Animate context popup menu around origin point

Also enables the context popup menu enter transition.

Bug: 25801140
Change-Id: Id7fb384e8ac8974189b32a052352bd2f6cbb176e
diff --git a/core/java/android/widget/ListPopupWindow.java b/core/java/android/widget/ListPopupWindow.java
index 595adc2..dcadb6a 100644
--- a/core/java/android/widget/ListPopupWindow.java
+++ b/core/java/android/widget/ListPopupWindow.java
@@ -74,6 +74,7 @@
     private int mDropDownVerticalOffset;
     private int mDropDownWindowLayoutType = WindowManager.LayoutParams.TYPE_APPLICATION_SUB_PANEL;
     private boolean mDropDownVerticalOffsetSet;
+    private boolean mIsAnimatedFromAnchor = true;
 
     private int mDropDownGravity = Gravity.NO_GRAVITY;
 
@@ -101,7 +102,13 @@
 
     private final Handler mHandler;
 
-    private Rect mTempRect = new Rect();
+    private final Rect mTempRect = new Rect();
+
+    /**
+     * Optional anchor-relative bounds to be used as the transition epicenter.
+     * When {@code null}, the anchor bounds are used as the epicenter.
+     */
+    private Rect mEpicenterBounds;
 
     private boolean mModal;
 
@@ -452,6 +459,17 @@
     }
 
     /**
+     * Specifies the anchor-relative bounds of the popup's transition
+     * epicenter.
+     *
+     * @param bounds anchor-relative bounds
+     * @hide
+     */
+    public void setEpicenterBounds(Rect bounds) {
+        mEpicenterBounds = bounds;
+    }
+
+    /**
      * Set the gravity of the dropdown list. This is commonly used to
      * set gravity to START or END for alignment with the anchor.
      *
@@ -649,6 +667,7 @@
             // only set this if the dropdown is not always visible
             mPopup.setOutsideTouchable(!mForceIgnoreOutsideTouch && !mDropDownAlwaysVisible);
             mPopup.setTouchInterceptor(mTouchInterceptor);
+            mPopup.setEpicenterBounds(mEpicenterBounds);
             mPopup.showAsDropDown(getAnchorView(), mDropDownHorizontalOffset,
                     mDropDownVerticalOffset, mDropDownGravity);
             mDropDownList.setSelection(ListView.INVALID_POSITION);
diff --git a/core/java/android/widget/PopupWindow.java b/core/java/android/widget/PopupWindow.java
index 7e98193..584df08 100644
--- a/core/java/android/widget/PopupWindow.java
+++ b/core/java/android/widget/PopupWindow.java
@@ -150,6 +150,7 @@
 
     private Transition mEnterTransition;
     private Transition mExitTransition;
+    private Rect mEpicenterBounds;
 
     private boolean mAboveAnchor;
     private int mWindowLayoutType = WindowManager.LayoutParams.TYPE_APPLICATION_PANEL;
@@ -345,6 +346,25 @@
         mExitTransition = exitTransition;
     }
 
+    /**
+     * Sets the bounds used as the epicenter of the enter and exit transitions.
+     * <p>
+     * Transitions use a point or Rect, referred to as the epicenter, to orient
+     * the direction of travel. For popup windows, the anchor view bounds are
+     * used as the default epicenter.
+     * <p>
+     * See {@link Transition#setEpicenterCallback(EpicenterCallback)} for more
+     * information about how transition epicenters.
+     *
+     * @param bounds the epicenter bounds relative to the anchor view, or
+     *               {@code null} to use the default epicenter
+     * @see #getTransitionEpicenter()
+     * @hide
+     */
+    public void setEpicenterBounds(Rect bounds) {
+        mEpicenterBounds = bounds;
+    }
+
     private Transition getTransition(int resId) {
         if (resId != 0 && resId != R.transition.no_transition) {
             final TransitionInflater inflater = TransitionInflater.from(mContext);
@@ -1621,7 +1641,7 @@
             p.flags |= LayoutParams.FLAG_NOT_FOCUSABLE;
             mWindowManager.updateViewLayout(decorView, p);
 
-            final Rect epicenter = getRelativeAnchorBounds();
+            final Rect epicenter = getTransitionEpicenter();
             exitTransition.setEpicenterCallback(new EpicenterCallback() {
                 @Override
                 public Rect onGetEpicenter(Transition transition) {
@@ -1646,7 +1666,17 @@
         }
     }
 
-    private Rect getRelativeAnchorBounds() {
+    /**
+     * Returns the window-relative epicenter bounds to be used by enter and
+     * exit transitions.
+     * <p>
+     * <strong>Note:</strong> This is distinct from the rect passed to
+     * {@link #setEpicenterBounds(Rect)}, which is anchor-relative.
+     *
+     * @return the window-relative epicenter bounds to be used by enter and
+     *         exit transitions
+     */
+    private Rect getTransitionEpicenter() {
         final View anchor = mAnchor != null ? mAnchor.get() : null;
         final View decor = mDecorView;
         if (anchor == null || decor == null) {
@@ -1659,6 +1689,15 @@
         // Compute the position of the anchor relative to the popup.
         final Rect bounds = new Rect(0, 0, anchor.getWidth(), anchor.getHeight());
         bounds.offset(anchorLocation[0] - popupLocation[0], anchorLocation[1] - popupLocation[1]);
+
+        // Use anchor-relative epicenter, if specified.
+        if (mEpicenterBounds != null) {
+            final int offsetX = bounds.left;
+            final int offsetY = bounds.top;
+            bounds.set(mEpicenterBounds);
+            bounds.offset(offsetX, offsetY);
+        }
+
         return bounds;
     }
 
@@ -2031,7 +2070,7 @@
                             observer.removeOnGlobalLayoutListener(this);
                         }
 
-                        final Rect epicenter = getRelativeAnchorBounds();
+                        final Rect epicenter = getTransitionEpicenter();
                         enterTransition.setEpicenterCallback(new EpicenterCallback() {
                             @Override
                             public Rect onGetEpicenter(Transition transition) {
diff --git a/core/java/com/android/internal/view/menu/CascadingMenuPopup.java b/core/java/com/android/internal/view/menu/CascadingMenuPopup.java
index 320de90..a502fcc 100644
--- a/core/java/com/android/internal/view/menu/CascadingMenuPopup.java
+++ b/core/java/com/android/internal/view/menu/CascadingMenuPopup.java
@@ -362,6 +362,7 @@
 
         final int x;
         final int y;
+        final Rect epicenterBounds;
         if (parentView != null) {
             // This menu is a cascading submenu anchored to a parent view.
             popupWindow.setTouchModal(false);
@@ -396,13 +397,16 @@
             }
 
             y = parentOffsetTop;
+            epicenterBounds = null;
         } else {
             x = mInitXOffset;
             y = mInitYOffset;
+            epicenterBounds = getEpicenterBounds();
         }
 
         popupWindow.setHorizontalOffset(x);
         popupWindow.setVerticalOffset(y);
+        popupWindow.setEpicenterBounds(epicenterBounds);
 
         final CascadingMenuInfo menuInfo = new CascadingMenuInfo(popupWindow, menu, mLastPosition);
         mShowingMenus.add(menuInfo);
diff --git a/core/java/com/android/internal/view/menu/MenuPopup.java b/core/java/com/android/internal/view/menu/MenuPopup.java
index b151f34..42b1a56 100644
--- a/core/java/com/android/internal/view/menu/MenuPopup.java
+++ b/core/java/com/android/internal/view/menu/MenuPopup.java
@@ -19,6 +19,7 @@
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.content.Context;
+import android.graphics.Rect;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.View.MeasureSpec;
@@ -37,6 +38,7 @@
  */
 public abstract class MenuPopup implements ShowableListMenu, MenuPresenter,
         AdapterView.OnItemClickListener {
+    private Rect mEpicenterBounds;
 
     public abstract void setForceShowIcon(boolean forceShow);
 
@@ -60,6 +62,23 @@
     public abstract void setVerticalOffset(int y);
 
     /**
+     * Specifies the anchor-relative bounds of the popup's transition
+     * epicenter.
+     *
+     * @param bounds anchor-relative bounds
+     */
+    public void setEpicenterBounds(Rect bounds) {
+        mEpicenterBounds = bounds;
+    }
+
+    /**
+     * @return anchor-relative bounds of the popup's transition epicenter
+     */
+    public Rect getEpicenterBounds() {
+        return mEpicenterBounds;
+    }
+
+    /**
      * Set whether a title entry should be shown in the popup menu (if a title exists for the
      * menu).
      *
diff --git a/core/java/com/android/internal/view/menu/MenuPopupHelper.java b/core/java/com/android/internal/view/menu/MenuPopupHelper.java
index 044ee6e..1f1e594 100644
--- a/core/java/com/android/internal/view/menu/MenuPopupHelper.java
+++ b/core/java/com/android/internal/view/menu/MenuPopupHelper.java
@@ -23,6 +23,8 @@
 import android.annotation.Nullable;
 import android.annotation.StyleRes;
 import android.content.Context;
+import android.graphics.Rect;
+import android.util.DisplayMetrics;
 import android.view.Gravity;
 import android.view.View;
 import android.widget.PopupWindow.OnDismissListener;
@@ -31,6 +33,8 @@
  * Presents a menu as a small, simple popup anchored to another view.
  */
 public class MenuPopupHelper implements MenuHelper {
+    private static final int TOUCH_EPICENTER_SIZE_DP = 48;
+
     private final Context mContext;
 
     // Immutable cached popup menu properties.
@@ -163,6 +167,11 @@
      * Shows the popup menu and makes a best-effort to anchor it to the
      * specified (x,y) coordinate relative to the anchor view.
      * <p>
+     * Additionally, the popup's transition epicenter (see
+     * {@link android.widget.PopupWindow#setEpicenterBounds(Rect)} will be
+     * centered on the specified coordinate, rather than using the bounds of
+     * the anchor view.
+     * <p>
      * If the popup's resolved gravity is {@link Gravity#LEFT}, this will
      * display the popup with its top-left corner at (x,y) relative to the
      * anchor view. If the resolved gravity is {@link Gravity#RIGHT}, the
@@ -222,8 +231,11 @@
         return popup;
     }
 
-    private void showPopup(int xOffset, int yOffset, boolean resolveOffsets, boolean showTitle) {
-        if (resolveOffsets) {
+    private void showPopup(int xOffset, int yOffset, boolean useOffsets, boolean showTitle) {
+        final MenuPopup popup = getPopup();
+        popup.setShowTitle(showTitle);
+
+        if (useOffsets) {
             // If the resolved drop-down gravity is RIGHT, the popup's right
             // edge will be aligned with the anchor view. Adjust by the anchor
             // width such that the top-right corner is at the X offset.
@@ -232,12 +244,21 @@
             if (hgrav == Gravity.RIGHT) {
                 xOffset -= mAnchorView.getWidth();
             }
+
+            popup.setHorizontalOffset(xOffset);
+            popup.setVerticalOffset(yOffset);
+
+            // Set the transition epicenter to be roughly finger (or mouse
+            // cursor) sized and centered around the offset position. This
+            // will give the appearance that the window is emerging from
+            // the touch point.
+            final float density = mContext.getResources().getDisplayMetrics().density;
+            final int halfSize = (int) (TOUCH_EPICENTER_SIZE_DP * density / 2);
+            final Rect epicenter = new Rect(xOffset - halfSize, yOffset - halfSize,
+                    xOffset + halfSize, yOffset + halfSize);
+            popup.setEpicenterBounds(epicenter);
         }
 
-        final MenuPopup popup = getPopup();
-        popup.setHorizontalOffset(xOffset);
-        popup.setVerticalOffset(yOffset);
-        popup.setShowTitle(showTitle);
         popup.show();
     }
 
diff --git a/core/java/com/android/internal/view/menu/StandardMenuPopup.java b/core/java/com/android/internal/view/menu/StandardMenuPopup.java
index a67e43a..2d4baa2 100644
--- a/core/java/com/android/internal/view/menu/StandardMenuPopup.java
+++ b/core/java/com/android/internal/view/menu/StandardMenuPopup.java
@@ -176,6 +176,7 @@
         mPopup.setInputMethodMode(PopupWindow.INPUT_METHOD_NOT_NEEDED);
         mPopup.setHorizontalOffset(mXOffset);
         mPopup.setVerticalOffset(mYOffset);
+        mPopup.setEpicenterBounds(getEpicenterBounds());
         mPopup.show();
 
         ListView listView = mPopup.getListView();
diff --git a/core/res/res/values/styles_material.xml b/core/res/res/values/styles_material.xml
index 3d5f6ab..84d9a2a 100644
--- a/core/res/res/values/styles_material.xml
+++ b/core/res/res/values/styles_material.xml
@@ -877,7 +877,6 @@
 
     <style name="Widget.Material.ContextPopupMenu" parent="Widget.Material.ListPopupWindow">
         <item name="overlapAnchor">true</item>
-        <item name="popupEnterTransition">@null</item>
     </style>
 
     <style name="Widget.Material.ActionButton">