diff --git a/res/values/config.xml b/res/values/config.xml
index fbce3a4..73de794 100644
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -20,6 +20,7 @@
 
 <!-- DragController -->
     <integer name="config_flingToDeleteMinVelocity">-1500</integer>
+    <item type="id" name="drag_event_parity" />
 
 <!-- AllApps & Launcher transitions -->
     <!-- The alpha of the AppsCustomize bg in spring loaded mode -->
diff --git a/src/com/android/launcher3/BaseRecyclerView.java b/src/com/android/launcher3/BaseRecyclerView.java
index b63ef78..8d418f9 100644
--- a/src/com/android/launcher3/BaseRecyclerView.java
+++ b/src/com/android/launcher3/BaseRecyclerView.java
@@ -16,15 +16,28 @@
 
 package com.android.launcher3;
 
+import android.animation.ObjectAnimator;
 import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Rect;
+import android.graphics.drawable.Drawable;
 import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
+import android.view.View;
+import android.view.ViewConfiguration;
+
 import com.android.launcher3.util.Thunk;
 
 /**
- * A base {@link RecyclerView}, which will NOT intercept a touch sequence unless the scrolling
- * velocity is below a predefined threshold.
+ * A base {@link RecyclerView}, which does the following:
+ * <ul>
+ *   <li> NOT intercept a touch unless the scrolling velocity is below a predefined threshold.
+ *   <li> Enable fast scroller.
+ * </ul>
  */
 public class BaseRecyclerView extends RecyclerView
         implements RecyclerView.OnItemTouchListener {
@@ -35,6 +48,53 @@
     @Thunk int mDy = 0;
     private float mDeltaThreshold;
 
+    //
+    // Keeps track of variables required for the second function of this class: fast scroller.
+    //
+
+    private static final float FAST_SCROLL_OVERLAY_Y_OFFSET_FACTOR = 1.5f;
+
+    /**
+     * The current scroll state of the recycler view.  We use this in updateVerticalScrollbarBounds()
+     * and scrollToPositionAtProgress() to determine the scroll position of the recycler view so
+     * that we can calculate what the scroll bar looks like, and where to jump to from the fast
+     * scroller.
+     */
+    public static class ScrollPositionState {
+        // The index of the first visible row
+        public int rowIndex;
+        // The offset of the first visible row
+        public int rowTopOffset;
+        // The height of a given row (they are currently all the same height)
+        public int rowHeight;
+    }
+    // Should be maintained inside overriden method #updateVerticalScrollbarBounds
+    public ScrollPositionState scrollPosState = new ScrollPositionState();
+    public Rect verticalScrollbarBounds = new Rect();
+
+    private boolean mDraggingFastScroller;
+
+    private Drawable mScrollbar;
+    private Drawable mFastScrollerBg;
+    private Rect mTmpFastScrollerInvalidateRect = new Rect();
+    private Rect mFastScrollerBounds = new Rect();
+
+    private String mFastScrollSectionName;
+    private Paint mFastScrollTextPaint;
+    private Rect mFastScrollTextBounds = new Rect();
+    private float mFastScrollAlpha;
+
+    private int mDownX;
+    private int mDownY;
+    private int mLastX;
+    private int mLastY;
+    private int mScrollbarWidth;
+    private int mScrollbarMinHeight;
+    private int mScrollbarInset;
+    private Rect mBackgroundPadding = new Rect();
+
+
+
     public BaseRecyclerView(Context context) {
         this(context, null);
     }
@@ -49,6 +109,24 @@
 
         ScrollListener listener = new ScrollListener();
         setOnScrollListener(listener);
+
+        Resources res = context.getResources();
+        int fastScrollerSize = res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_popup_size);
+        mScrollbar = res.getDrawable(R.drawable.all_apps_scrollbar_thumb);
+        mFastScrollerBg = res.getDrawable(R.drawable.all_apps_fastscroll_bg);
+        mFastScrollerBg.setBounds(0, 0, fastScrollerSize, fastScrollerSize);
+        mFastScrollTextPaint = new Paint();
+        mFastScrollTextPaint.setColor(Color.WHITE);
+        mFastScrollTextPaint.setAntiAlias(true);
+        mFastScrollTextPaint.setTextSize(res.getDimensionPixelSize(
+                R.dimen.all_apps_fast_scroll_text_size));
+        mScrollbarWidth = res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_bar_width);
+        mScrollbarMinHeight =
+                res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_bar_min_height);
+        mScrollbarInset =
+                res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_scrubber_touch_inset);
+        setFastScrollerAlpha(mFastScrollAlpha);
+        setOverScrollMode(View.OVER_SCROLL_NEVER);
     }
 
     private class ScrollListener extends OnScrollListener {
@@ -68,17 +146,74 @@
         addOnItemTouchListener(this);
     }
 
+    /**
+     * We intercept the touch handling only to support fast scrolling when initiated from the
+     * scroll bar.  Otherwise, we fall back to the default RecyclerView touch handling.
+     */
     @Override
     public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent ev) {
-        if (shouldStopScroll(ev)) {
-            stopScroll();
-        }
-        return false;
+        return handleTouchEvent(ev);
     }
 
     @Override
     public void onTouchEvent(RecyclerView rv, MotionEvent ev) {
-        // Do nothing.
+        handleTouchEvent(ev);
+    }
+
+    /**
+     * Handles the touch event and determines whether to show the fast scroller (or updates it if
+     * it is already showing).
+     */
+    private boolean handleTouchEvent(MotionEvent ev) {
+        ViewConfiguration config = ViewConfiguration.get(getContext());
+
+        int action = ev.getAction();
+        int x = (int) ev.getX();
+        int y = (int) ev.getY();
+        switch (action) {
+            case MotionEvent.ACTION_DOWN:
+                // Keep track of the down positions
+                mDownX = mLastX = x;
+                mDownY = mLastY = y;
+                if (shouldStopScroll(ev)) {
+                    stopScroll();
+                }
+                break;
+            case MotionEvent.ACTION_MOVE:
+                // Check if we are scrolling
+                if (!mDraggingFastScroller && isPointNearScrollbar(mDownX, mDownY) &&
+                        Math.abs(y - mDownY) > config.getScaledTouchSlop()) {
+                    getParent().requestDisallowInterceptTouchEvent(true);
+                    mDraggingFastScroller = true;
+                    animateFastScrollerVisibility(true);
+                }
+                if (mDraggingFastScroller) {
+                    mLastX = x;
+                    mLastY = y;
+
+                    // Scroll to the right position, and update the section name
+                    int top = getPaddingTop() + (mFastScrollerBg.getBounds().height() / 2);
+                    int bottom = getHeight() - getPaddingBottom() -
+                            (mFastScrollerBg.getBounds().height() / 2);
+                    float boundedY = (float) Math.max(top, Math.min(bottom, y));
+                    mFastScrollSectionName = scrollToPositionAtProgress((boundedY - top) /
+                            (bottom - top));
+
+                    // Combine the old and new fast scroller bounds to create the full invalidate
+                    // rect
+                    mTmpFastScrollerInvalidateRect.set(mFastScrollerBounds);
+                    updateFastScrollerBounds();
+                    mTmpFastScrollerInvalidateRect.union(mFastScrollerBounds);
+                    invalidateFastScroller(mTmpFastScrollerInvalidateRect);
+                }
+                break;
+            case MotionEvent.ACTION_UP:
+            case MotionEvent.ACTION_CANCEL:
+                mDraggingFastScroller = false;
+                animateFastScrollerVisibility(false);
+                break;
+        }
+        return mDraggingFastScroller;
     }
 
     public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
@@ -99,4 +234,127 @@
         }
         return false;
     }
+
+    @Override
+    protected void dispatchDraw(Canvas canvas) {
+        super.dispatchDraw(canvas);
+        drawVerticalScrubber(canvas);
+        drawFastScrollerPopup(canvas);
+    }
+
+    /**
+     * Draws the vertical scrollbar.
+     */
+    private void drawVerticalScrubber(Canvas canvas) {
+        updateVerticalScrollbarBounds();
+
+        // Draw the scroll bar
+        int restoreCount = canvas.save(Canvas.MATRIX_SAVE_FLAG);
+        canvas.translate(verticalScrollbarBounds.left, verticalScrollbarBounds.top);
+        mScrollbar.setBounds(0, 0, mScrollbarWidth, verticalScrollbarBounds.height());
+        mScrollbar.draw(canvas);
+        canvas.restoreToCount(restoreCount);
+    }
+
+    /**
+     * Draws the fast scroller popup.
+     */
+    private void drawFastScrollerPopup(Canvas canvas) {
+        if (mFastScrollAlpha > 0f && mFastScrollSectionName != null && !mFastScrollSectionName.isEmpty()) {
+            // Draw the fast scroller popup
+            int restoreCount = canvas.save(Canvas.MATRIX_SAVE_FLAG);
+            canvas.translate(mFastScrollerBounds.left, mFastScrollerBounds.top);
+            mFastScrollerBg.setAlpha((int) (mFastScrollAlpha * 255));
+            mFastScrollerBg.draw(canvas);
+            mFastScrollTextPaint.setAlpha((int) (mFastScrollAlpha * 255));
+            mFastScrollTextPaint.getTextBounds(mFastScrollSectionName, 0,
+                    mFastScrollSectionName.length(), mFastScrollTextBounds);
+            float textWidth = mFastScrollTextPaint.measureText(mFastScrollSectionName);
+            canvas.drawText(mFastScrollSectionName,
+                    (mFastScrollerBounds.width() - textWidth) / 2,
+                    mFastScrollerBounds.height() -
+                            (mFastScrollerBounds.height() - mFastScrollTextBounds.height()) / 2,
+                    mFastScrollTextPaint);
+            canvas.restoreToCount(restoreCount);
+        }
+    }
+
+    /**
+     * Returns the scroll bar width.
+     */
+    public int getScrollbarWidth() {
+        return mScrollbarWidth;
+    }
+
+    /**
+     * Sets the fast scroller alpha.
+     */
+    public void setFastScrollerAlpha(float alpha) {
+        mFastScrollAlpha = alpha;
+        invalidateFastScroller(mFastScrollerBounds);
+    }
+
+    /**
+     * Maps the touch (from 0..1) to the adapter position that should be visible.
+     * <p>Override in each subclass of this base class.
+     */
+    public String scrollToPositionAtProgress(float touchFraction) {
+        return null;
+    }
+
+    /**
+     * Updates the bounds for the scrollbar.
+     * <p>Override in each subclass of this base class.
+     */
+    public void updateVerticalScrollbarBounds() {};
+
+    /**
+     * Animates the visibility of the fast scroller popup.
+     */
+    private void animateFastScrollerVisibility(boolean visible) {
+        ObjectAnimator anim = ObjectAnimator.ofFloat(this, "fastScrollerAlpha", visible ? 1f : 0f);
+        anim.setDuration(visible ? 200 : 150);
+        anim.start();
+    }
+
+    /**
+     * Invalidates the fast scroller popup.
+     */
+    protected void invalidateFastScroller(Rect bounds) {
+        invalidate(bounds.left, bounds.top, bounds.right, bounds.bottom);
+    }
+
+    /**
+     * Returns whether a given point is near the scrollbar.
+     */
+    private boolean isPointNearScrollbar(int x, int y) {
+        // Check if we are scrolling
+        updateVerticalScrollbarBounds();
+        verticalScrollbarBounds.inset(mScrollbarInset, mScrollbarInset);
+        return verticalScrollbarBounds.contains(x, y);
+    }
+
+    /**
+     * Updates the bounds for the fast scroller.
+     */
+    private void updateFastScrollerBounds() {
+        if (mFastScrollAlpha > 0f && !mFastScrollSectionName.isEmpty()) {
+            int x;
+            int y;
+
+            // Calculate the position for the fast scroller popup
+            Rect bgBounds = mFastScrollerBg.getBounds();
+            if (Utilities.isRtl(getResources())) {
+                x = mBackgroundPadding.left + getScrollBarSize();
+            } else {
+                x = getWidth() - getPaddingRight() - getScrollBarSize() - bgBounds.width();
+            }
+            y = mLastY - (int) (FAST_SCROLL_OVERLAY_Y_OFFSET_FACTOR * bgBounds.height());
+            y = Math.max(getPaddingTop(), Math.min(y, getHeight() - getPaddingBottom() -
+                    bgBounds.height()));
+            mFastScrollerBounds.set(x, y, x + bgBounds.width(), y + bgBounds.height());
+        } else {
+            mFastScrollerBounds.setEmpty();
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/com/android/launcher3/CellLayout.java b/src/com/android/launcher3/CellLayout.java
index 2b1cfe0..61567ac 100644
--- a/src/com/android/launcher3/CellLayout.java
+++ b/src/com/android/launcher3/CellLayout.java
@@ -168,7 +168,6 @@
     private int[] mDirectionVector = new int[2];
     int[] mPreviousReorderDirection = new int[2];
     private static final int INVALID_DIRECTION = -100;
-    private DropTarget.DragEnforcer mDragEnforcer;
 
     private final Rect mTempRect = new Rect();
 
@@ -188,7 +187,6 @@
 
     public CellLayout(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
-        mDragEnforcer = new DropTarget.DragEnforcer(context);
 
         // A ViewGroup usually does not draw, but CellLayout needs to draw a rectangle to show
         // the user where a dragged item will land when dropped.
@@ -2637,7 +2635,6 @@
      * or it may have begun on another layout.
      */
     void onDragEnter() {
-        mDragEnforcer.onDragEnter();
         mDragging = true;
     }
 
@@ -2645,7 +2642,6 @@
      * Called when drag has left this CellLayout or has been completed (successfully or not)
      */
     void onDragExit() {
-        mDragEnforcer.onDragExit();
         // This can actually be called when we aren't in a drag, e.g. when adding a new
         // item to this layout via the customize drawer.
         // Guard against that case.
diff --git a/src/com/android/launcher3/DragLayer.java b/src/com/android/launcher3/DragLayer.java
index 423a9a3..41e053e 100644
--- a/src/com/android/launcher3/DragLayer.java
+++ b/src/com/android/launcher3/DragLayer.java
@@ -918,7 +918,7 @@
     void showPageHints() {
         mShowPageHints = true;
         Workspace workspace = mLauncher.getWorkspace();
-        getDescendantRectRelativeToSelf(workspace.getChildAt(workspace.getChildCount() - 1),
+        getDescendantRectRelativeToSelf(workspace.getChildAt(workspace.numCustomPages()),
                 mScrollChildPosition);
         invalidate();
     }
diff --git a/src/com/android/launcher3/DropTarget.java b/src/com/android/launcher3/DropTarget.java
index a3828c1..c8fac54 100644
--- a/src/com/android/launcher3/DropTarget.java
+++ b/src/com/android/launcher3/DropTarget.java
@@ -16,10 +16,8 @@
 
 package com.android.launcher3;
 
-import android.content.Context;
 import android.graphics.PointF;
 import android.graphics.Rect;
-import android.util.Log;
 
 /**
  * Interface defining an object that can receive a drag.
@@ -93,43 +91,6 @@
         }
     }
 
-    public static class DragEnforcer implements DragController.DragListener {
-        int dragParity = 0;
-
-        public DragEnforcer(Context context) {
-            Launcher launcher = (Launcher) context;
-            launcher.getDragController().addDragListener(this);
-        }
-
-        void onDragEnter() {
-            dragParity++;
-            if (dragParity != 1) {
-                Log.e(TAG, "onDragEnter: Drag contract violated: " + dragParity);
-            }
-        }
-
-        void onDragExit() {
-            dragParity--;
-            if (dragParity != 0) {
-                Log.e(TAG, "onDragExit: Drag contract violated: " + dragParity);
-            }
-        }
-
-        @Override
-        public void onDragStart(DragSource source, Object info, int dragAction) {
-            if (dragParity != 0) {
-                Log.e(TAG, "onDragEnter: Drag contract violated: " + dragParity);
-            }
-        }
-
-        @Override
-        public void onDragEnd() {
-            if (dragParity != 0) {
-                Log.e(TAG, "onDragExit: Drag contract violated: " + dragParity);
-            }
-        }
-    }
-
     /**
      * Used to temporarily disable certain drop targets
      *
diff --git a/src/com/android/launcher3/IconCache.java b/src/com/android/launcher3/IconCache.java
index 0c91a71..6dfca9e 100644
--- a/src/com/android/launcher3/IconCache.java
+++ b/src/com/android/launcher3/IconCache.java
@@ -49,10 +49,8 @@
 
 import java.util.HashMap;
 import java.util.HashSet;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
-import java.util.Map.Entry;
 import java.util.Stack;
 
 /**
@@ -75,8 +73,8 @@
 
     @Thunk static class CacheEntry {
         public Bitmap icon;
-        public CharSequence title;
-        public CharSequence contentDescription;
+        public CharSequence title = "";
+        public CharSequence contentDescription = "";
         public boolean isLowResIcon;
     }
 
@@ -367,13 +365,6 @@
     }
 
     /**
-     * Empty out the cache.
-     */
-    public synchronized void flush() {
-        mCache.clear();
-    }
-
-    /**
      * Fetches high-res icon for the provided ItemInfo and updates the caller when done.
      * @return a request ID that can be used to cancel the request.
      */
@@ -584,7 +575,7 @@
         CacheEntry entry = mCache.get(cacheKey);
         if (entry == null || (entry.isLowResIcon && !useLowResIcon)) {
             entry = new CacheEntry();
-            mCache.put(cacheKey, entry);
+            boolean entryUpdated = true;
 
             // Check the DB first.
             if (!getEntryFromDB(cn, user, entry, useLowResIcon)) {
@@ -609,8 +600,14 @@
 
                 } catch (NameNotFoundException e) {
                     if (DEBUG) Log.d(TAG, "Application not installed " + packageName);
+                    entryUpdated = false;
                 }
             }
+
+            // Only add a filled-out entry to the cache
+            if (entryUpdated) {
+                mCache.put(cacheKey, entry);
+            }
         }
         return entry;
     }
diff --git a/src/com/android/launcher3/InvariantDeviceProfile.java b/src/com/android/launcher3/InvariantDeviceProfile.java
index 92fdbde..7f34593 100644
--- a/src/com/android/launcher3/InvariantDeviceProfile.java
+++ b/src/com/android/launcher3/InvariantDeviceProfile.java
@@ -19,12 +19,13 @@
 import android.annotation.TargetApi;
 import android.content.Context;
 import android.graphics.Point;
-import android.graphics.PointF;
 import android.os.Build;
 import android.util.DisplayMetrics;
 import android.view.Display;
 import android.view.WindowManager;
+
 import com.android.launcher3.util.Thunk;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -34,61 +35,36 @@
     // This is a static that we use for the default icon size on a 4/5-inch phone
     private static float DEFAULT_ICON_SIZE_DP = 60;
 
-    private static final ArrayList<InvariantDeviceProfile> sDeviceProfiles = new ArrayList<>();
-    static {
-        sDeviceProfiles.add(new InvariantDeviceProfile("Super Short Stubby",
-                255, 300,  2, 3, 2, 3, 48, 13, 3, 48, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Shorter Stubby",
-                255, 400,  3, 3, 3, 3, 48, 13, 3, 48, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Short Stubby",
-                275, 420,  3, 4, 3, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Stubby",
-                255, 450,  3, 4, 3, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Nexus S",
-                296, 491.33f,  4, 4, 4, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Nexus 4",
-                335, 567,  4, 4, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Nexus 5",
-                359, 567,  4, 4, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_4x4));
-        sDeviceProfiles.add(new InvariantDeviceProfile("Large Phone",
-                406, 694,  5, 5, 4, 4,  64, 14.4f,  5, 56, R.xml.default_workspace_5x5));
-        // The tablet profile is odd in that the landscape orientation
-        // also includes the nav bar on the side
-        sDeviceProfiles.add(new InvariantDeviceProfile("Nexus 7",
-                575, 904,  5, 6, 4, 5, 72, 14.4f,  7, 60, R.xml.default_workspace_5x6));
-        // Larger tablet profiles always have system bars on the top & bottom
-        sDeviceProfiles.add(new InvariantDeviceProfile("Nexus 10",
-                727, 1207,  5, 6, 4, 5, 76, 14.4f,  7, 64, R.xml.default_workspace_5x6));
-        sDeviceProfiles.add(new InvariantDeviceProfile("20-inch Tablet",
-                1527, 2527,  7, 7, 6, 6, 100, 20,  7, 72, R.xml.default_workspace_4x4));
-    }
+    // Constants that affects the interpolation curve between statically defined device profile
+    // buckets.
+    private static float KNEARESTNEIGHBOR = 3;
+    private static float WEIGHT_POWER = 5;
 
-    private class DeviceProfileQuery {
-        InvariantDeviceProfile profile;
-        float widthDps;
-        float heightDps;
-        float value;
-        PointF dimens;
-
-        DeviceProfileQuery(InvariantDeviceProfile p, float v) {
-            widthDps = p.minWidthDps;
-            heightDps = p.minHeightDps;
-            value = v;
-            dimens = new PointF(widthDps, heightDps);
-            profile = p;
-        }
-    }
+    // used to offset float not being able to express extremely small weights in extreme cases.
+    private static float WEIGHT_EFFICIENT = 100000f;
 
     // Profile-defining invariant properties
     String name;
     float minWidthDps;
     float minHeightDps;
+
+    /**
+     * Number of icons per row and column in the workspace.
+     */
     public int numRows;
     public int numColumns;
+
+    /**
+     * Number of icons per row and column in the folder.
+     */
     public int numFolderRows;
     public int numFolderColumns;
     float iconSize;
     float iconTextSize;
+
+    /**
+     * Number of icons inside the hotseat area.
+     */
     float numHotseatIcons;
     float hotseatIconSize;
     int defaultLayoutId;
@@ -102,6 +78,12 @@
     InvariantDeviceProfile() {
     }
 
+    public InvariantDeviceProfile(InvariantDeviceProfile p) {
+        this(p.name, p.minWidthDps, p.minHeightDps, p.numRows, p.numColumns,
+                p.numFolderRows, p.numFolderColumns, p.iconSize, p.iconTextSize, p.numHotseatIcons,
+                p.hotseatIconSize, p.defaultLayoutId);
+    }
+
     InvariantDeviceProfile(String n, float w, float h, int r, int c, int fr, int fc,
             float is, float its, float hs, float his, int dlId) {
         // Ensure that we have an odd number of hotseat items (since we need to place all apps)
@@ -134,21 +116,16 @@
         Point largestSize = new Point();
         display.getCurrentSizeRange(smallestSize, largestSize);
 
+        // This guarantees that width < height
         minWidthDps = Utilities.dpiFromPx(Math.min(smallestSize.x, smallestSize.y), dm);
         minHeightDps = Utilities.dpiFromPx(Math.min(largestSize.x, largestSize.y), dm);
 
-        ArrayList<DeviceProfileQuery> points =
-                new ArrayList<DeviceProfileQuery>();
+        ArrayList<InvariantDeviceProfile> closestProfiles =
+                findClosestDeviceProfiles(minWidthDps, minHeightDps, getPredefinedDeviceProfiles());
+        InvariantDeviceProfile interpolatedDeviceProfileOut =
+                invDistWeightedInterpolate(minWidthDps,  minHeightDps, closestProfiles);
 
-        // Find the closes profile given the width/height
-        for (InvariantDeviceProfile p : sDeviceProfiles) {
-            points.add(new DeviceProfileQuery(p, 0f));
-        }
-
-        InvariantDeviceProfile closestProfile =
-                findClosestDeviceProfile(minWidthDps, minHeightDps, points);
-
-        // The following properties are inherited directly from the nearest archetypal profile
+        InvariantDeviceProfile closestProfile = closestProfiles.get(0);
         numRows = closestProfile.numRows;
         numColumns = closestProfile.numColumns;
         numHotseatIcons = closestProfile.numHotseatIcons;
@@ -157,24 +134,9 @@
         numFolderRows = closestProfile.numFolderRows;
         numFolderColumns = closestProfile.numFolderColumns;
 
-
-        // The following properties are interpolated based on proximity to nearby archetypal
-        // profiles
-        points.clear();
-        for (InvariantDeviceProfile p : sDeviceProfiles) {
-            points.add(new DeviceProfileQuery(p, p.iconSize));
-        }
-        iconSize = invDistWeightedInterpolate(minWidthDps, minHeightDps, points);
-        points.clear();
-        for (InvariantDeviceProfile p : sDeviceProfiles) {
-            points.add(new DeviceProfileQuery(p, p.iconTextSize));
-        }
-        iconTextSize = invDistWeightedInterpolate(minWidthDps, minHeightDps, points);
-        points.clear();
-        for (InvariantDeviceProfile p : sDeviceProfiles) {
-            points.add(new DeviceProfileQuery(p, p.hotseatIconSize));
-        }
-        hotseatIconSize = invDistWeightedInterpolate(minWidthDps, minHeightDps, points);
+        iconSize = interpolatedDeviceProfileOut.iconSize;
+        iconTextSize = interpolatedDeviceProfileOut.iconTextSize;
+        hotseatIconSize = interpolatedDeviceProfileOut.hotseatIconSize;
 
         // If the partner customization apk contains any grid overrides, apply them
         // Supported overrides: numRows, numColumns, iconSize
@@ -182,7 +144,7 @@
 
         Point realSize = new Point();
         display.getRealSize(realSize);
-        // The real size never changes. smallSide and largeSize will remain the
+        // The real size never changes. smallSide and largeSide will remain the
         // same in any orientation.
         int smallSide = Math.min(realSize.x, realSize.y);
         int largeSide = Math.max(realSize.x, realSize.y);
@@ -193,84 +155,112 @@
                 smallSide, largeSide, false /* isLandscape */);
     }
 
+    ArrayList<InvariantDeviceProfile> getPredefinedDeviceProfiles() {
+        ArrayList<InvariantDeviceProfile> predefinedDeviceProfiles = new ArrayList<>();
+        // width, height, #rows, #columns, #folder rows, #folder columns,
+        // iconSize, iconTextSize, #hotseat, #hotseatIconSize, defaultLayoutId.
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Super Short Stubby",
+                255, 300,     2, 3, 2, 3, 48, 13, 3, 48, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Shorter Stubby",
+                255, 400,     3, 3, 3, 3, 48, 13, 3, 48, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Short Stubby",
+                275, 420,     3, 4, 3, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Stubby",
+                255, 450,     3, 4, 3, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus S",
+                296, 491.33f, 4, 4, 4, 4, 48, 13, 5, 48, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 4",
+                335, 567,     4, 4, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 5",
+                359, 567,     4, 4, 4, 4, DEFAULT_ICON_SIZE_DP, 13, 5, 56, R.xml.default_workspace_4x4));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Large Phone",
+                406, 694,     5, 5, 4, 4,  64, 14.4f,  5, 56, R.xml.default_workspace_5x5));
+        // The tablet profile is odd in that the landscape orientation
+        // also includes the nav bar on the side
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 7",
+                575, 904,     5, 6, 4, 5, 72, 14.4f,  7, 60, R.xml.default_workspace_5x6));
+        // Larger tablet profiles always have system bars on the top & bottom
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("Nexus 10",
+                727, 1207,    5, 6, 4, 5, 76, 14.4f,  7, 64, R.xml.default_workspace_5x6));
+        predefinedDeviceProfiles.add(new InvariantDeviceProfile("20-inch Tablet",
+                1527, 2527,   7, 7, 6, 6, 100, 20,  7, 72, R.xml.default_workspace_4x4));
+        return predefinedDeviceProfiles;
+    }
+
+
     /**
      * Apply any Partner customization grid overrides.
      *
      * Currently we support: all apps row / column count.
      */
-    private void applyPartnerDeviceProfileOverrides(Context ctx, DisplayMetrics dm) {
-        Partner p = Partner.get(ctx.getPackageManager());
+    private void applyPartnerDeviceProfileOverrides(Context context, DisplayMetrics dm) {
+        Partner p = Partner.get(context.getPackageManager());
         if (p != null) {
             p.applyInvariantDeviceProfileOverrides(this, dm);
         }
     }
 
-    @Thunk float dist(PointF p0, PointF p1) {
-        return (float) Math.sqrt((p1.x - p0.x)*(p1.x-p0.x) +
-                (p1.y-p0.y)*(p1.y-p0.y));
+    @Thunk float dist(float x0, float y0, float x1, float y1) {
+        return (float) Math.hypot(x1 - x0, y1 - y0);
     }
 
-    private float weight(PointF a, PointF b,
-                        float pow) {
-        float d = dist(a, b);
-        if (d == 0f) {
-            return Float.POSITIVE_INFINITY;
-        }
-        return (float) (1f / Math.pow(d, pow));
-    }
-
-    /** Returns the closest device profile given the width and height and a list of profiles */
-    private InvariantDeviceProfile findClosestDeviceProfile(float width, float height,
-                                                   ArrayList<DeviceProfileQuery> points) {
-        return findClosestDeviceProfiles(width, height, points).get(0).profile;
-    }
-
-    /** Returns the closest device profiles ordered by closeness to the specified width and height */
-    private ArrayList<DeviceProfileQuery> findClosestDeviceProfiles(float width, float height,
-                                                   ArrayList<DeviceProfileQuery> points) {
-        final PointF xy = new PointF(width, height);
+    /**
+     * Returns the closest device profiles ordered by closeness to the specified width and height
+     */
+    // Package private visibility for testing.
+    ArrayList<InvariantDeviceProfile> findClosestDeviceProfiles(
+            final float width, final float height, ArrayList<InvariantDeviceProfile> points) {
 
         // Sort the profiles by their closeness to the dimensions
-        ArrayList<DeviceProfileQuery> pointsByNearness = points;
-        Collections.sort(pointsByNearness, new Comparator<DeviceProfileQuery>() {
-            public int compare(DeviceProfileQuery a, DeviceProfileQuery b) {
-                return (int) (dist(xy, a.dimens) - dist(xy, b.dimens));
+        ArrayList<InvariantDeviceProfile> pointsByNearness = points;
+        Collections.sort(pointsByNearness, new Comparator<InvariantDeviceProfile>() {
+            public int compare(InvariantDeviceProfile a, InvariantDeviceProfile b) {
+                return (int) (dist(width, height, a.minWidthDps, a.minHeightDps)
+                        - dist(width, height, b.minWidthDps, b.minHeightDps));
             }
         });
 
         return pointsByNearness;
     }
 
-    private float invDistWeightedInterpolate(float width, float height,
-                ArrayList<DeviceProfileQuery> points) {
-        float sum = 0;
+    // Package private visibility for testing.
+    InvariantDeviceProfile invDistWeightedInterpolate(float width, float height,
+                ArrayList<InvariantDeviceProfile> points) {
         float weights = 0;
-        float pow = 5;
-        float kNearestNeighbors = 3;
-        final PointF xy = new PointF(width, height);
 
-        ArrayList<DeviceProfileQuery> pointsByNearness = findClosestDeviceProfiles(width, height,
-                points);
-
-        for (int i = 0; i < pointsByNearness.size(); ++i) {
-            DeviceProfileQuery p = pointsByNearness.get(i);
-            if (i < kNearestNeighbors) {
-                float w = weight(xy, p.dimens, pow);
-                if (w == Float.POSITIVE_INFINITY) {
-                    return p.value;
-                }
-                weights += w;
-            }
+        InvariantDeviceProfile p = points.get(0);
+        if (dist(width, height, p.minWidthDps, p.minHeightDps) == 0) {
+            return p;
         }
 
-        for (int i = 0; i < pointsByNearness.size(); ++i) {
-            DeviceProfileQuery p = pointsByNearness.get(i);
-            if (i < kNearestNeighbors) {
-                float w = weight(xy, p.dimens, pow);
-                sum += w * p.value / weights;
-            }
+        InvariantDeviceProfile out = new InvariantDeviceProfile();
+        for (int i = 0; i < points.size() && i < KNEARESTNEIGHBOR; ++i) {
+            p = new InvariantDeviceProfile(points.get(i));
+            float w = weight(width, height, p.minWidthDps, p.minHeightDps, WEIGHT_POWER);
+            weights += w;
+            out.add(p.multiply(w));
         }
-
-        return sum;
+        return out.multiply(1.0f/weights);
     }
-}
+
+    private void add(InvariantDeviceProfile p) {
+        iconSize += p.iconSize;
+        iconTextSize += p.iconTextSize;
+        hotseatIconSize += p.hotseatIconSize;
+    }
+
+    private InvariantDeviceProfile multiply(float w) {
+        iconSize *= w;
+        iconTextSize *= w;
+        hotseatIconSize *= w;
+        return this;
+    }
+
+    private float weight(float x0, float y0, float x1, float y1, float pow) {
+        float d = dist(x0, y0, x1, y1);
+        if (Float.compare(d, 0f) == 0) {
+            return Float.POSITIVE_INFINITY;
+        }
+        return (float) (WEIGHT_EFFICIENT / Math.pow(d, pow));
+    }
+}
\ No newline at end of file
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index da6430a..51f0916 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -112,11 +112,8 @@
 import com.android.launcher3.widget.WidgetHostViewLoader;
 import com.android.launcher3.widget.WidgetsContainerView;
 
-import java.io.DataInputStream;
-import java.io.DataOutputStream;
 import java.io.File;
 import java.io.FileDescriptor;
-import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.PrintWriter;
@@ -311,8 +308,6 @@
     private boolean mHasFocus = false;
     private boolean mAttached = false;
 
-    @Thunk static LocaleConfiguration sLocaleConfiguration = null;
-
     private static LongArrayMap<FolderInfo> sFolders = new LongArrayMap<>();
 
     private View.OnTouchListener mHapticFeedbackTouchListener;
@@ -488,7 +483,6 @@
                     Environment.getExternalStorageDirectory() + "/launcher");
         }
 
-        checkForLocaleChange();
         setContentView(R.layout.launcher);
 
         setupViews();
@@ -667,108 +661,6 @@
         }
     }
 
-    @Thunk void checkForLocaleChange() {
-        if (sLocaleConfiguration == null) {
-            new AsyncTask<Void, Void, LocaleConfiguration>() {
-                @Override
-                protected LocaleConfiguration doInBackground(Void... unused) {
-                    LocaleConfiguration localeConfiguration = new LocaleConfiguration();
-                    readConfiguration(Launcher.this, localeConfiguration);
-                    return localeConfiguration;
-                }
-
-                @Override
-                protected void onPostExecute(LocaleConfiguration result) {
-                    sLocaleConfiguration = result;
-                    checkForLocaleChange();  // recursive, but now with a locale configuration
-                }
-            }.execute();
-            return;
-        }
-
-        final Configuration configuration = getResources().getConfiguration();
-
-        final String previousLocale = sLocaleConfiguration.locale;
-        final String locale = configuration.locale.toString();
-
-        final int previousMcc = sLocaleConfiguration.mcc;
-        final int mcc = configuration.mcc;
-
-        final int previousMnc = sLocaleConfiguration.mnc;
-        final int mnc = configuration.mnc;
-
-        boolean localeChanged = !locale.equals(previousLocale) || mcc != previousMcc || mnc != previousMnc;
-
-        if (localeChanged) {
-            sLocaleConfiguration.locale = locale;
-            sLocaleConfiguration.mcc = mcc;
-            sLocaleConfiguration.mnc = mnc;
-
-            mIconCache.flush();
-
-            final LocaleConfiguration localeConfiguration = sLocaleConfiguration;
-            new AsyncTask<Void, Void, Void>() {
-                public Void doInBackground(Void ... args) {
-                    writeConfiguration(Launcher.this, localeConfiguration);
-                    return null;
-                }
-            }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, (Void) null);
-        }
-    }
-
-    @Thunk static class LocaleConfiguration {
-        public String locale;
-        public int mcc = -1;
-        public int mnc = -1;
-    }
-
-    @Thunk static void readConfiguration(Context context, LocaleConfiguration configuration) {
-        DataInputStream in = null;
-        try {
-            in = new DataInputStream(context.openFileInput(LauncherFiles.LAUNCHER_PREFERENCES));
-            configuration.locale = in.readUTF();
-            configuration.mcc = in.readInt();
-            configuration.mnc = in.readInt();
-        } catch (FileNotFoundException e) {
-            // Ignore
-        } catch (IOException e) {
-            // Ignore
-        } finally {
-            if (in != null) {
-                try {
-                    in.close();
-                } catch (IOException e) {
-                    // Ignore
-                }
-            }
-        }
-    }
-
-    @Thunk static void writeConfiguration(Context context, LocaleConfiguration configuration) {
-        DataOutputStream out = null;
-        try {
-            out = new DataOutputStream(context.openFileOutput(
-                    LauncherFiles.LAUNCHER_PREFERENCES, MODE_PRIVATE));
-            out.writeUTF(configuration.locale);
-            out.writeInt(configuration.mcc);
-            out.writeInt(configuration.mnc);
-            out.flush();
-        } catch (FileNotFoundException e) {
-            // Ignore
-        } catch (IOException e) {
-            //noinspection ResultOfMethodCallIgnored
-            context.getFileStreamPath(LauncherFiles.LAUNCHER_PREFERENCES).delete();
-        } finally {
-            if (out != null) {
-                try {
-                    out.close();
-                } catch (IOException e) {
-                    // Ignore
-                }
-            }
-        }
-    }
-
     public Stats getStats() {
         return mStats;
     }
diff --git a/src/com/android/launcher3/LauncherFiles.java b/src/com/android/launcher3/LauncherFiles.java
index 4aeaef0..ec4e4f9 100644
--- a/src/com/android/launcher3/LauncherFiles.java
+++ b/src/com/android/launcher3/LauncherFiles.java
@@ -17,7 +17,6 @@
     public static final String DEFAULT_WALLPAPER_THUMBNAIL = "default_thumb2.jpg";
     public static final String DEFAULT_WALLPAPER_THUMBNAIL_OLD = "default_thumb.jpg";
     public static final String LAUNCHER_DB = "launcher.db";
-    public static final String LAUNCHER_PREFERENCES = "launcher.preferences";
     public static final String SHARED_PREFERENCES_KEY = "com.android.launcher3.prefs";
     public static final String WALLPAPER_CROP_PREFERENCES_KEY =
             "com.android.launcher3.WallpaperCropActivity";
@@ -33,7 +32,6 @@
             DEFAULT_WALLPAPER_THUMBNAIL,
             DEFAULT_WALLPAPER_THUMBNAIL_OLD,
             LAUNCHER_DB,
-            LAUNCHER_PREFERENCES,
             SHARED_PREFERENCES_KEY + XML,
             WALLPAPER_CROP_PREFERENCES_KEY + XML,
             WALLPAPER_IMAGES_DB,
@@ -46,5 +44,6 @@
     public static final List<String> OBSOLETE_FILES = Collections.unmodifiableList(Arrays.asList(
             "launches.log",
             "stats.log",
+            "launcher.preferences",
             "com.android.launcher3.compat.PackageInstallerCompatV16.queue"));
 }
diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index f099044..9271e8b 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -623,6 +623,11 @@
             if (mCurrentPage != getNextPage()) {
                 AccessibilityEvent ev =
                         AccessibilityEvent.obtain(AccessibilityEvent.TYPE_VIEW_SCROLLED);
+                ev.setScrollable(true);
+                ev.setScrollX(getScrollX());
+                ev.setScrollY(getScrollY());
+                ev.setMaxScrollX(mMaxScrollX);
+                ev.setMaxScrollY(0);
 
                 sendAccessibilityEventUnchecked(ev);
             }
@@ -843,7 +848,7 @@
         int offsetY = getViewportOffsetY();
 
         // Update the viewport offsets
-        mViewport.offset(offsetX,  offsetY);
+        mViewport.offset(offsetX, offsetY);
 
         final int startIndex = mIsRtl ? childCount - 1 : 0;
         final int endIndex = mIsRtl ? -1 : childCount;
@@ -2327,6 +2332,15 @@
         if (getCurrentPage() > 0) {
             info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD);
         }
+        info.setClassName(getClass().getName());
+
+        // Accessibility-wise, PagedView doesn't support long click, so disabling it.
+        // Besides disabling the accessibility long-click, this also prevents this view from getting
+        // accessibility focus.
+        info.setLongClickable(false);
+        if (Utilities.isLmpOrAbove()) {
+            info.removeAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_LONG_CLICK);
+        }
     }
 
     @Override
@@ -2340,7 +2354,7 @@
     @Override
     public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
         super.onInitializeAccessibilityEvent(event);
-        event.setScrollable(true);
+        event.setScrollable(getPageCount() > 1);
     }
 
     @Override
diff --git a/src/com/android/launcher3/Workspace.java b/src/com/android/launcher3/Workspace.java
index c0a1cfc..6d5affb 100644
--- a/src/com/android/launcher3/Workspace.java
+++ b/src/com/android/launcher3/Workspace.java
@@ -64,8 +64,8 @@
 import com.android.launcher3.LauncherSettings.Favorites;
 import com.android.launcher3.UninstallDropTarget.UninstallSource;
 import com.android.launcher3.accessibility.LauncherAccessibilityDelegate;
-import com.android.launcher3.accessibility.OverviewScreenAccessibilityDelegate;
 import com.android.launcher3.accessibility.LauncherAccessibilityDelegate.AccessibilityDragSource;
+import com.android.launcher3.accessibility.OverviewScreenAccessibilityDelegate;
 import com.android.launcher3.compat.UserHandleCompat;
 import com.android.launcher3.util.LongArrayMap;
 import com.android.launcher3.util.Thunk;
@@ -89,6 +89,8 @@
         Insettable, UninstallSource, AccessibilityDragSource {
     private static final String TAG = "Launcher.Workspace";
 
+    private static boolean ENFORCE_DRAG_EVENT_ORDER = false;
+
     protected static final int SNAP_OFF_EMPTY_SCREEN_DURATION = 400;
     protected static final int FADE_EMPTY_SCREEN_DURATION = 150;
 
@@ -215,7 +217,6 @@
     private FolderIcon mDragOverFolderIcon = null;
     private boolean mCreateUserFolderOnDrop = false;
     private boolean mAddToExistingFolderOnDrop = false;
-    private DropTarget.DragEnforcer mDragEnforcer;
     private float mMaxDistanceForFolderCreation;
 
     private final Canvas mCanvas = new Canvas();
@@ -301,9 +302,6 @@
 
         mOutlineHelper = HolographicOutlineHelper.obtain(context);
 
-        mDragEnforcer = new DropTarget.DragEnforcer(context);
-        // With workspace, data is available straight from the get-go
-
         mLauncher = (Launcher) context;
         mStateTransitionAnimation = new WorkspaceStateTransitionAnimation(mLauncher, this);
         final Resources res = getResources();
@@ -327,7 +325,6 @@
 
         // Disable multitouch across the workspace/all apps/customize tray
         setMotionEventSplittingEnabled(true);
-        setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
     }
 
     @Override
@@ -372,22 +369,23 @@
         return r;
     }
 
+    @Override
     public void onDragStart(final DragSource source, Object info, int dragAction) {
+        if (ENFORCE_DRAG_EVENT_ORDER) {
+            enfoceDragParity("onDragStart", 0, 0);
+        }
+
         mIsDragOccuring = true;
         updateChildrenLayersEnabled(false);
         mLauncher.lockScreenOrientation();
         mLauncher.onInteractionBegin();
         // Prevent any Un/InstallShortcutReceivers from updating the db while we are dragging
         InstallShortcutReceiver.enableInstallQueue();
-        post(new Runnable() {
-            @Override
-            public void run() {
-                if (mIsDragOccuring && mAddNewPageOnDrag) {
-                    mDeferRemoveExtraEmptyScreen = false;
-                    addExtraEmptyScreenOnDrag();
-                }
-            }
-        });
+
+        if (mAddNewPageOnDrag) {
+            mDeferRemoveExtraEmptyScreen = false;
+            addExtraEmptyScreenOnDrag();
+        }
     }
 
     public void setAddNewPageOnDrag(boolean addPage) {
@@ -398,7 +396,12 @@
         mDeferRemoveExtraEmptyScreen = true;
     }
 
+    @Override
     public void onDragEnd() {
+        if (ENFORCE_DRAG_EVENT_ORDER) {
+            enfoceDragParity("onDragEnd", 0, 0);
+        }
+
         if (!mDeferRemoveExtraEmptyScreen) {
             removeExtraEmptyScreen(true, mDragSourceInternal != null);
         }
@@ -731,6 +734,7 @@
                 fadeAndRemoveEmptyScreen(SNAP_OFF_EMPTY_SCREEN_DURATION, FADE_EMPTY_SCREEN_DURATION,
                         onComplete, stripEmptyScreens);
             } else {
+                snapToPage(getNextPage(), 0);
                 fadeAndRemoveEmptyScreen(0, FADE_EMPTY_SCREEN_DURATION,
                         onComplete, stripEmptyScreens);
             }
@@ -2014,14 +2018,9 @@
             for (int i = numCustomPages(); i < total; i++) {
                 updateAccessibilityFlags((CellLayout) getPageAt(i), i);
             }
-            if (mState == State.NORMAL) {
-                setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_NO);
-            } else {
-                setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
-            }
         } else {
             int accessible = mState == State.NORMAL ?
-                    IMPORTANT_FOR_ACCESSIBILITY_NO :
+                    IMPORTANT_FOR_ACCESSIBILITY_AUTO :
                         IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS;
             setImportantForAccessibility(accessible);
         }
@@ -2040,7 +2039,7 @@
             page.setAccessibilityDelegate(mPagesAccessibilityDelegate);
         } else {
             int accessible = mState == State.NORMAL ?
-                    IMPORTANT_FOR_ACCESSIBILITY_NO :
+                    IMPORTANT_FOR_ACCESSIBILITY_AUTO :
                         IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS;
             page.setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_NO);
             page.getShortcutsAndWidgets().setImportantForAccessibility(accessible);
@@ -2822,8 +2821,12 @@
         location[1] = vY - y;
     }
 
+    @Override
     public void onDragEnter(DragObject d) {
-        mDragEnforcer.onDragEnter();
+        if (ENFORCE_DRAG_EVENT_ORDER) {
+            enfoceDragParity("onDragEnter", 1, 1);
+        }
+
         mCreateUserFolderOnDrop = false;
         mAddToExistingFolderOnDrop = false;
 
@@ -2876,8 +2879,11 @@
         return null;
     }
 
+    @Override
     public void onDragExit(DragObject d) {
-        mDragEnforcer.onDragExit();
+        if (ENFORCE_DRAG_EVENT_ORDER) {
+            enfoceDragParity("onDragExit", -1, 0);
+        }
 
         // Here we store the final page that will be dropped to, if the workspace in fact
         // receives the drop
@@ -2909,6 +2915,24 @@
         mLauncher.getDragLayer().hidePageHints();
     }
 
+    private void enfoceDragParity(String event, int update, int expectedValue) {
+        enfoceDragParity(this, event, update, expectedValue);
+        for (int i = 0; i < getChildCount(); i++) {
+            enfoceDragParity(getChildAt(i), event, update, expectedValue);
+        }
+    }
+
+    private void enfoceDragParity(View v, String event, int update, int expectedValue) {
+        Object tag = v.getTag(R.id.drag_event_parity);
+        int value = tag == null ? 0 : (Integer) tag;
+        value += update;
+        v.setTag(R.id.drag_event_parity, value);
+
+        if (value != expectedValue) {
+            Log.e(TAG, event + ": Drag contract violated: " + value);
+        }
+    }
+
     void setCurrentDropLayout(CellLayout layout) {
         if (mDragTargetLayout != null) {
             mDragTargetLayout.revertTempState();
diff --git a/src/com/android/launcher3/accessibility/LauncherAccessibilityDelegate.java b/src/com/android/launcher3/accessibility/LauncherAccessibilityDelegate.java
index eeec8c5..93cf8d0 100644
--- a/src/com/android/launcher3/accessibility/LauncherAccessibilityDelegate.java
+++ b/src/com/android/launcher3/accessibility/LauncherAccessibilityDelegate.java
@@ -219,9 +219,13 @@
     }
 
     private ArrayList<Integer> getSupportedResizeActions(View host, LauncherAppWidgetInfo info) {
-        AppWidgetProviderInfo providerInfo = ((LauncherAppWidgetHostView) host).getAppWidgetInfo();
         ArrayList<Integer> actions = new ArrayList<>();
 
+        AppWidgetProviderInfo providerInfo = ((LauncherAppWidgetHostView) host).getAppWidgetInfo();
+        if (providerInfo == null) {
+            return actions;
+        }
+
         CellLayout layout = (CellLayout) host.getParent().getParent();
         if ((providerInfo.resizeMode & AppWidgetProviderInfo.RESIZE_HORIZONTAL) != 0) {
             if (layout.isRegionVacant(info.cellX + info.spanX, info.cellY, 1, info.spanY) ||
diff --git a/src/com/android/launcher3/allapps/AllAppsContainerView.java b/src/com/android/launcher3/allapps/AllAppsContainerView.java
index 60f9ab3..d81f97f 100644
--- a/src/com/android/launcher3/allapps/AllAppsContainerView.java
+++ b/src/com/android/launcher3/allapps/AllAppsContainerView.java
@@ -447,7 +447,6 @@
     @Override
     protected void onFixedBoundsUpdated() {
         // Update the number of items in the grid
-        LauncherAppState app = LauncherAppState.getInstance();
         DeviceProfile grid = mLauncher.getDeviceProfile();
         if (grid.updateAppsViewNumCols(getContext().getResources(), mFixedBounds.width())) {
             mNumAppsPerRow = grid.allAppsNumCols;
diff --git a/src/com/android/launcher3/allapps/AllAppsRecyclerView.java b/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
index e95fa32..cc5add3 100644
--- a/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
+++ b/src/com/android/launcher3/allapps/AllAppsRecyclerView.java
@@ -15,75 +15,34 @@
  */
 package com.android.launcher3.allapps;
 
-import android.animation.ObjectAnimator;
 import android.content.Context;
-import android.content.res.Resources;
-import android.graphics.Canvas;
-import android.graphics.Color;
-import android.graphics.Paint;
 import android.graphics.Rect;
 import android.graphics.drawable.Drawable;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
-import android.view.MotionEvent;
 import android.view.View;
-import android.view.ViewConfiguration;
+
 import com.android.launcher3.BaseRecyclerView;
 import com.android.launcher3.DeviceProfile;
 import com.android.launcher3.Launcher;
-import com.android.launcher3.R;
 import com.android.launcher3.Utilities;
 
 import java.util.List;
 
 /**
- * A RecyclerView with custom fastscroll support.  This is the main container for the all apps
- * icons.
+ * A RecyclerView with custom fast scroll support for the all apps view.
  */
 public class AllAppsRecyclerView extends BaseRecyclerView {
 
-    /**
-     * The current scroll state of the recycler view.  We use this in updateVerticalScrollbarBounds()
-     * and scrollToPositionAtProgress() to determine the scroll position of the recycler view so
-     * that we can calculate what the scroll bar looks like, and where to jump to from the fast
-     * scroller.
-     */
-    private static class ScrollPositionState {
-        // The index of the first visible row
-        int rowIndex;
-        // The offset of the first visible row
-        int rowTopOffset;
-        // The height of a given row (they are currently all the same height)
-        int rowHeight;
-    }
-
-    private static final float FAST_SCROLL_OVERLAY_Y_OFFSET_FACTOR = 1.5f;
-
     private AlphabeticalAppsList mApps;
     private int mNumAppsPerRow;
     private int mNumPredictedAppsPerRow;
 
-    private Drawable mScrollbar;
-    private Drawable mFastScrollerBg;
-    private Rect mTmpFastScrollerInvalidateRect = new Rect();
-    private Rect mFastScrollerBounds = new Rect();
-    private Rect mVerticalScrollbarBounds = new Rect();
-    private boolean mDraggingFastScroller;
-    private String mFastScrollSectionName;
-    private Paint mFastScrollTextPaint;
-    private Rect mFastScrollTextBounds = new Rect();
-    private float mFastScrollAlpha;
     private int mPredictionBarHeight;
-    private int mDownX;
-    private int mDownY;
-    private int mLastX;
-    private int mLastY;
-    private int mScrollbarWidth;
     private int mScrollbarMinHeight;
-    private int mScrollbarInset;
+
     private Rect mBackgroundPadding = new Rect();
-    private ScrollPositionState mScrollPosState = new ScrollPositionState();
 
     private Launcher mLauncher;
 
@@ -102,25 +61,7 @@
     public AllAppsRecyclerView(Context context, AttributeSet attrs, int defStyleAttr,
             int defStyleRes) {
         super(context, attrs, defStyleAttr);
-
         mLauncher = (Launcher) context;
-        Resources res = context.getResources();
-        int fastScrollerSize = res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_popup_size);
-        mScrollbar = res.getDrawable(R.drawable.all_apps_scrollbar_thumb);
-        mFastScrollerBg = res.getDrawable(R.drawable.all_apps_fastscroll_bg);
-        mFastScrollerBg.setBounds(0, 0, fastScrollerSize, fastScrollerSize);
-        mFastScrollTextPaint = new Paint();
-        mFastScrollTextPaint.setColor(Color.WHITE);
-        mFastScrollTextPaint.setAntiAlias(true);
-        mFastScrollTextPaint.setTextSize(res.getDimensionPixelSize(
-                R.dimen.all_apps_fast_scroll_text_size));
-        mScrollbarWidth = res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_bar_width);
-        mScrollbarMinHeight =
-                res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_bar_min_height);
-        mScrollbarInset =
-                res.getDimensionPixelSize(R.dimen.all_apps_fast_scroll_scrubber_touch_inset);
-        setFastScrollerAlpha(getFastScrollerAlpha());
-        setOverScrollMode(View.OVER_SCROLL_NEVER);
     }
 
     /**
@@ -158,28 +99,6 @@
     }
 
     /**
-     * Sets the fast scroller alpha.
-     */
-    public void setFastScrollerAlpha(float alpha) {
-        mFastScrollAlpha = alpha;
-        invalidateFastScroller(mFastScrollerBounds);
-    }
-
-    /**
-     * Gets the fast scroller alpha.
-     */
-    public float getFastScrollerAlpha() {
-        return mFastScrollAlpha;
-    }
-
-    /**
-     * Returns the scroll bar width.
-     */
-    public int getScrollbarWidth() {
-        return mScrollbarWidth;
-    }
-
-    /**
      * Scrolls this recycler view to the top.
      */
     public void scrollToTop() {
@@ -191,11 +110,11 @@
      */
     public int getScrollPosition() {
         List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
-        getCurScrollState(mScrollPosState, items);
-        if (mScrollPosState.rowIndex != -1) {
+        getCurScrollState(scrollPosState, items);
+        if (scrollPosState.rowIndex != -1) {
             int predictionBarHeight = mApps.getPredictedApps().isEmpty() ? 0 : mPredictionBarHeight;
-            return getPaddingTop() + (mScrollPosState.rowIndex * mScrollPosState.rowHeight) +
-                    predictionBarHeight - mScrollPosState.rowTopOffset;
+            return getPaddingTop() + (scrollPosState.rowIndex * scrollPosState.rowHeight) +
+                    predictionBarHeight - scrollPosState.rowTopOffset;
         }
         return 0;
     }
@@ -206,150 +125,11 @@
         addOnItemTouchListener(this);
     }
 
-    @Override
-    protected void dispatchDraw(Canvas canvas) {
-        super.dispatchDraw(canvas);
-        drawVerticalScrubber(canvas);
-        drawFastScrollerPopup(canvas);
-    }
-
-    /**
-     * We intercept the touch handling only to support fast scrolling when initiated from the
-     * scroll bar.  Otherwise, we fall back to the default RecyclerView touch handling.
-     */
-    @Override
-    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent ev) {
-        return handleTouchEvent(ev);
-    }
-
-    @Override
-    public void onTouchEvent(RecyclerView rv, MotionEvent ev) {
-        handleTouchEvent(ev);
-    }
-
-    /**
-     * Handles the touch event and determines whether to show the fast scroller (or updates it if
-     * it is already showing).
-     */
-    private boolean handleTouchEvent(MotionEvent ev) {
-        ViewConfiguration config = ViewConfiguration.get(getContext());
-
-        int action = ev.getAction();
-        int x = (int) ev.getX();
-        int y = (int) ev.getY();
-        switch (action) {
-            case MotionEvent.ACTION_DOWN:
-                // Keep track of the down positions
-                mDownX = mLastX = x;
-                mDownY = mLastY = y;
-                if (shouldStopScroll(ev)) {
-                    stopScroll();
-                }
-                break;
-            case MotionEvent.ACTION_MOVE:
-                // Check if we are scrolling
-                if (!mDraggingFastScroller && isPointNearScrollbar(mDownX, mDownY) &&
-                        Math.abs(y - mDownY) > config.getScaledTouchSlop()) {
-                    getParent().requestDisallowInterceptTouchEvent(true);
-                    mDraggingFastScroller = true;
-                    animateFastScrollerVisibility(true);
-                }
-                if (mDraggingFastScroller) {
-                    mLastX = x;
-                    mLastY = y;
-
-                    // Scroll to the right position, and update the section name
-                    int top = getPaddingTop() + (mFastScrollerBg.getBounds().height() / 2);
-                    int bottom = getHeight() - getPaddingBottom() -
-                            (mFastScrollerBg.getBounds().height() / 2);
-                    float boundedY = (float) Math.max(top, Math.min(bottom, y));
-                    mFastScrollSectionName = scrollToPositionAtProgress((boundedY - top) /
-                            (bottom - top));
-
-                    // Combine the old and new fast scroller bounds to create the full invalidate
-                    // rect
-                    mTmpFastScrollerInvalidateRect.set(mFastScrollerBounds);
-                    updateFastScrollerBounds();
-                    mTmpFastScrollerInvalidateRect.union(mFastScrollerBounds);
-                    invalidateFastScroller(mTmpFastScrollerInvalidateRect);
-                }
-                break;
-            case MotionEvent.ACTION_UP:
-            case MotionEvent.ACTION_CANCEL:
-                mDraggingFastScroller = false;
-                animateFastScrollerVisibility(false);
-                break;
-        }
-        return mDraggingFastScroller;
-    }
-
-    /**
-     * Animates the visibility of the fast scroller popup.
-     */
-    private void animateFastScrollerVisibility(boolean visible) {
-        ObjectAnimator anim = ObjectAnimator.ofFloat(this, "fastScrollerAlpha", visible ? 1f : 0f);
-        anim.setDuration(visible ? 200 : 150);
-        anim.start();
-    }
-
-    /**
-     * Returns whether a given point is near the scrollbar.
-     */
-    private boolean isPointNearScrollbar(int x, int y) {
-        // Check if we are scrolling
-        updateVerticalScrollbarBounds();
-        mVerticalScrollbarBounds.inset(mScrollbarInset, mScrollbarInset);
-        return mVerticalScrollbarBounds.contains(x, y);
-    }
-
-    /**
-     * Draws the fast scroller popup.
-     */
-    private void drawFastScrollerPopup(Canvas canvas) {
-        if (mFastScrollAlpha > 0f && !mFastScrollSectionName.isEmpty()) {
-            // Draw the fast scroller popup
-            int restoreCount = canvas.save(Canvas.MATRIX_SAVE_FLAG);
-            canvas.translate(mFastScrollerBounds.left, mFastScrollerBounds.top);
-            mFastScrollerBg.setAlpha((int) (mFastScrollAlpha * 255));
-            mFastScrollerBg.draw(canvas);
-            mFastScrollTextPaint.setAlpha((int) (mFastScrollAlpha * 255));
-            mFastScrollTextPaint.getTextBounds(mFastScrollSectionName, 0,
-                    mFastScrollSectionName.length(), mFastScrollTextBounds);
-            float textWidth = mFastScrollTextPaint.measureText(mFastScrollSectionName);
-            canvas.drawText(mFastScrollSectionName,
-                    (mFastScrollerBounds.width() - textWidth) / 2,
-                    mFastScrollerBounds.height() -
-                            (mFastScrollerBounds.height() - mFastScrollTextBounds.height()) / 2,
-                    mFastScrollTextPaint);
-            canvas.restoreToCount(restoreCount);
-        }
-    }
-
-    /**
-     * Draws the vertical scrollbar.
-     */
-    private void drawVerticalScrubber(Canvas canvas) {
-        updateVerticalScrollbarBounds();
-
-        // Draw the scroll bar
-        int restoreCount = canvas.save(Canvas.MATRIX_SAVE_FLAG);
-        canvas.translate(mVerticalScrollbarBounds.left, mVerticalScrollbarBounds.top);
-        mScrollbar.setBounds(0, 0, mScrollbarWidth, mVerticalScrollbarBounds.height());
-        mScrollbar.draw(canvas);
-        canvas.restoreToCount(restoreCount);
-    }
-
-    /**
-     * Invalidates the fast scroller popup.
-     */
-    private void invalidateFastScroller(Rect bounds) {
-        invalidate(bounds.left, bounds.top, bounds.right, bounds.bottom);
-    }
-
     /**
      * Maps the touch (from 0..1) to the adapter position that should be visible.
      */
-    private String scrollToPositionAtProgress(float touchFraction) {
+    @Override
+    public String scrollToPositionAtProgress(float touchFraction) {
         // Ensure that we have any sections
         List<AlphabeticalAppsList.FastScrollSectionInfo> fastScrollSections =
                 mApps.getFastScrollerSections();
@@ -393,77 +173,6 @@
         return lastScrollSection.sectionName;
     }
 
-    /**
-     * Updates the bounds for the scrollbar.
-     */
-    private void updateVerticalScrollbarBounds() {
-        List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
-
-        // Skip early if there are no items
-        if (items.isEmpty()) {
-            mVerticalScrollbarBounds.setEmpty();
-            return;
-        }
-
-        // Find the index and height of the first visible row (all rows have the same height)
-        int x;
-        int y;
-        int predictionBarHeight = mApps.getPredictedApps().isEmpty() ? 0 : mPredictionBarHeight;
-        int rowCount = getNumRows();
-        getCurScrollState(mScrollPosState, items);
-        if (mScrollPosState.rowIndex != -1) {
-            int height = getHeight() - getPaddingTop() - getPaddingBottom();
-            int totalScrollHeight = rowCount * mScrollPosState.rowHeight + predictionBarHeight;
-            if (totalScrollHeight > height) {
-                int scrollbarHeight = Math.max(mScrollbarMinHeight,
-                        (int) (height / ((float) totalScrollHeight / height)));
-
-                // Calculate the position and size of the scroll bar
-                if (Utilities.isRtl(getResources())) {
-                    x = mBackgroundPadding.left;
-                } else {
-                    x = getWidth() - mBackgroundPadding.right - mScrollbarWidth;
-                }
-
-                // To calculate the offset, we compute the percentage of the total scrollable height
-                // that the user has already scrolled and then map that to the scroll bar bounds
-                int availableY = totalScrollHeight - height;
-                int availableScrollY = height - scrollbarHeight;
-                y = (mScrollPosState.rowIndex * mScrollPosState.rowHeight) + predictionBarHeight
-                        - mScrollPosState.rowTopOffset;
-                y = getPaddingTop() +
-                        (int) (((float) (getPaddingTop() + y) / availableY) * availableScrollY);
-
-                mVerticalScrollbarBounds.set(x, y, x + mScrollbarWidth, y + scrollbarHeight);
-                return;
-            }
-        }
-        mVerticalScrollbarBounds.setEmpty();
-    }
-
-    /**
-     * Updates the bounds for the fast scroller.
-     */
-    private void updateFastScrollerBounds() {
-        if (mFastScrollAlpha > 0f && !mFastScrollSectionName.isEmpty()) {
-            int x;
-            int y;
-
-            // Calculate the position for the fast scroller popup
-            Rect bgBounds = mFastScrollerBg.getBounds();
-            if (Utilities.isRtl(getResources())) {
-                x = mBackgroundPadding.left + getScrollBarSize();
-            } else {
-                x = getWidth() - getPaddingRight() - getScrollBarSize() - bgBounds.width();
-            }
-            y = mLastY - (int) (FAST_SCROLL_OVERLAY_Y_OFFSET_FACTOR * bgBounds.height());
-            y = Math.max(getPaddingTop(), Math.min(y, getHeight() - getPaddingBottom() -
-                    bgBounds.height()));
-            mFastScrollerBounds.set(x, y, x + bgBounds.width(), y + bgBounds.height());
-        } else {
-            mFastScrollerBounds.setEmpty();
-        }
-    }
 
     /**
      * Returns the row index for a app index in the list.
@@ -496,6 +205,55 @@
         return rowCount;
     }
 
+
+    /**
+     * Updates the bounds for the scrollbar.
+     */
+    @Override
+    public void updateVerticalScrollbarBounds() {
+        List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
+
+        // Skip early if there are no items.
+        if (items.isEmpty()) {
+            verticalScrollbarBounds.setEmpty();
+            return;
+        }
+
+        // Find the index and height of the first visible row (all rows have the same height)
+        int x, y;
+        int predictionBarHeight = mApps.getPredictedApps().isEmpty() ? 0 : mPredictionBarHeight;
+        int rowCount = getNumRows();
+        getCurScrollState(scrollPosState, items);
+        if (scrollPosState.rowIndex != -1) {
+            int height = getHeight() - getPaddingTop() - getPaddingBottom();
+            int totalScrollHeight = rowCount * scrollPosState.rowHeight + predictionBarHeight;
+            if (totalScrollHeight > height) {
+                int scrollbarHeight = Math.max(mScrollbarMinHeight,
+                        (int) (height / ((float) totalScrollHeight / height)));
+
+                // Calculate the position and size of the scroll bar
+                if (Utilities.isRtl(getResources())) {
+                    x = mBackgroundPadding.left;
+                } else {
+                    x = getWidth() - mBackgroundPadding.right - getScrollbarWidth();
+                }
+
+                // To calculate the offset, we compute the percentage of the total scrollable height
+                // that the user has already scrolled and then map that to the scroll bar bounds
+                int availableY = totalScrollHeight - height;
+                int availableScrollY = height - scrollbarHeight;
+                y = (scrollPosState.rowIndex * scrollPosState.rowHeight) + predictionBarHeight
+                        - scrollPosState.rowTopOffset;
+                y = getPaddingTop() +
+                        (int) (((float) (getPaddingTop() + y) / availableY) * availableScrollY);
+
+                verticalScrollbarBounds.set(x, y, x + getScrollbarWidth(), y + scrollbarHeight);
+                return;
+            }
+        }
+        verticalScrollbarBounds.setEmpty();
+    }
+
     /**
      * Returns the current scroll state.
      */
diff --git a/src/com/android/launcher3/allapps/AlphabeticalAppsList.java b/src/com/android/launcher3/allapps/AlphabeticalAppsList.java
index 3d1503d..7a9dfa1 100644
--- a/src/com/android/launcher3/allapps/AlphabeticalAppsList.java
+++ b/src/com/android/launcher3/allapps/AlphabeticalAppsList.java
@@ -10,6 +10,8 @@
 import com.android.launcher3.compat.AlphabeticIndexCompat;
 import com.android.launcher3.model.AppNameComparator;
 
+import java.nio.charset.CharsetEncoder;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -130,46 +132,63 @@
      * Common interface for different merging strategies.
      */
     private interface MergeAlgorithm {
-        boolean continueMerging(int sectionAppCount, int numAppsPerRow, int mergeCount);
+        boolean continueMerging(SectionInfo section, SectionInfo withSection,
+                int sectionAppCount, int numAppsPerRow, int mergeCount);
     }
 
     /**
-     * The logic we use to merge sections on tablets.
+     * The logic we use to merge sections on tablets.  Currently, we don't show section names on
+     * tablet layouts, so just merge all the sections indiscriminately.
      */
     private static class TabletMergeAlgorithm implements MergeAlgorithm {
 
         @Override
-        public boolean continueMerging(int sectionAppCount, int numAppsPerRow, int mergeCount) {
+        public boolean continueMerging(SectionInfo section, SectionInfo withSection,
+                int sectionAppCount, int numAppsPerRow, int mergeCount) {
             // Merge EVERYTHING
             return true;
         }
     }
 
     /**
-     * The logic we use to merge sections on phones.
+     * The logic we use to merge sections on phones.  We only merge sections when their final row
+     * contains less than a certain number of icons, and stop at a specified max number of merges.
+     * In addition, we will try and not merge sections that identify apps from different scripts.
      */
     private static class PhoneMergeAlgorithm implements MergeAlgorithm {
 
         private int mMinAppsPerRow;
         private int mMinRowsInMergedSection;
         private int mMaxAllowableMerges;
+        private CharsetEncoder mAsciiEncoder;
 
         public PhoneMergeAlgorithm(int minAppsPerRow, int minRowsInMergedSection, int maxNumMerges) {
             mMinAppsPerRow = minAppsPerRow;
             mMinRowsInMergedSection = minRowsInMergedSection;
             mMaxAllowableMerges = maxNumMerges;
+            mAsciiEncoder = StandardCharsets.US_ASCII.newEncoder();
         }
 
         @Override
-        public boolean continueMerging(int sectionAppCount, int numAppsPerRow, int mergeCount) {
+        public boolean continueMerging(SectionInfo section, SectionInfo withSection,
+                int sectionAppCount, int numAppsPerRow, int mergeCount) {
             // Continue merging if the number of hanging apps on the final row is less than some
             // fixed number (ragged), the merged rows has yet to exceed some minimum row count,
             // and while the number of merged sections is less than some fixed number of merges
             int rows = sectionAppCount / numAppsPerRow;
             int cols = sectionAppCount % numAppsPerRow;
+
+            // Ensure that we do not merge across scripts, currently we only allow for english and
+            // native scripts so we can test if both can just be ascii encoded
+            boolean isCrossScript = false;
+            if (section.firstAppItem != null && withSection.firstAppItem != null) {
+                isCrossScript = mAsciiEncoder.canEncode(section.firstAppItem.sectionName) !=
+                        mAsciiEncoder.canEncode(withSection.firstAppItem.sectionName);
+            }
             return (0 < cols && cols < mMinAppsPerRow) &&
                     rows < mMinRowsInMergedSection &&
-                    mergeCount < mMaxAllowableMerges;
+                    mergeCount < mMaxAllowableMerges &&
+                    !isCrossScript;
         }
     }
 
@@ -521,15 +540,16 @@
         // Go through each section and try and merge some of the sections
         if (AllAppsContainerView.GRID_MERGE_SECTIONS && !hasFilter()) {
             int sectionAppCount = 0;
-            for (int i = 0; i < mSections.size(); i++) {
+            for (int i = 0; i < mSections.size() - 1; i++) {
                 SectionInfo section = mSections.get(i);
+                SectionInfo nextSection = mSections.get(i + 1);
                 sectionAppCount = section.numApps;
                 int mergeCount = 1;
 
                 // Merge rows based on the current strategy
-                while (mMergeAlgorithm.continueMerging(sectionAppCount, mNumAppsPerRow, mergeCount) &&
-                        (i + 1) < mSections.size()) {
-                    SectionInfo nextSection = mSections.remove(i + 1);
+                while (mMergeAlgorithm.continueMerging(section, nextSection, sectionAppCount,
+                        mNumAppsPerRow, mergeCount)) {
+                    nextSection = mSections.remove(i + 1);
 
                     // Remove the next section break
                     mAdapterItems.remove(nextSection.sectionBreakItem);
diff --git a/src/com/android/launcher3/widget/WidgetsContainerView.java b/src/com/android/launcher3/widget/WidgetsContainerView.java
index 05e842e..11c2107 100644
--- a/src/com/android/launcher3/widget/WidgetsContainerView.java
+++ b/src/com/android/launcher3/widget/WidgetsContainerView.java
@@ -35,7 +35,6 @@
 import com.android.launcher3.DragController;
 import com.android.launcher3.DragSource;
 import com.android.launcher3.DropTarget.DragObject;
-import com.android.launcher3.model.WidgetsModel;
 import com.android.launcher3.Folder;
 import com.android.launcher3.IconCache;
 import com.android.launcher3.ItemInfo;
@@ -46,6 +45,7 @@
 import com.android.launcher3.Utilities;
 import com.android.launcher3.WidgetPreviewLoader;
 import com.android.launcher3.Workspace;
+import com.android.launcher3.model.WidgetsModel;
 
 /**
  * The widgets list view container.
@@ -56,8 +56,6 @@
     private static final String TAG = "WidgetsContainerView";
     private static final boolean DEBUG = false;
 
-    private static final int SPRING_MODE_DELAY_MS = 150;
-
     /* Coefficient multiplied to the screen height for preloading widgets. */
     private static final int PRELOAD_SCREEN_HEIGHT_MULTIPLE = 1;
 
@@ -67,7 +65,7 @@
     private IconCache mIconCache;
 
     /* Recycler view related member variables */
-    private RecyclerView mView;
+    private WidgetsRecyclerView mView;
     private WidgetsListAdapter mAdapter;
 
     /* Touch handling related member variables. */
@@ -102,7 +100,7 @@
 
     @Override
     protected void onFinishInflate() {
-        mView = (RecyclerView) findViewById(R.id.widgets_list_view);
+        mView = (WidgetsRecyclerView) findViewById(R.id.widgets_list_view);
         mView.setAdapter(mAdapter);
 
         // This extends the layout space so that preloading happen for the {@link RecyclerView}
@@ -186,18 +184,11 @@
             Log.e(TAG, "Unexpected dragging view: " + v);
         }
 
-        // We delay entering spring-loaded mode slightly to make sure the UI
-        // thread is free of any work.
-        postDelayed(new Runnable() {
-            @Override
-            public void run() {
-                // We don't enter spring-loaded mode if the drag has been cancelled
-                if (mLauncher.getDragController().isDragging()) {
-                    // Go into spring loaded mode (must happen before we startDrag())
-                    mLauncher.enterSpringLoadedDragMode();
-                }
-            }
-        }, SPRING_MODE_DELAY_MS);
+        // We don't enter spring-loaded mode if the drag has been cancelled
+        if (mLauncher.getDragController().isDragging()) {
+            // Go into spring loaded mode (must happen before we startDrag())
+            mLauncher.enterSpringLoadedDragMode();
+        }
 
         return true;
     }
@@ -360,6 +351,7 @@
      * Initialize the widget data model.
      */
     public void addWidgets(WidgetsModel model) {
+        mView.setWidgets(model);
         mAdapter.setWidgetsModel(model);
         mAdapter.notifyDataSetChanged();
     }
diff --git a/src/com/android/launcher3/widget/WidgetsListAdapter.java b/src/com/android/launcher3/widget/WidgetsListAdapter.java
index 7439a44..e82c0a6 100644
--- a/src/com/android/launcher3/widget/WidgetsListAdapter.java
+++ b/src/com/android/launcher3/widget/WidgetsListAdapter.java
@@ -32,7 +32,6 @@
 
 import com.android.launcher3.BubbleTextView;
 import com.android.launcher3.DeviceProfile;
-import com.android.launcher3.IconCache;
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherAppState;
 import com.android.launcher3.LauncherAppWidgetProviderInfo;
diff --git a/src/com/android/launcher3/widget/WidgetsRecyclerView.java b/src/com/android/launcher3/widget/WidgetsRecyclerView.java
index 31ef5d6..bef2559 100644
--- a/src/com/android/launcher3/widget/WidgetsRecyclerView.java
+++ b/src/com/android/launcher3/widget/WidgetsRecyclerView.java
@@ -17,14 +17,23 @@
 package com.android.launcher3.widget;
 
 import android.content.Context;
+import android.graphics.Rect;
+import android.graphics.drawable.Drawable;
+import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
+import android.view.MotionEvent;
+
 import com.android.launcher3.BaseRecyclerView;
+import com.android.launcher3.model.WidgetsModel;
 
 /**
  * The widgets recycler view.
  */
 public class WidgetsRecyclerView extends BaseRecyclerView {
 
+    private WidgetsModel mWidgets;
+    private Rect mBackgroundPadding = new Rect();
+
     public WidgetsRecyclerView(Context context) {
         this(context, null);
     }
@@ -37,4 +46,67 @@
         super(context, attrs, defStyleAttr);
     }
 
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+        addOnItemTouchListener(this);
+    }
+
+    public void updateBackgroundPadding(Drawable background) {
+        background.getPadding(mBackgroundPadding);
+    }
+
+    /**
+     * Sets the widget model in this view, used to determine the fast scroll position.
+     */
+    public void setWidgets(WidgetsModel widgets) {
+        mWidgets = widgets;
+    }
+
+    /**
+     * Maps the touch (from 0..1) to the adapter position that should be visible.
+     */
+    @Override
+    public String scrollToPositionAtProgress(float touchFraction) {
+        // Ensure that we have any sections
+        return "";
+    }
+
+    /**
+     * Updates the bounds for the scrollbar.
+     */
+    @Override
+    public void updateVerticalScrollbarBounds() {
+        int rowCount = mWidgets.getPackageSize();
+
+        // Skip early if there are no items.
+        if (rowCount == 0) {
+            verticalScrollbarBounds.setEmpty();
+            return;
+        }
+
+        int x, y;
+        getCurScrollState(scrollPosState);
+        if (scrollPosState.rowIndex < 0) {
+            verticalScrollbarBounds.setEmpty();
+        }
+        // TODO
+    }
+
+    /**
+     * Returns the current scroll state.
+     */
+    private void getCurScrollState(ScrollPositionState stateOut) {
+        stateOut.rowIndex = -1;
+        stateOut.rowTopOffset = -1;
+        stateOut.rowHeight = -1;
+
+        int rowCount = mWidgets.getPackageSize();
+
+        // Return early if there are no items
+        if (rowCount == 0) {
+            return;
+        }
+        // TODO
+    }
 }
\ No newline at end of file
diff --git a/tests/src/com/android/launcher3/InvariantDeviceProfileTest.java b/tests/src/com/android/launcher3/InvariantDeviceProfileTest.java
new file mode 100644
index 0000000..1bc7c11
--- /dev/null
+++ b/tests/src/com/android/launcher3/InvariantDeviceProfileTest.java
@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2015 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.launcher3;
+
+import android.graphics.PointF;
+import android.test.AndroidTestCase;
+import android.test.suitebuilder.annotation.SmallTest;
+import android.util.Log;
+
+import com.android.launcher3.DeviceProfile;
+import com.android.launcher3.InvariantDeviceProfile;
+import com.android.launcher3.util.FocusLogic;
+
+import java.util.ArrayList;
+
+/**
+ * Tests the {@link DeviceProfile} and {@link InvariantDeviceProfile}.
+ */
+@SmallTest
+public class InvariantDeviceProfileTest extends AndroidTestCase {
+
+    private static final String TAG = "DeviceProfileTest";
+    private static final boolean DEBUG = false;
+
+    private InvariantDeviceProfile mInvariantProfile;
+    private ArrayList<InvariantDeviceProfile> mPredefinedDeviceProfiles;
+
+    @Override
+    protected void setUp() throws Exception {
+        super.setUp();
+        mInvariantProfile = new InvariantDeviceProfile(getContext());
+        mPredefinedDeviceProfiles = mInvariantProfile.getPredefinedDeviceProfiles();
+    }
+
+    @Override
+    protected void tearDown() throws Exception {
+        // Nothing to tear down as this class only tests static methods.
+    }
+
+    public void testFindClosestDeviceProfile2() {
+        for (InvariantDeviceProfile idf: mPredefinedDeviceProfiles) {
+            ArrayList<InvariantDeviceProfile> closestProfiles =
+                    mInvariantProfile.findClosestDeviceProfiles(
+                            idf.minWidthDps, idf.minHeightDps, mPredefinedDeviceProfiles);
+            assertTrue(closestProfiles.get(0).equals(idf));
+        }
+    }
+
+    /**
+     * Used to print out how the invDistWeightedInterpolate works between device profiles to
+     * tweak the two constants that control how the interpolation curve is shaped.
+     */
+    public void testInvInterpolation() {
+
+        InvariantDeviceProfile p1 = mPredefinedDeviceProfiles.get(7); // e.g., Large Phone
+        InvariantDeviceProfile p2 = mPredefinedDeviceProfiles.get(8); // e.g., Nexus 7
+
+        ArrayList<PointF> pts = createInterpolatedPoints(
+                new PointF(p1.minWidthDps, p1.minHeightDps),
+                new PointF(p2.minWidthDps, p2.minHeightDps),
+                20f);
+
+        for (int i = 0; i < pts.size(); i++) {
+            ArrayList<InvariantDeviceProfile> closestProfiles =
+                    mInvariantProfile.findClosestDeviceProfiles(
+                            pts.get(i).x, pts.get(i).y, mPredefinedDeviceProfiles);
+            InvariantDeviceProfile result =
+                    mInvariantProfile.invDistWeightedInterpolate(
+                            pts.get(i).x, pts.get(i).y, closestProfiles);
+            if (DEBUG) {
+                Log.d(TAG, String.format("width x height = (%f, %f)] iconSize = %f",
+                        pts.get(i).x, pts.get(i).y, result.iconSize));
+            }
+        }
+    }
+
+    private ArrayList<PointF> createInterpolatedPoints(PointF a, PointF b, float numPts) {
+        ArrayList<PointF> result = new ArrayList<PointF>();
+        result.add(a);
+        for (float i = 1; i < numPts; i = i + 1.0f) {
+            result.add(new PointF((b.x * i +  a.x * (numPts - i)) / numPts,
+                    (b.y * i + a.y * (numPts - i)) / numPts));
+        }
+        result.add(b);
+        return result;
+    }
+
+    /**
+     * Ensures that system calls (e.g., WindowManager, DisplayMetrics) that require contexts are
+     * properly working to generate minimum width and height of the display.
+     */
+    public void test_hammerhead() {
+        if (!android.os.Build.DEVICE.equals("hammerhead")) {
+            return;
+        }
+        assertEquals(mInvariantProfile.numRows, 4);
+        assertEquals(mInvariantProfile.numColumns, 4);
+        assertEquals((int) mInvariantProfile.numHotseatIcons, 5);
+
+        DeviceProfile landscapeProfile = mInvariantProfile.landscapeProfile;
+        DeviceProfile portraitProfile = mInvariantProfile.portraitProfile;
+
+        assertEquals(portraitProfile.allAppsNumCols, 3);
+        assertEquals(landscapeProfile.allAppsNumCols, 5); // not used
+    }
+
+    // Add more tests for other devices, however, running them once on a single device is enough
+    // for verifying that for a platform version, the WindowManager and DisplayMetrics is
+    // working as intended.
+}