Update gesture logic.

athena/home/home_card_gesture_manager.cc

Index: athena/home/home_card_gesture_manager.cc
diff --git a/athena/home/home_card_gesture_manager.cc b/athena/home/home_card_gesture_manager.cc
index 9d53e3500889ac2218329ddd2937af6ed8396023..cc7ee829d2431959fe8db6b7187ec3fd12d2a4da 100644
--- a/athena/home/home_card_gesture_manager.cc
+++ b/athena/home/home_card_gesture_manager.cc
@@ -9,9 +9,31 @@
 
 namespace athena {
 
+namespace {
+
+// The additional height to the minimized home. If the currently estimated
+// height is smaller than this buffer, it is considered as the minimized state.
+const int kMinimizedHomeBufferSize = 50;

[pkotwicz, 2014/09/18 21:11:50]

This might be slightly clearer:

// The maximum height, in pixels, of a home card with final state
VISIBLE_MINIMIZED.
const int kFinalStateMaxHeight = 50;

// The maximum height, in pixels, of an initially centered home card with final
state VISIBLE_MINIMIZED.
const int kMinimizedFinalStateMaxHeightInitiallyCentered = 90;

// The minimum height, as a percentage of the screen height, of a home card with
final state VISIBLE_CENTERED.
const int kCenteredFinalStateMinScreenRatio = 0.5f;

// The minimum height, as a percentage of the screen height, of an initially
minimized home card with final state VISIBLE_CENTERED.
const int kCenteredFinalStateMinScreenRatio = 0.3f;

[Jun Mukai, 2014/09/18 21:57:29]

Done.

+
+// Same as |kMinimizedHomeBufferSize| but this value is used when the original
+// state is centered.
+const int kMinimizedHomeBufferSizeForCentered = 90;
+
+// The height boundary between the bottom state and the centereed state. If
+// the currently estimated height is bigger than this, it is considered as the
+// centered state. Otherwise, it's bottom (or minimized if it's too way small).
+// This value is the rate to the actual screen height.
+const float kBottomBoundaryRate = 0.5f;
+
+// Same as |kBottomBoundaryRate| but used when the original state is minimized.
+const float kBottomBoundaryRateForMinimized = 0.3f;
+
+}
+
 HomeCardGestureManager::HomeCardGestureManager(Delegate* delegate,
                                                const gfx::Rect& screen_bounds)
     : delegate_(delegate),
+      original_state_(HomeCard::HIDDEN),
       y_offset_(0),
       last_estimated_height_(0),
       screen_bounds_(screen_bounds) {}
@@ -22,6 +44,8 @@ void HomeCardGestureManager::ProcessGestureEvent(ui::GestureEvent* event) {
   switch (event->type()) {
     case ui::ET_GESTURE_SCROLL_BEGIN:
       y_offset_ = event->location().y();
+      original_state_ = HomeCard::Get()->GetState();
+      DCHECK_NE(HomeCard::HIDDEN, original_state_);
       event->SetHandled();
       break;
     case ui::ET_GESTURE_SCROLL_END:
@@ -35,7 +59,17 @@ void HomeCardGestureManager::ProcessGestureEvent(ui::GestureEvent* event) {
       const ui::GestureEventDetails& details = event->details();
       const float kFlingCompletionVelocity = 100.0f;
       HomeCard::State final_state = GetClosestState();
-      if (::fabs(details.velocity_y()) > kFlingCompletionVelocity) {
+
+      // When the scroll updates don't move enough to switch to another states

[pkotwicz, 2014/09/18 21:11:50]

How about: "When the user does not drag far enough to switch the final state,
but a fling happens at the end of the gesture, the state should change based on
the direction of the fling.
Checking |final_state| == |original_state| may cause unexpected results for
gestures where the user flings in the opposite direction that they moved the
home card (e.g. drag home card up from minimized state and then fling down)
TODO(mukai): Consider this case once reported.

[Jun Mukai, 2014/09/18 21:57:29]

Done.

+      // but a fling happens at the end of a gesture, it should change the state
+      // in the direction to the fling velocity.
+      // This check of |final_state| and |original_state_| may cause unexpected
+      // results for some gestures, such like swipe up from minimized state ->
+      // move up to full screen -> fling down there. This type of gestures are
+      // considered rare.
+      // TODO(mukai): consider such case once reported.
+      if (final_state == original_state_ &&
+          ::fabs(details.velocity_y()) > kFlingCompletionVelocity) {
         if (details.velocity_y() > 0) {
           final_state = std::min(HomeCard::VISIBLE_MINIMIZED,
                                  static_cast<HomeCard::State>(final_state + 1));
@@ -54,17 +88,18 @@ void HomeCardGestureManager::ProcessGestureEvent(ui::GestureEvent* event) {
 }
 
 HomeCard::State HomeCardGestureManager::GetClosestState() const {

[pkotwicz, 2014/09/18 21:11:50]

GetFinalState() is probably a better name

[Jun Mukai, 2014/09/18 21:57:29]

Done.

-  const int kMinimizedHomeBufferSize = 50;
-  if (last_estimated_height_ <=
-      kHomeCardMinimizedHeight + kMinimizedHomeBufferSize) {
+  int buffer = (original_state_ == HomeCard::VISIBLE_CENTERED)
+      ? kMinimizedHomeBufferSizeForCentered
+      : kMinimizedHomeBufferSize;
+  if (last_estimated_height_ < kHomeCardMinimizedHeight + buffer)
     return HomeCard::VISIBLE_MINIMIZED;
-  }
 
-  int centered_height = screen_bounds_.height();
-  if (last_estimated_height_ - kHomeCardHeight <=
-      (centered_height - kHomeCardHeight) / 3) {
+  float multiplier = (original_state_ == HomeCard::VISIBLE_MINIMIZED)
+      ? kBottomBoundaryRateForMinimized
+      : kBottomBoundaryRate;
+  if (last_estimated_height_ < screen_bounds_.height() * multiplier)
     return HomeCard::VISIBLE_BOTTOM;
-  }
+
   return HomeCard::VISIBLE_CENTERED;
 }