[Android Client] Break down multi-threaded classes by thread

remoting/android/java/src/org/chromium/chromoting/jni/Display.java

+// Copyright 2016 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.chromoting.jni;
+
+import android.graphics.Bitmap;
+import android.graphics.Point;
+import android.os.Looper;
+
+import org.chromium.base.Log;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/**
+ * This class is for drawing the desktop on the canvas and controlling the lifetime of the
+ * corresponding C++ object. It only draws the desktop on the graphics (=display) thread but also
+ * has functions accessible on UI thread.
+ */
+@JNINamespace("remoting")
+public class Display {
+    private static final String TAG = "Chromoting";
+
+    // Pointer to the C++ object. Casted to |long|.
+    private long mNativeJniDisplayHandler;
+
+    /**
+     * Callback invoked on the graphics thread to repaint the desktop. Read on the UI and
+     * graphics threads. Write only on the UI thread.
+     */
+    private Runnable mRedrawCallback;
+
+    /**
+     * Protects access to {@link mRedrawCallback}.
+     * Locking is not required when reading on the UI thread.
+     */
+    private final Object mRedrawCallbackLock = new Object();
+
+    /** Protects access to {@link mFrameBitmap}. */
+    private final Object mFrameLock = new Object();
+
+    /** Bitmap holding a copy of the latest video frame. Accessed on the UI and graphics threads. */
+    private Bitmap mFrameBitmap;
+
+    /** Position of cursor hot-spot. Accessed on the graphics thread. */
+    private Point mCursorHotspot = new Point();
+
+    /** Bitmap holding the cursor shape. Accessed on the graphics thread. */
+    private Bitmap mCursorBitmap;
+
+    public Display() {
+        mNativeJniDisplayHandler = nativeInit();
+    }
+
+    /**
+     * @return the pointer to the native C++ object.
+     */
+    public long getNativePointer() {
+        return mNativeJniDisplayHandler;
+    }
+
+    /**
+     * Sets the redraw callback to the provided functor. Provide a value of null whenever the
+     * window is no longer visible so that we don't continue to draw onto it. Called on the UI
+     * thread.
+     */
+    public void provideRedrawCallback(Runnable redrawCallback) {
+        synchronized (mRedrawCallbackLock) {
+            mRedrawCallback = redrawCallback;
+        }
+    }
+
+    /**
+     * Destroys its resources and the native counterpart. Called on the UI thread.
+     */
+    public void destroy() {
+        // Drop the reference to free the Bitmap for GC.
+        synchronized (mFrameLock) {
+            mFrameBitmap = null;
+        }
+
+        provideRedrawCallback(null);
+        nativeDestroy(mNativeJniDisplayHandler);
+        mNativeJniDisplayHandler = 0;
+    }
+
+    /** Forces the native graphics thread to redraw to the canvas. Called on the UI thread. */
+    public boolean redrawGraphics() {
+        if (mRedrawCallback == null) return false;
+
+        nativeScheduleRedraw(mNativeJniDisplayHandler);
+        return true;
+    }
+
+    /**
+     * Called on the graphics thread to perform the redrawing callback requested by
+     * {@link #redrawGraphics}. This is a no-op if the window isn't visible (the callback is null).
+     */
+    @CalledByNative
+    void redrawGraphicsInternal() {
+        Runnable callback;
+        synchronized (mRedrawCallbackLock) {
+            callback = mRedrawCallback;
+        }
+        if (callback != null) {
+            callback.run();
+        }
+    }
+
+    /**
+     * Returns a bitmap of the latest video frame. Called on the native graphics thread when
+     * DesktopView is repainted.
+     */
+    public Bitmap getVideoFrame() {
+        if (Looper.myLooper() == Looper.getMainLooper()) {
+            Log.w(TAG, "Canvas being redrawn on UI thread");
+        }
+
+        synchronized (mFrameLock) {
+            return mFrameBitmap;
+        }
+    }
+
+    /**
+     * Set a new video frame. Called on the native graphics thread when a new frame is allocated.
+     */
+    @CalledByNative
+    void setVideoFrame(Bitmap bitmap) {
+        if (Looper.myLooper() == Looper.getMainLooper()) {
+            Log.w(TAG, "Video frame updated on UI thread");
+        }
+
+        synchronized (mFrameLock) {
+            mFrameBitmap = bitmap;
+        }
+    }
+
+    /**
+     * Creates a new Bitmap to hold video frame pixels. The returned Bitmap is referenced by native
+     * code which writes the decoded frame pixels to it.
+     */
+    @CalledByNative
+    static Bitmap newBitmap(int width, int height) {
+        return Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+    }
+
+    /**
+     * Updates the cursor shape. This is called on the graphics thread when receiving a new cursor
+     * shape from the host.
+     */
+    @CalledByNative
+    void updateCursorShape(int width, int height, int hotspotX, int hotspotY, ByteBuffer buffer) {
+        mCursorHotspot = new Point(hotspotX, hotspotY);
+
+        int[] data = new int[width * height];
+        buffer.order(ByteOrder.LITTLE_ENDIAN);
+        buffer.asIntBuffer().get(data, 0, data.length);
+        mCursorBitmap = Bitmap.createBitmap(data, width, height, Bitmap.Config.ARGB_8888);
+    }
+
+    /** Position of cursor hotspot within cursor image. Called on the graphics thread. */
+    public Point getCursorHotspot() {
+        return mCursorHotspot;
+    }
+
+    /** Returns the current cursor shape. Called on the graphics thread. */
+    public Bitmap getCursorBitmap() {
+        return mCursorBitmap;
+    }
+
+    private native long nativeInit();
+
+    private native void nativeDestroy(long nativeJniDisplayHandler);
+
+    /** Schedules a redraw on the native graphics thread. */
+    private native void nativeScheduleRedraw(long nativeJniDisplayHandler);
+}