ContentViewRenderView.java

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package org.chromium.content.browser;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Build;
import android.os.Handler;
import android.view.Surface;
import android.view.SurfaceView;
import android.view.SurfaceHolder;
import android.widget.FrameLayout;

import org.chromium.base.CalledByNative;
import org.chromium.base.JNINamespace;
import org.chromium.content.common.TraceEvent;

/***
 * This view is used by a ContentView to render its content.
 * Call {@link #setCurrentContentView(ContentView)} with the contentView that should be displayed.
 * Note that only one ContentView can be shown at a time.
 */
@JNINamespace("content")
public class ContentViewRenderView extends FrameLayout {
    private static final int MAX_SWAP_BUFFER_COUNT = 2;

    // The native side of this object.
    private int mNativeContentViewRenderView;
    private final SurfaceHolder.Callback mSurfaceCallback;

    private SurfaceView mSurfaceView;
    private VSyncAdapter mVSyncAdapter;

    private int mPendingRenders;
    private int mPendingSwapBuffers;
    private boolean mNeedToRender;

    private ContentView mCurrentContentView;

    private final Runnable mRenderRunnable = new Runnable() {
        @Override
        public void run() {
            render();
        }
    };

    /**
     * Constructs a new ContentViewRenderView that should be can to a view hierarchy.
     * Native code should add/remove the layers to be rendered through the ContentViewLayerRenderer.
     * @param context The context used to create this.
     */
    public ContentViewRenderView(Context context) {
        super(context);

        mNativeContentViewRenderView = nativeInit();
        assert mNativeContentViewRenderView != 0;

        setBackgroundColor(Color.WHITE);

        mSurfaceView = createSurfaceView(getContext());
        mSurfaceCallback = new SurfaceHolder.Callback() {
            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
                assert mNativeContentViewRenderView != 0;
                nativeSurfaceSetSize(mNativeContentViewRenderView, width, height);
                if (mCurrentContentView != null) {
                    mCurrentContentView.getContentViewCore().onPhysicalBackingSizeChanged(
                            width, height);
                }
            }

            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                assert mNativeContentViewRenderView != 0;
                nativeSurfaceCreated(mNativeContentViewRenderView, holder.getSurface());
                onReadyToRender();
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                assert mNativeContentViewRenderView != 0;
                nativeSurfaceDestroyed(mNativeContentViewRenderView);
            }
        };
        mSurfaceView.getHolder().addCallback(mSurfaceCallback);

        mVSyncAdapter = new VSyncAdapter(getContext());
        addView(mSurfaceView,
                new FrameLayout.LayoutParams(
                        FrameLayout.LayoutParams.MATCH_PARENT,
                        FrameLayout.LayoutParams.MATCH_PARENT));
    }

    private class VSyncAdapter implements VSyncManager.Provider, VSyncMonitor.Listener {
        private final VSyncMonitor mVSyncMonitor;
        private boolean mVSyncNotificationEnabled;
        private VSyncManager.Listener mVSyncListener;

        // The VSyncMonitor gives the timebase for the actual vsync, but we don't want render until
        // we have had a chance for input events to propagate to the compositor thread. This takes
        // 3 ms typically, so we adjust the vsync timestamps forward by a bit to give input events a
        // chance to arrive.
        private static final long INPUT_EVENT_LAG_FROM_VSYNC_MICROSECONDS = 3200;

        VSyncAdapter(Context context) {
            mVSyncMonitor = new VSyncMonitor(context, this);
        }

        @Override
        public void onVSync(VSyncMonitor monitor, long vsyncTimeMicros) {
            if (mNeedToRender) {
                if (mPendingSwapBuffers + mPendingRenders <= MAX_SWAP_BUFFER_COUNT) {
                    mNeedToRender = false;
                    mPendingRenders++;
                    render();
                } else {
                    TraceEvent.instant("ContentViewRenderView:bail");
                }
            }

            if (mVSyncListener != null) {
                if (mVSyncNotificationEnabled) {
                    mVSyncListener.onVSync(vsyncTimeMicros);
                    mVSyncMonitor.requestUpdate();
                } else {
                    // Compensate for input event lag. Input events are delivered immediately on
                    // pre-JB releases, so this adjustment is only done for later versions.
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                        vsyncTimeMicros += INPUT_EVENT_LAG_FROM_VSYNC_MICROSECONDS;
                    }
                    mVSyncListener.updateVSync(vsyncTimeMicros,
                            mVSyncMonitor.getVSyncPeriodInMicroseconds());
                }
            }
        }

        @Override
        public void registerVSyncListener(VSyncManager.Listener listener) {
            if (!mVSyncNotificationEnabled) mVSyncMonitor.requestUpdate();
            mVSyncNotificationEnabled = true;
        }

        @Override
        public void unregisterVSyncListener(VSyncManager.Listener listener) {
            mVSyncNotificationEnabled = false;
        }

        void setVSyncListener(VSyncManager.Listener listener) {
            mVSyncListener = listener;
            if (mVSyncListener != null) mVSyncMonitor.requestUpdate();
        }

        void requestUpdate() {
            mVSyncMonitor.requestUpdate();
        }
    }

    /**
     * Should be called when the ContentViewRenderView is not needed anymore so its associated
     * native resource can be freed.
     */
    public void destroy() {
        mSurfaceView.getHolder().removeCallback(mSurfaceCallback);
        nativeDestroy(mNativeContentViewRenderView);
        mNativeContentViewRenderView = 0;
    }

    /**
     * Makes the passed ContentView the one displayed by this ContentViewRenderView.
     */
    public void setCurrentContentView(ContentView contentView) {
        assert mNativeContentViewRenderView != 0;
        mCurrentContentView = contentView;

        ContentViewCore contentViewCore =
                contentView != null ? contentView.getContentViewCore() : null;

        nativeSetCurrentContentView(mNativeContentViewRenderView,
                contentViewCore != null ? contentViewCore.getNativeContentViewCore() : 0);

        if (contentViewCore != null) {
            contentViewCore.onPhysicalBackingSizeChanged(getWidth(), getHeight());
            mVSyncAdapter.setVSyncListener(contentViewCore.getVSyncListener(mVSyncAdapter));
        }
    }

    /**
     * This method should be subclassed to provide actions to be performed once the view is ready to
     * render.
     */
    protected void onReadyToRender() {
        mPendingSwapBuffers = 0;
        mPendingRenders = 0;
    }

    /**
     * This method could be subclassed optionally to provide a custom SurfaceView object to
     * this ContentViewRenderView.
     * @param context The context used to create the SurfaceView object.
     * @return The created SurfaceView object.
     */
    protected SurfaceView createSurfaceView(Context context) {
        return new SurfaceView(context) {
            @Override
            public void onDraw(Canvas canvas) {
                // We only need to draw to software canvases, which are used for taking screenshots.
                if (canvas.isHardwareAccelerated()) return;
                Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(),
                        Bitmap.Config.ARGB_8888);
                if (nativeCompositeToBitmap(mNativeContentViewRenderView, bitmap)) {
                    canvas.drawBitmap(bitmap, 0, 0, null);
                }
            }
        };
    }

    /**
     * @return whether the surface view is initialized and ready to render.
     */
    public boolean isInitialized() {
        return mSurfaceView.getHolder().getSurface() != null;
    }

    @CalledByNative
    private void requestRender() {
        ContentViewCore contentViewCore = mCurrentContentView != null ?
                mCurrentContentView.getContentViewCore() : null;

        boolean rendererHasFrame =
                contentViewCore != null && contentViewCore.consumePendingRendererFrame();

        if (rendererHasFrame && mPendingSwapBuffers + mPendingRenders < MAX_SWAP_BUFFER_COUNT) {
            TraceEvent.instant("requestRender:now");
            mNeedToRender = false;
            mPendingRenders++;

            // The handler can be null if we are detached from the window.  Calling
            // {@link View#post(Runnable)} properly handles this case, but we lose the front of
            // queue behavior.  That is okay for this edge case.
            Handler handler = getHandler();
            if (handler != null) {
                handler.postAtFrontOfQueue(mRenderRunnable);
            } else {
                post(mRenderRunnable);
            }
            mVSyncAdapter.requestUpdate();
        } else if (mPendingRenders <= 0) {
            assert mPendingRenders == 0;
            TraceEvent.instant("requestRender:later");
            mNeedToRender = true;
            mVSyncAdapter.requestUpdate();
        }
    }

    @CalledByNative
    private void onSwapBuffersCompleted() {
        TraceEvent.instant("onSwapBuffersCompleted");

        if (mPendingSwapBuffers == MAX_SWAP_BUFFER_COUNT && mNeedToRender) requestRender();
        if (mPendingSwapBuffers > 0) mPendingSwapBuffers--;
    }

    private void didCompositeAndDraw() {
        if (mCurrentContentView == null) return;
        ContentViewCore contentViewCore = mCurrentContentView.getContentViewCore();
        if (contentViewCore == null || !contentViewCore.isReady() || getBackground() == null) {
            return;
        }
        if (getBackground() != null) {
            post(new Runnable() {
                @Override
                public void run() {
                    setBackgroundResource(0);
                }
            });
        }
    }

    private void render() {
        if (mPendingRenders > 0) mPendingRenders--;

        boolean didDraw = nativeComposite(mNativeContentViewRenderView);
        if (didDraw) {
            mPendingSwapBuffers++;
            didCompositeAndDraw();
        }
    }

    private native int nativeInit();
    private native void nativeDestroy(int nativeContentViewRenderView);
    private native void nativeSetCurrentContentView(int nativeContentViewRenderView,
            int nativeContentView);
    private native void nativeSurfaceCreated(int nativeContentViewRenderView, Surface surface);
    private native void nativeSurfaceDestroyed(int nativeContentViewRenderView);
    private native void nativeSurfaceSetSize(int nativeContentViewRenderView,
            int width, int height);
    private native boolean nativeComposite(int nativeContentViewRenderView);
    private native boolean nativeCompositeToBitmap(int nativeContentViewRenderView, Bitmap bitmap);
}