src/com/android/gallery3d/ui/TileImageView.java - LeafOS-Project/android_packages_apps_Gallery2 - Gitiles

 /*
  * Copyright (C) 2010 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.gallery3d.ui;

 import com.android.gallery3d.app.GalleryContext;
 import com.android.gallery3d.common.Utils;
 import com.android.gallery3d.data.DecodeUtils;
 import com.android.gallery3d.util.Future;
 import com.android.gallery3d.util.ThreadPool;
 import com.android.gallery3d.util.ThreadPool.CancelListener;
 import com.android.gallery3d.util.ThreadPool.JobContext;

 import android.graphics.Bitmap;
 import android.graphics.Rect;
 import android.graphics.RectF;

 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;

 public class TileImageView extends GLView {
     public static final int SIZE_UNKNOWN = -1;

     @SuppressWarnings("unused")
     private static final String TAG = "TileImageView";

     // TILE_SIZE must be 2^N - 2. We put one pixel border in each side of the
     // texture to avoid seams between tiles.
     private static final int TILE_SIZE = 254;
     private static final int TILE_BORDER = 1;
     private static final int UPLOAD_LIMIT = 1;

     /*
      *  This is the tile state in the CPU side.
      *  Life of a Tile:
      *      ACTIVATED (initial state)
      *              --> IN_QUEUE - by queueForDecode()
      *              --> RECYCLED - by recycleTile()
      *      IN_QUEUE --> DECODING - by decodeTile()
      *               --> RECYCLED - by recycleTile)
      *      DECODING --> RECYCLING - by recycleTile()
      *               --> DECODED  - by decodeTile()
      *      RECYCLING --> RECYCLED - by decodeTile()
      *      DECODED --> ACTIVATED - (after the decoded bitmap is uploaded)
      *      DECODED --> RECYCLED - by recycleTile()
      *      RECYCLED --> ACTIVATED - by obtainTile()
      */
     private static final int STATE_ACTIVATED = 0x01;
     private static final int STATE_IN_QUEUE = 0x02;
     private static final int STATE_DECODING = 0x04;
     private static final int STATE_DECODED = 0x08;
     private static final int STATE_RECYCLING = 0x10;
     private static final int STATE_RECYCLED = 0x20;

     private Model mModel;
     protected BitmapTexture mBackupImage;
     protected int mLevelCount;  // cache the value of mScaledBitmaps.length

     // The mLevel variable indicates which level of bitmap we should use.
     // Level 0 means the original full-sized bitmap, and a larger value means
     // a smaller scaled bitmap (The width and height of each scaled bitmap is
     // half size of the previous one). If the value is in [0, mLevelCount), we
     // use the bitmap in mScaledBitmaps[mLevel] for display, otherwise the value
     // is mLevelCount, and that means we use mBackupTexture for display.
     private int mLevel = 0;

     // The offsets of the (left, top) of the upper-left tile to the (left, top)
     // of the view.
     private int mOffsetX;
     private int mOffsetY;

     private int mUploadQuota;
     private boolean mRenderComplete;

     private final RectF mSourceRect = new RectF();
     private final RectF mTargetRect = new RectF();

     private final HashMap<Long, Tile> mActiveTiles = new HashMap<Long, Tile>();

     // The following three queue is guarded by TileImageView.this
     private TileQueue mRecycledQueue = new TileQueue();
     private TileQueue mUploadQueue = new TileQueue();
     private TileQueue mDecodeQueue = new TileQueue();

     // The width and height of the full-sized bitmap
     protected int mImageWidth = SIZE_UNKNOWN;
     protected int mImageHeight = SIZE_UNKNOWN;

     protected int mCenterX;
     protected int mCenterY;
     protected float mScale;
     protected int mRotation;

     // Temp variables to avoid memory allocation
     private final Rect mTileRange = new Rect();
     private final Rect mActiveRange[] = {new Rect(), new Rect()};

     private final TileUploader mTileUploader = new TileUploader();
     private boolean mIsTextureFreed;
     private Future<Void> mTileDecoder;
     private ThreadPool mThreadPool;
     private boolean mBackgroundTileUploaded;

     public static interface Model {
         public int getLevelCount();
         public Bitmap getBackupImage();
         public int getImageWidth();
         public int getImageHeight();

         // The method would be called in another thread
         public Bitmap getTile(int level, int x, int y, int tileSize);
         public boolean isFailedToLoad();
     }

     public TileImageView(GalleryContext context) {
         mThreadPool = context.getThreadPool();
         mTileDecoder = mThreadPool.submit(new TileDecoder());
     }

     public void setModel(Model model) {
         mModel = model;
         if (model != null) notifyModelInvalidated();
     }

     private void updateBackupTexture(Bitmap backup) {
         if (backup == null) {
             if (mBackupImage != null) mBackupImage.recycle();
             mBackupImage = null;
         } else {
             if (mBackupImage != null) {
                 if (mBackupImage.getBitmap() != backup) {
                     mBackupImage.recycle();
                     mBackupImage = new BitmapTexture(backup);
                 }
             } else {
                 mBackupImage = new BitmapTexture(backup);
             }
         }
     }

     public void notifyModelInvalidated() {
         invalidateTiles();
         if (mModel == null) {
             mBackupImage = null;
             mImageWidth = 0;
             mImageHeight = 0;
             mLevelCount = 0;
         } else {
             updateBackupTexture(mModel.getBackupImage());
             mImageWidth = mModel.getImageWidth();
             mImageHeight = mModel.getImageHeight();
             mLevelCount = mModel.getLevelCount();
         }
         layoutTiles(mCenterX, mCenterY, mScale, mRotation);
         invalidate();
     }

     @Override
     protected void onLayout(
             boolean changeSize, int left, int top, int right, int bottom) {
         super.onLayout(changeSize, left, top, right, bottom);
         if (changeSize) layoutTiles(mCenterX, mCenterY, mScale, mRotation);
     }

     // Prepare the tiles we want to use for display.
     //
     // 1. Decide the tile level we want to use for display.
     // 2. Decide the tile levels we want to keep as texture (in addition to
     //    the one we use for display).
     // 3. Recycle unused tiles.
     // 4. Activate the tiles we want.
     private void layoutTiles(int centerX, int centerY, float scale, int rotation) {
         // The width and height of this view.
         int width = getWidth();
         int height = getHeight();

         // The tile levels we want to keep as texture is in the range
         // [fromLevel, endLevel).
         int fromLevel;
         int endLevel;

         // We want to use a texture larger than or equal to the display size.
         mLevel = Utils.clamp(Utils.floorLog2(1f / scale), 0, mLevelCount);

         // We want to keep one more tile level as texture in addition to what
         // we use for display. So it can be faster when the scale moves to the
         // next level. We choose a level closer to the current scale.
         if (mLevel != mLevelCount) {
             Rect range = mTileRange;
             getRange(range, centerX, centerY, mLevel, scale, rotation);
             mOffsetX = Math.round(width / 2f + (range.left - centerX) * scale);
             mOffsetY = Math.round(height / 2f + (range.top - centerY) * scale);
             fromLevel = scale * (1 << mLevel) > 0.75f ? mLevel - 1 : mLevel;
         } else {
             // Activate the tiles of the smallest two levels.
             fromLevel = mLevel - 2;
             mOffsetX = Math.round(width / 2f - centerX * scale);
             mOffsetY = Math.round(height / 2f - centerY * scale);
         }

         fromLevel = Math.max(0, Math.min(fromLevel, mLevelCount - 2));
         endLevel = Math.min(fromLevel + 2, mLevelCount);

         Rect range[] = mActiveRange;
         for (int i = fromLevel; i < endLevel; ++i) {
             getRange(range[i - fromLevel], centerX, centerY, i, rotation);
         }

         // If rotation is transient, don't update the tile.
         if (rotation % 90 != 0) return;

         synchronized (this) {
             mDecodeQueue.clean();
             mUploadQueue.clean();
             mBackgroundTileUploaded = false;
         }

         // Recycle unused tiles: if the level of the active tile is outside the
         // range [fromLevel, endLevel) or not in the visible range.
         Iterator<Map.Entry<Long, Tile>>
                 iter = mActiveTiles.entrySet().iterator();
         while (iter.hasNext()) {
             Tile tile = iter.next().getValue();
             int level = tile.mTileLevel;
             if (level < fromLevel || level >= endLevel
                     || !range[level - fromLevel].contains(tile.mX, tile.mY)) {
                 iter.remove();
                 recycleTile(tile);
             }
         }

         for (int i = fromLevel; i < endLevel; ++i) {
             int size = TILE_SIZE << i;
             Rect r = range[i - fromLevel];
             for (int y = r.top, bottom = r.bottom; y < bottom; y += size) {
                 for (int x = r.left, right = r.right; x < right; x += size) {
                     activateTile(x, y, i);
                 }
             }
         }
         invalidate();
     }

     protected synchronized void invalidateTiles() {
         mDecodeQueue.clean();
         mUploadQueue.clean();
         // TODO disable decoder
         for (Tile tile : mActiveTiles.values()) {
             recycleTile(tile);
         }
         mActiveTiles.clear();
     }

     private void getRange(Rect out, int cX, int cY, int level, int rotation) {
         getRange(out, cX, cY, level, 1f / (1 << (level + 1)), rotation);
     }

     // If the bitmap is scaled by the given factor "scale", return the
     // rectangle containing visible range. The left-top coordinate returned is
     // aligned to the tile boundary.
     //
     // (cX, cY) is the point on the original bitmap which will be put in the
     // center of the ImageViewer.
     private void getRange(Rect out,
             int cX, int cY, int level, float scale, int rotation) {

         double radians = Math.toRadians(-rotation);
         double w = getWidth();
         double h = getHeight();

         double cos = Math.cos(radians);
         double sin = Math.sin(radians);
         int width = (int) Math.ceil(Math.max(
                 Math.abs(cos * w - sin * h), Math.abs(cos * w + sin * h)));
         int height = (int) Math.ceil(Math.max(
                 Math.abs(sin * w + cos * h), Math.abs(sin * w - cos * h)));

         int left = (int) Math.floor(cX - width / (2f * scale));
         int top = (int) Math.floor(cY - height / (2f * scale));
         int right = (int) Math.ceil(left + width / scale);
         int bottom = (int) Math.ceil(top + height / scale);

         // align the rectangle to tile boundary
         int size = TILE_SIZE << level;
         left = Math.max(0, size * (left / size));
         top = Math.max(0, size * (top / size));
         right = Math.min(mImageWidth, right);
         bottom = Math.min(mImageHeight, bottom);

         out.set(left, top, right, bottom);
     }

     public boolean setPosition(int centerX, int centerY, float scale, int rotation) {
         if (mCenterX == centerX
                 && mCenterY == centerY && mScale == scale) return false;
         mCenterX = centerX;
         mCenterY = centerY;
         mScale = scale;
         mRotation = rotation;
         layoutTiles(centerX, centerY, scale, rotation);
         invalidate();
         return true;
     }

     public void freeTextures() {
         mIsTextureFreed = true;

         if (mTileDecoder != null) {
             mTileDecoder.cancel();
             mTileDecoder.get();
             mTileDecoder = null;
         }

         for (Tile texture : mActiveTiles.values()) {
             texture.recycle();
         }
         mTileRange.set(0, 0, 0, 0);
         mActiveTiles.clear();

         synchronized (this) {
             mUploadQueue.clean();
             mDecodeQueue.clean();
             Tile tile = mRecycledQueue.pop();
             while (tile != null) {
                 tile.recycle();
                 tile = mRecycledQueue.pop();
             }
         }
         updateBackupTexture(null);
     }

     public void prepareTextures() {
         if (mTileDecoder == null) {
             mTileDecoder = mThreadPool.submit(new TileDecoder());
         }
         if (mIsTextureFreed) {
             layoutTiles(mCenterX, mCenterY, mScale, mRotation);
             mIsTextureFreed = false;
             updateBackupTexture(mModel.getBackupImage());
         }
     }

     @Override
     protected void render(GLCanvas canvas) {
         mUploadQuota = UPLOAD_LIMIT;
         mRenderComplete = true;

         int level = mLevel;
         int rotation = mRotation;

         if (rotation != 0) {
             canvas.save(GLCanvas.SAVE_FLAG_MATRIX);
             int centerX = getWidth() / 2, centerY = getHeight() / 2;
             canvas.translate(centerX, centerY, 0);
             canvas.rotate(rotation, 0, 0, 1);
             canvas.translate(-centerX, -centerY, 0);
         }
         try {
             if (level != mLevelCount) {
                 int size = (TILE_SIZE << level);
                 float length = size * mScale;
                 Rect r = mTileRange;

                 for (int ty = r.top, i = 0; ty < r.bottom; ty += size, i++) {
                     float y = mOffsetY + i * length;
                     for (int tx = r.left, j = 0; tx < r.right; tx += size, j++) {
                         float x = mOffsetX + j * length;
                         drawTile(canvas, tx, ty, level, x, y, length);
                     }
                 }
             } else if (mBackupImage != null) {
                 mBackupImage.draw(canvas, mOffsetX, mOffsetY,
                         Math.round(mImageWidth * mScale),
                         Math.round(mImageHeight * mScale));
             }
         } finally {
             if (rotation != 0) canvas.restore();
         }

         if (mRenderComplete) {
             if (!mBackgroundTileUploaded) uploadBackgroundTiles(canvas);
         } else {
             invalidate();
         }
     }

     private void uploadBackgroundTiles(GLCanvas canvas) {
         mBackgroundTileUploaded = true;
         for (Tile tile : mActiveTiles.values()) {
             if (!tile.isContentValid(canvas)) queueForDecode(tile);
         }
     }

     void queueForUpload(Tile tile) {
         synchronized (this) {
             mUploadQueue.push(tile);
         }
         if (mTileUploader.mActive.compareAndSet(false, true)) {
             getGLRoot().addOnGLIdleListener(mTileUploader);
         }
     }

     synchronized void queueForDecode(Tile tile) {
         if (tile.mTileState == STATE_ACTIVATED) {
             tile.mTileState = STATE_IN_QUEUE;
             if (mDecodeQueue.push(tile)) notifyAll();
         }
     }

     boolean decodeTile(Tile tile) {
         synchronized (this) {
             if (tile.mTileState != STATE_IN_QUEUE) return false;
             tile.mTileState = STATE_DECODING;
         }
         boolean decodeComplete = tile.decode();
         synchronized (this) {
             if (tile.mTileState == STATE_RECYCLING) {
                 tile.mTileState = STATE_RECYCLED;
                 tile.mDecodedTile = null;
                 mRecycledQueue.push(tile);
                 return false;
             }
             tile.mTileState = STATE_DECODED;
             return decodeComplete;
         }
     }

     private synchronized Tile obtainTile(int x, int y, int level) {
         Tile tile = mRecycledQueue.pop();
         if (tile != null) {
             tile.mTileState = STATE_ACTIVATED;
             tile.update(x, y, level);
             return tile;
         }
         return new Tile(x, y, level);
     }

     synchronized void recycleTile(Tile tile) {
         if (tile.mTileState == STATE_DECODING) {
             tile.mTileState = STATE_RECYCLING;
             return;
         }
         tile.mTileState = STATE_RECYCLED;
         tile.mDecodedTile = null;
         mRecycledQueue.push(tile);
     }

     private void activateTile(int x, int y, int level) {
         Long key = makeTileKey(x, y, level);
         Tile tile = mActiveTiles.get(key);
         if (tile != null) {
             if (tile.mTileState == STATE_IN_QUEUE) {
                 tile.mTileState = STATE_ACTIVATED;
             }
             return;
         }
         tile = obtainTile(x, y, level);
         mActiveTiles.put(key, tile);
     }

     private Tile getTile(int x, int y, int level) {
         return mActiveTiles.get(makeTileKey(x, y, level));
     }

     private static Long makeTileKey(int x, int y, int level) {
         long result = x;
         result = (result << 16) | y;
         result = (result << 16) | level;
         return Long.valueOf(result);
     }

     private class TileUploader implements GLRoot.OnGLIdleListener {
         AtomicBoolean mActive = new AtomicBoolean(false);

         @Override
         public boolean onGLIdle(GLRoot root, GLCanvas canvas) {
             int quota = UPLOAD_LIMIT;
             Tile tile;
             while (true) {
                 synchronized (TileImageView.this) {
                     tile = mUploadQueue.pop();
                 }
                 if (tile == null || quota <= 0) break;
                 if (!tile.isContentValid(canvas)) {
                     Utils.assertTrue(tile.mTileState == STATE_DECODED);
                     tile.updateContent(canvas);
                     --quota;
                 }
             }
             mActive.set(tile != null);
             return tile != null;
         }
     }

     // Draw the tile to a square at canvas that locates at (x, y) and
     // has a side length of length.
     public void drawTile(GLCanvas canvas,
             int tx, int ty, int level, float x, float y, float length) {
         RectF source = mSourceRect;
         RectF target = mTargetRect;
         target.set(x, y, x + length, y + length);
         source.set(0, 0, TILE_SIZE, TILE_SIZE);

         Tile tile = getTile(tx, ty, level);
         if (tile != null) {
             if (!tile.isContentValid(canvas)) {
                 if (tile.mTileState == STATE_DECODED) {
                     if (mUploadQuota > 0) {
                         --mUploadQuota;
                         tile.updateContent(canvas);
                     } else {
                         mRenderComplete = false;
                     }
                 } else {
                     mRenderComplete = false;
                     queueForDecode(tile);
                 }
             }
             if (drawTile(tile, canvas, source, target)) return;
         }
         if (mBackupImage != null) {
             BasicTexture backup = mBackupImage;
             int size = TILE_SIZE << level;
             float scaleX = (float) backup.getWidth() / mImageWidth;
             float scaleY = (float) backup.getHeight() / mImageHeight;
             source.set(tx * scaleX, ty * scaleY, (tx + size) * scaleX,
                     (ty + size) * scaleY);
             canvas.drawTexture(backup, source, target);
         }
     }

     // TODO: avoid drawing the unused part of the textures.
     static boolean drawTile(
             Tile tile, GLCanvas canvas, RectF source, RectF target) {
         while (true) {
             if (tile.isContentValid(canvas)) {
                 // offset source rectangle for the texture border.
                 source.offset(TILE_BORDER, TILE_BORDER);
                 canvas.drawTexture(tile, source, target);
                 return true;
             }

             // Parent can be divided to four quads and tile is one of the four.
             Tile parent = tile.getParentTile();
             if (parent == null) return false;
             if (tile.mX == parent.mX) {
                 source.left /= 2f;
                 source.right /= 2f;
             } else {
                 source.left = (TILE_SIZE + source.left) / 2f;
                 source.right = (TILE_SIZE + source.right) / 2f;
             }
             if (tile.mY == parent.mY) {
                 source.top /= 2f;
                 source.bottom /= 2f;
             } else {
                 source.top = (TILE_SIZE + source.top) / 2f;
                 source.bottom = (TILE_SIZE + source.bottom) / 2f;
             }
             tile = parent;
         }
     }

     private class Tile extends UploadedTexture {
         int mX;
         int mY;
         int mTileLevel;
         Tile mNext;
         Bitmap mDecodedTile;
         volatile int mTileState = STATE_ACTIVATED;

         public Tile(int x, int y, int level) {
             mX = x;
             mY = y;
             mTileLevel = level;
         }

         @Override
         protected void onFreeBitmap(Bitmap bitmap) {
             bitmap.recycle();
         }

         boolean decode() {
             // Get a tile from the original image. The tile is down-scaled
             // by (1 << mTilelevel) from a region in the original image.
             int tileLength = (TILE_SIZE + 2 * TILE_BORDER);
             int borderLength = TILE_BORDER << mTileLevel;
             try {
                 mDecodedTile = DecodeUtils.ensureGLCompatibleBitmap(mModel.getTile(
                         mTileLevel, mX - borderLength, mY - borderLength, tileLength));
                 return mDecodedTile != null;
             } catch (Throwable t) {
                 Log.w(TAG, "fail to decode tile", t);
                 return false;
             }
         }

         @Override
         protected Bitmap onGetBitmap() {
             Utils.assertTrue(mTileState == STATE_DECODED);
             Bitmap bitmap = mDecodedTile;
             mDecodedTile = null;
             mTileState = STATE_ACTIVATED;
             return bitmap;
         }

         public void update(int x, int y, int level) {
             mX = x;
             mY = y;
             mTileLevel = level;
             invalidateContent();
         }

         public Tile getParentTile() {
             if (mTileLevel + 1 == mLevelCount) return null;
             int size = TILE_SIZE << (mTileLevel + 1);
             int x = size * (mX / size);
             int y = size * (mY / size);
             return getTile(x, y, mTileLevel + 1);
         }

         @Override
         public String toString() {
             return String.format("tile(%s, %s, %s / %s)",
                     mX / TILE_SIZE, mY / TILE_SIZE, mLevel, mLevelCount);
         }
     }

     private static class TileQueue {
         private Tile mHead;

         public Tile pop() {
             Tile tile = mHead;
             if (tile != null) mHead = tile.mNext;
             return tile;
         }

         public boolean push(Tile tile) {
             boolean wasEmpty = mHead == null;
             tile.mNext = mHead;
             mHead = tile;
             return wasEmpty;
         }

         public void clean() {
             mHead = null;
         }
     }

     private class TileDecoder implements ThreadPool.Job<Void> {

         private CancelListener mNotifier = new CancelListener() {
             @Override
             public void onCancel() {
                 synchronized (TileImageView.this) {
                     TileImageView.this.notifyAll();
                 }
             }
         };

         @Override
         public Void run(JobContext jc) {
             jc.setMode(ThreadPool.MODE_NONE);
             jc.setCancelListener(mNotifier);
             while (!jc.isCancelled()) {
                 Tile tile = null;
                 synchronized(TileImageView.this) {
                     tile = mDecodeQueue.pop();
                     if (tile == null && !jc.isCancelled()) {
                         Utils.waitWithoutInterrupt(TileImageView.this);
                     }
                 }
                 if (tile == null) continue;
                 if (decodeTile(tile)) queueForUpload(tile);
             }
             return null;
         }
     }
 }
	/*
	* Copyright (C) 2010 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.gallery3d.ui;

	import com.android.gallery3d.app.GalleryContext;
	import com.android.gallery3d.common.Utils;
	import com.android.gallery3d.data.DecodeUtils;
	import com.android.gallery3d.util.Future;
	import com.android.gallery3d.util.ThreadPool;
	import com.android.gallery3d.util.ThreadPool.CancelListener;
	import com.android.gallery3d.util.ThreadPool.JobContext;

	import android.graphics.Bitmap;
	import android.graphics.Rect;
	import android.graphics.RectF;

	import java.util.HashMap;
	import java.util.Iterator;
	import java.util.Map;
	import java.util.concurrent.atomic.AtomicBoolean;

	public class TileImageView extends GLView {
	public static final int SIZE_UNKNOWN = -1;

	@SuppressWarnings("unused")
	private static final String TAG = "TileImageView";

	// TILE_SIZE must be 2^N - 2. We put one pixel border in each side of the
	// texture to avoid seams between tiles.
	private static final int TILE_SIZE = 254;
	private static final int TILE_BORDER = 1;
	private static final int UPLOAD_LIMIT = 1;

	/*
	* This is the tile state in the CPU side.
	* Life of a Tile:
	* ACTIVATED (initial state)
	* --> IN_QUEUE - by queueForDecode()
	* --> RECYCLED - by recycleTile()
	* IN_QUEUE --> DECODING - by decodeTile()
	* --> RECYCLED - by recycleTile)
	* DECODING --> RECYCLING - by recycleTile()
	* --> DECODED - by decodeTile()
	* RECYCLING --> RECYCLED - by decodeTile()
	* DECODED --> ACTIVATED - (after the decoded bitmap is uploaded)
	* DECODED --> RECYCLED - by recycleTile()
	* RECYCLED --> ACTIVATED - by obtainTile()
	*/
	private static final int STATE_ACTIVATED = 0x01;
	private static final int STATE_IN_QUEUE = 0x02;
	private static final int STATE_DECODING = 0x04;
	private static final int STATE_DECODED = 0x08;
	private static final int STATE_RECYCLING = 0x10;
	private static final int STATE_RECYCLED = 0x20;

	private Model mModel;
	protected BitmapTexture mBackupImage;
	protected int mLevelCount; // cache the value of mScaledBitmaps.length

	// The mLevel variable indicates which level of bitmap we should use.
	// Level 0 means the original full-sized bitmap, and a larger value means
	// a smaller scaled bitmap (The width and height of each scaled bitmap is
	// half size of the previous one). If the value is in [0, mLevelCount), we
	// use the bitmap in mScaledBitmaps[mLevel] for display, otherwise the value
	// is mLevelCount, and that means we use mBackupTexture for display.
	private int mLevel = 0;

	// The offsets of the (left, top) of the upper-left tile to the (left, top)
	// of the view.
	private int mOffsetX;
	private int mOffsetY;

	private int mUploadQuota;
	private boolean mRenderComplete;

	private final RectF mSourceRect = new RectF();
	private final RectF mTargetRect = new RectF();

	private final HashMap<Long, Tile> mActiveTiles = new HashMap<Long, Tile>();

	// The following three queue is guarded by TileImageView.this
	private TileQueue mRecycledQueue = new TileQueue();
	private TileQueue mUploadQueue = new TileQueue();
	private TileQueue mDecodeQueue = new TileQueue();

	// The width and height of the full-sized bitmap
	protected int mImageWidth = SIZE_UNKNOWN;
	protected int mImageHeight = SIZE_UNKNOWN;

	protected int mCenterX;
	protected int mCenterY;
	protected float mScale;
	protected int mRotation;

	// Temp variables to avoid memory allocation
	private final Rect mTileRange = new Rect();
	private final Rect mActiveRange[] = {new Rect(), new Rect()};

	private final TileUploader mTileUploader = new TileUploader();
	private boolean mIsTextureFreed;
	private Future<Void> mTileDecoder;
	private ThreadPool mThreadPool;
	private boolean mBackgroundTileUploaded;

	public static interface Model {
	public int getLevelCount();
	public Bitmap getBackupImage();
	public int getImageWidth();
	public int getImageHeight();

	// The method would be called in another thread
	public Bitmap getTile(int level, int x, int y, int tileSize);
	public boolean isFailedToLoad();
	}

	public TileImageView(GalleryContext context) {
	mThreadPool = context.getThreadPool();
	mTileDecoder = mThreadPool.submit(new TileDecoder());
	}

	public void setModel(Model model) {
	mModel = model;
	if (model != null) notifyModelInvalidated();
	}

	private void updateBackupTexture(Bitmap backup) {
	if (backup == null) {
	if (mBackupImage != null) mBackupImage.recycle();
	mBackupImage = null;
	} else {
	if (mBackupImage != null) {
	if (mBackupImage.getBitmap() != backup) {
	mBackupImage.recycle();
	mBackupImage = new BitmapTexture(backup);
	}
	} else {
	mBackupImage = new BitmapTexture(backup);
	}
	}
	}

	public void notifyModelInvalidated() {
	invalidateTiles();
	if (mModel == null) {
	mBackupImage = null;
	mImageWidth = 0;
	mImageHeight = 0;
	mLevelCount = 0;
	} else {
	updateBackupTexture(mModel.getBackupImage());
	mImageWidth = mModel.getImageWidth();
	mImageHeight = mModel.getImageHeight();
	mLevelCount = mModel.getLevelCount();
	}
	layoutTiles(mCenterX, mCenterY, mScale, mRotation);
	invalidate();
	}

	@Override
	protected void onLayout(
	boolean changeSize, int left, int top, int right, int bottom) {
	super.onLayout(changeSize, left, top, right, bottom);
	if (changeSize) layoutTiles(mCenterX, mCenterY, mScale, mRotation);
	}

	// Prepare the tiles we want to use for display.
	//
	// 1. Decide the tile level we want to use for display.
	// 2. Decide the tile levels we want to keep as texture (in addition to
	// the one we use for display).
	// 3. Recycle unused tiles.
	// 4. Activate the tiles we want.
	private void layoutTiles(int centerX, int centerY, float scale, int rotation) {
	// The width and height of this view.
	int width = getWidth();
	int height = getHeight();

	// The tile levels we want to keep as texture is in the range
	// [fromLevel, endLevel).
	int fromLevel;
	int endLevel;

	// We want to use a texture larger than or equal to the display size.
	mLevel = Utils.clamp(Utils.floorLog2(1f / scale), 0, mLevelCount);

	// We want to keep one more tile level as texture in addition to what
	// we use for display. So it can be faster when the scale moves to the
	// next level. We choose a level closer to the current scale.
	if (mLevel != mLevelCount) {
	Rect range = mTileRange;
	getRange(range, centerX, centerY, mLevel, scale, rotation);
	mOffsetX = Math.round(width / 2f + (range.left - centerX) * scale);
	mOffsetY = Math.round(height / 2f + (range.top - centerY) * scale);
	fromLevel = scale * (1 << mLevel) > 0.75f ? mLevel - 1 : mLevel;
	} else {
	// Activate the tiles of the smallest two levels.
	fromLevel = mLevel - 2;
	mOffsetX = Math.round(width / 2f - centerX * scale);
	mOffsetY = Math.round(height / 2f - centerY * scale);
	}

	fromLevel = Math.max(0, Math.min(fromLevel, mLevelCount - 2));
	endLevel = Math.min(fromLevel + 2, mLevelCount);

	Rect range[] = mActiveRange;
	for (int i = fromLevel; i < endLevel; ++i) {
	getRange(range[i - fromLevel], centerX, centerY, i, rotation);
	}

	// If rotation is transient, don't update the tile.
	if (rotation % 90 != 0) return;

	synchronized (this) {
	mDecodeQueue.clean();
	mUploadQueue.clean();
	mBackgroundTileUploaded = false;
	}

	// Recycle unused tiles: if the level of the active tile is outside the
	// range [fromLevel, endLevel) or not in the visible range.
	Iterator<Map.Entry<Long, Tile>>
	iter = mActiveTiles.entrySet().iterator();
	while (iter.hasNext()) {
	Tile tile = iter.next().getValue();
	int level = tile.mTileLevel;
	if (level < fromLevel \|\| level >= endLevel
	\|\| !range[level - fromLevel].contains(tile.mX, tile.mY)) {
	iter.remove();
	recycleTile(tile);
	}
	}

	for (int i = fromLevel; i < endLevel; ++i) {
	int size = TILE_SIZE << i;
	Rect r = range[i - fromLevel];
	for (int y = r.top, bottom = r.bottom; y < bottom; y += size) {
	for (int x = r.left, right = r.right; x < right; x += size) {
	activateTile(x, y, i);
	}
	}
	}
	invalidate();
	}

	protected synchronized void invalidateTiles() {
	mDecodeQueue.clean();
	mUploadQueue.clean();
	// TODO disable decoder
	for (Tile tile : mActiveTiles.values()) {
	recycleTile(tile);
	}
	mActiveTiles.clear();
	}

	private void getRange(Rect out, int cX, int cY, int level, int rotation) {
	getRange(out, cX, cY, level, 1f / (1 << (level + 1)), rotation);
	}

	// If the bitmap is scaled by the given factor "scale", return the
	// rectangle containing visible range. The left-top coordinate returned is
	// aligned to the tile boundary.
	//
	// (cX, cY) is the point on the original bitmap which will be put in the
	// center of the ImageViewer.
	private void getRange(Rect out,
	int cX, int cY, int level, float scale, int rotation) {

	double radians = Math.toRadians(-rotation);
	double w = getWidth();
	double h = getHeight();

	double cos = Math.cos(radians);
	double sin = Math.sin(radians);
	int width = (int) Math.ceil(Math.max(
	Math.abs(cos * w - sin * h), Math.abs(cos * w + sin * h)));
	int height = (int) Math.ceil(Math.max(
	Math.abs(sin * w + cos * h), Math.abs(sin * w - cos * h)));

	int left = (int) Math.floor(cX - width / (2f * scale));
	int top = (int) Math.floor(cY - height / (2f * scale));
	int right = (int) Math.ceil(left + width / scale);
	int bottom = (int) Math.ceil(top + height / scale);

	// align the rectangle to tile boundary
	int size = TILE_SIZE << level;
	left = Math.max(0, size * (left / size));
	top = Math.max(0, size * (top / size));
	right = Math.min(mImageWidth, right);
	bottom = Math.min(mImageHeight, bottom);

	out.set(left, top, right, bottom);
	}

	public boolean setPosition(int centerX, int centerY, float scale, int rotation) {
	if (mCenterX == centerX
	&& mCenterY == centerY && mScale == scale) return false;
	mCenterX = centerX;
	mCenterY = centerY;
	mScale = scale;
	mRotation = rotation;
	layoutTiles(centerX, centerY, scale, rotation);
	invalidate();
	return true;
	}

	public void freeTextures() {
	mIsTextureFreed = true;

	if (mTileDecoder != null) {
	mTileDecoder.cancel();
	mTileDecoder.get();
	mTileDecoder = null;
	}

	for (Tile texture : mActiveTiles.values()) {
	texture.recycle();
	}
	mTileRange.set(0, 0, 0, 0);
	mActiveTiles.clear();

	synchronized (this) {
	mUploadQueue.clean();
	mDecodeQueue.clean();
	Tile tile = mRecycledQueue.pop();
	while (tile != null) {
	tile.recycle();
	tile = mRecycledQueue.pop();
	}
	}
	updateBackupTexture(null);
	}

	public void prepareTextures() {
	if (mTileDecoder == null) {
	mTileDecoder = mThreadPool.submit(new TileDecoder());
	}
	if (mIsTextureFreed) {
	layoutTiles(mCenterX, mCenterY, mScale, mRotation);
	mIsTextureFreed = false;
	updateBackupTexture(mModel.getBackupImage());
	}
	}

	@Override
	protected void render(GLCanvas canvas) {
	mUploadQuota = UPLOAD_LIMIT;
	mRenderComplete = true;

	int level = mLevel;
	int rotation = mRotation;

	if (rotation != 0) {
	canvas.save(GLCanvas.SAVE_FLAG_MATRIX);
	int centerX = getWidth() / 2, centerY = getHeight() / 2;
	canvas.translate(centerX, centerY, 0);
	canvas.rotate(rotation, 0, 0, 1);
	canvas.translate(-centerX, -centerY, 0);
	}
	try {
	if (level != mLevelCount) {
	int size = (TILE_SIZE << level);
	float length = size * mScale;
	Rect r = mTileRange;

	for (int ty = r.top, i = 0; ty < r.bottom; ty += size, i++) {
	float y = mOffsetY + i * length;
	for (int tx = r.left, j = 0; tx < r.right; tx += size, j++) {
	float x = mOffsetX + j * length;
	drawTile(canvas, tx, ty, level, x, y, length);
	}
	}
	} else if (mBackupImage != null) {
	mBackupImage.draw(canvas, mOffsetX, mOffsetY,
	Math.round(mImageWidth * mScale),
	Math.round(mImageHeight * mScale));
	}
	} finally {
	if (rotation != 0) canvas.restore();
	}

	if (mRenderComplete) {
	if (!mBackgroundTileUploaded) uploadBackgroundTiles(canvas);
	} else {
	invalidate();
	}
	}

	private void uploadBackgroundTiles(GLCanvas canvas) {
	mBackgroundTileUploaded = true;
	for (Tile tile : mActiveTiles.values()) {
	if (!tile.isContentValid(canvas)) queueForDecode(tile);
	}
	}

	void queueForUpload(Tile tile) {
	synchronized (this) {
	mUploadQueue.push(tile);
	}
	if (mTileUploader.mActive.compareAndSet(false, true)) {
	getGLRoot().addOnGLIdleListener(mTileUploader);
	}
	}

	synchronized void queueForDecode(Tile tile) {
	if (tile.mTileState == STATE_ACTIVATED) {
	tile.mTileState = STATE_IN_QUEUE;
	if (mDecodeQueue.push(tile)) notifyAll();
	}
	}

	boolean decodeTile(Tile tile) {
	synchronized (this) {
	if (tile.mTileState != STATE_IN_QUEUE) return false;
	tile.mTileState = STATE_DECODING;
	}
	boolean decodeComplete = tile.decode();
	synchronized (this) {
	if (tile.mTileState == STATE_RECYCLING) {
	tile.mTileState = STATE_RECYCLED;
	tile.mDecodedTile = null;
	mRecycledQueue.push(tile);
	return false;
	}
	tile.mTileState = STATE_DECODED;
	return decodeComplete;
	}
	}

	private synchronized Tile obtainTile(int x, int y, int level) {
	Tile tile = mRecycledQueue.pop();
	if (tile != null) {
	tile.mTileState = STATE_ACTIVATED;
	tile.update(x, y, level);
	return tile;
	}
	return new Tile(x, y, level);
	}

	synchronized void recycleTile(Tile tile) {
	if (tile.mTileState == STATE_DECODING) {
	tile.mTileState = STATE_RECYCLING;
	return;
	}
	tile.mTileState = STATE_RECYCLED;
	tile.mDecodedTile = null;
	mRecycledQueue.push(tile);
	}

	private void activateTile(int x, int y, int level) {
	Long key = makeTileKey(x, y, level);
	Tile tile = mActiveTiles.get(key);
	if (tile != null) {
	if (tile.mTileState == STATE_IN_QUEUE) {
	tile.mTileState = STATE_ACTIVATED;
	}
	return;
	}
	tile = obtainTile(x, y, level);
	mActiveTiles.put(key, tile);
	}

	private Tile getTile(int x, int y, int level) {
	return mActiveTiles.get(makeTileKey(x, y, level));
	}

	private static Long makeTileKey(int x, int y, int level) {
	long result = x;
	result = (result << 16) \| y;
	result = (result << 16) \| level;
	return Long.valueOf(result);
	}

	private class TileUploader implements GLRoot.OnGLIdleListener {
	AtomicBoolean mActive = new AtomicBoolean(false);

	@Override
	public boolean onGLIdle(GLRoot root, GLCanvas canvas) {
	int quota = UPLOAD_LIMIT;
	Tile tile;
	while (true) {
	synchronized (TileImageView.this) {
	tile = mUploadQueue.pop();
	}
	if (tile == null \|\| quota <= 0) break;
	if (!tile.isContentValid(canvas)) {
	Utils.assertTrue(tile.mTileState == STATE_DECODED);
	tile.updateContent(canvas);
	--quota;
	}
	}
	mActive.set(tile != null);
	return tile != null;
	}
	}

	// Draw the tile to a square at canvas that locates at (x, y) and
	// has a side length of length.
	public void drawTile(GLCanvas canvas,
	int tx, int ty, int level, float x, float y, float length) {
	RectF source = mSourceRect;
	RectF target = mTargetRect;
	target.set(x, y, x + length, y + length);
	source.set(0, 0, TILE_SIZE, TILE_SIZE);

	Tile tile = getTile(tx, ty, level);
	if (tile != null) {
	if (!tile.isContentValid(canvas)) {
	if (tile.mTileState == STATE_DECODED) {
	if (mUploadQuota > 0) {
	--mUploadQuota;
	tile.updateContent(canvas);
	} else {
	mRenderComplete = false;
	}
	} else {
	mRenderComplete = false;
	queueForDecode(tile);
	}
	}
	if (drawTile(tile, canvas, source, target)) return;
	}
	if (mBackupImage != null) {
	BasicTexture backup = mBackupImage;
	int size = TILE_SIZE << level;
	float scaleX = (float) backup.getWidth() / mImageWidth;
	float scaleY = (float) backup.getHeight() / mImageHeight;
	source.set(tx * scaleX, ty * scaleY, (tx + size) * scaleX,
	(ty + size) * scaleY);
	canvas.drawTexture(backup, source, target);
	}
	}

	// TODO: avoid drawing the unused part of the textures.
	static boolean drawTile(
	Tile tile, GLCanvas canvas, RectF source, RectF target) {
	while (true) {
	if (tile.isContentValid(canvas)) {
	// offset source rectangle for the texture border.
	source.offset(TILE_BORDER, TILE_BORDER);
	canvas.drawTexture(tile, source, target);
	return true;
	}

	// Parent can be divided to four quads and tile is one of the four.
	Tile parent = tile.getParentTile();
	if (parent == null) return false;
	if (tile.mX == parent.mX) {
	source.left /= 2f;
	source.right /= 2f;
	} else {
	source.left = (TILE_SIZE + source.left) / 2f;
	source.right = (TILE_SIZE + source.right) / 2f;
	}
	if (tile.mY == parent.mY) {
	source.top /= 2f;
	source.bottom /= 2f;
	} else {
	source.top = (TILE_SIZE + source.top) / 2f;
	source.bottom = (TILE_SIZE + source.bottom) / 2f;
	}
	tile = parent;
	}
	}

	private class Tile extends UploadedTexture {
	int mX;
	int mY;
	int mTileLevel;
	Tile mNext;
	Bitmap mDecodedTile;
	volatile int mTileState = STATE_ACTIVATED;

	public Tile(int x, int y, int level) {
	mX = x;
	mY = y;
	mTileLevel = level;
	}

	@Override
	protected void onFreeBitmap(Bitmap bitmap) {
	bitmap.recycle();
	}

	boolean decode() {
	// Get a tile from the original image. The tile is down-scaled
	// by (1 << mTilelevel) from a region in the original image.
	int tileLength = (TILE_SIZE + 2 * TILE_BORDER);
	int borderLength = TILE_BORDER << mTileLevel;
	try {
	mDecodedTile = DecodeUtils.ensureGLCompatibleBitmap(mModel.getTile(
	mTileLevel, mX - borderLength, mY - borderLength, tileLength));
	return mDecodedTile != null;
	} catch (Throwable t) {
	Log.w(TAG, "fail to decode tile", t);
	return false;
	}
	}

	@Override
	protected Bitmap onGetBitmap() {
	Utils.assertTrue(mTileState == STATE_DECODED);
	Bitmap bitmap = mDecodedTile;
	mDecodedTile = null;
	mTileState = STATE_ACTIVATED;
	return bitmap;
	}

	public void update(int x, int y, int level) {
	mX = x;
	mY = y;
	mTileLevel = level;
	invalidateContent();
	}

	public Tile getParentTile() {
	if (mTileLevel + 1 == mLevelCount) return null;
	int size = TILE_SIZE << (mTileLevel + 1);
	int x = size * (mX / size);
	int y = size * (mY / size);
	return getTile(x, y, mTileLevel + 1);
	}

	@Override
	public String toString() {
	return String.format("tile(%s, %s, %s / %s)",
	mX / TILE_SIZE, mY / TILE_SIZE, mLevel, mLevelCount);
	}
	}

	private static class TileQueue {
	private Tile mHead;

	public Tile pop() {
	Tile tile = mHead;
	if (tile != null) mHead = tile.mNext;
	return tile;
	}

	public boolean push(Tile tile) {
	boolean wasEmpty = mHead == null;
	tile.mNext = mHead;
	mHead = tile;
	return wasEmpty;
	}

	public void clean() {
	mHead = null;
	}
	}

	private class TileDecoder implements ThreadPool.Job<Void> {

	private CancelListener mNotifier = new CancelListener() {
	@Override
	public void onCancel() {
	synchronized (TileImageView.this) {
	TileImageView.this.notifyAll();
	}
	}
	};

	@Override
	public Void run(JobContext jc) {
	jc.setMode(ThreadPool.MODE_NONE);
	jc.setCancelListener(mNotifier);
	while (!jc.isCancelled()) {
	Tile tile = null;
	synchronized(TileImageView.this) {
	tile = mDecodeQueue.pop();
	if (tile == null && !jc.isCancelled()) {
	Utils.waitWithoutInterrupt(TileImageView.this);
	}
	}
	if (tile == null) continue;
	if (decodeTile(tile)) queueForUpload(tile);
	}
	return null;
	}
	}
	}