Improvements for home to overview gesture

*   Updates the target drag distance at which the home screen stops
    scaling - instead of extending for a fixed point from the threshold
    at which transition is allowed, that target is set to the center of
    the screen
*   Significantly shortens the timeout to trigger transition
*   Allows transition if pointer is moving, provided that the velocity
    is below certain threshold (instead of requiring pointer to stay
    still)

BUG=1005366, 1025283

Change-Id: Ic322932a3ae519a1989ef343f6f2e960dca29709
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1912993
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715844}

ash/home_screen/swipe_home_to_overview_controller.cc

@@ -29,16 +29,16 @@ namespace {
 constexpr float kTargetHomeScale = 0.92f;
 
 // The home UI will be scaled down towards center of the screen as drag location
-// approaches the threshold for the transition to overview. The target threshold
-// for scaling is extended above the actual threshold to make the UI change more
-// noticeable to the user as drag approaches the threshold - this is the ratio
-// by which the projected threshold is extended.
-constexpr float kExtendedVerticalThresholdForOverviewTransitionRatio = 0.5f;
-
-// The amount of time the drag has to remain still before the transition to the
-// overview starts.
+// moves upwards. The target threshold for scaling is extended above the actual
+// threshold for transition so the UI keeps changing even when the gesture goes
+// over the threshold. This is the target home screen scaling threshold in terms
+// of ratio of the display height.
+constexpr float kHomeScalingThresholdDisplayHeightRatio = 0.5f;
+
+// The amount of time the drag has to remain bellow velocity threshold before
+// the transition to the overview starts.
 constexpr base::TimeDelta kOverviewTransitionDelay =
-    base::TimeDelta::FromMilliseconds(350);
+    base::TimeDelta::FromMilliseconds(150);
 
 // The duration of transition from the home screen current scaled state to the
 // initial (unscaled) state when the gesture is canceled.
@@ -90,27 +90,19 @@ void SwipeHomeToOverviewController::Drag(const gfx::PointF& location_in_screen,
 
     overview_transition_threshold_y_ =
         shelf_top - kVerticalThresholdForOverviewTransition;
+    scaling_threshold_y_ =
+        display.bounds().y() +
+        display.bounds().height() * kHomeScalingThresholdDisplayHeightRatio;
     state_ = State::kTrackingDrag;
   } else {
-    const bool over_overview_transition_threshold =
-        location_in_screen.y() <= overview_transition_threshold_y_;
-
-    // Ignore small drag updates, unless they move the drag above the overview
-    // transition threshold.
-    if (std::abs(location_in_screen.y() - last_location_in_screen_.y()) <
-            kMovementThreshold &&
-        (!over_overview_transition_threshold ||
-         overview_transition_timer_.IsRunning())) {
-      return;
-    }
-
-    if (over_overview_transition_threshold)
+    if (location_in_screen.y() <= overview_transition_threshold_y_ &&
+        std::abs(scroll_x) + std::abs(scroll_y) <= kMovementVelocityThreshold) {
       ScheduleFinalizeDragAndShowOverview();
-    else
+    } else {
       overview_transition_timer_.Stop();
+    }
   }
 
-  last_location_in_screen_ = location_in_screen;
 
   // Update the home screen scale to match progress during the drag.
   // Use extended threshold as the projected final transition position - UI
@@ -118,15 +110,10 @@ void SwipeHomeToOverviewController::Drag(const gfx::PointF& location_in_screen,
   // more likely to keep dragging up when they get really close to the threshold
   // for transition to overview (and reduce false negatives for detecting
   // transition to overview).
-  const float extended_threshold =
-      overview_transition_threshold_y_ -
-      kVerticalThresholdForOverviewTransition *
-          kExtendedVerticalThresholdForOverviewTransitionRatio;
-
-  const float distance = location_in_screen.y() - extended_threshold;
-  const float target_distance =
-      kVerticalThresholdForOverviewTransition *
-      (1.f + kExtendedVerticalThresholdForOverviewTransitionRatio);
+  const float distance = location_in_screen.y() - scaling_threshold_y_;
+  const float target_distance = overview_transition_threshold_y_ -
+                                scaling_threshold_y_ +
+                                kVerticalThresholdForOverviewTransition;
 
   const float progress = gfx::Tween::CalculateValue(
       gfx::Tween::FAST_OUT_SLOW_IN,
@@ -156,7 +143,6 @@ void SwipeHomeToOverviewController::CancelDrag() {
   }
 
   overview_transition_timer_.Stop();
-  last_location_in_screen_ = gfx::PointF();
   overview_transition_threshold_y_ = 0;
   state_ = State::kFinished;
 
@@ -171,6 +157,9 @@ void SwipeHomeToOverviewController::CancelDrag() {
 }
 
 void SwipeHomeToOverviewController::ScheduleFinalizeDragAndShowOverview() {
+  if (overview_transition_timer_.IsRunning())
+    return;
+
   overview_transition_timer_.Start(
       FROM_HERE, kOverviewTransitionDelay,
       base::BindOnce(
@@ -179,7 +168,6 @@ void SwipeHomeToOverviewController::ScheduleFinalizeDragAndShowOverview() {
 }
 
 void SwipeHomeToOverviewController::FinalizeDragAndShowOverview() {
-  last_location_in_screen_ = gfx::PointF();
   state_ = State::kFinished;
   overview_transition_threshold_y_ = 0;
 

ash/home_screen/swipe_home_to_overview_controller.h

@@ -25,9 +25,8 @@ class ASH_EXPORT SwipeHomeToOverviewController {
   // work area for the gesture to trigger transition to overview.
   static constexpr int kVerticalThresholdForOverviewTransition = 56;
 
-  // The min location change distance required for a drag update to be
-  // registered.
-  static constexpr int kMovementThreshold = 3;
+  // The max pointer velocity at which home transitions to overview.
+  static constexpr int kMovementVelocityThreshold = 10;
 
   // The constructor that uses default tick clock for
   // |overview_transition_timer_|. Should be preferred outside of test
@@ -56,7 +55,7 @@ class ASH_EXPORT SwipeHomeToOverviewController {
  private:
   enum class State { kInitial, kTrackingDrag, kFinished };
 
-  // (Re)starts |overview_transition_timer_|.
+  // Starts |overview_transition_timer_|. No-op if the timer is already running.
   void ScheduleFinalizeDragAndShowOverview();
 
   // Finalizes the drag sequence, and starts overview session.
@@ -68,15 +67,17 @@ class ASH_EXPORT SwipeHomeToOverviewController {
 
   State state_ = State::kInitial;
 
-  // The last detected drag location.
-  gfx::PointF last_location_in_screen_;
-
   // The y in-screen coordinate at which drag, when stopped, will cause
   // transition to overview. Overview session will be started iff the drag stops
   // above this line.
   // The value is set when the controller transitions to kStarted state.
   int overview_transition_threshold_y_ = 0;
 
+  // Home screen is scaled down depending on gesture vertical distance from the
+  // shelf - this is the target gesture vertical location at which home screen
+  // should be scaled by the target scale factor.
+  int scaling_threshold_y_ = 0;
+
   // The timer to run FinalizeDragAndShowOverview().
   base::OneShotTimer overview_transition_timer_;
 

ash/home_screen/swipe_home_to_overview_controller_unittest.cc

@@ -296,12 +296,24 @@ TEST_F(SwipeHomeToOverviewControllerTest, DragMovementRestartsTimeout) {
       GetTimerDesiredRunTime() - tick_clock_.NowTicks();
   EXPECT_GT(delay, base::TimeDelta());
 
-  // Advance clock, and simulate another drag.
-  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
+  const float max_allowed_velocity =
+      SwipeHomeToOverviewController::kMovementVelocityThreshold;
+  // Advance clock, and simulate another drag whose speed is above the max
+  // allowed.
+  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(1));
   Drag(shelf_bounds.top_center() - gfx::Vector2d(0, 2 * transition_threshold),
-       0.f, 1.f);
+       0.f, max_allowed_velocity + 10);
+
+  // Verify the timer was stopped.
+  EXPECT_FALSE(OverviewTransitionTimerRunning());
+  EXPECT_FALSE(OverviewStarted());
+
+  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(1));
+
+  // Another slow drag should restart the timer.
+  Drag(shelf_bounds.top_center() - gfx::Vector2d(0, 2 * transition_threshold),
+       0.f, max_allowed_velocity / 2);
 
-  // Verify the expected timer run time was updated.
   EXPECT_TRUE(OverviewTransitionTimerRunning());
   EXPECT_FALSE(OverviewStarted());
 
@@ -337,33 +349,30 @@ TEST_F(SwipeHomeToOverviewControllerTest,
       GetTimerDesiredRunTime() - tick_clock_.NowTicks();
   EXPECT_GT(delay, base::TimeDelta());
 
-  const int movement_threshold =
-      SwipeHomeToOverviewController::kMovementThreshold;
-  // Advance clock, and simulate another drag, but for small amount.
-  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
+  const float movement_threshold =
+      SwipeHomeToOverviewController::kMovementVelocityThreshold;
+
+  // Advance clock, and simulate another drag, for an amount below the movement
+  // threshold.
+  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(1));
   Drag(shelf_bounds.top_center() -
            gfx::Vector2d(0, transition_threshold + movement_threshold - 1),
-       0.f, 1.f);
+       0.f, movement_threshold / 2);
 
   // Verify the expected timer run time was not updated.
   EXPECT_TRUE(OverviewTransitionTimerRunning());
   EXPECT_FALSE(OverviewStarted());
 
-  EXPECT_EQ(delay - base::TimeDelta::FromMilliseconds(10),
+  EXPECT_EQ(delay - base::TimeDelta::FromMilliseconds(1),
             GetTimerDesiredRunTime() - tick_clock_.NowTicks());
 
-  // Advance clock, and simulate another small drag (the total distance from the
-  // last position being over the movement detection threshold) - verify the
-  // timer is updated.
-  tick_clock_.Advance(base::TimeDelta::FromMilliseconds(10));
+  // Movement with velocity above the allowed threshold restarts the timer.
   Drag(shelf_bounds.top_center() -
-           gfx::Vector2d(0, transition_threshold + movement_threshold),
-       0.f, 1.f);
+           gfx::Vector2d(0, transition_threshold + movement_threshold - 1),
+       0.f, movement_threshold + 1);
 
-  EXPECT_TRUE(OverviewTransitionTimerRunning());
+  EXPECT_FALSE(OverviewTransitionTimerRunning());
   EXPECT_FALSE(OverviewStarted());
-
-  EXPECT_EQ(delay, GetTimerDesiredRunTime() - tick_clock_.NowTicks());
 }
 
 TEST_F(SwipeHomeToOverviewControllerTest, DragBellowThresholdStopsTimer) {