Mac: Don't allow history swiping after substantial vertical motion.

Previously, the logic for history swiping depended on the relative Y distance
of the gesture's current location from the gesture's start location. Gestures
which consisted of a large up motion, followed by a large down motion, followed
by a horizontal motion could still cause history swiping. The new logic depends
on the total Y distance of the gesture, which fixes this problem.

This CL also includes a change to allowed the gesture recognizer state machine
to enter the state kCancelled directly from the state kPending. Previously, it
was possible for the history overlay to show for a very brief period of time
even if the gesture was about to be cancelled.

This CL also includes a minor refactor:
 - Renamed several methods to better reflect their intended purpose.
 - Removed lastProcessedGestureId_ and currentGestureId_, which did not cause a
 functional change.

BUG=421629

Review URL: https://codereview.chromium.org/657323003

Cr-Commit-Position: refs/heads/master@{#300199}

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.h

@@ -13,10 +13,10 @@ class WebMouseWheelEvent;
 
 @class HistorySwiper;
 @protocol HistorySwiperDelegate
-// Return NO from this method is the view/render_widget_host should not
+// Return NO from this method if the view/render_widget_host should not
 // allow history swiping.
 - (BOOL)shouldAllowHistorySwiping;
-// The history overlay is added to the view returning from this method.
+// The history overlay is added to the view returned from this method.
 - (NSView*)viewThatWantsHistoryOverlay;
 @end
 
@@ -25,6 +25,11 @@ enum NavigationDirection {
   kBackwards = 0,
   kForwards,
 };
+
+// The states of a state machine that recognizes the history swipe gesture.
+// When a gesture first begins, the state is reset to kPending. The state
+// machine only applies to trackpad gestures. Magic Mouse gestures use a
+// different mechanism.
 enum RecognitionState {
   // Waiting to see whether the renderer will handle the event with phase
   // NSEventPhaseBegan. The state machine will also stay in this state if
@@ -97,13 +102,13 @@ enum RecognitionState {
 //   then this class will transition to the state kTracking. Events are
 //   consumed, and not passed to the renderer.
 //
-// There are multiple APIs that provide information about gestures on the
-// trackpad. This class uses two different set of APIs.
-//   1. The -[NSView touches*WithEvent:] APIs provide detailed information
+// There are multiple callbacks that provide information about gestures on the
+// trackpad. This class uses two different sets of callbacks.
+//   1. The -[NSView touches*WithEvent:] callbacks provide detailed information
 //   about the touches within a gesture. The callbacks happen with more
-//   frequency, and have higher accuracy. These APIs are used to transition
-//   between all state, exception for kPending -> kPotential.
-//   2. The -[NSView scrollWheel:] API provides less information, but the
+//   frequency, and have higher accuracy. These callbacks are used to
+//   transition between all states except for kPending -> kPotential.
+//   2. The -[NSView scrollWheel:] callback provides less information, but the
 //   events are passed to the renderer. This class must process these events so
 //   that it can decide whether to consume the events and prevent them from
 //   being passed to the renderer. This API is used to transition from kPending
@@ -113,13 +118,12 @@ enum RecognitionState {
  @private
   // This controller will exist if and only if the UI is in history swipe mode.
   HistoryOverlayController* historyOverlay_;
-  // Each gesture received by the window is given a unique id.
-  // The id is monotonically increasing.
-  int currentGestureId_;
   // The location of the fingers when the gesture started.
   NSPoint gestureStartPoint_;
   // The current location of the fingers in the gesture.
   NSPoint gestureCurrentPoint_;
+  // The total Y distance moved since the beginning of the gesture.
+  CGFloat gestureTotalY_;
   // A flag that indicates that there is an ongoing gesture. Only used to
   // determine whether swipe events are coming from a Magic Mouse.
   BOOL inGesture_;
@@ -128,11 +132,13 @@ enum RecognitionState {
   // Each time a new gesture begins, we must get a new start point.
   // This ivar determines whether the start point is valid.
   int gestureStartPointValid_;
-  // The id of the last gesture that we processed as a history swipe.
-  int lastProcessedGestureId_;
-  // A flag that indicates the user's intended direction with the history swipe.
+
+  // The user's intended direction with the history swipe. Set during the
+  // transition from kPending -> kPotential.
   history_swiper::NavigationDirection historySwipeDirection_;
-  // A flag that indicates whether the gesture has its direction inverted.
+
+  // Whether the history swipe gesture has its direction inverted. Set during
+  // the transition from kPending -> kPotential.
   BOOL historySwipeDirectionInverted_;
 
   // Whether the event with phase NSEventPhaseBegan was not consumed by the

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm

@@ -17,10 +17,8 @@
 - (BOOL)browserCanNavigateInDirection:
         (history_swiper::NavigationDirection)forward
                                 event:(NSEvent*)event;
-- (void)endHistorySwipe;
-- (void)beginHistorySwipeInDirection:
-        (history_swiper::NavigationDirection)goForward
-                               event:(NSEvent*)event;
+- (void)removeHistoryOverlay;
+- (void)showHistoryOverlay:(history_swiper::NavigationDirection)direction;
 - (void)navigateBrowserInDirection:(history_swiper::NavigationDirection)forward;
 - (void)initiateMagicMouseHistorySwipe:(BOOL)isRightScroll
                                  event:(NSEvent*)event;
@@ -51,22 +49,18 @@ class MacHistorySwiperTest : public CocoaTest {
         browserCanNavigateInDirection:history_swiper::kBackwards
                                 event:[OCMArg any]];
     [[[[mockHistorySwiper stub] andDo:^(NSInvocation* invocation) {
-      ++begin_count_;
-      // beginHistorySwipeInDirection: calls endHistorySwipe internally.
-      --end_count_;
-    }] andForwardToRealObject]
-        beginHistorySwipeInDirection:history_swiper::kForwards
-                               event:[OCMArg any]];
+        ++begin_count_;
+        // showHistoryOverlay: calls removeHistoryOverlay internally.
+        --end_count_;
+    }] andForwardToRealObject] showHistoryOverlay:history_swiper::kForwards];
     [[[[mockHistorySwiper stub] andDo:^(NSInvocation* invocation) {
-      ++begin_count_;
-      // beginHistorySwipeInDirection: calls endHistorySwipe internally.
-      --end_count_;
-    }] andForwardToRealObject]
-        beginHistorySwipeInDirection:history_swiper::kBackwards
-                               event:[OCMArg any]];
+        ++begin_count_;
+        // showHistoryOverlay: calls removeHistoryOverlay internally.
+        --end_count_;
+    }] andForwardToRealObject] showHistoryOverlay:history_swiper::kBackwards];
     [[[[mockHistorySwiper stub] andDo:^(NSInvocation* invocation) {
-      ++end_count_;
-    }] andForwardToRealObject] endHistorySwipe];
+        ++end_count_;
+    }] andForwardToRealObject] removeHistoryOverlay];
     [[[mockHistorySwiper stub] andDo:^(NSInvocation* invocation) {
         navigated_right_ = true;
     }] navigateBrowserInDirection:history_swiper::kForwards];
@@ -287,7 +281,7 @@ TEST_F(MacHistorySwiperTest, SwipeDiagonal) {
   moveGestureAtPoint(makePoint(0.6, 0.59));
   endGestureAtPoint(makePoint(0.6, 0.59));
 
-  EXPECT_EQ(begin_count_, 1);
+  EXPECT_EQ(begin_count_, 0);
   EXPECT_EQ(end_count_, 1);
   EXPECT_FALSE(navigated_right_);
   EXPECT_FALSE(navigated_left_);
@@ -380,7 +374,7 @@ TEST_F(MacHistorySwiperTest, NoSwipe) {
   // No movement.
   endGestureAtPoint(makePoint(0.44, 0.44));
 
-  EXPECT_EQ(begin_count_, 1);
+  EXPECT_EQ(begin_count_, 0);
   EXPECT_EQ(end_count_, 1);
   EXPECT_FALSE(navigated_right_);
   EXPECT_FALSE(navigated_left_);
@@ -451,3 +445,30 @@ TEST_F(MacHistorySwiperTest, SwipeRightEventOrdering) {
   EXPECT_TRUE(navigated_right_);
   EXPECT_FALSE(navigated_left_);
 }
+
+// Substantial vertical scrolling followed by horizontal scrolling should not
+// result in navigation.
+TEST_F(MacHistorySwiperTest, SubstantialVerticalThenHorizontal) {
+  // These tests require 10.7+ APIs.
+  if (![NSEvent
+          respondsToSelector:@selector(isSwipeTrackingFromScrollEventsEnabled)])
+    return;
+
+  startGestureInMiddle();
+  moveGestureInMiddle();
+
+  // Move up, then move down.
+  for (CGFloat y = 0.51; y < 0.6; y += 0.01)
+    moveGestureAtPoint(makePoint(0.5, y));
+  for (CGFloat y = 0.59; y > 0.5; y -= 0.01)
+    moveGestureAtPoint(makePoint(0.5, y));
+
+  // Large movement to the right.
+  moveGestureAtPoint(makePoint(0.6, 0.51));
+  endGestureAtPoint(makePoint(0.6, 0.51));
+
+  EXPECT_EQ(begin_count_, 0);
+  EXPECT_EQ(end_count_, 1);
+  EXPECT_FALSE(navigated_right_);
+  EXPECT_FALSE(navigated_left_);
+}