Upstream Chrome on iOS source code [4/11].

ios/chrome/browser/ui/collection_view/collection_view_controller.mm

+// Copyright 2016 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/collection_view/collection_view_controller.h"
+
+#include "base/logging.h"
+#include "base/mac/foundation_util.h"
+#import "base/mac/scoped_nsobject.h"
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
+#import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
+#import "ios/chrome/browser/ui/material_components/utils.h"
+#import "ios/third_party/material_components_ios/src/components/AppBar/src/MaterialAppBar.h"
+#import "ios/third_party/material_components_ios/src/components/CollectionCells/src/MaterialCollectionCells.h"
+
+@implementation CollectionViewController {
+  // The implementation of this controller follows the guidelines from
+  // https://github.com/material-components/material-components-ios/tree/develop/components/AppBar
+  base::scoped_nsobject<MDCAppBar> _appBar;
+  base::scoped_nsobject<CollectionViewModel> _collectionViewModel;
+}
+
+- (instancetype)initWithStyle:(CollectionViewControllerStyle)style {
+  UICollectionViewLayout* layout =
+      [[[MDCCollectionViewFlowLayout alloc] init] autorelease];
+  self = [super initWithCollectionViewLayout:layout];
+  if (self) {
+    if (style == CollectionViewControllerStyleAppBar) {
+      _appBar.reset([[MDCAppBar alloc] init]);
+      [self addChildViewController:_appBar.get().headerViewController];
+    }
+  }
+  return self;
+}
+
+- (void)viewDidLoad {
+  [super viewDidLoad];
+
+  // Configure the app bar, if there is one.
+  if (self.appBar) {
+    // Configure the app bar style.
+    ConfigureAppBarWithCardStyle(self.appBar);
+    // Set the header view's tracking scroll view.
+    self.appBar.headerViewController.headerView.trackingScrollView =
+        self.collectionView;
+    // After all other views have been registered.
+    [self.appBar addSubviewsToParent];
+  }
+}
+
+- (UIViewController*)childViewControllerForStatusBarHidden {
+  return self.appBar.headerViewController;
+}
+
+- (UIViewController*)childViewControllerForStatusBarStyle {
+  return self.appBar.headerViewController;
+}
+
+- (MDCAppBar*)appBar {
+  return _appBar.get();
+}
+
+- (CollectionViewModel*)collectionViewModel {
+  return _collectionViewModel.get();
+}
+
+- (void)loadModel {
+  _collectionViewModel.reset([[CollectionViewModel alloc] init]);
+}
+
+- (void)reconfigureCellsForItems:(NSArray*)items
+         inSectionWithIdentifier:(NSInteger)sectionIdentifier {
+  for (CollectionViewItem* item in items) {
+    NSIndexPath* indexPath =
+        [_collectionViewModel indexPathForItem:item
+                       inSectionWithIdentifier:sectionIdentifier];
+    MDCCollectionViewCell* cell =
+        base::mac::ObjCCastStrict<MDCCollectionViewCell>(
+            [self.collectionView cellForItemAtIndexPath:indexPath]);
+
+    // |cell| may be nil if the row is not currently on screen.
+    if (cell) {
+      [item configureCell:cell];
+    }
+  }
+}
+
+#pragma mark MDCCollectionViewEditingDelegate
+
+- (void)collectionView:(UICollectionView*)collectionView
+    willDeleteItemsAtIndexPaths:(NSArray*)indexPaths {
+  // Check that the parent class doesn't implement this method. Otherwise, it
+  // would need to be called here.
+  DCHECK([self isKindOfClass:[MDCCollectionViewController class]]);
+  DCHECK(![MDCCollectionViewController instancesRespondToSelector:_cmd]);
+
+  // Sort and enumerate in reverse order to delete the items from the collection
+  // view model.
+  NSArray* sortedIndexPaths =
+      [indexPaths sortedArrayUsingSelector:@selector(compare:)];
+  for (NSIndexPath* indexPath in [sortedIndexPaths reverseObjectEnumerator]) {
+    NSInteger sectionIdentifier =
+        [_collectionViewModel sectionIdentifierForSection:indexPath.section];
+    NSInteger itemType = [_collectionViewModel itemTypeForIndexPath:indexPath];
+    NSUInteger index =
+        [_collectionViewModel indexInItemTypeForIndexPath:indexPath];
+    [_collectionViewModel removeItemWithType:itemType
+                   fromSectionWithIdentifier:sectionIdentifier
+                                     atIndex:index];
+  }
+}
+
+- (void)collectionView:(UICollectionView*)collectionView
+    willMoveItemAtIndexPath:(NSIndexPath*)indexPath
+                toIndexPath:(NSIndexPath*)newIndexPath {
+  // Check that the parent class doesn't implement this method. Otherwise, it
+  // would need to be called here.
+  DCHECK([self isKindOfClass:[MDCCollectionViewController class]]);
+  DCHECK(![MDCCollectionViewController instancesRespondToSelector:_cmd]);
+
+  // Retain the item to be able to move it.
+  base::scoped_nsobject<CollectionViewItem> item(
+      [[self.collectionViewModel itemAtIndexPath:indexPath] retain]);
+
+  // Item coordinates.
+  NSInteger sectionIdentifier =
+      [self.collectionViewModel sectionIdentifierForSection:indexPath.section];
+  NSInteger itemType =
+      [self.collectionViewModel itemTypeForIndexPath:indexPath];
+  NSUInteger indexInItemType =
+      [self.collectionViewModel indexInItemTypeForIndexPath:indexPath];
+
+  // Move the item.
+  [self.collectionViewModel removeItemWithType:itemType
+                     fromSectionWithIdentifier:sectionIdentifier
+                                       atIndex:indexInItemType];
+  NSInteger section = [self.collectionViewModel
+      sectionIdentifierForSection:newIndexPath.section];
+  [self.collectionViewModel insertItem:item
+               inSectionWithIdentifier:section
+                               atIndex:newIndexPath.item];
+}
+
+#pragma mark UICollectionViewDataSource
+
+- (NSInteger)numberOfSectionsInCollectionView:
+    (UICollectionView*)collectionView {
+  return [_collectionViewModel numberOfSections];
+}
+
+- (NSInteger)collectionView:(UICollectionView*)collectionView
+     numberOfItemsInSection:(NSInteger)section {
+  return [_collectionViewModel numberOfItemsInSection:section];
+}
+
+- (UICollectionViewCell*)collectionView:(UICollectionView*)collectionView
+                 cellForItemAtIndexPath:(NSIndexPath*)indexPath {
+  CollectionViewItem* item = [_collectionViewModel itemAtIndexPath:indexPath];
+  Class cellClass = [item cellClass];
+  NSString* reuseIdentifier = NSStringFromClass(cellClass);
+  [self.collectionView registerClass:cellClass
+          forCellWithReuseIdentifier:reuseIdentifier];
+  MDCCollectionViewCell* cell = [self.collectionView
+      dequeueReusableCellWithReuseIdentifier:reuseIdentifier
+                                forIndexPath:indexPath];
+  [item configureCell:cell];
+  return cell;
+}
+
+- (UICollectionReusableView*)collectionView:(UICollectionView*)collectionView
+          viewForSupplementaryElementOfKind:(NSString*)kind
+                                atIndexPath:(NSIndexPath*)indexPath {
+  CollectionViewItem* item = nil;
+  UIAccessibilityTraits traits = UIAccessibilityTraitNone;
+  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
+    item = [_collectionViewModel headerForSection:indexPath.section];
+    traits = UIAccessibilityTraitHeader;
+  } else if ([kind isEqualToString:UICollectionElementKindSectionFooter]) {
+    item = [_collectionViewModel footerForSection:indexPath.section];
+  } else {
+    return [super collectionView:collectionView
+        viewForSupplementaryElementOfKind:kind
+                              atIndexPath:indexPath];
+  }
+
+  Class cellClass = [item cellClass];
+  NSString* reuseIdentifier = NSStringFromClass(cellClass);
+  [self.collectionView registerClass:cellClass
+          forSupplementaryViewOfKind:kind
+                 withReuseIdentifier:reuseIdentifier];
+  MDCCollectionViewCell* cell = [self.collectionView
+      dequeueReusableSupplementaryViewOfKind:kind
+                         withReuseIdentifier:reuseIdentifier
+                                forIndexPath:indexPath];
+  [item configureCell:cell];
+  cell.accessibilityTraits |= traits;
+  return cell;
+};
+
+#pragma mark - UICollectionViewDelegateFlowLayout
+
+- (CGSize)collectionView:(UICollectionView*)collectionView
+                             layout:
+                                 (UICollectionViewLayout*)collectionViewLayout
+    referenceSizeForHeaderInSection:(NSInteger)section {
+  CollectionViewItem* item = [_collectionViewModel headerForSection:section];
+
+  if (item) {
+    // TODO(crbug.com/635604): Support arbitrary sized headers.
+    return CGSizeMake(0, MDCCellDefaultOneLineHeight);
+  }
+  return CGSizeZero;
+}
+
+- (CGSize)collectionView:(UICollectionView*)collectionView
+                             layout:
+                                 (UICollectionViewLayout*)collectionViewLayout
+    referenceSizeForFooterInSection:(NSInteger)section {
+  CollectionViewItem* item = [_collectionViewModel footerForSection:section];
+
+  if (item) {
+    // TODO(crbug.com/635604): Support arbitrary sized footers.
+    return CGSizeMake(0, MDCCellDefaultOneLineHeight);
+  }
+  return CGSizeZero;
+}
+
+#pragma mark UIScrollViewDelegate
+
+- (void)scrollViewDidScroll:(UIScrollView*)scrollView {
+  MDCFlexibleHeaderView* headerView =
+      self.appBar.headerViewController.headerView;
+  if (scrollView == headerView.trackingScrollView) {
+    [headerView trackingScrollViewDidScroll];
+  }
+}
+
+- (void)scrollViewDidEndDecelerating:(UIScrollView*)scrollView {
+  MDCFlexibleHeaderView* headerView =
+      self.appBar.headerViewController.headerView;
+  if (scrollView == headerView.trackingScrollView) {
+    [headerView trackingScrollViewDidEndDecelerating];
+  }
+}
+
+- (void)scrollViewDidEndDragging:(UIScrollView*)scrollView
+                  willDecelerate:(BOOL)decelerate {
+  MDCFlexibleHeaderView* headerView =
+      self.appBar.headerViewController.headerView;
+  if (scrollView == headerView.trackingScrollView) {
+    [headerView trackingScrollViewDidEndDraggingWillDecelerate:decelerate];
+  }
+}
+
+- (void)scrollViewWillEndDragging:(UIScrollView*)scrollView
+                     withVelocity:(CGPoint)velocity
+              targetContentOffset:(inout CGPoint*)targetContentOffset {
+  MDCFlexibleHeaderView* headerView =
+      self.appBar.headerViewController.headerView;
+  if (scrollView == headerView.trackingScrollView) {
+    [headerView
+        trackingScrollViewWillEndDraggingWithVelocity:velocity
+                                  targetContentOffset:targetContentOffset];
+  }
+}
+
+@end