayList<RenderTask>();
         mLastFrameTime = System.nanoTime();
         mVertScrollLayer = new ScrollbarLayer(this, scrollbarImage, size, true);
         mHorizScrollLayer = new ScrollbarLayer(this, diagonalFlip(scrollbarImage), new IntSize(size.height, size.width), false);
         mFadeRunnable = new FadeRunnable();
         mFrameTimings = new int[60];
         mCurrentFrame = mFrameTimingsSum = mDroppedFrames = 0;
         // Initialize the FloatBuffer that will be used to store all vertices and texture
         // coordinates in draw() commands.
         mCoordByteBuffer = DirectBufferAllocator.allocate(COORD_BUFFER_SIZE * 4);
         mCoordByteBuffer.order(ByteOrder.nativeOrder());
         mCoordBuffer = mCoordByteBuffer.asFloatBuffer();
         Tabs.registerOnTabsChangedListener(this);
     }
     private Bitmap expandCanvasToPowerOfTwo(Bitmap image, IntSize size) {
         IntSize potSize = size.nextPowerOfTwo();
         if (size.equals(potSize)) {
             return image;
         }
         // make the bitmap size a power-of-two in both dimensions if it's not already.
         Bitmap potImage = Bitmap.createBitmap(potSize.width, potSize.height, image.getConfig());
         new Canvas(potImage).drawBitmap(image, new Matrix(), null);
         return potImage;
     }
     private Bitmap diagonalFlip(Bitmap image) {
         Matrix rotation = new Matrix();
         rotation.setValues(new float[] { 0, 1, 0, 1, 0, 0, 0, 0, 1 }); // transform (x,y) into (y,x)
         Bitmap rotated = Bitmap.createBitmap(image, 0, 0, image.getWidth(), image.getHeight(), rotation, true);
         return rotated;
     }
     public void destroy() {
         DirectBufferAllocator.free(mCoordByteBuffer);
         mCoordByteBuffer = null;
         mCoordBuffer = null;
         mHorizScrollLayer.destroy();
         mVertScrollLayer.destroy();
         if (mFrameRateLayer != null) {
             mFrameRateLayer.destroy();
         }
         Tabs.unregisterOnTabsChangedListener(this);
     }
     void onSurfaceCreated(EGLConfig config) {
         checkMonitoringEnabled();
         createDefaultProgram();
         activateDefaultProgram();
     }
     public void createDefaultProgram() {
         int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, DEFAULT_VERTEX_SHADER);
         int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, DEFAULT_FRAGMENT_SHADER);
         mProgram = GLES20.glCreateProgram();
         GLES20.glAttachShader(mProgram, vertexShader);   // add the vertex shader to program
         GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
         GLES20.glLinkProgram(mProgram);                  // creates OpenGL program executables
         // Get handles to the vertex shader's vPosition, aTexCoord, sTexture, and uTMatrix members.
         mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
         mTextureHandle = GLES20.glGetAttribLocation(mProgram, "aTexCoord");
         mSampleHandle = GLES20.glGetUniformLocation(mProgram, "sTexture");
         mTMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uTMatrix");
         int maxTextureSizeResult[] = new int[1];
         GLES20.glGetIntegerv(GLES20.GL_MAX_TEXTURE_SIZE, maxTextureSizeResult, 0);
         mMaxTextureSize = maxTextureSizeResult[0];
     }
     // Activates the shader program.
     public void activateDefaultProgram() {
         // Add the program to the OpenGL environment
         GLES20.glUseProgram(mProgram);
         // Set the transformation matrix
         GLES20.glUniformMatrix4fv(mTMatrixHandle, 1, false, DEFAULT_TEXTURE_MATRIX, 0);
         // Enable the arrays from which we get the vertex and texture coordinates
         GLES20.glEnableVertexAttribArray(mPositionHandle);
         GLES20.glEnableVertexAttribArray(mTextureHandle);
         GLES20.glUniform1i(mSampleHandle, 0);
         // TODO: Move these calls into a separate deactivate() call that is called after the
         // underlay and overlay are rendered.
     }
     // Deactivates the shader program. This must be done to avoid crashes after returning to the
     // Gecko C++ compositor from Java.
     public void deactivateDefaultProgram() {
         GLES20.glDisableVertexAttribArray(mTextureHandle);
         GLES20.glDisableVertexAttribArray(mPositionHandle);
         GLES20.glUseProgram(0);
     }
     public int getMaxTextureSize() {
         return mMaxTextureSize;
     }
     public void postRenderTask(RenderTask aTask) {
         mTasks.add(aTask);
         mView.requestRender();
     }
     public void removeRenderTask(RenderTask aTask) {
         mTasks.remove(aTask);
     }
     private void runRenderTasks(CopyOnWriteArrayList<RenderTask> tasks, boolean after, long frameStartTime) {
         for (RenderTask task : tasks) {
             if (task.runAfter != after) {
                 continue;
             }
             boolean stillRunning = task.run(frameStartTime - mLastFrameTime, frameStartTime);
             // Remove the task from the list if its finished
             if (!stillRunning) {
                 tasks.remove(task);
             }
         }
     }
     public void addLayer(Layer layer) {
         synchronized (mExtraLayers) {
             if (mExtraLayers.contains(layer)) {
                 mExtraLayers.remove(layer);
             }
             mExtraLayers.add(layer);
         }
     }
     public void removeLayer(Layer layer) {
         synchronized (mExtraLayers) {
             mExtraLayers.remove(layer);
         }
     }
     private void printCheckerboardStats() {
         Log.d(PROFTAG, "Frames rendered over last 1000ms: " + mCompleteFramesRendered + "/" + mFramesRendered);
         mFramesRendered = 0;
         mCompleteFramesRendered = 0;
     }
     /** Used by robocop for testing purposes. Not for production use! */
     IntBuffer getPixels() {
         IntBuffer pixelBuffer = IntBuffer.allocate(mView.getWidth() * mView.getHeight());
         synchronized (pixelBuffer) {
             mPixelBuffer = pixelBuffer;
             mView.requestRender();
             try {
                 pixelBuffer.wait();
             } catch (InterruptedException ie) {
             }
             mPixelBuffer = null;
         }
         return pixelBuffer;
     }
     private RenderContext createScreenContext(ImmutableViewportMetrics metrics, PointF offset) {
         RectF viewport = new RectF(0.0f, 0.0f, metrics.getWidth(), metrics.getHeight());
         RectF pageRect = metrics.getPageRect();
         return createContext(viewport, pageRect, 1.0f, offset);
     }
     private RenderContext createPageContext(ImmutableViewportMetrics metrics, PointF offset) {
         RectF viewport = metrics.getViewport();
         RectF pageRect = metrics.getPageRect();
         float zoomFactor = metrics.zoomFactor;
         return createContext(new RectF(RectUtils.round(viewport)), pageRect, zoomFactor, offset);
     }
     private RenderContext createContext(RectF viewport, RectF pageRect, float zoomFactor, PointF offset) {
         if (mCoordBuffer == null) {
             throw new IllegalStateException();
         }
         return new RenderContext(viewport, pageRect, zoomFactor, offset, mPositionHandle, mTextureHandle,
                                  mCoordBuffer);
     }
     private void updateDroppedFrames(long frameStartTime) {
         int frameElapsedTime = (int)((System.nanoTime() - frameStartTime) / NANOS_PER_MS);
         /* Update the running statistics. */
         mFrameTimingsSum -= mFrameTimings[mCurrentFrame];
         mFrameTimingsSum += frameElapsedTime;
         mDroppedFrames -= (mFrameTimings[mCurrentFrame] + 1) / MAX_FRAME_TIME;
         mDroppedFrames += (frameElapsedTime + 1) / MAX_FRAME_TIME;
         mFrameTimings[mCurrentFrame] = frameElapsedTime;
         mCurrentFrame = (mCurrentFrame + 1) % mFrameTimings.length;
         int averageTime = mFrameTimingsSum / mFrameTimings.length;
         mFrameRateLayer.beginTransaction();     // called on compositor thread
         try {
             mFrameRateLayer.setText(averageTime + " ms/" + mDroppedFrames);
         } finally {
             mFrameRateLayer.endTransaction();
         }
     }
     /* Given the new dimensions for the surface, moves the frame rate layer appropriately. */
     private void moveFrameRateLayer(int width, int height) {
         mFrameRateLayer.beginTransaction();     // called on compositor thread
         try {
             Rect position = new Rect(width - FRAME_RATE_METER_WIDTH - 8,
                                     height - FRAME_RATE_METER_HEIGHT + 8,
                                     width - 8,
                                     height + 8);
             mFrameRateLayer.setPosition(position);
         } finally {
             mFrameRateLayer.endTransaction();
         }
     }
     void checkMonitoringEnabled() {
         /* Do this I/O off the main thread to minimize its impact on startup time. */
         new Thread(new Runnable() {
             @Override
             public void run() {
                 Context context = mView.getContext();
                 SharedPreferences preferences = context.getSharedPreferences("GeckoApp", 0);
                 if (preferences.getBoolean("showFrameRate", false)) {
                     IntSize frameRateLayerSize = new IntSize(FRAME_RATE_METER_WIDTH, FRAME_RATE_METER_HEIGHT);
                     mFrameRateLayer = TextLayer.create(frameRateLayerSize, "-- ms/--");
                     moveFrameRateLayer(mView.getWidth(), mView.getHeight());
                 }
                 mProfileRender = Log.isLoggable(PROFTAG, Log.DEBUG);
             }
         }).start();
     }
     /*
      * create a vertex shader type (GLES20.GL_VERTEX_SHADER)
      * or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
      */
     public static int loadShader(int type, String shaderCode) {
         int shader = GLES20.glCreateShader(type);
         GLES20.glShaderSource(shader, shaderCode);
         GLES20.glCompileShader(shader);
         return shader;
     }
     public Frame createFrame(ImmutableViewportMetrics metrics) {
         return new Frame(metrics);
     }
     class FadeRunnable implements Runnable {
         private boolean mStarted;
         private long mRunAt;
         void scheduleStartFade(long delay) {
             mRunAt = SystemClock.elapsedRealtime() + delay;
             if (!mStarted) {
                 mView.postDelayed(this, delay);
                 mStarted = true;
             }
         }
         void scheduleNextFadeFrame() {
             if (mStarted) {
                 Log.e(LOGTAG, "scheduleNextFadeFrame() called while scheduled for starting fade");
             }
             mView.postDelayed(this, 1000L / 60L); // request another frame at 60fps
         }
         boolean timeToFade() {
             return !mStarted;
         }
         @Override
         public void run() {
             long timeDelta = mRunAt - SystemClock.elapsedRealtime();
             if (timeDelta > 0) {
                 // the run-at time was pushed back, so reschedule
                 mView.postDelayed(this, timeDelta);
             } else {
                 // reached the run-at time, execute
                 mStarted = false;
                 mView.requestRender();
             }
         }
     }
     public class Frame {
         // The timestamp recording the start of this frame.
         private long mFrameStartTime;
         // A fixed snapshot of the viewport metrics that this frame is using to render content.
         private ImmutableViewportMetrics mFrameMetrics;
         // A rendering context for page-positioned layers, and one for screen-positioned layers.
         private RenderContext mPageContext, mScreenContext;
         // Whether a layer was updated.
         private boolean mUpdated;
         private final Rect mPageRect;
         private final Rect mAbsolutePageRect;
         private final PointF mRenderOffset;
         public Frame(ImmutableViewportMetrics metrics) {
             mFrameMetrics = metrics;
             // Work out the offset due to margins
             Layer rootLayer = mView.getLayerClient().getRoot();
             mRenderOffset = mFrameMetrics.getMarginOffset();
             mPageContext = createPageContext(metrics, mRenderOffset);
             mScreenContext = createScreenContext(metrics, mRenderOffset);
             RectF pageRect = mFrameMetrics.getPageRect();
             mAbsolutePageRect = RectUtils.round(pageRect);
             PointF origin = mFrameMetrics.getOrigin();
             pageRect.offset(-origin.x, -origin.y);
             mPageRect = RectUtils.round(pageRect);
         }
         private void setScissorRect() {
             Rect scissorRect = transformToScissorRect(mPageRect);
             GLES20.glEnable(GLES20.GL_SCISSOR_TEST);
             GLES20.glScissor(scissorRect.left, scissorRect.top,
                              scissorRect.width(), scissorRect.height());
         }
         private Rect transformToScissorRect(Rect rect) {
             IntSize screenSize = new IntSize(mFrameMetrics.getSize());
             int left = Math.max(0, rect.left);
             int top = Math.max(0, rect.top);
             int right = Math.min(screenSize.width, rect.right);
             int bottom = Math.min(screenSize.height, rect.bottom);
             Rect scissorRect = new Rect(left, screenSize.height - bottom, right,
                                         (screenSize.height - bottom) + (bottom - top));
             scissorRect.offset(Math.round(-mRenderOffset.x), Math.round(-mRenderOffset.y));
             return scissorRect;
         }
         /** This function is invoked via JNI; be careful when modifying signature. */
         @JNITarget
         public void beginDrawing() {
             mFrameStartTime = System.nanoTime();
             TextureReaper.get().reap();
             TextureGenerator.get().fill();
             mUpdated = true;
             Layer rootLayer = mView.getLayerClient().getRoot();
             // Run through pre-render tasks
             runRenderTasks(mTasks, false, mFrameStartTime);
             if (!mPageContext.fuzzyEquals(mLastPageContext) && !mView.isFullScreen()) {
                 // The viewport or page changed, so show the scrollbars again
                 // as per UX decision. Don't do this if we're in full-screen mode though.
                 mVertScrollLayer.unfade();
                 mHorizScrollLayer.unfade();
                 mFadeRunnable.scheduleStartFade(ScrollbarLayer.FADE_DELAY);
             } else if (mFadeRunnable.timeToFade()) {
                 boolean stillFading = mVertScrollLayer.fade() | mHorizScrollLayer.fade();
                 if (stillFading) {
                     mFadeRunnable.scheduleNextFadeFrame();
                 }
             }
             mLastPageContext = mPageContext;
             /* Update layers. */
             if (rootLayer != null) {
                 // Called on compositor thread.
                 mUpdated &= rootLayer.update(mPageContext);
             }
             if (mFrameRateLayer != null) {
                 // Called on compositor thread.
                 mUpdated &= mFrameRateLayer.update(mScreenContext);
             }
             mUpdated &= mVertScrollLayer.update(mPageContext);  // called on compositor thread
             mUpdated &= mHorizScrollLayer.update(mPageContext); // called on compositor thread
             for (Layer layer : mExtraLayers) {
                 mUpdated &= layer.update(mPageContext); // called on compositor thread
             }
         }
         /** Retrieves the bounds for the layer, rounded in such a way that it
          * can be used as a mask for something that will render underneath it.
          * This will round the bounds inwards, but stretch the mask towards any
          * near page edge, where near is considered to be 'within 2 pixels'.
          * Returns null if the given layer is null.
          */
         private Rect getMaskForLayer(Layer layer) {
             if (layer == null) {
                 return null;
             }
             RectF bounds = RectUtils.contract(layer.getBounds(mPageContext), 1.0f, 1.0f);
             Rect mask = RectUtils.roundIn(bounds);
             // If the mask is within two pixels of any page edge, stretch it over
             // that edge. This is to avoid drawing thin slivers when masking
             // layers.
             if (mask.top <= 2) {
                 mask.top = -1;
             }
             if (mask.left <= 2) {
                 mask.left = -1;
             }
             // Because we're drawing relative to the page-rect, we only need to
             // take into account its width and height (and not its origin)
             int pageRight = mPageRect.width();
             int pageBottom = mPageRect.height();
             if (mask.right >= pageRight - 2) {
                 mask.right = pageRight + 1;
             }
             if (mask.bottom >= pageBottom - 2) {
                 mask.bottom = pageBottom + 1;
             }
             return mask;
         }
         private void clear(int color) {
             GLES20.glClearColor(((color >> 16) & 0xFF) / 255.0f,
                                 ((color >> 8) & 0xFF) / 255.0f,
                                 (color & 0xFF) / 255.0f,
 .0f);
             // The bits set here need to match up with those used
             // in gfx/layers/opengl/LayerManagerOGL.cpp.
             GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT |
                            GLES20.GL_DEPTH_BUFFER_BIT);
         }
         /** This function is invoked via JNI; be careful when modifying signature. */
         @JNITarget
         public void drawBackground() {
             // Any GL state which is changed here must be restored in
             // CompositorOGL::RestoreState
             GLES20.glDisable(GLES20.GL_SCISSOR_TEST);
             // Draw the overscroll background area as a solid color
             clear(mOverscrollColor);
             // Update background color.
             mBackgroundColor = mView.getBackgroundColor();
             // Clear the page area to the page background colour.
             setScissorRect();
             clear(mBackgroundColor);
             GLES20.glDisable(GLES20.GL_SCISSOR_TEST);
         }
         // Draws the layer the client added to us.
         void drawRootLayer() {
             Layer rootLayer = mView.getLayerClient().getRoot();
             if (rootLayer == null) {
                 return;
             }
             rootLayer.draw(mPageContext);
         }
         @JNITarget
         public void drawForeground() {
             // Any GL state which is changed here must be restored in
             // CompositorOGL::RestoreState
             /* Draw any extra layers that were added (likely plugins) */
             if (mExtraLayers.size() > 0) {
                 for (Layer layer : mExtraLayers) {
                     layer.draw(mPageContext);
                 }
             }
             /* Draw the vertical scrollbar. */
             if (mPageRect.height() > mFrameMetrics.getHeight())
                 mVertScrollLayer.draw(mPageContext);
             /* Draw the horizontal scrollbar. */
             if (mPageRect.width() > mFrameMetrics.getWidth())
                 mHorizScrollLayer.draw(mPageContext);
             /* Measure how much of the screen is checkerboarding */
             Layer rootLayer = mView.getLayerClient().getRoot();
             if ((rootLayer != null) &&
                 (mProfileRender || PanningPerfAPI.isRecordingCheckerboard())) {
                 // Calculate the incompletely rendered area of the page
                 float checkerboard =  1.0f - GeckoAppShell.computeRenderIntegrity();
                 PanningPerfAPI.recordCheckerboard(checkerboard);
                 if (checkerboard < 0.0f || checkerboard > 1.0f) {
                     Log.e(LOGTAG, "Checkerboard value out of bounds: " + checkerboard);
                 }
                 mCompleteFramesRendered += 1.0f - checkerboard;
                 mFramesRendered ++;
                 if (mFrameStartTime - mProfileOutputTime > NANOS_PER_SECOND) {
                     mProfileOutputTime = mFrameStartTime;
                     printCheckerboardStats();
                 }
             }
             runRenderTasks(mTasks, true, mFrameStartTime);
             /* Draw the FPS. */
             if (mFrameRateLayer != null) {
                 updateDroppedFrames(mFrameStartTime);
                 GLES20.glEnable(GLES20.GL_BLEND);
                 GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);
                 mFrameRateLayer.draw(mScreenContext);
             }
         }
         /** This function is invoked via JNI; be careful when modifying signature. */
         @JNITarget
         public void endDrawing() {
             // If a layer update requires further work, schedule another redraw
             if (!mUpdated)
                 mView.requestRender();
             PanningPerfAPI.recordFrameTime();
             /* Used by robocop for testing purposes */
             IntBuffer pixelBuffer = mPixelBuffer;
             if (mUpdated && pixelBuffer != null) {
                 synchronized (pixelBuffer) {
                     pixelBuffer.position(0);
                     GLES20.glReadPixels(0, 0, (int)mScreenContext.viewport.width(),
                                         (int)mScreenContext.viewport.height(), GLES20.GL_RGBA,
                                         GLES20.GL_UNSIGNED_BYTE, pixelBuffer);
                     pixelBuffer.notify();
                 }
             }
             // Remove background color once we've painted. GeckoLayerClient is
             // responsible for setting this flag before current document is
             // composited.
             if (mView.getPaintState() == LayerView.PAINT_BEFORE_FIRST) {
                 mView.post(new Runnable() {
                     @Override
                     public void run() {
                         mView.getChildAt(0).setBackgroundColor(Color.TRANSPARENT);
                     }
                 });
                 mView.setPaintState(LayerView.PAINT_AFTER_FIRST);
             }
             mLastFrameTime = mFrameStartTime;
         }
     }
     @Override
     public void onTabChanged(final Tab tab, Tabs.TabEvents msg, Object data) {
         // Sets the background of the newly selected tab. This background color
         // gets cleared in endDrawing(). This function runs on the UI thread,
         // but other code that touches the paint state is run on the compositor
         // thread, so this may need to be changed if any problems appear.
         if (msg == Tabs.TabEvents.SELECTED) {
             if (mView != null) {
                 if (mView.getChildAt(0) != null) {
                     mView.getChildAt(0).setBackgroundColor(tab.getBackgroundColor());
                 }
                 mView.setPaintState(LayerView.PAINT_START);
             }
         }
     }
 }

The Tor Browser / annotate

mobile/android/base/gfx/LayerRenderer.java@b8a032363ba2 (annotated)

mobile/android/base/gfx/LayerRenderer.java