[iOS] Adjust SideSwipe animations

This CL updates the SideSwipe animations, using transforms instead of
modifying frames. Modifying frames wasn't working as expected as the
cards are positioned using autolayout.

Bug: 867968
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I3532a50a50078c07ee68e4c47f59c426c7dd461c
Reviewed-on: https://chromium-review.googlesource.com/1158824Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581174}

ios/chrome/browser/ui/side_swipe/card_side_swipe_view.mm

@@ -257,29 +257,22 @@ const CGFloat kResizeFactor = 4;
   self.backgroundTopConstraint.constant = -StatusBarHeight();
 }
 
-- (CGRect)cardFrame {
-  return self.bounds;
+- (CGFloat)cardWidth {
+  return CGRectGetWidth(self.bounds);
 }
 
 // Set up left and right card views depending on current tab and swipe
 // direction.
 - (void)updateViewsForDirection:(UISwipeGestureRecognizerDirection)direction {
   _direction = direction;
-  CGRect cardFrame = [self cardFrame];
   NSUInteger currentIndex = [model_ indexOfTab:model_.currentTab];
   CGFloat offset = UseRTLLayout() ? -1 : 1;
   if (_direction == UISwipeGestureRecognizerDirectionRight) {
     [self setupCard:_rightCard withIndex:currentIndex];
-    [_rightCard setFrame:cardFrame];
     [self setupCard:_leftCard withIndex:currentIndex - offset];
-    cardFrame.origin.x -= cardFrame.size.width + kCardHorizontalSpacing;
-    [_leftCard setFrame:cardFrame];
   } else {
     [self setupCard:_leftCard withIndex:currentIndex];
-    [_leftCard setFrame:cardFrame];
     [self setupCard:_rightCard withIndex:currentIndex + offset];
-    cardFrame.origin.x += cardFrame.size.width + kCardHorizontalSpacing;
-    [_rightCard setFrame:cardFrame];
   }
 }
 
@@ -336,40 +329,26 @@ const CGFloat kResizeFactor = 4;
       });
 }
 
-// Place cards around |currentPoint_.x|, and lean towards each card near the
-// X edges of |bounds|.  Shrink cards as they are dragged towards the middle of
-// the |bounds|, and edge cards only drag |kEdgeCardDragPercentage| of |bounds|.
+// Move cards according to |currentPoint_.x|. Edge cards only drag
+// |kEdgeCardDragPercentage| of |bounds|.
 - (void)updateCardPositions {
-  CGRect bounds = [self cardFrame];
-  [_rightCard setFrame:bounds];
-  [_leftCard setFrame:bounds];
+  CGFloat width = [self cardWidth];
 
-  CGFloat width = CGRectGetWidth([self cardFrame]);
-  CGPoint center = CGPointMake(bounds.origin.x + bounds.size.width / 2,
-                               bounds.origin.y + bounds.size.height / 2);
   if ([self isEdgeSwipe]) {
     // If an edge card, don't allow the card to be dragged across the screen.
     // Instead, drag across |kEdgeCardDragPercentage| of the screen.
-    center.x = currentPoint_.x - width / 2 -
-               (currentPoint_.x - width) / width *
-                   (width * (1 - kEdgeCardDragPercentage));
-    [_leftCard setCenter:center];
-    center.x = currentPoint_.x / width * (width * kEdgeCardDragPercentage) +
-               bounds.size.width / 2;
-    [_rightCard setCenter:center];
+    _rightCard.transform = CGAffineTransformMakeTranslation(
+        (currentPoint_.x) * kEdgeCardDragPercentage, 0);
+    _leftCard.transform = CGAffineTransformMakeTranslation(
+        (currentPoint_.x - width) * kEdgeCardDragPercentage, 0);
   } else {
-    // Place cards around the finger as it is dragged across the screen.
-    // Place the finger between the cards in the middle of the screen, on the
-    // right card border when on the left side of the screen, and on the left
-    // card border when on the right side of the screen.
     CGFloat rightXBuffer = kCardHorizontalSpacing * currentPoint_.x / width;
     CGFloat leftXBuffer = kCardHorizontalSpacing - rightXBuffer;
 
-    center.x = currentPoint_.x - leftXBuffer - width / 2;
-    [_leftCard setCenter:center];
-
-    center.x = currentPoint_.x + rightXBuffer + width / 2;
-    [_rightCard setCenter:center];
+    _rightCard.transform =
+        CGAffineTransformMakeTranslation(currentPoint_.x + rightXBuffer, 0);
+    _leftCard.transform = CGAffineTransformMakeTranslation(
+        -width + currentPoint_.x - leftXBuffer, 0);
   }
 }
 
@@ -380,7 +359,7 @@ const CGFloat kResizeFactor = 4;
 
   // Since it's difficult to touch the very edge of the screen (touches tend to
   // sit near x ~ 4), push the touch towards the edge.
-  CGFloat width = CGRectGetWidth([self cardFrame]);
+  CGFloat width = [self cardWidth];
   CGFloat half = floor(width / 2);
   CGFloat padding = floor(std::abs(currentPoint_.x - half) / half);
 
@@ -420,38 +399,41 @@ const CGFloat kResizeFactor = 4;
   if (currentIndex == NSNotFound)
     return [_delegate sideSwipeViewDismissAnimationDidEnd:self];
 
-  CGRect finalSize = [self cardFrame];
-  CGFloat width = CGRectGetWidth([self cardFrame]);
-  CGRect leftFrame, rightFrame;
+  CGFloat width = [self cardWidth];
+  CGAffineTransform rightTransform, leftTransform;
   SwipeView* dominantCard;
   Tab* destinationTab = model_.currentTab;
   CGFloat offset = UseRTLLayout() ? -1 : 1;
   if (_direction == UISwipeGestureRecognizerDirectionRight) {
     // If swipe is right and |currentPoint_.x| is over the first 1/3, move left.
     if (currentPoint_.x > width / 3.0 && ![self isEdgeSwipe]) {
+      rightTransform =
+          CGAffineTransformMakeTranslation(width + kCardHorizontalSpacing, 0);
+      leftTransform = CGAffineTransformIdentity;
       destinationTab = [model_ tabAtIndex:currentIndex - offset];
       dominantCard = _leftCard;
-      rightFrame = leftFrame = finalSize;
-      rightFrame.origin.x += rightFrame.size.width + kCardHorizontalSpacing;
       base::RecordAction(UserMetricsAction("MobileStackSwipeCompleted"));
     } else {
+      leftTransform =
+          CGAffineTransformMakeTranslation(-width - kCardHorizontalSpacing, 0);
+      rightTransform = CGAffineTransformIdentity;
       dominantCard = _rightCard;
-      leftFrame = rightFrame = finalSize;
-      leftFrame.origin.x -= rightFrame.size.width + kCardHorizontalSpacing;
       base::RecordAction(UserMetricsAction("MobileStackSwipeCancelled"));
     }
   } else {
     // If swipe is left and |currentPoint_.x| is over the first 1/3, move right.
     if (currentPoint_.x < (width / 3.0) * 2.0 && ![self isEdgeSwipe]) {
+      leftTransform =
+          CGAffineTransformMakeTranslation(-width - kCardHorizontalSpacing, 0);
+      rightTransform = CGAffineTransformIdentity;
       destinationTab = [model_ tabAtIndex:currentIndex + offset];
       dominantCard = _rightCard;
-      leftFrame = rightFrame = finalSize;
-      leftFrame.origin.x -= rightFrame.size.width + kCardHorizontalSpacing;
       base::RecordAction(UserMetricsAction("MobileStackSwipeCompleted"));
     } else {
+      rightTransform =
+          CGAffineTransformMakeTranslation(width + kCardHorizontalSpacing, 0);
+      leftTransform = CGAffineTransformIdentity;
       dominantCard = _leftCard;
-      rightFrame = leftFrame = finalSize;
-      rightFrame.origin.x += rightFrame.size.width + kCardHorizontalSpacing;
       base::RecordAction(UserMetricsAction("MobileStackSwipeCancelled"));
     }
   }
@@ -467,10 +449,8 @@ const CGFloat kResizeFactor = 4;
 
   [UIView animateWithDuration:kAnimationDuration
       animations:^{
-        [_leftCard setTransform:CGAffineTransformIdentity];
-        [_rightCard setTransform:CGAffineTransformIdentity];
-        [_leftCard setFrame:leftFrame];
-        [_rightCard setFrame:rightFrame];
+        _leftCard.transform = leftTransform;
+        _rightCard.transform = rightTransform;
       }
       completion:^(BOOL finished) {
         [_leftCard setImage:nil];