Make sure the bottom toolbar is never stuck invisible

components/browser/toolbar/src/main/java/mozilla/components/browser/toolbar/behavior/BrowserToolbarBottomBehavior.kt

@@ -44,6 +44,8 @@ class BrowserToolbarBottomBehavior(
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
     internal var shouldSnapAfterScroll: Boolean = false
 
+    private var lastSnapStartedWasUp = false
+
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
     internal var snapAnimator: ValueAnimator = ValueAnimator().apply {
         interpolator = DecelerateInterpolator()
@@ -147,6 +149,7 @@ class BrowserToolbarBottomBehavior(
 
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
     internal fun animateSnap(child: View, direction: SnapDirection) = with(snapAnimator) {
+        lastSnapStartedWasUp = direction == SnapDirection.UP
         addUpdateListener { child.translationY = it.animatedValue as Float }
         setFloatValues(child.translationY, if (direction == SnapDirection.UP) 0f else child.height.toFloat())
         start()
@@ -188,6 +191,15 @@ class BrowserToolbarBottomBehavior(
         if (shouldScroll) {
             browserToolbar.translationY =
                 max(0f, min(browserToolbar.height.toFloat(), browserToolbar.translationY + distance))
+        } else {
+            // Force expand the toolbar if the user scrolled up, it is not already expanded and
+            // an animation to expand it is not already in progress,
+            // otherwise the user could get stuck in a state where they cannot show the toolbar
+            val isAnimatingUp = snapAnimator.isStarted && lastSnapStartedWasUp
+            if (distance < 0 && browserToolbar.translationY != 0f && !isAnimatingUp) {
+                snapAnimator.cancel()
+                forceExpand(browserToolbar)
+            }
         }
     }
 

components/browser/toolbar/src/test/java/mozilla/components/browser/toolbar/behavior/BrowserToolbarBottomBehaviorTest.kt

@@ -153,6 +153,8 @@ class BrowserToolbarBottomBehaviorTest {
     fun `Behavior will apply translation to toolbar only for vertical scrolls`() {
         val behavior = spy(BrowserToolbarBottomBehavior(testContext, attrs = null))
         behavior.initGesturesDetector(behavior.createGestureDetector())
+        val child = spy(BrowserToolbar(testContext, null, 0))
+        behavior.browserToolbar = child
         val downEvent = TestUtils.getMotionEvent(ACTION_DOWN, 0f, 0f)
         val moveEvent = TestUtils.getMotionEvent(ACTION_MOVE, 0f, 100f, downEvent)
 
@@ -317,4 +319,28 @@ class BrowserToolbarBottomBehaviorTest {
 
         verify(behavior).animateSnap(toolbar, SnapDirection.UP)
     }
+
+    @Test
+    fun `Behavior will forceExpand when scrolling up and !shouldScroll`() {
+        val behavior = spy(BrowserToolbarBottomBehavior(testContext, attrs = null))
+        behavior.initGesturesDetector(behavior.createGestureDetector())
+        doReturn(false).`when`(behavior).shouldScroll
+        val toolbar: BrowserToolbar = spy(BrowserToolbar(testContext, null, 0))
+        behavior.browserToolbar = toolbar
+        val animator: ValueAnimator = mock()
+        behavior.snapAnimator = animator
+        doReturn(false).`when`(animator).isStarted
+
+        doReturn(100).`when`(toolbar).height
+        doReturn(100f).`when`(toolbar).translationY
+
+        val downEvent = TestUtils.getMotionEvent(ACTION_DOWN, 0f, 0f)
+        val moveEvent = TestUtils.getMotionEvent(ACTION_MOVE, 0f, 30f, downEvent)
+
+        behavior.onInterceptTouchEvent(mock(), mock(), downEvent)
+        behavior.onInterceptTouchEvent(mock(), mock(), moveEvent)
+
+        verify(behavior).tryToScrollVertically(-30f)
+        verify(behavior).forceExpand(toolbar)
+    }
 }