Refactor. Make the code simpler.

Change-Id: I2d3b7a1cfed17afcf6b7ee3e7bf1ca13ada8d9c3

12 files changed, 269 insertions, 447 deletions

diff --git a/src/com/android/gallery3d/app/AlbumPage.java b/src/com/android/gallery3d/app/AlbumPage.java
index 818a2ff3d..8bd2badf8 100644
--- a/src/com/android/gallery3d/app/AlbumPage.java
+++ b/src/com/android/gallery3d/app/AlbumPage.java
@@ -82,6 +82,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
     private AlbumView mAlbumView;
     private Path mMediaSetPath;
     private String mParentMediaSetString;
+    private SlotView mSlotView;
 
     private AlbumDataAdapter mAlbumDataAdapter;
 
@@ -129,7 +130,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
                 mAlbumView.setSelectionDrawer(mGridDrawer);
             }
 
-            mAlbumView.layout(0, slotViewTop, slotViewRight, slotViewBottom);
+            mSlotView.layout(0, slotViewTop, slotViewRight, slotViewBottom);
             GalleryUtils.setViewPointMatrix(mMatrix,
                     (right - left) / 2, (bottom - top) / 2, -mUserDistance);
             // Reset position offset after the layout is changed.
@@ -153,7 +154,8 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         } else if (mSelectionManager.inSelectionMode()) {
             mSelectionManager.leaveSelectionMode();
         } else {
-            mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
+            // TODO: fix this regression
+            // mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
             super.onBackPressed();
         }
     }
@@ -162,12 +164,12 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         MediaItem item = mAlbumDataAdapter.get(index);
         Path path = (item == null) ? null : item.getPath();
         mSelectionManager.setPressedPath(path);
-        mAlbumView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onUp() {
         mSelectionManager.setPressedPath(null);
-        mAlbumView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onSingleTapUp(int slotIndex) {
@@ -185,7 +187,8 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
             } else {
                 // Get into the PhotoPage.
                 Bundle data = new Bundle();
-                mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
+
+                // mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
                 data.putInt(PhotoPage.KEY_INDEX_HINT, slotIndex);
                 data.putParcelable(PhotoPage.KEY_OPEN_ANIMATION_RECT,
                         getSlotRect(slotIndex));
@@ -199,17 +202,17 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         } else {
             mSelectionManager.toggle(item.getPath());
             mDetailsSource.findIndex(slotIndex);
-            mAlbumView.invalidate();
+            mSlotView.invalidate();
         }
     }
 
     private Rect getSlotRect(int slotIndex) {
         // Get slot rectangle relative to this root pane.
         Rect offset = new Rect();
-        mRootPane.getBoundsOf(mAlbumView, offset);
-        Rect r = mAlbumView.getSlotRect(slotIndex);
-        r.offset(offset.left - mAlbumView.getScrollX(),
-                offset.top - mAlbumView.getScrollY());
+        mRootPane.getBoundsOf(mSlotView, offset);
+        Rect r = mSlotView.getSlotRect(slotIndex);
+        r.offset(offset.left - mSlotView.getScrollX(),
+                offset.top - mSlotView.getScrollY());
         return r;
     }
 
@@ -244,7 +247,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
             mSelectionManager.setAutoLeaveSelectionMode(true);
             mSelectionManager.toggle(item.getPath());
             mDetailsSource.findIndex(slotIndex);
-            mAlbumView.invalidate();
+            mSlotView.invalidate();
         }
     }
 
@@ -260,7 +263,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
                     GalleryActionBar.getClusterByTypeString(context, clusterType));
         }
 
-        mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
+        // mAlbumView.savePositions(PositionRepository.getInstance(mActivity));
         mActivity.getStateManager().startStateForResult(
                 AlbumSetPage.class, REQUEST_DO_ANIMATION, data);
     }
@@ -287,7 +290,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
     private void startTransition() {
         final PositionRepository repository =
                 PositionRepository.getInstance(mActivity);
-        mAlbumView.startTransition(new PositionProvider() {
+        mSlotView.startTransition(new PositionProvider() {
             private final Position mTempPosition = new Position();
             public Position getPosition(int identity, Position target) {
                 Position p = repository.get(identity);
@@ -306,7 +309,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
                 ? null
                 : data.getIntArray(KEY_SET_CENTER);
         final Random random = new Random();
-        mAlbumView.startTransition(new PositionProvider() {
+        mSlotView.startTransition(new PositionProvider() {
             private final Position mTempPosition = new Position();
             public Position getPosition(int identity, Position target) {
                 Position p = repository.get(identity);
@@ -331,7 +334,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         setContentPane(mRootPane);
         // Reset position offset for resuming.
         PositionRepository.getInstance(mActivity).setOffset(
-                mAlbumView.bounds().left, mAlbumView.bounds().top);
+                mSlotView.bounds().left, mSlotView.bounds().top);
 
         Path path = mMediaSet.getPath();
         boolean enableHomeButton = (mActivity.getStateManager().getStateCount() > 1) |
@@ -380,11 +383,13 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         mSelectionManager.setSelectionListener(this);
         mGridDrawer = new GridDrawer((Context) mActivity, mSelectionManager);
         Config.AlbumPage config = Config.AlbumPage.get((Context) mActivity);
-        mAlbumView = new AlbumView(mActivity, config.slotViewSpec,
-                0 /* don't cache thumbnail */);
+        mSlotView = new SlotView((Context) mActivity, config.slotViewSpec);
+        mAlbumView = new AlbumView(
+                mActivity, mSlotView, 0/* don't cache thumbnail */);
+        mSlotView.setSlotRenderer(mAlbumView);
         mAlbumView.setSelectionDrawer(mGridDrawer);
-        mRootPane.addComponent(mAlbumView);
-        mAlbumView.setListener(new SlotView.SimpleListener() {
+        mRootPane.addComponent(mSlotView);
+        mSlotView.setListener(new SlotView.SimpleListener() {
             @Override
             public void onDown(int index) {
                 AlbumPage.this.onDown(index);
@@ -446,7 +451,7 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
         mShowDetails = false;
         mDetailsHelper.hide();
         mAlbumView.setSelectionDrawer(mGridDrawer);
-        mAlbumView.invalidate();
+        mSlotView.invalidate();
     }
 
     @Override
@@ -540,13 +545,13 @@ public class AlbumPage extends ActivityState implements GalleryActionBar.Cluster
                 // data could be null, if there is no images in the album
                 if (data == null) return;
                 mFocusIndex = data.getIntExtra(SlideshowPage.KEY_PHOTO_INDEX, 0);
-                mAlbumView.setCenterIndex(mFocusIndex);
+                mSlotView.setCenterIndex(mFocusIndex);
                 break;
             }
             case REQUEST_PHOTO: {
                 if (data == null) return;
                 mFocusIndex = data.getIntExtra(PhotoPage.KEY_INDEX_HINT, 0);
-                mAlbumView.setCenterIndex(mFocusIndex);
+                mSlotView.setCenterIndex(mFocusIndex);
                 startTransition();
                 break;
             }
diff --git a/src/com/android/gallery3d/app/AlbumSetPage.java b/src/com/android/gallery3d/app/AlbumSetPage.java
index d00c03c4f..d526b667c 100644
--- a/src/com/android/gallery3d/app/AlbumSetPage.java
+++ b/src/com/android/gallery3d/app/AlbumSetPage.java
@@ -73,6 +73,7 @@ public class AlbumSetPage extends ActivityState implements
     private static final int BIT_LOADING_SYNC = 2;
 
     private boolean mIsActive = false;
+    private SlotView mSlotView;
     private AlbumSetView mAlbumSetView;
 
     private MediaSet mMediaSet;
@@ -131,7 +132,8 @@ public class AlbumSetPage extends ActivityState implements
                 mAlbumSetView.setSelectionDrawer(mGridDrawer);
             }
 
-            mAlbumSetView.layout(0, slotViewTop, slotViewRight, slotViewBottom);
+            mSlotView.layout(0, slotViewTop, slotViewRight, slotViewBottom);
+
             // Reset position offset after the layout is changed.
             PositionRepository.getInstance(mActivity).setOffset(
                     0, slotViewTop);
@@ -165,19 +167,21 @@ public class AlbumSetPage extends ActivityState implements
         } else if (mSelectionManager.inSelectionMode()) {
             mSelectionManager.leaveSelectionMode();
         } else {
-            mAlbumSetView.savePositions(
-                    PositionRepository.getInstance(mActivity));
+            // TODO: fix this regression during refactoring
+            // mSlotView.savePositions(
+            //        PositionRepository.getInstance(mActivity));
             super.onBackPressed();
         }
     }
 
     private void savePositions(int slotIndex, int center[]) {
         Rect offset = new Rect();
-        mRootPane.getBoundsOf(mAlbumSetView, offset);
-        mAlbumSetView.savePositions(PositionRepository.getInstance(mActivity));
-        Rect r = mAlbumSetView.getSlotRect(slotIndex);
-        int scrollX = mAlbumSetView.getScrollX();
-        int scrollY = mAlbumSetView.getScrollY();
+        mRootPane.getBoundsOf(mSlotView, offset);
+        // TODO: fix this regression during refactoring
+        // mSlotView.savePositions(PositionRepository.getInstance(mActivity));
+        Rect r = mSlotView.getSlotRect(slotIndex);
+        int scrollX = mSlotView.getScrollX();
+        int scrollY = mSlotView.getScrollY();
         center[0] = offset.left + (r.left + r.right) / 2 - scrollX;
         center[1] = offset.top + (r.top + r.bottom) / 2 - scrollY;
     }
@@ -220,7 +224,7 @@ public class AlbumSetPage extends ActivityState implements
             }
         } else {
             mSelectionManager.toggle(targetSet.getPath());
-            mAlbumSetView.invalidate();
+            mSlotView.invalidate();
         }
     }
 
@@ -228,12 +232,12 @@ public class AlbumSetPage extends ActivityState implements
         MediaSet set = mAlbumSetDataAdapter.getMediaSet(index);
         Path path = (set == null) ? null : set.getPath();
         mSelectionManager.setPressedPath(path);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onUp() {
         mSelectionManager.setPressedPath(null);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     public void onLongTap(int slotIndex) {
@@ -246,7 +250,7 @@ public class AlbumSetPage extends ActivityState implements
             mSelectionManager.setAutoLeaveSelectionMode(true);
             mSelectionManager.toggle(set.getPath());
             mDetailsSource.findIndex(slotIndex);
-            mAlbumSetView.invalidate();
+            mSlotView.invalidate();
         }
     }
 
@@ -256,7 +260,6 @@ public class AlbumSetPage extends ActivityState implements
         Bundle data = new Bundle(getData());
         data.putString(AlbumSetPage.KEY_MEDIA_PATH, newPath);
         data.putInt(KEY_SELECTED_CLUSTER_TYPE, clusterType);
-        mAlbumSetView.savePositions(PositionRepository.getInstance(mActivity));
         mActivity.getStateManager().switchState(this, AlbumSetPage.class, data);
     }
 
@@ -330,7 +333,7 @@ public class AlbumSetPage extends ActivityState implements
         setContentPane(mRootPane);
         // Reset position offset for resuming.
         PositionRepository.getInstance(mActivity).setOffset(
-                mAlbumSetView.bounds().left, mAlbumSetView.bounds().top);
+                mSlotView.bounds().left, mSlotView.bounds().top);
 
         // Set the reload bit here to prevent it exit this page in clearLoadingBit().
         setLoadingBit(BIT_LOADING_RELOAD);
@@ -364,9 +367,11 @@ public class AlbumSetPage extends ActivityState implements
 
         mGridDrawer = new GridDrawer((Context) mActivity, mSelectionManager);
         Config.AlbumSetPage config = Config.AlbumSetPage.get((Context) mActivity);
-        mAlbumSetView = new AlbumSetView(mActivity, mGridDrawer,
-                config.slotViewSpec, config.labelSpec);
-        mAlbumSetView.setListener(new SlotView.SimpleListener() {
+        mSlotView = new SlotView((Context) mActivity, config.slotViewSpec);
+        mAlbumSetView = new AlbumSetView(
+                mActivity, mGridDrawer, mSlotView, config.labelSpec);
+        mSlotView.setSlotRenderer(mAlbumSetView);
+        mSlotView.setListener(new SlotView.SimpleListener() {
             @Override
             public void onDown(int index) {
                 AlbumSetPage.this.onDown(index);
@@ -394,7 +399,7 @@ public class AlbumSetPage extends ActivityState implements
                 return onItemSelected(item);
             }
         });
-        mRootPane.addComponent(mAlbumSetView);
+        mRootPane.addComponent(mSlotView);
     }
 
     @Override
@@ -511,7 +516,7 @@ public class AlbumSetPage extends ActivityState implements
     private void startTransition() {
         final PositionRepository repository =
                 PositionRepository.getInstance(mActivity);
-        mAlbumSetView.startTransition(new PositionProvider() {
+        mSlotView.startTransition(new PositionProvider() {
             private final Position mTempPosition = new Position();
             public Position getPosition(int identity, Position target) {
                 Position p = repository.get(identity);
@@ -569,7 +574,7 @@ public class AlbumSetPage extends ActivityState implements
         mShowDetails = false;
         mDetailsHelper.hide();
         mAlbumSetView.setSelectionDrawer(mGridDrawer);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void showDetails() {
diff --git a/src/com/android/gallery3d/app/ManageCachePage.java b/src/com/android/gallery3d/app/ManageCachePage.java
index 124eb7bf0..718c59fbf 100644
--- a/src/com/android/gallery3d/app/ManageCachePage.java
+++ b/src/com/android/gallery3d/app/ManageCachePage.java
@@ -66,6 +66,7 @@ public class ManageCachePage extends ActivityState implements
     private static final int MSG_REQUEST_LAYOUT = 2;
     private static final int PROGRESS_BAR_MAX = 10000;
 
+    private SlotView mSlotView;
     private AlbumSetView mAlbumSetView;
 
     private MediaSet mMediaSet;
@@ -122,7 +123,7 @@ public class ManageCachePage extends ActivityState implements
                 slotViewBottom = location[1];
             }
 
-            mAlbumSetView.layout(0, slotViewTop, right - left, slotViewBottom);
+            mSlotView.layout(0, slotViewTop, right - left, slotViewBottom);
         }
 
         @Override
@@ -149,12 +150,12 @@ public class ManageCachePage extends ActivityState implements
         MediaSet set = mAlbumSetDataAdapter.getMediaSet(index);
         Path path = (set == null) ? null : set.getPath();
         mSelectionManager.setPressedPath(path);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onUp() {
         mSelectionManager.setPressedPath(null);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     public void onSingleTapUp(int slotIndex) {
@@ -190,7 +191,7 @@ public class ManageCachePage extends ActivityState implements
         refreshCacheStorageInfo();
 
         mSelectionManager.toggle(path);
-        mAlbumSetView.invalidate();
+        mSlotView.invalidate();
     }
 
     @Override
@@ -294,9 +295,11 @@ public class ManageCachePage extends ActivityState implements
         Config.ManageCachePage config = Config.ManageCachePage.get(activity);
         mSelectionDrawer = new ManageCacheDrawer((Context) mActivity,
                 mSelectionManager, config.cachePinSize, config.cachePinMargin);
+        mSlotView = new SlotView((Context) mActivity, config.slotViewSpec);
         mAlbumSetView = new AlbumSetView(mActivity, mSelectionDrawer,
-                config.slotViewSpec, config.labelSpec);
-        mAlbumSetView.setListener(new SlotView.SimpleListener() {
+                mSlotView, config.labelSpec);
+        mSlotView.setSlotRenderer(mAlbumSetView);
+        mSlotView.setListener(new SlotView.SimpleListener() {
             @Override
             public void onDown(int index) {
                 ManageCachePage.this.onDown(index);
@@ -312,7 +315,7 @@ public class ManageCachePage extends ActivityState implements
                 ManageCachePage.this.onSingleTapUp(slotIndex);
             }
         });
-        mRootPane.addComponent(mAlbumSetView);
+        mRootPane.addComponent(mSlotView);
         initializeFooterViews();
     }
 
diff --git a/src/com/android/gallery3d/ui/AlbumSetSlidingWindow.java b/src/com/android/gallery3d/ui/AlbumSetSlidingWindow.java
index 5bead6297..1d94c69a1 100644
--- a/src/com/android/gallery3d/ui/AlbumSetSlidingWindow.java
+++ b/src/com/android/gallery3d/ui/AlbumSetSlidingWindow.java
@@ -41,9 +41,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
 
     public static interface Listener {
         public void onSizeChanged(int size);
-        public void onContentInvalidated();
-        public void onWindowContentChanged(
-                int slot, AlbumSetItem old, AlbumSetItem update);
+        public void onContentChanged();
     }
 
     private final AlbumSetView.Model mSource;
@@ -276,7 +274,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
             original.cacheStatus = identifyCacheStatus(set);
             original.setPath = set == null ? null : set.getPath();
             ((LabelDisplayItem) original.labelItem).updateContent();
-            if (mListener != null) mListener.onContentInvalidated();
+            if (mListener != null) mListener.onContentChanged();
             return;
         }
 
@@ -284,7 +282,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
         AlbumSetItem update = data[pos];
 
         if (mListener != null && isActiveSlot(slotIndex)) {
-            mListener.onWindowContentChanged(slotIndex, original, update);
+            mListener.onContentChanged();
         }
         if (original != null) {
             for (DisplayItem item : original.covers) {
@@ -370,7 +368,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
                 } else {
                     updateContent(texture);
                 }
-                if (mListener != null) mListener.onContentInvalidated();
+                if (mListener != null) mListener.onContentChanged();
             }
         }
 
@@ -416,7 +414,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
 
             if ((mContent instanceof FadeInTexture) &&
                     ((FadeInTexture) mContent).isAnimating()) {
-                return RENDER_MORE_FRAME;
+                return SlotView.RENDER_MORE_FRAME;
             } else {
                 return 0;
             }
@@ -561,6 +559,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
         }
     }
 
+    @Override
     public void onSizeChanged(int size) {
         if (mIsActive && mSize != size) {
             mSize = size;
@@ -568,6 +567,7 @@ public class AlbumSetSlidingWindow implements AlbumSetView.ModelListener {
         }
     }
 
+    @Override
     public void onWindowContentChanged(int index) {
         if (!mIsActive) {
             // paused, ignore slot changed event
diff --git a/src/com/android/gallery3d/ui/AlbumSetView.java b/src/com/android/gallery3d/ui/AlbumSetView.java
index 577d54e33..7a4b651a6 100644
--- a/src/com/android/gallery3d/ui/AlbumSetView.java
+++ b/src/com/android/gallery3d/ui/AlbumSetView.java
@@ -16,33 +16,21 @@
 
 package com.android.gallery3d.ui;
 
-import android.graphics.Rect;
-
 import com.android.gallery3d.app.GalleryActivity;
-import com.android.gallery3d.common.Utils;
 import com.android.gallery3d.data.MediaItem;
 import com.android.gallery3d.data.MediaSet;
-import com.android.gallery3d.ui.PositionRepository.Position;
-
-import java.util.Random;
 
-public class AlbumSetView extends SlotView {
+public class AlbumSetView implements SlotView.SlotRenderer {
     @SuppressWarnings("unused")
     private static final String TAG = "AlbumSetView";
     private static final int CACHE_SIZE = 32;
-    private static final float PHOTO_DISTANCE = 35f;
-
-    private int mVisibleStart;
-    private int mVisibleEnd;
-
-    private final Random mRandom = new Random();
-    private final long mSeed = mRandom.nextLong();
 
     private AlbumSetSlidingWindow mDataWindow;
     private final GalleryActivity mActivity;
     private final LabelSpec mLabelSpec;
 
     private SelectionDrawer mSelectionDrawer;
+    private SlotView mSlotView;
 
     public static interface Model {
         public MediaItem[] getCoverItems(int index);
@@ -74,12 +62,11 @@ public class AlbumSetView extends SlotView {
     }
 
     public AlbumSetView(GalleryActivity activity, SelectionDrawer drawer,
-            SlotView.Spec slotViewSpec, LabelSpec labelSpec) {
-        super(activity.getAndroidContext());
+            SlotView slotView, LabelSpec labelSpec) {
         mActivity = activity;
         setSelectionDrawer(drawer);
-        setSlotSpec(slotViewSpec);
         mLabelSpec = labelSpec;
+        mSlotView = slotView;
     }
 
     public void setSelectionDrawer(SelectionDrawer drawer) {
@@ -92,151 +79,69 @@ public class AlbumSetView extends SlotView {
     public void setModel(AlbumSetView.Model model) {
         if (mDataWindow != null) {
             mDataWindow.setListener(null);
-            setSlotCount(0);
             mDataWindow = null;
+            mSlotView.setSlotCount(0);
         }
         if (model != null) {
             mDataWindow = new AlbumSetSlidingWindow(mActivity, mLabelSpec,
                     mSelectionDrawer, model, CACHE_SIZE);
             mDataWindow.setListener(new MyCacheListener());
-            setSlotCount(mDataWindow.size());
-            updateVisibleRange(getVisibleStart(), getVisibleEnd());
+            mSlotView.setSlotCount(mDataWindow.size());
         }
     }
 
-    private void putSlotContent(int slotIndex, AlbumSetItem entry) {
-        // Get displayItems from mItemsetMap or create them from MediaSet.
-        Utils.assertTrue(entry != null);
-        Rect rect = getSlotRect(slotIndex);
-
-        DisplayItem[] items = entry.covers;
-        mRandom.setSeed(slotIndex ^ mSeed);
-
-        int x = (rect.left + rect.right) / 2;
-        int y = (rect.top + rect.bottom) / 2;
-
-        Position basePosition = new Position(x, y, 0);
+    @Override
+    public int renderSlot(GLCanvas canvas, int index, int pass, int width, int height) {
+        AlbumSetItem entry = mDataWindow.get(index);
+        DisplayItem cover = entry.covers.length > 0 ? entry.covers[0] : null;
+        DisplayItem label = entry.labelItem;
 
         // Put the cover items in reverse order, so that the first item is on
         // top of the rest.
-        Position position = new Position(x, y, 0f);
-        putDisplayItem(position, position, entry.labelItem);
-
-        for (int i = 0, n = items.length; i < n; ++i) {
-            DisplayItem item = items[i];
-            float dx = 0;
-            float dy = 0;
-            float dz = 0f;
-            float theta = 0;
-            if (i != 0) {
-                dz = i * PHOTO_DISTANCE;
-            }
-            position = new Position(x + dx, y + dy, dz);
-            position.theta = theta;
-            putDisplayItem(position, basePosition, item);
+        canvas.translate(width / 2, height / 2);
+        int r = 0;
+        if (cover != null) {
+            cover.setBox(width, height);
+            r |= cover.render(canvas, pass);
         }
-
-    }
-
-    private void freeSlotContent(int index, AlbumSetItem entry) {
-        if (entry == null) return;
-        for (DisplayItem item : entry.covers) {
-            removeDisplayItem(item);
+        if (label != null) {
+            label.setBox(width, height);
+            r |= entry.labelItem.render(canvas, pass);
         }
-        removeDisplayItem(entry.labelItem);
+        canvas.translate(-width / 2, -height / 2);
+        return r;
     }
 
     @Override
-    public void onLayoutChanged(int width, int height) {
-        updateVisibleRange(0, 0);
-        updateVisibleRange(getVisibleStart(), getVisibleEnd());
-    }
-
-    @Override
-    public void onScrollPositionChanged(int position) {
-        super.onScrollPositionChanged(position);
-        updateVisibleRange(getVisibleStart(), getVisibleEnd());
-    }
-
-    private void updateVisibleRange(int start, int end) {
-        if (start == mVisibleStart && end == mVisibleEnd) {
-            // we need to set the mDataWindow active range in any case.
-            mDataWindow.setActiveWindow(start, end);
-            return;
-        }
-        if (start >= mVisibleEnd || mVisibleStart >= end) {
-            for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-                freeSlotContent(i, mDataWindow.get(i));
-            }
-            mDataWindow.setActiveWindow(start, end);
-            for (int i = start; i < end; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-        } else {
-            for (int i = mVisibleStart; i < start; ++i) {
-                freeSlotContent(i, mDataWindow.get(i));
-            }
-            for (int i = end, n = mVisibleEnd; i < n; ++i) {
-                freeSlotContent(i, mDataWindow.get(i));
-            }
-            mDataWindow.setActiveWindow(start, end);
-            for (int i = start, n = mVisibleStart; i < n; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-            for (int i = mVisibleEnd; i < end; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-        }
-        mVisibleStart = start;
-        mVisibleEnd = end;
-
-        invalidate();
-    }
-
-    @Override
-    protected void render(GLCanvas canvas) {
+    public void prepareDrawing() {
         mSelectionDrawer.prepareDrawing();
-        super.render(canvas);
     }
 
     private class MyCacheListener implements AlbumSetSlidingWindow.Listener {
 
+        @Override
         public void onSizeChanged(int size) {
-            if (setSlotCount(size)) {
-                // If the layout parameters are changed, we need reput all items.
-                // We keep the visible range at the same center but with size 0.
-                // So that we can:
-                //     1.) flush all visible items
-                //     2.) keep the cached data
-                int center = (getVisibleStart() + getVisibleEnd()) / 2;
-                updateVisibleRange(center, center);
-            }
-            updateVisibleRange(getVisibleStart(), getVisibleEnd());
-            invalidate();
+            mSlotView.setSlotCount(size);
         }
 
-        public void onWindowContentChanged(int slot, AlbumSetItem old, AlbumSetItem update) {
-            freeSlotContent(slot, old);
-            putSlotContent(slot, update);
-            invalidate();
-        }
-
-        public void onContentInvalidated() {
-            invalidate();
+        @Override
+        public void onContentChanged() {
+            mSlotView.invalidate();
         }
     }
 
     public void pause() {
-        for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-            freeSlotContent(i, mDataWindow.get(i));
-        }
         mDataWindow.pause();
     }
 
     public void resume() {
         mDataWindow.resume();
-        for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-            putSlotContent(i, mDataWindow.get(i));
+    }
+
+    @Override
+    public void onVisibleRangeChanged(int visibleStart, int visibleEnd) {
+        if (mDataWindow != null) {
+            mDataWindow.setActiveWindow(visibleStart, visibleEnd);
         }
     }
 }
diff --git a/src/com/android/gallery3d/ui/AlbumSlidingWindow.java b/src/com/android/gallery3d/ui/AlbumSlidingWindow.java
index 3f1a18bd1..056bb5a51 100644
--- a/src/com/android/gallery3d/ui/AlbumSlidingWindow.java
+++ b/src/com/android/gallery3d/ui/AlbumSlidingWindow.java
@@ -44,9 +44,7 @@ public class AlbumSlidingWindow implements AlbumView.ModelListener {
 
     public static interface Listener {
         public void onSizeChanged(int size);
-        public void onContentInvalidated();
-        public void onWindowContentChanged(
-                int slot, DisplayItem old, DisplayItem update);
+        public void onContentChanged();
     }
 
     private final AlbumView.Model mSource;
@@ -242,7 +240,7 @@ public class AlbumSlidingWindow implements AlbumView.ModelListener {
         data[index] = update;
         boolean isActive = isActiveSlot(slotIndex);
         if (mListener != null && isActive) {
-            mListener.onWindowContentChanged(slotIndex, original, update);
+            mListener.onContentChanged();
         }
         if (original != null) {
             if (isActive && original.isRequestInProgress()) {
@@ -318,7 +316,7 @@ public class AlbumSlidingWindow implements AlbumView.ModelListener {
                     updateContent(texture);
                 }
                 if (mListener != null && isActiveSlot) {
-                    mListener.onContentInvalidated();
+                    mListener.onContentChanged();
                 }
             }
         }
@@ -351,11 +349,11 @@ public class AlbumSlidingWindow implements AlbumView.ModelListener {
                 }
                 int result = 0;
                 if (mFocusIndex == mSlotIndex) {
-                    result |= RENDER_MORE_PASS;
+                    result |= SlotView.RENDER_MORE_PASS;
                 }
                 if ((mContent instanceof FadeInTexture) &&
                         ((FadeInTexture) mContent).isAnimating()) {
-                    result |= RENDER_MORE_FRAME;
+                    result |= SlotView.RENDER_MORE_FRAME;
                 }
                 return result;
             } else if (pass == 1) {
diff --git a/src/com/android/gallery3d/ui/AlbumView.java b/src/com/android/gallery3d/ui/AlbumView.java
index 634485178..bf07ab2b1 100644
--- a/src/com/android/gallery3d/ui/AlbumView.java
+++ b/src/com/android/gallery3d/ui/AlbumView.java
@@ -16,26 +16,20 @@
 
 package com.android.gallery3d.ui;
 
-import android.graphics.Rect;
-
 import com.android.gallery3d.app.GalleryActivity;
 import com.android.gallery3d.data.MediaItem;
-import com.android.gallery3d.ui.PositionRepository.Position;
 
-public class AlbumView extends SlotView {
+public class AlbumView implements SlotView.SlotRenderer {
     @SuppressWarnings("unused")
     private static final String TAG = "AlbumView";
     private static final int CACHE_SIZE = 64;
 
-    private int mVisibleStart = 0;
-    private int mVisibleEnd = 0;
-
     private AlbumSlidingWindow mDataWindow;
     private final GalleryActivity mActivity;
     private SelectionDrawer mSelectionDrawer;
     private int mCacheThumbSize;
 
-    private boolean mIsActive = false;
+    private final SlotView mSlotView;
 
     public static interface Model {
         public int size();
@@ -49,11 +43,10 @@ public class AlbumView extends SlotView {
         public void onSizeChanged(int size);
     }
 
-    public AlbumView(GalleryActivity activity, SlotView.Spec spec,
+    public AlbumView(GalleryActivity activity, SlotView  slotView,
             int cacheThumbSize) {
-        super(activity.getAndroidContext());
         mCacheThumbSize = cacheThumbSize;
-        setSlotSpec(spec);
+        mSlotView = slotView;
         mActivity = activity;
     }
 
@@ -65,7 +58,7 @@ public class AlbumView extends SlotView {
     public void setModel(Model model) {
         if (mDataWindow != null) {
             mDataWindow.setListener(null);
-            setSlotCount(0);
+            mSlotView.setSlotCount(0);
             mDataWindow = null;
         }
         if (model != null) {
@@ -74,8 +67,7 @@ public class AlbumView extends SlotView {
                     mCacheThumbSize);
             mDataWindow.setSelectionDrawer(mSelectionDrawer);
             mDataWindow.setListener(new MyDataModelListener());
-            setSlotCount(model.size());
-            updateVisibleRange(getVisibleStart(), getVisibleEnd());
+            mSlotView.setSlotCount(model.size());
         }
     }
 
@@ -85,117 +77,48 @@ public class AlbumView extends SlotView {
         }
     }
 
-    private void putSlotContent(int slotIndex, DisplayItem item) {
-        Rect rect = getSlotRect(slotIndex);
-        Position position = new Position(
-                (rect.left + rect.right) / 2, (rect.top + rect.bottom) / 2, 0);
-        putDisplayItem(position, position, item);
-    }
-
-    private void updateVisibleRange(int start, int end) {
-        if (start == mVisibleStart && end == mVisibleEnd) {
-            // we need to set the mDataWindow active range in any case.
-            mDataWindow.setActiveWindow(start, end);
-            return;
-        }
-
-        if (!mIsActive) {
-            mVisibleStart = start;
-            mVisibleEnd = end;
-            mDataWindow.setActiveWindow(start, end);
-            return;
-        }
-
-        if (start >= mVisibleEnd || mVisibleStart >= end) {
-            for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-                DisplayItem item = mDataWindow.get(i);
-                if (item != null) removeDisplayItem(item);
-            }
-            mDataWindow.setActiveWindow(start, end);
-            for (int i = start; i < end; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-        } else {
-            for (int i = mVisibleStart; i < start; ++i) {
-                DisplayItem item = mDataWindow.get(i);
-                if (item != null) removeDisplayItem(item);
-            }
-            for (int i = end, n = mVisibleEnd; i < n; ++i) {
-                DisplayItem item = mDataWindow.get(i);
-                if (item != null) removeDisplayItem(item);
-            }
-            mDataWindow.setActiveWindow(start, end);
-            for (int i = start, n = mVisibleStart; i < n; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-            for (int i = mVisibleEnd; i < end; ++i) {
-                putSlotContent(i, mDataWindow.get(i));
-            }
-        }
-
-        mVisibleStart = start;
-        mVisibleEnd = end;
-    }
-
-    @Override
-    protected void onLayoutChanged(int width, int height) {
-        // Reput all the items
-        updateVisibleRange(0, 0);
-        updateVisibleRange(getVisibleStart(), getVisibleEnd());
-    }
-
-    @Override
-    protected void onScrollPositionChanged(int position) {
-        super.onScrollPositionChanged(position);
-        updateVisibleRange(getVisibleStart(), getVisibleEnd());
-    }
-
     @Override
-    protected void render(GLCanvas canvas) {
-        mSelectionDrawer.prepareDrawing();
-        super.render(canvas);
+    public int renderSlot(GLCanvas canvas, int index, int pass, int width, int height) {
+        DisplayItem item = mDataWindow.get(index);
+        if (item != null) {
+            canvas.translate(width / 2, height / 2);
+            item.setBox(width, height);
+            int r = item.render(canvas, pass);
+            canvas.translate(-width / 2, -height / 2);
+            return r;
+        }
+        return 0;
     }
 
     private class MyDataModelListener implements AlbumSlidingWindow.Listener {
-
-        public void onContentInvalidated() {
-            invalidate();
+        @Override
+        public void onContentChanged() {
+            mSlotView.invalidate();
         }
 
+        @Override
         public void onSizeChanged(int size) {
-            if (setSlotCount(size)) {
-                // If the layout parameters are changed, we need reput all items.
-                // We keep the visible range at the same center but with size 0.
-                // So that we can:
-                //     1.) flush all visible items
-                //     2.) keep the cached data
-                int center = (getVisibleStart() + getVisibleEnd()) / 2;
-                updateVisibleRange(center, center);
-            }
-            updateVisibleRange(getVisibleStart(), getVisibleEnd());
-            invalidate();
-        }
-
-        public void onWindowContentChanged(
-                int slotIndex, DisplayItem old, DisplayItem update) {
-            removeDisplayItem(old);
-            putSlotContent(slotIndex, update);
+            mSlotView.setSlotCount(size);
         }
     }
 
     public void resume() {
-        mIsActive = true;
         mDataWindow.resume();
-        for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-            putSlotContent(i, mDataWindow.get(i));
-        }
     }
 
     public void pause() {
-        mIsActive = false;
-        for (int i = mVisibleStart, n = mVisibleEnd; i < n; ++i) {
-            removeDisplayItem(mDataWindow.get(i));
-        }
         mDataWindow.pause();
     }
+
+    @Override
+    public void prepareDrawing() {
+        mSelectionDrawer.prepareDrawing();
+    }
+
+    @Override
+    public void onVisibleRangeChanged(int visibleStart, int visibleEnd) {
+        if (mDataWindow != null) {
+            mDataWindow.setActiveWindow(visibleStart, visibleEnd);
+        }
+    }
 }
diff --git a/src/com/android/gallery3d/ui/DisplayItem.java b/src/com/android/gallery3d/ui/DisplayItem.java
index 8d0226212..b389daebc 100644
--- a/src/com/android/gallery3d/ui/DisplayItem.java
+++ b/src/com/android/gallery3d/ui/DisplayItem.java
@@ -29,12 +29,6 @@ public abstract class DisplayItem {
         mBoxHeight = height;
     }
 
-    // Return values of render():
-    // RENDER_MORE_PASS: more pass is needed for this item
-    // RENDER_MORE_FRAME: need to render next frame (used for animation)
-    public static final int RENDER_MORE_PASS = 1;
-    public static final int RENDER_MORE_FRAME = 2;
-
     public abstract int render(GLCanvas canvas, int pass);
 
     public abstract int getIdentity();
diff --git a/src/com/android/gallery3d/ui/FilmStripView.java b/src/com/android/gallery3d/ui/FilmStripView.java
index 58a01dae5..6f339e2a9 100644
--- a/src/com/android/gallery3d/ui/FilmStripView.java
+++ b/src/com/android/gallery3d/ui/FilmStripView.java
@@ -42,6 +42,7 @@ public class FilmStripView extends GLView implements UserInteractionListener {
     private int mTopMargin, mMidMargin, mBottomMargin;
     private int mContentSize, mBarSize, mGripSize;
     private AlbumView mAlbumView;
+    private SlotView mSlotView;
     private ScrollBarView mScrollBarView;
     private AlbumDataAdapter mAlbumDataAdapter;
     private StripDrawer mStripDrawer;
@@ -77,10 +78,12 @@ public class FilmStripView extends GLView implements UserInteractionListener {
         SlotView.Spec spec = new SlotView.Spec();
         spec.slotWidth = thumbSize;
         spec.slotHeight = thumbSize;
-        mAlbumView = new AlbumView(activity, spec, thumbSize);
-        mAlbumView.setOverscrollEffect(SlotView.OVERSCROLL_NONE);
+        mSlotView = new SlotView((Context) activity, spec);
+        mAlbumView = new AlbumView(activity, mSlotView, thumbSize);
+        mSlotView.setSlotRenderer(mAlbumView);
+        mSlotView.setOverscrollEffect(SlotView.OVERSCROLL_NONE);
         mAlbumView.setSelectionDrawer(mStripDrawer);
-        mAlbumView.setListener(new SlotView.SimpleListener() {
+        mSlotView.setListener(new SlotView.SimpleListener() {
             @Override
             public void onDown(int index) {
                 FilmStripView.this.onDown(index);
@@ -102,9 +105,9 @@ public class FilmStripView extends GLView implements UserInteractionListener {
                 FilmStripView.this.onScrollPositionChanged(position, total);
             }
         });
-        mAlbumView.setUserInteractionListener(this);
+        mSlotView.setUserInteractionListener(this);
         mAlbumDataAdapter = new AlbumDataAdapter(activity, mediaSet);
-        addComponent(mAlbumView);
+        addComponent(mSlotView);
         mScrollBarView = new ScrollBarView(activity.getAndroidContext(),
                 mGripSize, gripWidth);
         addComponent(mScrollBarView);
@@ -156,7 +159,7 @@ public class FilmStripView extends GLView implements UserInteractionListener {
     protected void onLayout(
             boolean changed, int left, int top, int right, int bottom) {
         if (!changed) return;
-        mAlbumView.layout(0, mTopMargin, right - left, mTopMargin + mContentSize);
+        mSlotView.layout(0, mTopMargin, right - left, mTopMargin + mContentSize);
         int barStart = mTopMargin + mContentSize + mMidMargin;
         mScrollBarView.layout(0, barStart, right - left, barStart + mBarSize);
         int width = right - left;
@@ -197,12 +200,12 @@ public class FilmStripView extends GLView implements UserInteractionListener {
         MediaItem item = mAlbumDataAdapter.get(index);
         Path path = (item == null) ? null : item.getPath();
         mStripDrawer.setPressedPath(path);
-        mAlbumView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onUp() {
         mStripDrawer.setPressedPath(null);
-        mAlbumView.invalidate();
+        mSlotView.invalidate();
     }
 
     private void onSingleTapUp(int slotIndex) {
@@ -239,11 +242,11 @@ public class FilmStripView extends GLView implements UserInteractionListener {
 
     public void setFocusIndex(int slotIndex) {
         mAlbumView.setFocusIndex(slotIndex);
-        mAlbumView.makeSlotVisible(slotIndex);
+        mSlotView.makeSlotVisible(slotIndex);
     }
 
     public void setStartIndex(int slotIndex) {
-        mAlbumView.setStartIndex(slotIndex);
+        mSlotView.setStartIndex(slotIndex);
     }
 
     public void pause() {
diff --git a/src/com/android/gallery3d/ui/Paper.java b/src/com/android/gallery3d/ui/Paper.java
index 36d1f7515..3b67a049a 100644
--- a/src/com/android/gallery3d/ui/Paper.java
+++ b/src/com/android/gallery3d/ui/Paper.java
@@ -16,12 +16,12 @@
 
 package com.android.gallery3d.ui;
 
+import android.graphics.Rect;
 import android.opengl.Matrix;
 import android.view.animation.DecelerateInterpolator;
 import android.view.animation.Interpolator;
 
 import com.android.gallery3d.common.Utils;
-import com.android.gallery3d.ui.PositionRepository.Position;
 
 // This class does the overscroll effect.
 class Paper {
@@ -65,11 +65,10 @@ class Paper {
         mHeight = height;
     }
 
-    public float[] getTransform(Position target, Position base,
-            float scrollX, float scrollY) {
+    public float[] getTransform(Rect rect, float scrollX) {
         float left = mAnimationLeft.getValue();
         float right = mAnimationRight.getValue();
-        float screenX = target.x - scrollX;
+        float screenX = rect.centerX() - scrollX;
         // We linearly interpolate the value [left, right] for the screenX
         // range int [-1/4, 5/4]*mWidth. So if part of the thumbnail is outside
         // the screen, we still get some transform.
@@ -82,10 +81,9 @@ class Paper {
         float degrees =
                 (1 / (1 + (float) Math.exp(-t * ROTATE_FACTOR)) - 0.5f) * 2 * -45;
         Matrix.setIdentityM(mMatrix, 0);
-        Matrix.translateM(mMatrix, 0, mMatrix, 0, base.x, base.y, base.z);
+        Matrix.translateM(mMatrix, 0, mMatrix, 0, rect.centerX(), rect.centerY(), 0);
         Matrix.rotateM(mMatrix, 0, degrees, 0, 1, 0);
-        Matrix.translateM(mMatrix, 0, mMatrix, 0,
-                target.x - base.x, target.y - base.y, target.z - base.z);
+        Matrix.translateM(mMatrix, 0, mMatrix, 0, -rect.width() / 2, -rect.height() / 2, 0);
         return mMatrix;
     }
 }
diff --git a/src/com/android/gallery3d/ui/RelativePosition.java b/src/com/android/gallery3d/ui/RelativePosition.java
new file mode 100644
index 000000000..98292e36f
--- /dev/null
+++ b/src/com/android/gallery3d/ui/RelativePosition.java
@@ -0,0 +1,42 @@
+/*
+ * 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;
+
+public class RelativePosition {
+    private float mAbsoluteX;
+    private float mAbsoluteY;
+    private float mReferenceX;
+    private float mReferenceY;
+
+    public void setAbsolute(int absoluteX, int absoluteY) {
+        mAbsoluteX = absoluteX;
+        mAbsoluteY = absoluteY;
+    }
+
+    public void setReference(int x, int y) {
+        mReferenceX = x;
+        mReferenceY = y;
+    }
+
+    public float getX() {
+        return mAbsoluteX - mReferenceX;
+    }
+
+    public float getY() {
+        return mAbsoluteY - mReferenceY;
+    }
+}
diff --git a/src/com/android/gallery3d/ui/SlotView.java b/src/com/android/gallery3d/ui/SlotView.java
index 863e66869..529a496d3 100644
--- a/src/com/android/gallery3d/ui/SlotView.java
+++ b/src/com/android/gallery3d/ui/SlotView.java
@@ -25,20 +25,17 @@ import android.view.animation.DecelerateInterpolator;
 
 import com.android.gallery3d.anim.Animation;
 import com.android.gallery3d.common.Utils;
-import com.android.gallery3d.ui.PositionRepository.Position;
-import com.android.gallery3d.util.LinkedNode;
-
-import java.util.ArrayList;
-import java.util.HashMap;
 
 public class SlotView extends GLView {
     @SuppressWarnings("unused")
     private static final String TAG = "SlotView";
 
     private static final boolean WIDE = true;
-
     private static final int INDEX_NONE = -1;
 
+    public static final int RENDER_MORE_PASS = 1;
+    public static final int RENDER_MORE_FRAME = 2;
+
     public interface Listener {
         public void onDown(int index);
         public void onUp();
@@ -48,11 +45,17 @@ public class SlotView extends GLView {
     }
 
     public static class SimpleListener implements Listener {
-        public void onDown(int index) {}
-        public void onUp() {}
-        public void onSingleTapUp(int index) {}
-        public void onLongTap(int index) {}
-        public void onScrollPositionChanged(int position, int total) {}
+        @Override public void onDown(int index) {}
+        @Override public void onUp() {}
+        @Override public void onSingleTapUp(int index) {}
+        @Override public void onLongTap(int index) {}
+        @Override public void onScrollPositionChanged(int position, int total) {}
+    }
+
+    public static interface SlotRenderer {
+        public void prepareDrawing();
+        public void onVisibleRangeChanged(int visibleStart, int visibleEnd);
+        public int renderSlot(GLCanvas canvas, int index, int pass, int width, int height);
     }
 
     private final GestureDetector mGestureDetector;
@@ -62,21 +65,9 @@ public class SlotView extends GLView {
     private Listener mListener;
     private UserInteractionListener mUIListener;
 
-    // Use linked hash map to keep the rendering order
-    private final HashMap<DisplayItem, ItemEntry> mItems =
-            new HashMap<DisplayItem, ItemEntry>();
-
-    public LinkedNode.List<ItemEntry> mItemList = LinkedNode.newList();
-
-    // This is used for multipass rendering
-    private ArrayList<ItemEntry> mCurrentItems = new ArrayList<ItemEntry>();
-    private ArrayList<ItemEntry> mNextItems = new ArrayList<ItemEntry>();
-
     private boolean mMoreAnimation = false;
     private MyAnimation mAnimation = null;
-    private final Position mTempPosition = new Position();
     private final Layout mLayout = new Layout();
-    private PositionProvider mPositions;
     private int mStartIndex = INDEX_NONE;
 
     // whether the down action happened while the view is scrolling.
@@ -84,15 +75,27 @@ public class SlotView extends GLView {
     private int mOverscrollEffect = OVERSCROLL_3D;
     private final Handler mHandler;
 
+    private SlotRenderer mRenderer;
+
+    private int[] mRequestRenderSlots = new int[16];
+
     public static final int OVERSCROLL_3D = 0;
     public static final int OVERSCROLL_SYSTEM = 1;
     public static final int OVERSCROLL_NONE = 2;
 
-    public SlotView(Context context) {
+    public SlotView(Context context, Spec spec) {
         mGestureDetector =
                 new GestureDetector(context, new MyGestureListener());
         mScroller = new ScrollerHelper(context);
         mHandler = new Handler(context.getMainLooper());
+        setSlotSpec(spec);
+    }
+
+    public void setSlotRenderer(SlotRenderer slotDrawer) {
+        mRenderer = slotDrawer;
+        if (mRenderer != null) {
+            mRenderer.onVisibleRangeChanged(getVisibleStart(), getVisibleEnd());
+        }
     }
 
     public void setCenterIndex(int index) {
@@ -163,25 +166,11 @@ public class SlotView extends GLView {
     protected void onLayoutChanged(int width, int height) {
     }
 
+    // TODO: Fix this regression. Transition is disabled in this change
     public void startTransition(PositionProvider position) {
-        mPositions = position;
         mAnimation = new MyAnimation();
         mAnimation.start();
-        if (mItems.size() != 0) invalidate();
-    }
-
-    public void savePositions(PositionRepository repository) {
-        repository.clear();
-        LinkedNode.List<ItemEntry> list = mItemList;
-        ItemEntry entry = list.getFirst();
-        Position position = new Position();
-        while (entry != null) {
-            position.set(entry.target);
-            position.x -= mScrollX;
-            position.y -= mScrollY;
-            repository.putPosition(entry.item.getIdentity(), position);
-            entry = list.nextOf(entry);
-        }
+        if (mLayout.mSlotCount != 0) invalidate();
     }
 
     private void updateScrollPosition(int position, boolean force) {
@@ -200,18 +189,6 @@ public class SlotView extends GLView {
         mListener.onScrollPositionChanged(newPosition, limit);
     }
 
-    public void putDisplayItem(Position target, Position base, DisplayItem item) {
-        item.setBox(mLayout.getSlotWidth(), mLayout.getSlotHeight());
-        ItemEntry entry = new ItemEntry(item, target, base);
-        mItemList.insertLast(entry);
-        mItems.put(item, entry);
-    }
-
-    public void removeDisplayItem(DisplayItem item) {
-        ItemEntry entry = mItems.remove(item);
-        if (entry != null) entry.remove();
-    }
-
     public Rect getSlotRect(int slotIndex) {
         return mLayout.getSlotRect(slotIndex);
     }
@@ -246,10 +223,20 @@ public class SlotView extends GLView {
         mScroller.setOverfling(kind == OVERSCROLL_SYSTEM);
     }
 
+    private static int[] expandIntArray(int array[], int capacity) {
+        while (array.length < capacity) {
+            array = new int[array.length * 2];
+        }
+        return array;
+    }
+
     @Override
     protected void render(GLCanvas canvas) {
         super.render(canvas);
 
+        if (mRenderer == null) return;
+        mRenderer.prepareDrawing();
+
         long animTime = AnimationTime.get();
         boolean more = mScroller.advanceAnimation(animTime);
         int oldX = mScrollX;
@@ -280,45 +267,30 @@ public class SlotView extends GLView {
             interpolate = mAnimation.value;
         }
 
-        if (WIDE) {
-            canvas.translate(-mScrollX, 0);
-        } else {
-            canvas.translate(0, -mScrollY);
-        }
+        canvas.translate(-mScrollX, -mScrollY);
 
-        LinkedNode.List<ItemEntry> list = mItemList;
-        for (ItemEntry entry = list.getLast(); entry != null;) {
-            int r = renderItem(canvas, entry, interpolate, 0, paperActive);
-            if ((r & DisplayItem.RENDER_MORE_PASS) != 0) {
-                mCurrentItems.add(entry);
-            }
-            more |= ((r & DisplayItem.RENDER_MORE_FRAME) != 0);
-            entry = list.previousOf(entry);
+        int requestCount = 0;
+        int requestedSlot[] = expandIntArray(mRequestRenderSlots,
+                mLayout.mVisibleEnd - mLayout.mVisibleStart);
+
+        for (int i = mLayout.mVisibleStart; i < mLayout.mVisibleEnd; ++i) {
+            int r = renderItem(canvas, i, 0, interpolate, paperActive);
+            if ((r & RENDER_MORE_FRAME) != 0) more = true;
+            if ((r & RENDER_MORE_PASS) != 0) requestedSlot[requestCount++] = i;
         }
 
-        int pass = 1;
-        while (!mCurrentItems.isEmpty()) {
-            for (int i = 0, n = mCurrentItems.size(); i < n; i++) {
-                ItemEntry entry = mCurrentItems.get(i);
-                int r = renderItem(canvas, entry, interpolate, pass, paperActive);
-                if ((r & DisplayItem.RENDER_MORE_PASS) != 0) {
-                    mNextItems.add(entry);
-                }
-                more |= ((r & DisplayItem.RENDER_MORE_FRAME) != 0);
+        for (int pass = 1; requestCount != 0; ++pass) {
+            int newCount = 0;
+            for (int i = 0; i < requestCount; ++i) {
+                int r = renderItem(canvas,
+                        requestedSlot[i], pass, interpolate, paperActive);
+                if ((r & RENDER_MORE_FRAME) != 0) more = true;
+                if ((r & RENDER_MORE_PASS) != 0) requestedSlot[newCount++] = i;
             }
-            mCurrentItems.clear();
-            // swap mNextItems with mCurrentItems
-            ArrayList<ItemEntry> tmp = mNextItems;
-            mNextItems = mCurrentItems;
-            mCurrentItems = tmp;
-            pass += 1;
+            requestCount = newCount;
         }
 
-        if (WIDE) {
-            canvas.translate(mScrollX, 0);
-        } else {
-            canvas.translate(0, mScrollY);
-        }
+        canvas.translate(mScrollX, mScrollY);
 
         if (more) invalidate();
 
@@ -334,36 +306,19 @@ public class SlotView extends GLView {
         mMoreAnimation = more;
     }
 
-    private int renderItem(GLCanvas canvas, ItemEntry entry,
-            float interpolate, int pass, boolean paperActive) {
+    private int renderItem(GLCanvas canvas,
+            int index, int pass, float interpolate, boolean paperActive) {
         canvas.save(GLCanvas.SAVE_FLAG_ALPHA | GLCanvas.SAVE_FLAG_MATRIX);
-        Position position = entry.target;
-        if (mPositions != null) {
-            position = mTempPosition;
-            position.set(entry.target);
-            position.x -= mScrollX;
-            position.y -= mScrollY;
-            Position source = mPositions
-                    .getPosition(entry.item.getIdentity(), position);
-            source.x += mScrollX;
-            source.y += mScrollY;
-            position = mTempPosition;
-            Position.interpolate(
-                    source, entry.target, position, interpolate);
-        }
-        canvas.multiplyAlpha(position.alpha);
+        Rect rect = getSlotRect(index);
         if (paperActive) {
-            canvas.multiplyMatrix(mPaper.getTransform(
-                    position, entry.base, mScrollX, mScrollY), 0);
+            canvas.multiplyMatrix(mPaper.getTransform(rect, mScrollX), 0);
         } else {
-            canvas.translate(position.x, position.y, position.z);
+            canvas.translate(rect.left, rect.top, 0);
         }
-        if (position.theta != 0) {
-            canvas.rotate(position.theta, 0, 0, 1);
-        }
-        int more = entry.item.render(canvas, pass);
+        int result = mRenderer.renderSlot(
+                canvas, index, pass, rect.right - rect.left, rect.bottom - rect.top);
         canvas.restore();
-        return more;
+        return result;
     }
 
     public static class MyAnimation extends Animation {
@@ -380,18 +335,6 @@ public class SlotView extends GLView {
         }
     }
 
-    private static class ItemEntry extends LinkedNode {
-        public DisplayItem item;
-        public Position target;
-        public Position base;
-
-        public ItemEntry(DisplayItem item, Position target, Position base) {
-            this.item = item;
-            this.target = target;
-            this.base = base;
-        }
-    }
-
     // This Spec class is used to specify the size of each slot in the SlotView.
     // There are two ways to do it:
     //
@@ -412,7 +355,7 @@ public class SlotView extends GLView {
         public int slotGap = -1;
     }
 
-    public static class Layout {
+    public class Layout {
 
         private int mVisibleStart;
         private int mVisibleEnd;
@@ -570,6 +513,9 @@ public class SlotView extends GLView {
             } else {
                 mVisibleStart = mVisibleEnd = 0;
             }
+            if (mRenderer != null) {
+                mRenderer.onVisibleRangeChanged(mVisibleStart, mVisibleEnd);
+            }
         }
 
         public int getVisibleStart() {