[CRD iOS] Finish up the host list UI

remoting/ios/app/host_collection_view_controller.mm

 // Copyright 2017 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.
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 #import "remoting/ios/app/host_collection_view_controller.h"
 
 #import "ios/third_party/material_components_ios/src/components/Ink/src/MaterialInk.h"
 #import "ios/third_party/material_components_ios/src/components/NavigationBar/src/MaterialNavigationBar.h"
 #import "ios/third_party/material_components_ios/src/components/ShadowElevations/src/MaterialShadowElevations.h"
 #import "ios/third_party/material_components_ios/src/components/ShadowLayer/src/MaterialShadowLayer.h"
+#import "remoting/ios/app/host_collection_header_view.h"
 
 static NSString* const kReusableIdentifierItem =
     @"remotingHostCollectionViewControllerItem";
 
 static CGFloat kHostCollectionViewControllerCellHeight = 70.f;
+static CGFloat kHostCollectionHeaderViewHeight = 25.f;
 
 @implementation HostCollectionViewController
 
 @synthesize delegate = _delegate;
 @synthesize flexHeaderContainerViewController =
     _flexHeaderContainerViewController;
 
 - (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout*)layout {
   self = [super initWithCollectionViewLayout:layout];
   if (self) {
     self.collectionView.backgroundColor = [UIColor clearColor];
     [self.collectionView registerClass:[HostCollectionViewCell class]
             forCellWithReuseIdentifier:NSStringFromClass(
                                            [HostCollectionViewCell class])];
+
+    [self.collectionView registerClass:[HostCollectionHeaderView class]
+            forSupplementaryViewOfKind:UICollectionElementKindSectionHeader
+                   withReuseIdentifier:UICollectionElementKindSectionHeader];
   }
   return self;
 }
 
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {
   [super viewDidLoad];
-  self.styler.cellStyle = MDCCollectionViewCellStyleGrouped;
+  self.styler.cellStyle = MDCCollectionViewCellStyleDefault;
   self.styler.cellLayoutType = MDCCollectionViewCellLayoutTypeList;
 }
 
 - (void)viewWillTransitionToSize:(CGSize)size
        withTransitionCoordinator:
            (id<UIViewControllerTransitionCoordinator>)coordinator {
   [self.collectionView.collectionViewLayout invalidateLayout];
 }
 
 - (void)viewWillAppear:(BOOL)animated {
@@ skipping 14 matching lines @@
       [collectionView dequeueReusableCellWithReuseIdentifier:
                           NSStringFromClass([HostCollectionViewCell class])
                                                 forIndexPath:indexPath];
   HostInfo* host = [_delegate getHostAtIndexPath:indexPath];
   if (host) {
     [cell populateContentWithHostInfo:host];
   }
   return cell;
 }
 
+- (UICollectionReusableView*)collectionView:(UICollectionView*)collectionView
+          viewForSupplementaryElementOfKind:(NSString*)kind
+                                atIndexPath:(NSIndexPath*)indexPath {
+  HostCollectionHeaderView* supplementaryView =
+      [collectionView dequeueReusableSupplementaryViewOfKind:kind
+                                         withReuseIdentifier:kind
+                                                forIndexPath:indexPath];
+  if ([kind isEqualToString:UICollectionElementKindSectionHeader]) {
+    supplementaryView.text = @"Remote devices";
+  }
+  return supplementaryView;
+}
+
 #pragma mark - UICollectionViewDelegate
 
 - (void)collectionView:(UICollectionView*)collectionView
     didSelectItemAtIndexPath:(NSIndexPath*)indexPath {
   [super collectionView:collectionView didSelectItemAtIndexPath:indexPath];
   HostCollectionViewCell* cell = (HostCollectionViewCell*)[collectionView
       cellForItemAtIndexPath:indexPath];
   [_delegate didSelectCell:cell
                 completion:^{
                 }];
 }
 
 #pragma mark - MDCCollectionViewStylingDelegate
 
 - (CGFloat)collectionView:(UICollectionView*)collectionView
     cellHeightAtIndexPath:(NSIndexPath*)indexPath {
   return kHostCollectionViewControllerCellHeight;
 }
 
 #pragma mark - UIScrollViewDelegate
 
 - (void)scrollViewDidScroll:(UIScrollView*)scrollView {
   [self.flexHeaderContainerViewController.headerViewController
       scrollViewDidScroll:scrollView];
 }
 
+#pragma mark - UICollectionViewDelegateFlowLayout
+
+- (CGSize)collectionView:(UICollectionView*)collectionView
+                             layout:
+                                 (UICollectionViewLayout*)collectionViewLayout
+    referenceSizeForHeaderInSection:(NSInteger)section {
+  return CGSizeMake(collectionView.bounds.size.width,
+                    kHostCollectionHeaderViewHeight);
+}
+
 #pragma mark - Private
 
 - (void)setFlexHeaderContainerViewController:
     (MDCFlexibleHeaderContainerViewController*)
         flexHeaderContainerViewController {
   _flexHeaderContainerViewController = flexHeaderContainerViewController;
   MDCFlexibleHeaderView* headerView =
       _flexHeaderContainerViewController.headerViewController.headerView;
   headerView.trackingScrollView = self.collectionView;
   headerView.backgroundColor = [UIColor clearColor];
 
   // Use a custom shadow under the flexible header.
   MDCShadowLayer* shadowLayer = [MDCShadowLayer layer];
   [headerView setShadowLayer:shadowLayer
       intensityDidChangeBlock:^(CALayer* layer, CGFloat intensity) {
         CGFloat elevation = MDCShadowElevationAppBar * intensity;
         [(MDCShadowLayer*)layer setElevation:elevation];
       }];
 }
 
 @end