Adding an empty page in Recents view corresponding to workspace

The page is aligned to the workspace card and shows a widgets button
in the empty region

Change-Id: I479c47a2fbac4b3ef1aaf833d9fe82b5d7e10ddc
diff --git a/quickstep/res/drawable/bg_workspace_card_button.xml b/quickstep/res/drawable/bg_workspace_card_button.xml
new file mode 100644
index 0000000..3ba47bb
--- /dev/null
+++ b/quickstep/res/drawable/bg_workspace_card_button.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+/*
+**
+** Copyright 2017, 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.
+*/
+-->
+
+<ripple xmlns:android="http://schemas.android.com/apk/res/android"
+    android:color="?android:attr/colorControlHighlight">
+    <item android:id="@android:id/mask">
+        <color android:color="#ffffffff" />
+    </item>
+
+    <item>
+        <color android:color="#77FFFFFF" />
+    </item>
+</ripple>
diff --git a/quickstep/res/layout/overview_panel.xml b/quickstep/res/layout/overview_panel.xml
index 22f014a..78238fa 100644
--- a/quickstep/res/layout/overview_panel.xml
+++ b/quickstep/res/layout/overview_panel.xml
@@ -22,4 +22,36 @@
     android:clipChildren="false"
     android:clipToPadding="false"
     android:alpha="0.0"
-    android:visibility="invisible" />
\ No newline at end of file
+    android:visibility="invisible" >
+
+    <com.android.launcher3.uioverrides.WorkspaceCard
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:paddingTop="@dimen/task_thumbnail_top_margin" >
+
+        <View
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:id="@+id/workspace_click_target" />
+
+        <FrameLayout
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:id="@+id/widget_button"
+            android:background="@drawable/bg_workspace_card_button" >
+
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:text="@string/widget_button_text"
+                android:drawableStart="@drawable/ic_widget"
+                android:textColor="?attr/workspaceTextColor"
+                android:drawableTint="?attr/workspaceTextColor"
+                android:gravity="center"
+                android:layout_gravity="center"
+                android:drawablePadding="20dp" />
+        </FrameLayout>
+
+    </com.android.launcher3.uioverrides.WorkspaceCard>
+
+</com.android.quickstep.RecentsView>
\ No newline at end of file
diff --git a/quickstep/src/com/android/launcher3/uioverrides/OverviewState.java b/quickstep/src/com/android/launcher3/uioverrides/OverviewState.java
index 267c4d0..f34aa85 100644
--- a/quickstep/src/com/android/launcher3/uioverrides/OverviewState.java
+++ b/quickstep/src/com/android/launcher3/uioverrides/OverviewState.java
@@ -22,6 +22,7 @@
 
 import com.android.launcher3.Launcher;
 import com.android.launcher3.LauncherState;
+import com.android.launcher3.Utilities;
 import com.android.launcher3.Workspace;
 import com.android.launcher3.userevent.nano.LauncherLogProto.ContainerType;
 import com.android.quickstep.RecentsView;
@@ -31,8 +32,9 @@
  */
 public class OverviewState extends LauncherState {
 
-    private static final int STATE_FLAGS = FLAG_SHOW_SCRIM
-            | FLAG_WORKSPACE_ICONS_CAN_BE_DRAGGED;
+    public static final float WORKSPACE_SCALE_ON_SCROLL = 0.9f;
+
+    private static final int STATE_FLAGS = FLAG_SHOW_SCRIM | FLAG_WORKSPACE_ICONS_CAN_BE_DRAGGED;
 
     public OverviewState(int id) {
         super(id, ContainerType.WORKSPACE, OVERVIEW_TRANSITION_MS, 1f, STATE_FLAGS);
@@ -42,18 +44,15 @@
     public float[] getWorkspaceScaleAndTranslation(Launcher launcher) {
         Rect pageRect = new Rect();
         RecentsView.getPageRect(launcher, pageRect);
-        Workspace ws = launcher.getWorkspace();
-        float childWidth = ws.getNormalChildWidth();
-        if (childWidth <= 0 || pageRect.isEmpty()) {
+        if (launcher.getWorkspace().getNormalChildWidth() <= 0 || pageRect.isEmpty()) {
             return super.getWorkspaceScaleAndTranslation(launcher);
         }
 
-        Rect insets = launcher.getDragLayer().getInsets();
-        float scale = pageRect.width() / childWidth;
-
-        float halfHeight = ws.getHeight() / 2;
-        float childTop = halfHeight - scale * (halfHeight - ws.getPaddingTop() - insets.top);
-        return new float[] {scale, pageRect.top - childTop};
+        RecentsView rv = launcher.getOverviewPanel();
+        if (rv.getCurrentPage() >= rv.getFirstTaskIndex()) {
+            Utilities.scaleRectAboutCenter(pageRect, WORKSPACE_SCALE_ON_SCROLL);
+        }
+        return getScaleAndTranslationForPageRect(launcher, pageRect);
     }
 
     @Override
@@ -77,4 +76,16 @@
     public View getFinalFocus(Launcher launcher) {
         return launcher.getOverviewPanel();
     }
+
+    public static float[] getScaleAndTranslationForPageRect(Launcher launcher, Rect pageRect) {
+        Workspace ws = launcher.getWorkspace();
+        float childWidth = ws.getNormalChildWidth();
+
+        Rect insets = launcher.getDragLayer().getInsets();
+        float scale = pageRect.width() / childWidth;
+
+        float halfHeight = ws.getHeight() / 2;
+        float childTop = halfHeight - scale * (halfHeight - ws.getPaddingTop() - insets.top);
+        return new float[] {scale, pageRect.top - childTop};
+    }
 }
diff --git a/quickstep/src/com/android/launcher3/uioverrides/RecentsViewStateController.java b/quickstep/src/com/android/launcher3/uioverrides/RecentsViewStateController.java
index 60cd0c2..1f6ffe9 100644
--- a/quickstep/src/com/android/launcher3/uioverrides/RecentsViewStateController.java
+++ b/quickstep/src/com/android/launcher3/uioverrides/RecentsViewStateController.java
@@ -30,10 +30,13 @@
 import com.android.quickstep.AnimatedFloat;
 import com.android.quickstep.RecentsView;
 
+import static com.android.launcher3.LauncherState.OVERVIEW;
+
 public class RecentsViewStateController implements StateHandler {
 
     private final Launcher mLauncher;
     private final RecentsView mRecentsView;
+    private final WorkspaceCard mWorkspaceCard;
 
     private final AnimatedFloat mTransitionProgress = new AnimatedFloat(this::applyProgress);
     // The fraction representing the visibility of the RecentsView. This allows delaying the
@@ -44,24 +47,40 @@
         mLauncher = launcher;
         mRecentsView = launcher.getOverviewPanel();
         mRecentsView.setStateController(this);
+
+        mWorkspaceCard = (WorkspaceCard) mRecentsView.getChildAt(0);
+        mWorkspaceCard.setup(launcher);
     }
 
     @Override
     public void setState(LauncherState state) {
-        setVisibility(state == LauncherState.OVERVIEW);
-        setTransitionProgress(state == LauncherState.OVERVIEW ? 1 : 0);
+        mWorkspaceCard.setWorkspaceScrollingEnabled(state == OVERVIEW);
+        setVisibility(state == OVERVIEW);
+        setTransitionProgress(state == OVERVIEW ? 1 : 0);
     }
 
     @Override
-    public void setStateWithAnimation(LauncherState toState,
+    public void setStateWithAnimation(final LauncherState toState,
             AnimatorSetBuilder builder, AnimationConfig config) {
         ObjectAnimator progressAnim =
-                mTransitionProgress.animateToValue(toState == LauncherState.OVERVIEW ? 1 : 0);
+                mTransitionProgress.animateToValue(toState == OVERVIEW ? 1 : 0);
         progressAnim.setDuration(config.duration);
         progressAnim.setInterpolator(Interpolators.LINEAR);
+        progressAnim.addListener(new AnimationSuccessListener() {
+
+            @Override
+            public void onAnimationStart(Animator animation) {
+                mWorkspaceCard.setWorkspaceScrollingEnabled(false);
+            }
+
+            @Override
+            public void onAnimationSuccess(Animator animator) {
+                mWorkspaceCard.setWorkspaceScrollingEnabled(toState == OVERVIEW);
+            }
+        });
         builder.play(progressAnim);
 
-        ObjectAnimator visibilityAnim = animateVisibility(toState == LauncherState.OVERVIEW);
+        ObjectAnimator visibilityAnim = animateVisibility(toState == OVERVIEW);
         visibilityAnim.setDuration(config.duration);
         visibilityAnim.setInterpolator(Interpolators.LINEAR);
         builder.play(visibilityAnim);
diff --git a/quickstep/src/com/android/launcher3/uioverrides/WorkspaceCard.java b/quickstep/src/com/android/launcher3/uioverrides/WorkspaceCard.java
new file mode 100644
index 0000000..990d286
--- /dev/null
+++ b/quickstep/src/com/android/launcher3/uioverrides/WorkspaceCard.java
@@ -0,0 +1,186 @@
+/*
+ * Copyright (C) 2017 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.uioverrides;
+
+import static com.android.launcher3.LauncherState.NORMAL;
+import static com.android.launcher3.uioverrides.OverviewState.WORKSPACE_SCALE_ON_SCROLL;
+import static com.android.quickstep.RecentsView.SCROLL_TYPE_WORKSPACE;
+
+import android.animation.FloatArrayEvaluator;
+import android.content.Context;
+import android.graphics.Rect;
+import android.util.AttributeSet;
+import android.view.View;
+import android.view.View.OnClickListener;
+import android.widget.FrameLayout;
+
+import com.android.launcher3.Launcher;
+import com.android.launcher3.R;
+import com.android.launcher3.Utilities;
+import com.android.launcher3.Workspace;
+import com.android.launcher3.widget.WidgetsFullSheet;
+import com.android.quickstep.RecentsView;
+import com.android.quickstep.RecentsView.PageCallbacks;
+import com.android.quickstep.RecentsView.ScrollState;
+
+public class WorkspaceCard extends FrameLayout implements PageCallbacks, OnClickListener {
+
+    private final Rect mTempRect = new Rect();
+    private final float[] mEvaluatedFloats = new float[2];
+    private final FloatArrayEvaluator mEvaluator = new FloatArrayEvaluator(mEvaluatedFloats);
+
+    // UI related information
+    private float[] mScaleAndTranslatePage0, mScaleAndTranslatePage1;
+    private boolean mUIDataValid = false;
+
+    private Launcher mLauncher;
+    private Workspace mWorkspace;
+
+    private boolean mIsWorkspaceScrollingEnabled;
+
+    private View mWorkspaceClickTarget;
+    private View mWidgetsButton;
+
+    public WorkspaceCard(Context context) {
+        super(context);
+    }
+
+    public WorkspaceCard(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public WorkspaceCard(Context context, AttributeSet attrs, int defStyleAttr) {
+        super(context, attrs, defStyleAttr);
+    }
+
+    @Override
+    protected void onFinishInflate() {
+        super.onFinishInflate();
+
+        mWorkspaceClickTarget = findViewById(R.id.workspace_click_target);
+        mWidgetsButton = findViewById(R.id.widget_button);
+
+        mWorkspaceClickTarget.setOnClickListener(this);
+        mWidgetsButton.setOnClickListener(this);
+    }
+
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        // We measure the dimensions of the PagedView to be larger than the pages so that when we
+        // zoom out (and scale down), the view is still contained in the parent
+        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
+        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
+        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
+        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
+
+        if (widthMode == MeasureSpec.UNSPECIFIED || heightMode == MeasureSpec.UNSPECIFIED) {
+            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+            return;
+        }
+
+        // Return early if we aren't given a proper dimension
+        if (widthSize <= 0 || heightSize <= 0) {
+            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+            return;
+        }
+
+        int childWidthSpec = MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.EXACTLY);
+
+        int pageHeight = mWorkspace.getNormalChildHeight() * widthSize /
+                mWorkspace.getNormalChildWidth();
+        mWorkspaceClickTarget.measure(childWidthSpec,
+                MeasureSpec.makeMeasureSpec(pageHeight, MeasureSpec.EXACTLY));
+
+        int buttonHeight = heightSize - pageHeight - getPaddingTop() - getPaddingBottom();
+        mWidgetsButton.measure(childWidthSpec,
+                MeasureSpec.makeMeasureSpec(buttonHeight, MeasureSpec.EXACTLY));
+
+        setMeasuredDimension(widthSize, heightSize);
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+        int y1 = getPaddingTop();
+        int y2 = y1 + mWorkspaceClickTarget.getMeasuredHeight();
+
+        mWorkspaceClickTarget.layout(getPaddingLeft(), y1,
+                mWorkspaceClickTarget.getMeasuredWidth(), y2);
+
+        mWidgetsButton.layout(getPaddingLeft(), y2, mWidgetsButton.getMeasuredWidth(),
+                mWidgetsButton.getMeasuredHeight() + y2);
+
+        mUIDataValid = false;
+    }
+
+    @Override
+    public void onClick(View view) {
+        if (view == mWorkspaceClickTarget) {
+            mLauncher.getStateManager().goToState(NORMAL);
+        } else if (view == mWidgetsButton) {
+            WidgetsFullSheet.show(mLauncher, true);
+        }
+    }
+
+    @Override
+    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
+        super.onSizeChanged(w, h, oldw, oldh);
+        mUIDataValid = false;
+    }
+
+    public void setup(Launcher launcher) {
+        mLauncher = launcher;
+        mWorkspace = mLauncher.getWorkspace();
+    }
+
+    public void setWorkspaceScrollingEnabled(boolean isEnabled) {
+        mIsWorkspaceScrollingEnabled = isEnabled;
+    }
+
+    @Override
+    public int onPageScroll(ScrollState scrollState) {
+        setTranslationX(scrollState.distanceFromScreenCenter);
+
+        float factor = scrollState.linearInterpolation;
+        float scale = factor * WORKSPACE_SCALE_ON_SCROLL + (1 - factor);
+        setScaleX(scale);
+        setScaleY(scale);
+
+        if (mIsWorkspaceScrollingEnabled) {
+            initUiData();
+
+            mEvaluator.evaluate(factor, mScaleAndTranslatePage0, mScaleAndTranslatePage1);
+            mWorkspace.setScaleX(mEvaluatedFloats[0]);
+            mWorkspace.setScaleY(mEvaluatedFloats[0]);
+            mWorkspace.setTranslationY(mEvaluatedFloats[1]);
+        }
+        return SCROLL_TYPE_WORKSPACE;
+    }
+
+    private void initUiData() {
+        if (mUIDataValid && mScaleAndTranslatePage0 != null) {
+            return;
+        }
+
+        RecentsView.getPageRect(mLauncher, mTempRect);
+        mScaleAndTranslatePage0 = OverviewState
+                .getScaleAndTranslationForPageRect(mLauncher, mTempRect);
+        Rect scaledDown = new Rect(mTempRect);
+        Utilities.scaleRectAboutCenter(scaledDown, WORKSPACE_SCALE_ON_SCROLL);
+        mScaleAndTranslatePage1 = OverviewState
+                .getScaleAndTranslationForPageRect(mLauncher, scaledDown);
+        mUIDataValid = true;
+    }
+}
diff --git a/quickstep/src/com/android/quickstep/NavBarSwipeInteractionHandler.java b/quickstep/src/com/android/quickstep/NavBarSwipeInteractionHandler.java
index 43a01a7..095b445 100644
--- a/quickstep/src/com/android/quickstep/NavBarSwipeInteractionHandler.java
+++ b/quickstep/src/com/android/quickstep/NavBarSwipeInteractionHandler.java
@@ -250,6 +250,7 @@
 
     private void setTaskPlanToUi() {
         mRecentsView.update(mLoadPlan);
+        mRecentsView.initToPage(mRecentsView.getFirstTaskIndex());
         ObjectAnimator anim = mStateController.animateVisibility(true /* isVisible */)
                 .setDuration(RECENTS_VIEW_VISIBILITY_DURATION);
         anim.addListener(new AnimationSuccessListener() {
diff --git a/quickstep/src/com/android/quickstep/RecentsView.java b/quickstep/src/com/android/quickstep/RecentsView.java
index fd9010d..6161858 100644
--- a/quickstep/src/com/android/quickstep/RecentsView.java
+++ b/quickstep/src/com/android/quickstep/RecentsView.java
@@ -17,7 +17,6 @@
 package com.android.quickstep;
 
 import android.animation.LayoutTransition;
-import android.animation.TimeInterpolator;
 import android.content.Context;
 import android.graphics.Rect;
 import android.util.AttributeSet;
@@ -47,17 +46,11 @@
  */
 public class RecentsView extends PagedView {
 
-    /** Designates how "curvy" the carousel is from 0 to 1, where 0 is a straight line. */
-    private static final float CURVE_FACTOR = 0.25f;
-    /** A circular curve of x from 0 to 1, where 0 is the center of the screen and 1 is the edge. */
-    private static final TimeInterpolator CURVE_INTERPOLATOR
-        = x -> (float) (1 - Math.sqrt(1 - Math.pow(x, 2)));
-    /**
-     * The alpha of a black scrim on a page in the carousel as it leaves the screen.
-     * In the resting position of the carousel, the adjacent pages have about half this scrim.
-     */
-    private static final float MAX_PAGE_SCRIM_ALPHA = 0.8f;
+    public static final int SCROLL_TYPE_NONE = 0;
+    public static final int SCROLL_TYPE_TASK = 1;
+    public static final int SCROLL_TYPE_WORKSPACE = 2;
 
+    private final ScrollState mScrollState = new ScrollState();
     private boolean mOverviewStateEnabled;
     private boolean mTaskStackListenerRegistered;
     private LayoutTransition mLayoutTransition;
@@ -65,7 +58,7 @@
     private TaskStackChangeListener mTaskStackListener = new TaskStackChangeListener() {
         @Override
         public void onTaskSnapshotChanged(int taskId, ThumbnailData snapshot) {
-            for (int i = 0; i < getChildCount(); i++) {
+            for (int i = mFirstTaskIndex; i < getChildCount(); i++) {
                 final TaskView taskView = (TaskView) getChildAt(i);
                 if (taskView.getTask().key.id == taskId) {
                     taskView.getThumbnail().setThumbnail(snapshot);
@@ -76,6 +69,7 @@
     };
 
     private RecentsViewStateController mStateController;
+    private int mFirstTaskIndex;
 
     public RecentsView(Context context) {
         this(context, null);
@@ -87,10 +81,12 @@
 
     public RecentsView(Context context, AttributeSet attrs, int defStyleAttr) {
         super(context, attrs, defStyleAttr);
-        setWillNotDraw(false);
-        setPageSpacing((int) getResources().getDimension(R.dimen.recents_page_spacing));
+        setPageSpacing(getResources().getDimensionPixelSize(R.dimen.recents_page_spacing));
         enableFreeScroll(true);
+        setClipChildren(true);
         setupLayoutTransition();
+
+        mScrollState.isRtl = mIsRtl;
     }
 
     private void setupLayoutTransition() {
@@ -110,6 +106,8 @@
 
         Rect padding = getPadding(Launcher.getLauncher(getContext()));
         setPadding(padding.left, padding.top, padding.right, padding.bottom);
+
+        mFirstTaskIndex = getPageCount();
     }
 
     @Override
@@ -130,6 +128,10 @@
         updateTaskStackListenerState();
     }
 
+    public int getFirstTaskIndex() {
+        return mFirstTaskIndex;
+    }
+
     public void setStateController(RecentsViewStateController stateController) {
         mStateController = stateController;
     }
@@ -145,10 +147,6 @@
 
     public void update(RecentsTaskLoadPlan loadPlan) {
         final RecentsTaskLoader loader = TouchInteractionService.getRecentsTaskLoader();
-        setCurrentPage(0);
-        if (getPageAt(mCurrentPage) instanceof TaskView) {
-            ((TaskView) getPageAt(mCurrentPage)).setIconScale(0);
-        }
         TaskStack stack = loadPlan != null ? loadPlan.getTaskStack() : null;
         if (stack == null) {
             removeAllViews();
@@ -160,11 +158,13 @@
         final LayoutInflater inflater = LayoutInflater.from(getContext());
         final ArrayList<Task> tasks = stack.getTasks();
         setLayoutTransition(null);
-        for (int i = getChildCount(); i < tasks.size(); i++) {
+        int requiredChildCount = tasks.size() + mFirstTaskIndex;
+
+        for (int i = getChildCount(); i < requiredChildCount; i++) {
             final TaskView taskView = (TaskView) inflater.inflate(R.layout.task, this, false);
             addView(taskView);
         }
-        while (getChildCount() > tasks.size()) {
+        while (getChildCount() > requiredChildCount) {
             final TaskView taskView = (TaskView) getChildAt(getChildCount() - 1);
             removeView(taskView);
             loader.unloadTaskData(taskView.getTask());
@@ -174,14 +174,21 @@
         // Rebind all task views
         for (int i = tasks.size() - 1; i >= 0; i--) {
             final Task task = tasks.get(i);
-            final TaskView taskView = (TaskView) getChildAt(tasks.size() - i - 1);
+            final TaskView taskView = (TaskView) getChildAt(tasks.size() - i - 1 + mFirstTaskIndex);
             taskView.bind(task);
             loader.loadTaskData(task);
         }
     }
 
+    public void initToPage(int pageNo) {
+        setCurrentPage(pageNo);
+        if (getPageAt(mCurrentPage) instanceof TaskView) {
+            ((TaskView) getPageAt(mCurrentPage)).setIconScale(0);
+        }
+    }
+
     public void launchTaskWithId(int taskId) {
-        for (int i = 0; i < getChildCount(); i++) {
+        for (int i = mFirstTaskIndex; i < getChildCount(); i++) {
             final TaskView taskView = (TaskView) getChildAt(i);
             if (taskView.getTask().key.id == taskId) {
                 taskView.launchTask(false /* animate */);
@@ -245,35 +252,50 @@
         }
         final int halfScreenWidth = getMeasuredWidth() / 2;
         final int screenCenter = halfScreenWidth + getScrollX();
-        final int pageSpacing = getResources().getDimensionPixelSize(R.dimen.recents_page_spacing);
+        final int pageSpacing = mPageSpacing;
+        final int halfPageWidth = mScrollState.halfPageWidth = getNormalChildWidth() / 2;
+        mScrollState.lastScrollType = SCROLL_TYPE_NONE;
+
         final int pageCount = getPageCount();
         for (int i = 0; i < pageCount; i++) {
             View page = getPageAt(i);
-            int pageWidth = page.getMeasuredWidth();
-            int halfPageWidth = pageWidth / 2;
             int pageCenter = page.getLeft() + halfPageWidth;
-            float distanceFromScreenCenter = Math.abs(pageCenter - screenCenter);
+            mScrollState.distanceFromScreenCenter = screenCenter - pageCenter;
             float distanceToReachEdge = halfScreenWidth + halfPageWidth + pageSpacing;
-            float linearInterpolation = Math.min(1, distanceFromScreenCenter / distanceToReachEdge);
-            float curveInterpolation = CURVE_INTERPOLATOR.getInterpolation(linearInterpolation);
-            float scale = 1 - curveInterpolation * CURVE_FACTOR;
-            page.setScaleX(scale);
-            page.setScaleY(scale);
-            // Make sure the biggest card (i.e. the one in front) shows on top of the adjacent ones.
-            page.setTranslationZ(scale);
-            page.setTranslationX((screenCenter - pageCenter) * curveInterpolation * CURVE_FACTOR);
-            if (page instanceof TaskView) {
-                TaskThumbnailView thumbnail = ((TaskView) page).getThumbnail();
-                thumbnail.setDimAlpha(1 - curveInterpolation * MAX_PAGE_SCRIM_ALPHA);
-            }
+            mScrollState.linearInterpolation = Math.min(1,
+                    Math.abs(mScrollState.distanceFromScreenCenter) / distanceToReachEdge);
+            mScrollState.lastScrollType = ((PageCallbacks) page).onPageScroll(mScrollState);
         }
     }
 
     public void onTaskDismissed(TaskView taskView) {
         ActivityManagerWrapper.getInstance().removeTask(taskView.getTask().key.id);
         removeView(taskView);
-        if (getChildCount() == 0) {
+        if (getChildCount() == mFirstTaskIndex) {
             Launcher.getLauncher(getContext()).getStateManager().goToState(LauncherState.NORMAL);
         }
     }
+
+    public interface PageCallbacks {
+
+        /**
+         * Updates the page UI based on scroll params and returns the type of scroll
+         * effect performed.
+         *
+         * @see #SCROLL_TYPE_NONE
+         * @see #SCROLL_TYPE_TASK
+         * @see #SCROLL_TYPE_WORKSPACE
+         */
+        int onPageScroll(ScrollState scrollState);
+    }
+
+    public static class ScrollState {
+
+        public boolean isRtl;
+        public int lastScrollType;
+
+        public int halfPageWidth;
+        public float distanceFromScreenCenter;
+        public float linearInterpolation;
+    }
 }
diff --git a/quickstep/src/com/android/quickstep/TaskView.java b/quickstep/src/com/android/quickstep/TaskView.java
index d834881..6b37ada 100644
--- a/quickstep/src/com/android/quickstep/TaskView.java
+++ b/quickstep/src/com/android/quickstep/TaskView.java
@@ -16,9 +16,13 @@
 
 package com.android.quickstep;
 
+import static com.android.quickstep.RecentsView.SCROLL_TYPE_TASK;
+import static com.android.quickstep.RecentsView.SCROLL_TYPE_WORKSPACE;
+
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
+import android.animation.TimeInterpolator;
 import android.animation.ValueAnimator;
 import android.app.ActivityOptions;
 import android.content.Context;
@@ -35,6 +39,8 @@
 import com.android.launcher3.Utilities;
 import com.android.launcher3.anim.Interpolators;
 import com.android.launcher3.touch.SwipeDetector;
+import com.android.quickstep.RecentsView.PageCallbacks;
+import com.android.quickstep.RecentsView.ScrollState;
 import com.android.systemui.shared.recents.model.Task;
 import com.android.systemui.shared.recents.model.Task.TaskCallbacks;
 import com.android.systemui.shared.recents.model.ThumbnailData;
@@ -49,7 +55,20 @@
 /**
  * A task in the Recents view.
  */
-public class TaskView extends FrameLayout implements TaskCallbacks, SwipeDetector.Listener {
+public class TaskView extends FrameLayout implements TaskCallbacks, SwipeDetector.Listener,
+        PageCallbacks {
+
+    /** Designates how "curvy" the carousel is from 0 to 1, where 0 is a straight line. */
+    private static final float CURVE_FACTOR = 0.25f;
+    /** A circular curve of x from 0 to 1, where 0 is the center of the screen and 1 is the edge. */
+    private static final TimeInterpolator CURVE_INTERPOLATOR
+            = x -> (float) (1 - Math.sqrt(1 - Math.pow(x, 2)));
+
+    /**
+     * The alpha of a black scrim on a page in the carousel as it leaves the screen.
+     * In the resting position of the carousel, the adjacent pages have about half this scrim.
+     */
+    private static final float MAX_PAGE_SCRIM_ALPHA = 0.8f;
 
     private static final int SWIPE_DIRECTIONS = SwipeDetector.DIRECTION_POSITIVE;
 
@@ -288,4 +307,35 @@
             mIconView.setScaleY(mIconScale);
         }
     }
+
+    @Override
+    public int onPageScroll(ScrollState scrollState) {
+        float curveInterpolation =
+                CURVE_INTERPOLATOR.getInterpolation(scrollState.linearInterpolation);
+        float scale = 1 - curveInterpolation * CURVE_FACTOR;
+        setScaleX(scale);
+        setScaleY(scale);
+
+        // Make sure the biggest card (i.e. the one in front) shows on top of the adjacent ones.
+        setTranslationZ(scale);
+
+        mSnapshotView.setDimAlpha(1 - curveInterpolation * MAX_PAGE_SCRIM_ALPHA);
+
+        float translation =
+                scrollState.distanceFromScreenCenter * curveInterpolation * CURVE_FACTOR;
+        setTranslationX(translation);
+
+        if (scrollState.lastScrollType == SCROLL_TYPE_WORKSPACE) {
+            // Make sure that the task cards do not overlap with the workspace card
+            float min = scrollState.halfPageWidth * (1 - scale);
+            if (scrollState.isRtl) {
+                setTranslationX(Math.min(translation, min));
+            } else {
+                setTranslationX(Math.max(translation, -min));
+            }
+        } else {
+            setTranslationX(translation);
+        }
+        return SCROLL_TYPE_TASK;
+    }
 }
diff --git a/res/layout-land/launcher.xml b/res/layout-land/launcher.xml
index f6bdd25..0a4fec1 100644
--- a/res/layout-land/launcher.xml
+++ b/res/layout-land/launcher.xml
@@ -50,6 +50,10 @@
             android:layout_gravity="bottom|left"
             android:background="@drawable/all_apps_handle_landscape" />
 
+        <include layout="@layout/overview_panel"
+            android:id="@+id/overview_panel"
+            android:visibility="gone" />
+
         <com.android.launcher3.views.AllAppsScrim
             android:layout_width="match_parent"
             android:layout_height="match_parent"
@@ -68,10 +72,6 @@
             android:id="@+id/drop_target_bar"
             layout="@layout/drop_target_bar_vert" />
 
-        <include layout="@layout/overview_panel"
-            android:id="@+id/overview_panel"
-            android:visibility="gone" />
-
         <include layout="@layout/all_apps"
             android:id="@+id/apps_view"
             android:layout_width="match_parent"
diff --git a/res/layout-port/launcher.xml b/res/layout-port/launcher.xml
index 5d670e6..33b350a 100644
--- a/res/layout-port/launcher.xml
+++ b/res/layout-port/launcher.xml
@@ -44,6 +44,10 @@
             launcher:pageIndicator="@+id/page_indicator">
         </com.android.launcher3.Workspace>
 
+        <include layout="@layout/overview_panel"
+            android:id="@+id/overview_panel"
+            android:visibility="gone" />
+
         <com.android.launcher3.views.AllAppsScrim
             android:layout_width="match_parent"
             android:layout_height="match_parent"
@@ -57,10 +61,6 @@
             android:layout_height="match_parent"
             launcher:layout_ignoreInsets="true" />
 
-        <include layout="@layout/overview_panel"
-            android:id="@+id/overview_panel"
-            android:visibility="gone" />
-
         <!-- Keep these behind the workspace so that they are not visible when
              we go into AllApps -->
         <include layout="@layout/page_indicator"
diff --git a/res/layout-sw720dp/launcher.xml b/res/layout-sw720dp/launcher.xml
index 483fb96..d7e931a 100644
--- a/res/layout-sw720dp/launcher.xml
+++ b/res/layout-sw720dp/launcher.xml
@@ -43,6 +43,10 @@
             launcher:pageIndicator="@id/page_indicator">
         </com.android.launcher3.Workspace>
 
+        <include layout="@layout/overview_panel"
+            android:id="@+id/overview_panel"
+            android:visibility="gone" />
+
         <com.android.launcher3.views.AllAppsScrim
             android:layout_width="match_parent"
             android:layout_height="match_parent"
@@ -60,10 +64,6 @@
             android:id="@+id/drop_target_bar"
             layout="@layout/drop_target_bar_horz" />
 
-        <include layout="@layout/overview_panel"
-            android:id="@+id/overview_panel"
-            android:visibility="gone" />
-
         <!-- Keep these behind the workspace so that they are not visible when
              we go into AllApps -->
         <include layout="@layout/page_indicator"
diff --git a/res/layout/gradient_bg.xml b/res/layout/widgets_bottom_sheet_scrim.xml
similarity index 100%
rename from res/layout/gradient_bg.xml
rename to res/layout/widgets_bottom_sheet_scrim.xml
diff --git a/src/com/android/launcher3/CellLayout.java b/src/com/android/launcher3/CellLayout.java
index 79a34a0..01b6ca9 100644
--- a/src/com/android/launcher3/CellLayout.java
+++ b/src/com/android/launcher3/CellLayout.java
@@ -106,7 +106,7 @@
     final PreviewBackground mFolderLeaveBehind = new PreviewBackground();
 
     private static final int[] BACKGROUND_STATE_ACTIVE = new int[] { android.R.attr.state_active };
-    private static final int[] BACKGROUND_STATE_DEFAULT = new int[0];
+    private static final int[] BACKGROUND_STATE_DEFAULT = EMPTY_STATE_SET;
     private final Drawable mBackground;
 
     // These values allow a fixed measurement to be set on the CellLayout.
diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index d6b5656..5ed722c 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -106,7 +106,7 @@
     protected LauncherScroller mScroller;
     private Interpolator mDefaultInterpolator;
     private VelocityTracker mVelocityTracker;
-    @Thunk int mPageSpacing = 0;
+    protected int mPageSpacing = 0;
 
     private float mParentDownMotionX;
     private float mParentDownMotionY;
diff --git a/src/com/android/launcher3/views/AllAppsScrim.java b/src/com/android/launcher3/views/AllAppsScrim.java
index 1ada251..d1354ad 100644
--- a/src/com/android/launcher3/views/AllAppsScrim.java
+++ b/src/com/android/launcher3/views/AllAppsScrim.java
@@ -20,8 +20,6 @@
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
-import android.graphics.Rect;
-import android.graphics.RectF;
 import android.support.v4.graphics.ColorUtils;
 import android.util.AttributeSet;
 import android.view.View;
@@ -41,7 +39,7 @@
     private static final int MIN_ALPHA_PORTRAIT = 100;
     private static final int MIN_ALPHA_LANDSCAPE = MAX_ALPHA;
 
-    private final WallpaperColorInfo mWallpaperColorInfo;
+    protected final WallpaperColorInfo mWallpaperColorInfo;
     private final Paint mFillPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
 
     private final float mRadius;
diff --git a/src/com/android/launcher3/widget/WidgetsBottomSheet.java b/src/com/android/launcher3/widget/WidgetsBottomSheet.java
index 7fa5ff0..6a9013d 100644
--- a/src/com/android/launcher3/widget/WidgetsBottomSheet.java
+++ b/src/com/android/launcher3/widget/WidgetsBottomSheet.java
@@ -57,7 +57,7 @@
         mInsets = new Rect();
 
         mGradientView = (GradientView) mLauncher.getLayoutInflater().inflate(
-                R.layout.gradient_bg, mLauncher.getDragLayer(), false);
+                R.layout.widgets_bottom_sheet_scrim, mLauncher.getDragLayer(), false);
         mGradientView.setProgress(1, false);
         mContent = this;
     }