[iOS] Upstream changes to swipe recognizer

ios/chrome/browser/ui/side_swipe_gesture_recognizer.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/side_swipe_gesture_recognizer.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 
 namespace {
 
 // The absolute maximum swipe angle from |x = y| for a swipe to begin.
 const CGFloat kMaxSwipeYAngle = 65;
 // The distance between touches for a swipe to begin.
 const CGFloat kMinSwipeXThreshold = 4;
 
 }  // namespace
 
 @implementation SideSwipeGestureRecognizer {
-  // Starting point of swipe.
-  CGPoint _startPoint;
   // Expected direction of the swipe, based on starting point.
   UISwipeGestureRecognizerDirection _direction;
 }
 
 @synthesize swipeEdge = _swipeEdge;
 @synthesize direction = _direction;
 @synthesize swipeOffset = _swipeOffset;
+@synthesize startPoint = _startPoint;
 
 // To quickly avoid interference with other gesture recognizers, fail
 // immediately if the touches aren't at the edge of the touched view.
 - (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
   [super touchesBegan:touches withEvent:event];
   UITouch* touch = [[event allTouches] anyObject];
   CGPoint location = [touch locationInView:self.view];
-  if (location.x > _swipeEdge &&
-      location.x < CGRectGetMaxX([self.view bounds]) - _swipeEdge) {
-    self.state = UIGestureRecognizerStateFailed;
+  if (_swipeEdge > 0) {
+    if (location.x > _swipeEdge &&
+        location.x < CGRectGetMaxX([self.view bounds]) - _swipeEdge) {
+      self.state = UIGestureRecognizerStateFailed;
+    } else {
+      if (location.x < _swipeEdge) {
+        _direction = UISwipeGestureRecognizerDirectionRight;
+      } else {
+        _direction = UISwipeGestureRecognizerDirectionLeft;
+      }
+      _startPoint = location;
+    }
   } else {
-    if (location.x < _swipeEdge) {
-      _direction = UISwipeGestureRecognizerDirectionRight;
-    } else {
-      _direction = UISwipeGestureRecognizerDirectionLeft;
-    }
     _startPoint = location;
+    _direction = 0;
   }
 }
 
 - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
   // Revert to normal pan gesture recognizer characteristics after state began.
   if (self.state != UIGestureRecognizerStatePossible) {
     [super touchesMoved:touches withEvent:event];
     return;
   }
 
@@ skipping 16 matching lines @@
 
   // Don't recognize swipe in the wrong direction.
   if ((_direction == UISwipeGestureRecognizerDirectionRight &&
        currentPoint.x - _startPoint.x < 0) ||
       (_direction == UISwipeGestureRecognizerDirectionLeft &&
        currentPoint.x - _startPoint.x > 0)) {
     self.state = UIGestureRecognizerStateFailed;
     return;
   }
 
+  if (_swipeEdge == 0 && _direction == 0) {
+    if (currentPoint.x > _startPoint.x) {
+      _direction = UISwipeGestureRecognizerDirectionRight;
+    } else {
+      _direction = UISwipeGestureRecognizerDirectionLeft;
+    }
+  }
+
   // Begin recognizer after |kMinSwipeXThreshold| distance swiped.
   if (std::abs(currentPoint.x - _startPoint.x) > kMinSwipeXThreshold) {
     if (_direction == UISwipeGestureRecognizerDirectionRight) {
       _swipeOffset = currentPoint.x;
     } else {
       _swipeOffset = -(CGRectGetMaxX([self.view bounds]) - currentPoint.x);
     }
 
     self.state = UIGestureRecognizerStateBegan;
     return;
   }
 }
 
 - (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
   _startPoint = CGPointZero;
   [super touchesEnded:touches withEvent:event];
 }
 
 - (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event {
   _startPoint = CGPointZero;
   [super touchesCancelled:touches withEvent:event];
 }
 
 @end