[ios] Updates the internal structure of MainPresentingViewController.

The TabSwitcher is now displayed as a contained child, while BVCs are presented
inside a container VC.  This structure allows for BVCs to be presented even
before a TabSwitcher is created, and it allows incognito/non-incognito BVCs to
be swapped without having to dismiss and re-present view controllers.

More details can be found in the design doc at
https://docs.google.com/document/d/11kI9oH8NUl0oJU_ZRHt6amblGyzPSwhvB_7JWsKayGY/view

BUG=768563

Change-Id: I971cf80c1c2714d801f9885369ce1d0fb95afb28
Reviewed-on: https://chromium-review.googlesource.com/723940Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Rohit Rao (ping after 24h) <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509919}

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

@@ -10,58 +10,138 @@
 #error "This file requires ARC support."
 #endif
 
+@interface BVCContainerViewController : UIViewController
+
+@property(nonatomic, weak) UIViewController* currentBVC;
+
+@end
+
+@implementation BVCContainerViewController
+
+- (UIViewController*)currentBVC {
+  return [self.childViewControllers firstObject];
+}
+
+- (void)setCurrentBVC:(UIViewController*)bvc {
+  DCHECK(bvc);
+  if (self.currentBVC == bvc) {
+    return;
+  }
+
+  // Remove the current bvc, if any.
+  if (self.currentBVC) {
+    [self.currentBVC willMoveToParentViewController:nil];
+    [self.currentBVC.view removeFromSuperview];
+    [self.currentBVC removeFromParentViewController];
+  }
+
+  DCHECK_EQ(nil, self.currentBVC);
+  DCHECK_EQ(0U, self.view.subviews.count);
+
+  // Add the new active view controller.
+  [self addChildViewController:bvc];
+  bvc.view.frame = self.view.bounds;
+  [self.view addSubview:bvc.view];
+  [bvc didMoveToParentViewController:self];
+
+  // Let the system know that the child has changed so appearance updates can
+  // be made.
+  [self setNeedsStatusBarAppearanceUpdate];
+
+  DCHECK(self.currentBVC == bvc);
+}
+
+- (UIViewController*)childViewControllerForStatusBarHidden {
+  return self.currentBVC;
+}
+
+- (UIViewController*)childViewControllerForStatusBarStyle {
+  return self.currentBVC;
+}
+
+- (BOOL)shouldAutorotate {
+  return self.currentBVC ? [self.currentBVC shouldAutorotate]
+                         : [super shouldAutorotate];
+}
+
+@end
+
+@interface MainPresentingViewController ()
+
+@property(nonatomic, weak) UIViewController<TabSwitcher>* tabSwitcher;
+@property(nonatomic, strong) BVCContainerViewController* bvcContainer;
+
+@end
+
 @implementation MainPresentingViewController
+@synthesize tabSwitcher = _tabSwitcher;
+@synthesize bvcContainer = _bvcContainer;
 
 - (UIViewController*)activeViewController {
-  return self.presentedViewController;
+  if (self.bvcContainer) {
+    DCHECK_EQ(self.bvcContainer, self.presentedViewController);
+    DCHECK(self.bvcContainer.currentBVC);
+    return self.bvcContainer.currentBVC;
+  } else if (self.tabSwitcher) {
+    DCHECK_EQ(self.tabSwitcher, [self.childViewControllers firstObject]);
+    return self.tabSwitcher;
+  }
+
+  return nil;
 }
 
 - (void)showTabSwitcher:(UIViewController<TabSwitcher>*)tabSwitcher
              completion:(ProceduralBlock)completion {
-  [self setActiveViewController:tabSwitcher completion:completion];
+  DCHECK(tabSwitcher);
+
+  // Don't remove and re-add the tabSwitcher if it hasn't changed.
+  if (self.tabSwitcher != tabSwitcher) {
+    // Remove any existing tab switchers first.
+    if (self.tabSwitcher) {
+      [self.tabSwitcher willMoveToParentViewController:nil];
+      [self.tabSwitcher.view removeFromSuperview];
+      [self.tabSwitcher removeFromParentViewController];
+    }
+
+    // Add the new tab switcher as a child VC.
+    [self addChildViewController:tabSwitcher];
+    tabSwitcher.view.frame = self.view.bounds;
+    [self.view addSubview:tabSwitcher.view];
+    [tabSwitcher didMoveToParentViewController:self];
+    self.tabSwitcher = tabSwitcher;
+  }
+
+  // If a BVC is currently being presented, dismiss it.  This will trigger any
+  // necessary animations.
+  if (self.bvcContainer) {
+    self.bvcContainer = nil;
+    [super dismissViewControllerAnimated:YES completion:completion];
+  } else {
+    if (completion) {
+      completion();
+    }
+  }
 }
 
 - (void)showTabViewController:(UIViewController*)viewController
                    completion:(ProceduralBlock)completion {
-  [self setActiveViewController:viewController completion:completion];
-}
+  DCHECK(viewController);
 
-// Presents the given view controller, first dismissing any other view
-// controllers that are currently presented.  Runs the given |completion| block
-// after the view controller is visible.
-- (void)setActiveViewController:(UIViewController*)activeViewController
-                     completion:(void (^)())completion {
-  DCHECK(activeViewController);
-  if (self.activeViewController == activeViewController) {
+  // If another BVC is already being presented, swap this one into the
+  // container.
+  if (self.bvcContainer) {
+    self.bvcContainer.currentBVC = viewController;
     if (completion) {
       completion();
     }
     return;
   }
 
-  // TODO(crbug.com/546189): DCHECK here that there isn't a modal view
-  // controller showing once the known violations of that are fixed.
-
-  if (self.activeViewController) {
-    // This call must be to super, as the override of
-    // dismissViewControllerAnimated:completion: below tries to dismiss using
-    // self.activeViewController, but this call explicitly needs to present
-    // using the MainPresentingViewController itself.
-    [super dismissViewControllerAnimated:NO completion:nil];
-  }
-
-  // This call must be to super, as the override of
-  // presentViewController:animated:completion: below tries to present using
-  // self.activeViewController, but this call explicitly needs to present
-  // using the MainPresentingViewController itself.
-  [super presentViewController:activeViewController
-                      animated:NO
-                    completion:^{
-                      DCHECK(self.activeViewController == activeViewController);
-                      if (completion) {
-                        completion();
-                      }
-                    }];
+  self.bvcContainer = [[BVCContainerViewController alloc] init];
+  self.bvcContainer.currentBVC = viewController;
+  [super presentViewController:self.bvcContainer
+                      animated:(self.tabSwitcher != nil)
+                    completion:completion];
 }
 
 #pragma mark - UIViewController methods

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

@@ -18,52 +18,144 @@
 
 namespace {
 
-using MainPresentingViewControllerTest = MainViewControllerTest;
+class MainPresentingViewControllerTest : public MainViewControllerTest {
+ public:
+  MainPresentingViewControllerTest() {
+    main_view_controller_ = [[MainPresentingViewController alloc] init];
+    SetRootViewController(main_view_controller_);
+    CGRect windowRect = CGRectMake(0, 0, 200, 200);
+    main_view_controller_.view.frame = windowRect;
+
+    tab_switcher_ = CreateTestTabSwitcher();
+    tab_switcher_.view.frame = CGRectMake(0, 0, 10, 10);
+
+    normal_tab_view_controller_ = [[UIViewController alloc] init];
+    normal_tab_view_controller_.view.frame = CGRectMake(20, 20, 10, 10);
+
+    incognito_tab_view_controller_ = [[UIViewController alloc] init];
+    incognito_tab_view_controller_.view.frame = CGRectMake(40, 40, 10, 10);
+  }
+
+  ~MainPresentingViewControllerTest() override {}
+
+ protected:
+  // The MainPresentingViewController that is under test.  The test fixture sets
+  // this VC as the root VC for the window.
+  MainPresentingViewController* main_view_controller_;
+
+  // The following view controllers are created by the test fixture and are
+  // available for use in tests.
+  UIViewController<TabSwitcher>* tab_switcher_;
+  UIViewController* normal_tab_view_controller_;
+  UIViewController* incognito_tab_view_controller_;
+};
+
+// Tests that there is no activeViewController for a newly constructed instance.
+TEST_F(MainPresentingViewControllerTest, NoActiveViewController) {
+  EXPECT_EQ(nil, main_view_controller_.activeViewController);
+}
+
+// Tests that it is possible to set a TabViewController without first setting a
+// TabSwitcher.
+TEST_F(MainPresentingViewControllerTest, TabViewControllerBeforeTabSwitcher) {
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(normal_tab_view_controller_,
+            main_view_controller_.activeViewController);
+
+  // Now setting a TabSwitcher will make the switcher active.
+  [main_view_controller_ showTabSwitcher:tab_switcher_ completion:nil];
+  EXPECT_EQ(tab_switcher_, main_view_controller_.activeViewController);
+}
+
+// Tests that it is possible to set a TabViewController after setting a
+// TabSwitcher.
+TEST_F(MainPresentingViewControllerTest, TabViewControllerAfterTabSwitcher) {
+  [main_view_controller_ showTabSwitcher:tab_switcher_ completion:nil];
+  EXPECT_EQ(tab_switcher_, main_view_controller_.activeViewController);
+
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(normal_tab_view_controller_,
+            main_view_controller_.activeViewController);
+
+  // Showing the TabSwitcher again will make it active.
+  [main_view_controller_ showTabSwitcher:tab_switcher_ completion:nil];
+  EXPECT_EQ(tab_switcher_, main_view_controller_.activeViewController);
+}
+
+// Tests swapping between two TabViewControllers.
+TEST_F(MainPresentingViewControllerTest, SwapTabViewControllers) {
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(normal_tab_view_controller_,
+            main_view_controller_.activeViewController);
+
+  [main_view_controller_ showTabViewController:incognito_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(incognito_tab_view_controller_,
+            main_view_controller_.activeViewController);
+}
+
+// Tests calling showTabSwitcher twice in a row with the same VC.
+TEST_F(MainPresentingViewControllerTest, ShowTabSwitcherTwice) {
+  [main_view_controller_ showTabSwitcher:tab_switcher_ completion:nil];
+  EXPECT_EQ(tab_switcher_, main_view_controller_.activeViewController);
+
+  [main_view_controller_ showTabSwitcher:tab_switcher_ completion:nil];
+  EXPECT_EQ(tab_switcher_, main_view_controller_.activeViewController);
+}
+
+// Tests calling showTabViewController twice in a row with the same VC.
+TEST_F(MainPresentingViewControllerTest, ShowTabViewControllerTwice) {
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(normal_tab_view_controller_,
+            main_view_controller_.activeViewController);
+
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:nil];
+  EXPECT_EQ(normal_tab_view_controller_,
+            main_view_controller_.activeViewController);
+}
 
 // Tests that setting the active view controller work and that completion
 // handlers are called properly after the new view controller is made active.
-TEST_F(MainPresentingViewControllerTest, SetActiveVCAndCompletionHandlers) {
-  MainPresentingViewController* main_view_controller =
-      [[MainPresentingViewController alloc] init];
-  SetRootViewController(main_view_controller);
-  CGRect windowRect = CGRectMake(0, 0, 200, 200);
-  [main_view_controller view].frame = windowRect;
-
-  UIViewController<TabSwitcher>* child_view_controller_1 =
-      CreateTestTabSwitcher();
-  [child_view_controller_1 view].frame = CGRectMake(0, 0, 10, 10);
-
-  UIViewController<TabSwitcher>* child_view_controller_2 =
-      CreateTestTabSwitcher();
-  [child_view_controller_2 view].frame = CGRectMake(20, 20, 10, 10);
-
-  // Tests that the completion handler is called when there is no preexisting
-  // active view controller.
+TEST_F(MainPresentingViewControllerTest, CompletionHandlers) {
+  // Tests that the completion handler is called when showing the switcher.
   __block BOOL completion_handler_was_called = false;
-  [main_view_controller showTabSwitcher:child_view_controller_1
-                             completion:^{
-                               completion_handler_was_called = YES;
-                             }];
+  [main_view_controller_ showTabSwitcher:tab_switcher_
+                              completion:^{
+                                completion_handler_was_called = YES;
+                              }];
+  base::test::ios::WaitUntilCondition(^bool() {
+    return completion_handler_was_called;
+  });
+  ASSERT_TRUE(completion_handler_was_called);
+
+  // Tests that the completion handler is called when showing a tab view
+  // controller.
+  completion_handler_was_called = NO;
+  [main_view_controller_ showTabViewController:normal_tab_view_controller_
+                                    completion:^{
+                                      completion_handler_was_called = YES;
+                                    }];
   base::test::ios::WaitUntilCondition(^bool() {
     return completion_handler_was_called;
   });
   ASSERT_TRUE(completion_handler_was_called);
-  EXPECT_EQ(main_view_controller.presentedViewController,
-            child_view_controller_1);
 
-  // Tests that the completion handler is called when replacing an existing
-  // active view controller.
+  // Tests that the completion handler is called when replacing an existing tab
+  // view controller.
   completion_handler_was_called = NO;
-  [main_view_controller showTabViewController:child_view_controller_2
-                                   completion:^{
-                                     completion_handler_was_called = YES;
-                                   }];
+  [main_view_controller_ showTabViewController:incognito_tab_view_controller_
+                                    completion:^{
+                                      completion_handler_was_called = YES;
+                                    }];
   base::test::ios::WaitUntilCondition(^bool() {
     return completion_handler_was_called;
   });
   ASSERT_TRUE(completion_handler_was_called);
-  EXPECT_EQ(main_view_controller.presentedViewController,
-            child_view_controller_2);
 }
 
 }  // namespace