Fix one-icon shelf flicker on lockscreen swipe-up

The flicker happens because floating point comparison
for viewStart and shelfStart is off by ~0.001f sometimes,
such that the notification is thought to be above the shelf,
causing the shelf to hide since it no longer has a full view.

Bug: 222123657
Test: NotificationShelfTest
Test: on lockscreen, swipe up with one icon in shelf
      => no flickering
Change-Id: Iad2bb24d4a51d5a831aa3193de10f768fa7c41be

packages/SystemUI/src/com/android/systemui/statusbar/NotificationShelf.java

@@ -326,9 +326,9 @@ public class NotificationShelf extends ActivatableNotificationView implements
                     || child.isPinned();
             boolean isLastChild = child == lastChild;
             final float viewStart = child.getTranslationY();
-
-            final float inShelfAmount = updateShelfTransformation(i, child, scrollingFast,
-                    expandingAnimated, isLastChild);
+            final float shelfClipStart = getTranslationY() - mPaddingBetweenElements;
+            final float inShelfAmount = getAmountInShelf(i, child, scrollingFast,
+                    expandingAnimated, isLastChild, shelfClipStart);
 
             // TODO(b/172289889) scale mPaddingBetweenElements with expansion amount
             if ((isLastChild && !child.isInShelf()) || aboveShelf || backgroundForceHidden) {
@@ -609,10 +609,18 @@ public class NotificationShelf extends ActivatableNotificationView implements
     }
 
     /**
-     * @return the amount how much this notification is in the shelf
+     * @param i Index of the view in the host layout.
+     * @param view The current ExpandableView.
+     * @param scrollingFast Whether we are scrolling fast.
+     * @param expandingAnimated Whether we are expanding a notification.
+     * @param isLastChild Whether this is the last view.
+     * @param shelfClipStart The point at which notifications start getting clipped by the shelf.
+     * @return The amount how much this notification is in the shelf.
+     *         0f is not in shelf. 1f is completely in shelf.
      */
-    private float updateShelfTransformation(int i, ExpandableView view, boolean scrollingFast,
-            boolean expandingAnimated, boolean isLastChild) {
+    @VisibleForTesting
+    public float getAmountInShelf(int i, ExpandableView view, boolean scrollingFast,
+            boolean expandingAnimated, boolean isLastChild, float shelfClipStart) {
 
         // Let's calculate how much the view is in the shelf
         float viewStart = view.getTranslationY();
@@ -635,29 +643,33 @@ public class NotificationShelf extends ActivatableNotificationView implements
         float viewEnd = viewStart + fullHeight;
         float fullTransitionAmount = 0.0f;
         float iconTransitionAmount = 0.0f;
-        float shelfStart = getTranslationY() - mPaddingBetweenElements;
+
+        // Don't animate shelf icons during shade expansion.
         if (mAmbientState.isExpansionChanging() && !mAmbientState.isOnKeyguard()) {
             // TODO(b/172289889) handle icon placement for notification that is clipped by the shelf
             if (mIndexOfFirstViewInShelf != -1 && i >= mIndexOfFirstViewInShelf) {
                 fullTransitionAmount = 1f;
                 iconTransitionAmount = 1f;
             }
-        } else if (viewEnd >= shelfStart
+
+        } else if (viewEnd >= shelfClipStart
                 && (!mAmbientState.isUnlockHintRunning() || view.isInShelf())
                 && (mAmbientState.isShadeExpanded()
                 || (!view.isPinned() && !view.isHeadsUpAnimatingAway()))) {
 
-            if (viewStart < shelfStart) {
-                float fullAmount = (shelfStart - viewStart) / fullHeight;
+            if (viewStart < shelfClipStart && Math.abs(viewStart - shelfClipStart) > 0.001f) {
+                // Partially clipped by shelf.
+                float fullAmount = (shelfClipStart - viewStart) / fullHeight;
                 fullAmount = Math.min(1.0f, fullAmount);
                 fullTransitionAmount = 1.0f - fullAmount;
                 if (isLastChild) {
                     // Reduce icon transform distance to completely fade in shelf icon
                     // by the time the notification icon fades out, and vice versa
-                    iconTransitionAmount = (shelfStart - viewStart)
+                    iconTransitionAmount = (shelfClipStart - viewStart)
                             / (iconTransformStart - viewStart);
                 } else {
-                    iconTransitionAmount = (shelfStart - iconTransformStart) / transformDistance;
+                    iconTransitionAmount = (shelfClipStart - iconTransformStart)
+                            / transformDistance;
                 }
                 iconTransitionAmount = MathUtils.constrain(iconTransitionAmount, 0.0f, 1.0f);
                 iconTransitionAmount = 1.0f - iconTransitionAmount;
@@ -772,6 +784,9 @@ public class NotificationShelf extends ActivatableNotificationView implements
     }
 
     private NotificationIconContainer.IconState getIconState(StatusBarIconView icon) {
+        if (mShelfIcons == null) {
+            return null;
+        }
         return mShelfIcons.getIconState(icon);
     }
 

packages/SystemUI/tests/src/com/android/systemui/statusbar/notification/stack/NotificationShelfTest.kt

@@ -5,8 +5,9 @@ import android.testing.TestableLooper.RunWithLooper
 import androidx.test.filters.SmallTest
 import com.android.systemui.SysuiTestCase
 import com.android.systemui.statusbar.NotificationShelf
-import junit.framework.Assert.assertFalse
-import junit.framework.Assert.assertTrue
+import com.android.systemui.statusbar.StatusBarIconView
+import com.android.systemui.statusbar.notification.row.ExpandableView
+import junit.framework.Assert.*
 import org.junit.Before
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -143,6 +144,113 @@ class NotificationShelfTest : SysuiTestCase() {
         assertFalse(isYBelowShelfInView)
     }
 
+    @Test
+    fun getAmountInShelf_lastViewBelowShelf_completelyInShelf() {
+        val shelfClipStart = 0f
+        val viewStart = 1f
+
+        val expandableView = mock(ExpandableView::class.java)
+        whenever(expandableView.shelfIcon).thenReturn(mock(StatusBarIconView::class.java))
+        whenever(expandableView.translationY).thenReturn(viewStart)
+        whenever(expandableView.actualHeight).thenReturn(20)
+
+        whenever(expandableView.minHeight).thenReturn(20)
+        whenever(expandableView.shelfTransformationTarget).thenReturn(null)  // use translationY
+        whenever(expandableView.isInShelf).thenReturn(true)
+
+        whenever(ambientState.isOnKeyguard).thenReturn(true)
+        whenever(ambientState.isExpansionChanging).thenReturn(false)
+        whenever(ambientState.isShadeExpanded).thenReturn(true)
+
+        val amountInShelf = shelf.getAmountInShelf(/* i= */ 0,
+                /* view= */ expandableView,
+                /* scrollingFast= */ false,
+                /* expandingAnimated= */ false,
+                /* isLastChild= */ true,
+                shelfClipStart)
+        assertEquals(1f, amountInShelf)
+    }
+
+    @Test
+    fun getAmountInShelf_lastViewAlmostBelowShelf_completelyInShelf() {
+        val viewStart = 0f
+        val shelfClipStart = 0.001f
+
+        val expandableView = mock(ExpandableView::class.java)
+        whenever(expandableView.shelfIcon).thenReturn(mock(StatusBarIconView::class.java))
+        whenever(expandableView.translationY).thenReturn(viewStart)
+        whenever(expandableView.actualHeight).thenReturn(20)
+
+        whenever(expandableView.minHeight).thenReturn(20)
+        whenever(expandableView.shelfTransformationTarget).thenReturn(null)  // use translationY
+        whenever(expandableView.isInShelf).thenReturn(true)
+
+        whenever(ambientState.isOnKeyguard).thenReturn(true)
+        whenever(ambientState.isExpansionChanging).thenReturn(false)
+        whenever(ambientState.isShadeExpanded).thenReturn(true)
+
+        val amountInShelf = shelf.getAmountInShelf(/* i= */ 0,
+                /* view= */ expandableView,
+                /* scrollingFast= */ false,
+                /* expandingAnimated= */ false,
+                /* isLastChild= */ true,
+                shelfClipStart)
+        assertEquals(1f, amountInShelf)
+    }
+
+    @Test
+    fun getAmountInShelf_lastViewHalfClippedByShelf_halfInShelf() {
+        val viewStart = 0f
+        val shelfClipStart = 10f
+
+        val expandableView = mock(ExpandableView::class.java)
+        whenever(expandableView.shelfIcon).thenReturn(mock(StatusBarIconView::class.java))
+        whenever(expandableView.translationY).thenReturn(viewStart)
+        whenever(expandableView.actualHeight).thenReturn(25)
+
+        whenever(expandableView.minHeight).thenReturn(25)
+        whenever(expandableView.shelfTransformationTarget).thenReturn(null)  // use translationY
+        whenever(expandableView.isInShelf).thenReturn(true)
+
+        whenever(ambientState.isOnKeyguard).thenReturn(true)
+        whenever(ambientState.isExpansionChanging).thenReturn(false)
+        whenever(ambientState.isShadeExpanded).thenReturn(true)
+
+        val amountInShelf = shelf.getAmountInShelf(/* i= */ 0,
+                /* view= */ expandableView,
+                /* scrollingFast= */ false,
+                /* expandingAnimated= */ false,
+                /* isLastChild= */ true,
+                shelfClipStart)
+        assertEquals(0.5f, amountInShelf)
+    }
+
+    @Test
+    fun getAmountInShelf_lastViewAboveShelf_notInShelf() {
+        val viewStart = 0f
+        val shelfClipStart = 15f
+
+        val expandableView = mock(ExpandableView::class.java)
+        whenever(expandableView.shelfIcon).thenReturn(mock(StatusBarIconView::class.java))
+        whenever(expandableView.translationY).thenReturn(viewStart)
+        whenever(expandableView.actualHeight).thenReturn(10)
+
+        whenever(expandableView.minHeight).thenReturn(10)
+        whenever(expandableView.shelfTransformationTarget).thenReturn(null)  // use translationY
+        whenever(expandableView.isInShelf).thenReturn(false)
+
+        whenever(ambientState.isExpansionChanging).thenReturn(false)
+        whenever(ambientState.isOnKeyguard).thenReturn(true)
+
+        val amountInShelf = shelf.getAmountInShelf(/* i= */ 0,
+                /* view= */ expandableView,
+                /* scrollingFast= */ false,
+                /* expandingAnimated= */ false,
+                /* isLastChild= */ true,
+                shelfClipStart)
+        assertEquals(0f, amountInShelf)
+    }
+
     private fun setFractionToShade(fraction: Float) {
         whenever(ambientState.fractionToShade).thenReturn(fraction)
     }