Tweaking layout to make two-task stacks to closer match design.

- In the small-stack cases, set the initial state to top-align the
  back-most task.  In addition to offsetting the position, ensure that
  the dim for the back-most task is offset by this new position.
- Fixing issue with wrong return value when update insets.
- Fixing issue where tasks disappear after rotating while scrolling the
  stack, due to the scrollering setting the stack scroll to an invalid
  scroll position in the new layout in the new orientation.

Bug: 27859654
Change-Id: Ia4aaa3fe445032493c94a8dee7f6fea33bee36ec

2 files changed, 63 insertions, 17 deletions

diff --git a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackLayoutAlgorithm.java b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackLayoutAlgorithm.java
index 77b733881a0f..e3fe1abf8b20 100644
--- a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackLayoutAlgorithm.java
+++ b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackLayoutAlgorithm.java
@@ -404,7 +404,7 @@ public class TaskStackLayoutAlgorithm {
      * Sets the system insets.
      */
     public boolean setSystemInsets(Rect systemInsets) {
-        boolean changed = mSystemInsets.equals(systemInsets);
+        boolean changed = !mSystemInsets.equals(systemInsets);
         mSystemInsets.set(systemInsets);
         return changed;
     }
@@ -583,11 +583,25 @@ public class TaskStackLayoutAlgorithm {
         if (getInitialFocusState() == STATE_UNFOCUSED && mNumStackTasks > 1) {
             if (ignoreScrollToFront || (!launchState.launchedWithAltTab && !scrollToFront)) {
                 // Set the initial scroll to the predefined state (which differs from the stack)
-                float [] initialNormX = new float[] {
-                        getNormalizedXFromUnfocusedY(mSystemInsets.bottom + mInitialBottomOffset,
-                                FROM_BOTTOM),
-                        getNormalizedXFromUnfocusedY(mInitialTopOffset, FROM_TOP)
-                };
+                float [] initialNormX = null;
+                float minBottomTaskNormX = getNormalizedXFromUnfocusedY(mSystemInsets.bottom +
+                        mInitialBottomOffset, FROM_BOTTOM);
+                float maxBottomTaskNormX = getNormalizedXFromUnfocusedY(mFocusedTopPeekHeight +
+                        mTaskRect.height() - mMinMargin, FROM_TOP);
+                if (mNumStackTasks <= 2) {
+                    // For small stacks, position the tasks so that they are top aligned to under
+                    // the action button, but ensure that it is at least a certain offset from the
+                    // bottom of the stack
+                    initialNormX = new float[] {
+                            Math.min(maxBottomTaskNormX, minBottomTaskNormX),
+                            getNormalizedXFromUnfocusedY(mFocusedTopPeekHeight, FROM_TOP)
+                    };
+                } else {
+                    initialNormX = new float[] {
+                            minBottomTaskNormX,
+                            getNormalizedXFromUnfocusedY(mInitialTopOffset, FROM_TOP)
+                    };
+                }
 
                 mUnfocusedRange.offset(0f);
                 List<Task> tasks = stack.getStackTasks();
@@ -881,14 +895,7 @@ public class TaskStackLayoutAlgorithm {
             TaskViewTransform frontTransform, boolean ignoreSingleTaskCase, boolean forceUpdate) {
         SystemServicesProxy ssp = Recents.getSystemServices();
 
-        // Compute the focused and unfocused offset
-        float boundedStackScroll = Utilities.clamp(stackScroll, mMinScrollP, mMaxScrollP);
-        mUnfocusedRange.offset(boundedStackScroll);
-        mFocusedRange.offset(boundedStackScroll);
-        float boundedScrollUnfocusedRangeX = mUnfocusedRange.getNormalizedX(taskProgress);
-        float boundedScrollFocusedRangeX = mFocusedRange.getNormalizedX(taskProgress);
-        float boundedScrollUnfocusedNonOverrideRangeX =
-                mUnfocusedRange.getNormalizedX(nonOverrideTaskProgress);
+        // Ensure that the task is in range
         mUnfocusedRange.offset(stackScroll);
         mFocusedRange.offset(stackScroll);
         boolean unfocusedVisible = mUnfocusedRange.isInRange(taskProgress);
@@ -900,9 +907,30 @@ public class TaskStackLayoutAlgorithm {
             return;
         }
 
+        // Map the absolute task progress to the normalized x at the stack scroll.  We use this to
+        // calculate positions along the curve.
+        mUnfocusedRange.offset(stackScroll);
+        mFocusedRange.offset(stackScroll);
         float unfocusedRangeX = mUnfocusedRange.getNormalizedX(taskProgress);
         float focusedRangeX = mFocusedRange.getNormalizedX(taskProgress);
 
+        // Map the absolute task progress to the normalized x at the bounded stack scroll.  We use
+        // this to calculate bounded properties, like translationZ and outline alpha.
+        float boundedStackScroll = Utilities.clamp(stackScroll, mMinScrollP, mMaxScrollP);
+        mUnfocusedRange.offset(boundedStackScroll);
+        mFocusedRange.offset(boundedStackScroll);
+        float boundedScrollUnfocusedRangeX = mUnfocusedRange.getNormalizedX(taskProgress);
+        float boundedScrollUnfocusedNonOverrideRangeX =
+                mUnfocusedRange.getNormalizedX(nonOverrideTaskProgress);
+
+        // Map the absolute task progress to the normalized x at the upper bounded stack scroll.
+        // We use this to calculate the dim, which is bounded only on one end.
+        float lowerBoundedStackScroll = Utilities.clamp(stackScroll, -Float.MAX_VALUE, mMaxScrollP);
+        mUnfocusedRange.offset(lowerBoundedStackScroll);
+        mFocusedRange.offset(lowerBoundedStackScroll);
+        float lowerBoundedUnfocusedRangeX = mUnfocusedRange.getNormalizedX(taskProgress);
+        float lowerBoundedFocusedRangeX = mFocusedRange.getNormalizedX(taskProgress);
+
         int x = (mStackRect.width() - mTaskRect.width()) / 2;
         int y;
         float z;
@@ -917,7 +945,8 @@ public class TaskStackLayoutAlgorithm {
             y = centerYOffset + getYForDeltaP(tmpP, 0);
             z = mMaxTranslationZ;
             dimAlpha = 0f;
-            viewOutlineAlpha = (OUTLINE_ALPHA_MIN_VALUE + OUTLINE_ALPHA_MAX_VALUE) / 2f;
+            viewOutlineAlpha = OUTLINE_ALPHA_MIN_VALUE +
+                    (OUTLINE_ALPHA_MAX_VALUE - OUTLINE_ALPHA_MIN_VALUE) / 2f;
 
         } else {
             // Otherwise, update the task to the stack layout
@@ -926,9 +955,22 @@ public class TaskStackLayoutAlgorithm {
             int focusedY = (int) ((1f - mFocusedCurveInterpolator.getInterpolation(
                     focusedRangeX)) * mStackRect.height());
             float unfocusedDim = mUnfocusedDimCurveInterpolator.getInterpolation(
-                    boundedScrollUnfocusedRangeX);
+                    lowerBoundedUnfocusedRangeX);
             float focusedDim = mFocusedDimCurveInterpolator.getInterpolation(
-                    boundedScrollFocusedRangeX);
+                    lowerBoundedFocusedRangeX);
+
+            // Special case, because we override the initial task positions differently for small
+            // stacks, we clamp the dim to 0 in the initial position, and then only modulate the
+            // dim when the task is scrolled back towards the top of the screen
+            if (mNumStackTasks <= 2 && nonOverrideTaskProgress == 0f) {
+                if (boundedScrollUnfocusedRangeX >= 0.5f) {
+                    unfocusedDim = 0f;
+                } else {
+                    float offset = mUnfocusedDimCurveInterpolator.getInterpolation(0.5f);
+                    unfocusedDim -= offset;
+                    unfocusedDim *= MAX_DIM / (MAX_DIM - offset);
+                }
+            }
 
             y = (mStackRect.top - mTaskRect.top) +
                     (int) Utilities.mapRange(focusState, unfocusedY, focusedY);
diff --git a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
index 0d9f77c5d2fa..231360e46ae9 100644
--- a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
+++ b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
@@ -1996,6 +1996,10 @@ public class TaskStackView extends FrameLayout implements TaskStack.TaskStackCal
         if (event.fromDeviceOrientationChange) {
             mDisplayOrientation = Utilities.getAppConfiguration(mContext).orientation;
             mDisplayRect = Recents.getSystemServices().getDisplayRect();
+
+            // Always stop the scroller, otherwise, we may continue setting the stack scroll to the
+            // wrong bounds in the new layout
+            mStackScroller.stopScroller();
         }
         reloadOnConfigurationChange();