Fixed a bug in the notification stack algorithm

Bad holes could occur when a notification was at the same time in
the top and the bottom stack. This also improves the landscape /
smallscreen interaction with the shade.

Bug: 16715133
Change-Id: Icbb4d080e658f4ddbd39b7d08652ca5311a47978

Author: Selim Cinek

packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java

@@ -279,6 +279,8 @@ protected void onLayout(boolean changed, int left, int top, int right, int botto
             positionClockAndNotifications();
             mNotificationStackScroller.setStackHeight(getExpandedHeight());
         }
+        mNotificationStackScroller.updateIsSmallScreen(
+                mHeader.getCollapsedHeight() + mQsPeekHeight);
     }
 
     @Override

packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java

@@ -2164,6 +2164,14 @@ public float getBottomMostNotificationBottom() {
         return max + getTranslationY();
     }
 
+    /**
+     * @param qsMinHeight The minimum height of the quick settings including padding
+     *                    See {@link StackScrollAlgorithm#updateIsSmallScreen}.
+     */
+    public void updateIsSmallScreen(int qsMinHeight) {
+        mStackScrollAlgorithm.updateIsSmallScreen(mMaxLayoutHeight - qsMinHeight);
+    }
+
     /**
      * A listener that is notified when some child locations might have changed.
      */

packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java

@@ -71,6 +71,8 @@ public class StackScrollAlgorithm {
     private int mBottomStackSlowDownLength;
     private int mTopStackSlowDownLength;
     private int mCollapseSecondCardPadding;
+    private boolean mIsSmallScreen;
+    private int mMaxNotificationHeight;
 
     public StackScrollAlgorithm(Context context) {
         initConstants(context);
@@ -106,6 +108,8 @@ private void initConstants(Context context) {
                 .getDimensionPixelSize(R.dimen.notification_padding);
         mCollapsedSize = context.getResources()
                 .getDimensionPixelSize(R.dimen.notification_min_height);
+        mMaxNotificationHeight = context.getResources()
+                .getDimensionPixelSize(R.dimen.notification_max_height);
         mTopStackPeekSize = context.getResources()
                 .getDimensionPixelSize(R.dimen.top_stack_peek_amount);
         mBottomStackPeekSize = context.getResources()
@@ -377,14 +381,17 @@ private void updatePositionsForState(StackScrollState resultState,
                 // We are in the top Stack
                 updateStateForTopStackChild(algorithmState,
                         numberOfElementsCompletelyIn, i, childHeight, childViewState, scrollOffset);
-                clampYTranslation(childViewState, childHeight);
+                clampPositionToTopStackEnd(childViewState, childHeight);
+
                 // check if we are overlapping with the bottom stack
                 if (childViewState.yTranslation + childHeight + mPaddingBetweenElements
                         >= bottomStackStart && !mIsExpansionChanging && i != 0) {
-                    // TODO: handle overlapping sizes with end stack better
-                    // we just collapse this element
-                    childViewState.height = mCollapsedSize;
+                    // we just collapse this element slightly
+                    int newSize = (int) Math.max(bottomStackStart - mPaddingBetweenElements -
+                            childViewState.yTranslation, mCollapsedSize);
+                    childViewState.height = newSize;
                 }
+                clampPositionToBottomStackStart(childViewState, childViewState.height);
             } else if (nextYPosition >= bottomStackStart) {
                 // Case 2:
                 // We are in the bottom stack.
@@ -489,11 +496,17 @@ private void updateStateForChildTransitioningInBottom(StackScrollAlgorithmState
         // the offset starting at the transitionPosition of the bottom stack
         float offset = mBottomStackIndentationFunctor.getValue(algorithmState.partialInBottom);
         algorithmState.itemsInBottomStack += algorithmState.partialInBottom;
-        childViewState.yTranslation = transitioningPositionStart + offset - childHeight
+        int newHeight = childHeight;
+        if (childHeight > mCollapsedSize && mIsSmallScreen) {
+            newHeight = (int) Math.max(Math.min(transitioningPositionStart + offset -
+                    mPaddingBetweenElements - currentYPosition, childHeight), mCollapsedSize);
+            childViewState.height = newHeight;
+        }
+        childViewState.yTranslation = transitioningPositionStart + offset - newHeight
                 - mPaddingBetweenElements;
-        
+
         // We want at least to be at the end of the top stack when collapsing
-        clampPositionToTopStackEnd(childViewState, childHeight);
+        clampPositionToTopStackEnd(childViewState, newHeight);
         childViewState.location = StackScrollState.ViewState.LOCATION_MAIN_AREA;
     }
 
@@ -705,6 +718,20 @@ private void updateInnerHeight() {
         mInnerHeight = mLayoutHeight - mTopPadding;
     }
 
+
+    /**
+     * Update whether the device is very small, i.e. Notifications can be in both the top and the
+     * bottom stack at the same time
+     *
+     * @param panelHeight The normal height of the panel when it's open
+     */
+    public void updateIsSmallScreen(int panelHeight) {
+        mIsSmallScreen = panelHeight <
+                mCollapsedSize  /* top stack */
+                + mBottomStackSlowDownLength + mBottomStackPeekSize /* bottom stack */
+                + mMaxNotificationHeight; /* max notification height */
+    }
+
     public void onExpansionStarted(StackScrollState currentState) {
         mIsExpansionChanging = true;
         mExpandedOnStart = mIsExpanded;