Change ViewRevealingVerticalPanHandler's base view height when the user

rotates the screen.

Update the ViewRevealingVerticalPanHandler's base view height when the
BVC transitions to a different size. Keep track of whether the BVC is
positioned at the bottom of the screen and reposition it on rotation if
needed.

Bug: 1123729, 1127604
Change-Id: I8fb2ee0f531204ff3788845af8f32b515f101931
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414393Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Roberto Moura <mouraroberto@google.com>
Cr-Commit-Position: refs/heads/master@{#807822}

ios/chrome/browser/ui/browser_view/browser_view_controller.mm

@@ -493,6 +493,9 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 // Whether BVC prefers to hide the status bar. This value is used to determine
 // the response from the |prefersStatusBarHidden| method.
 @property(nonatomic, assign) BOOL hideStatusBar;
+// Whether the BVC is positioned at the bottom of the window, for example after
+// switching from thumb strip to tab grid.
+@property(nonatomic, assign) BOOL bottomPosition;
 // Coordinator for displaying a modal overlay with activity indicator to prevent
 // the user from interacting with the browser view.
 @property(nonatomic, strong)
@@ -1648,6 +1651,16 @@ NSString* const kBrowserViewControllerSnackbarCategory =
           [strongSelf.tabStripCoordinator tabStripSizeDidChange];
         }
       }];
+
+  if (IsThumbStripEnabled()) {
+    CGFloat baseViewHeight = size.height;
+    self.thumbStripPanHandler.baseViewHeight = baseViewHeight;
+    // On rotation, reposition the BVC container if positioned at the bottom.
+    if (self.bottomPosition) {
+      self.view.superview.transform = CGAffineTransformMakeTranslation(
+          0, self.thumbStripPanHandler.revealedHeight);
+    }
+  }
 }
 
 - (void)dismissViewControllerAnimated:(BOOL)flag
@@ -2778,6 +2791,7 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 - (void)didAnimateViewReveal:(ViewRevealState)viewRevealState {
   self.tabStripView.hidden = (viewRevealState != ViewRevealState::Hidden);
   [self.tabStripSnapshot removeFromSuperview];
+  self.bottomPosition = (viewRevealState == ViewRevealState::Revealed);
 }
 
 #pragma mark - BubblePresenterDelegate

ios/chrome/browser/ui/gestures/view_revealing_vertical_pan_handler.h

@@ -14,8 +14,6 @@
 // TODO(crbug.com/1123512): Add support for going straight from a Hidden state
 // to a revealed state (and vice-versa) if the gesture's translation and
 // velocity are enough to trigger such transition.
-// TODO(crbug.com/1123729): Change base view size when the user rotates the
-// screen.
 @interface ViewRevealingVerticalPanHandler : NSObject
 
 // |peekedHeight| is the height of the view when peeked (partially revealed).
@@ -41,6 +39,8 @@
 @property(nonatomic, assign, readonly) CGFloat peekedHeight;
 // Height of the revealed view after the transition to Revealed state.
 @property(nonatomic, assign, readonly) CGFloat revealedHeight;
+// Height of the base view. It changes when the user rotates the screen.
+@property(nonatomic, assign) CGFloat baseViewHeight;
 
 @end
 

ios/chrome/browser/ui/gestures/view_revealing_vertical_pan_handler.mm

@@ -36,8 +36,6 @@ const CGFloat kAnimationDuration = 0.25f;
 // Total distance between the Peeked state and Revealed state. Equal to
 // |revealedHeight| - |peekedHeight|.
 @property(nonatomic, assign, readonly) CGFloat remainingHeight;
-// Height of the base view.
-@property(nonatomic, assign, readonly) CGFloat baseViewHeight;
 // Height of the cover view (the view in front of the view that will be
 // revealed) that will still be visible after the remaining reveal transition.
 @property(nonatomic, assign, readonly) CGFloat revealedCoverHeight;
@@ -81,6 +79,12 @@ const CGFloat kAnimationDuration = 0.25f;
   [self.animatees addObject:animatee];
 }
 
+- (void)setBaseViewHeight:(CGFloat)baseViewHeight {
+  _baseViewHeight = baseViewHeight;
+  _revealedHeight = baseViewHeight - _revealedCoverHeight;
+  _remainingHeight = _revealedHeight - _peekedHeight;
+}
+
 #pragma mark - Private Methods: Animating
 
 // Called right before an animation block to warn all animatees of a transition