[iOS][Thumb Strip] Transform BVC Container directly

This CL applies the BVCContainer transforms directly to it instead of
BVC applying them to its superview. Previous approach had a race
condition where in some cases the BVC was already removed from it's
container leaving the BVCContainer in the previous state.

It also contains a few readability fixes in the involved methods.

Bug: 1164978
Change-Id: I6e6cce85dca0478a062f04f7ba93aba14a051d74
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2629968Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Robbie Gibson <rkgibson@google.com>
Commit-Queue: Javier Flores <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844929}

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

@@ -2959,33 +2959,33 @@ NSString* const kBrowserViewControllerSnackbarCategory =
 }
 
 - (void)animateViewReveal:(ViewRevealState)nextViewRevealState {
+  CGFloat tabStripHeight = self.tabStripView.frame.size.height;
+  CGFloat hideHeight = tabStripHeight + self.headerOffset;
   switch (nextViewRevealState) {
     case ViewRevealState::Hidden:
-      self.view.superview.transform = CGAffineTransformIdentity;
       self.view.transform = CGAffineTransformIdentity;
-      if (!base::FeatureList::IsEnabled(kModernTabStrip))
+      if (!base::FeatureList::IsEnabled(kModernTabStrip)) {
         self.tabStripSnapshot.transform =
             [self.tabStripView adjustTransformForRTL:CGAffineTransformIdentity];
+      }
       break;
     case ViewRevealState::Peeked:
-      self.view.superview.transform = CGAffineTransformMakeTranslation(
-          0, self.thumbStripPanHandler.peekedHeight);
-      self.view.transform = CGAffineTransformMakeTranslation(
-          0, -self.tabStripView.frame.size.height - self.headerOffset);
-      if (!base::FeatureList::IsEnabled(kModernTabStrip))
-        self.tabStripSnapshot.transform = [self.tabStripView
-            adjustTransformForRTL:CGAffineTransformMakeTranslation(
-                                      0, self.tabStripView.frame.size.height)];
+      self.view.transform = CGAffineTransformMakeTranslation(0, -hideHeight);
+      if (!base::FeatureList::IsEnabled(kModernTabStrip)) {
+        CGAffineTransform transform =
+            CGAffineTransformMakeTranslation(0, tabStripHeight);
+        self.tabStripSnapshot.transform =
+            [self.tabStripView adjustTransformForRTL:transform];
+      }
       break;
     case ViewRevealState::Revealed:
-      self.view.superview.transform = CGAffineTransformMakeTranslation(
-          0, self.thumbStripPanHandler.revealedHeight);
-      self.view.transform = CGAffineTransformMakeTranslation(
-          0, -self.tabStripView.frame.size.height - self.headerOffset);
-      if (!base::FeatureList::IsEnabled(kModernTabStrip))
-        self.tabStripSnapshot.transform = [self.tabStripView
-            adjustTransformForRTL:CGAffineTransformMakeTranslation(
-                                      0, self.tabStripView.frame.size.height)];
+      self.view.transform = CGAffineTransformMakeTranslation(0, -hideHeight);
+      if (!base::FeatureList::IsEnabled(kModernTabStrip)) {
+        CGAffineTransform transform =
+            CGAffineTransformMakeTranslation(0, tabStripHeight);
+        self.tabStripSnapshot.transform =
+            [self.tabStripView adjustTransformForRTL:transform];
+      }
       break;
   }
 }

ios/chrome/browser/ui/main/BUILD.gn

@@ -205,6 +205,7 @@ source_set("main") {
     "//ios/chrome/browser/ui/commands",
     "//ios/chrome/browser/ui/coordinators:chrome_coordinators",
     "//ios/chrome/browser/ui/download",
+    "//ios/chrome/browser/ui/gestures",
     "//ios/chrome/browser/ui/incognito_reauth:incognito_reauth_scene_agent",
     "//ios/chrome/browser/ui/page_info:coordinator",
     "//ios/chrome/browser/ui/print",
@@ -213,6 +214,7 @@ source_set("main") {
     "//ios/chrome/browser/ui/recent_tabs",
     "//ios/chrome/browser/ui/settings/sync",
     "//ios/chrome/browser/ui/snackbar",
+    "//ios/chrome/browser/ui/thumb_strip",
     "//ios/chrome/browser/ui/thumb_strip:feature_flags",
     "//ios/chrome/browser/ui/translate:legacy_translate",
     "//ios/chrome/browser/ui/util:multiwindow_util",

ios/chrome/browser/ui/main/bvc_container_view_controller.h

@@ -7,6 +7,9 @@
 
 #import <UIKit/UIKit.h>
 
+#import "ios/chrome/browser/ui/gestures/view_revealing_animatee.h"
+#import "ios/chrome/browser/ui/thumb_strip/thumb_strip_attacher.h"
+
 // A UIViewController instance designed to contain an instance of
 // BrowserViewController ("BVC") as a child. Since the BVC itself often
 // implements a great deal of custom logic around handling view controller
@@ -16,7 +19,8 @@
 // This class isn't coupled to any implementation details of the BVC; it could
 // be used as a generic forwarding container if needed. In that case, its name
 // should be changed.
-@interface BVCContainerViewController : UIViewController
+@interface BVCContainerViewController
+    : UIViewController <ThumbStripAttacher, ViewRevealingAnimatee>
 
 // The BVC instance being contained. If this is set, the current BVC (if any)
 // will be removed as a child view controller, and the new |currentBVC| will

ios/chrome/browser/ui/main/bvc_container_view_controller.mm

@@ -7,6 +7,7 @@
 #include <ostream>
 
 #include "base/check_op.h"
+#import "ios/chrome/browser/ui/gestures/view_revealing_vertical_pan_handler.h"
 #import "ios/chrome/browser/ui/thumb_strip/thumb_strip_feature.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
@@ -15,6 +16,8 @@
 
 @implementation BVCContainerViewController
 
+@synthesize thumbStripPanHandler = _thumbStripPanHandler;
+
 #pragma mark - public property implementation
 
 - (UIViewController*)currentBVC {
@@ -96,4 +99,30 @@
                          : [super shouldAutorotate];
 }
 
+#pragma mark - ViewRevealingAnimatee
+
+- (void)willAnimateViewReveal:(ViewRevealState)currentViewRevealState {
+  // No-op.
+}
+
+- (void)animateViewReveal:(ViewRevealState)nextViewRevealState {
+  switch (nextViewRevealState) {
+    case ViewRevealState::Hidden:
+      self.view.transform = CGAffineTransformIdentity;
+      break;
+    case ViewRevealState::Peeked:
+      self.view.transform = CGAffineTransformMakeTranslation(
+          0, self.thumbStripPanHandler.peekedHeight);
+      break;
+    case ViewRevealState::Revealed:
+      self.view.transform = CGAffineTransformMakeTranslation(
+          0, self.thumbStripPanHandler.revealedHeight);
+      break;
+  }
+}
+
+- (void)didAnimateViewReveal:(ViewRevealState)viewRevealState {
+  // No-op.
+}
+
 @end

ios/chrome/browser/ui/tab_switcher/tab_grid/tab_grid_coordinator.mm

@@ -279,6 +279,12 @@
 
   self.bvcContainer = [[BVCContainerViewController alloc] init];
   self.bvcContainer.currentBVC = viewController;
+  if (IsThumbStripEnabled()) {
+    self.bvcContainer.thumbStripPanHandler =
+        self.thumbStripCoordinator.panHandler;
+    [self.thumbStripCoordinator.panHandler addAnimatee:self.bvcContainer];
+  }
+
   BOOL animated = !self.animationsDisabledForTesting;
   // Never animate the first time.
   if (self.firstPresentation)