Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/tab_switcher/tab_switcher_header_cell.mm

+// Copyright 2015 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/tab_switcher/tab_switcher_header_cell.h"
+
+#include "base/logging.h"
+#include "base/mac/scoped_nsobject.h"
+#import "ios/chrome/browser/ui/tab_switcher/tab_switcher_session_cell_data.h"
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
+#import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
+#import "ios/third_party/material_components_ios/src/components/Typography/src/MaterialTypography.h"
+
+namespace {
+// View alpha value used when the header cell is not selected.
+const CGFloat kInactiveAlpha = 0.54;
+const CGFloat kImageViewWidth = 24;
+}
+
+@interface TabSwitcherHeaderCell () {
+  base::scoped_nsobject<UIImageView> _imageView;
+  base::scoped_nsobject<UILabel> _label;
+}
+@end
+
+@implementation TabSwitcherHeaderCell
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    self.backgroundColor = [[MDCPalette greyPalette] tint900];
+    [self loadSubviews];
+    [self setSelected:NO];
+  }
+  return self;
+}
+
++ (NSString*)identifier {
+  return @"TabSwitcherHeaderCell";
+}
+
+- (NSString*)reuseIdentifier {
+  return [[self class] identifier];
+}
+
+- (void)loadSessionCellData:(SessionCellData*)sessionCellData {
+  [_imageView setImage:sessionCellData.image];
+  [_label setText:sessionCellData.title];
+  [self setNeedsLayout];
+}
+
+- (void)setSelected:(BOOL)selected {
+  [super setSelected:selected];
+  [_imageView setAlpha:selected ? 1. : kInactiveAlpha];
+  [_label setAlpha:selected ? 1. : kInactiveAlpha];
+  [self setNeedsLayout];
+}
+
+#pragma mark - Private
+
+- (void)loadSubviews {
+  _imageView.reset([[UIImageView alloc] initWithFrame:CGRectZero]);
+  [_imageView setContentMode:UIViewContentModeCenter];
+  [_imageView setTranslatesAutoresizingMaskIntoConstraints:NO];
+  [_imageView setTintColor:[UIColor whiteColor]];
+  _label.reset([[UILabel alloc] initWithFrame:CGRectZero]);
+  [_label setBackgroundColor:[UIColor clearColor]];
+  [_label setTranslatesAutoresizingMaskIntoConstraints:NO];
+  [_label setTextColor:[UIColor whiteColor]];
+  [_label setFont:[MDCTypography body2Font]];
+
+  // Configure layout.
+  // The icon and the title are centered within |contentView|, have a spacing of
+  // one-third of icon width and the icon is on the leading side of title.
+  base::scoped_nsobject<UIStackView> stackView(
+      [[UIStackView alloc] initWithArrangedSubviews:@[ _imageView, _label ]]);
+  [stackView setSpacing:kImageViewWidth / 3];
+  [self.contentView addSubview:stackView];
+
+  [stackView setTranslatesAutoresizingMaskIntoConstraints:NO];
+  [NSLayoutConstraint activateConstraints:@[
+    [self.contentView.centerYAnchor
+        constraintEqualToAnchor:[stackView centerYAnchor]],
+    [self.contentView.centerXAnchor
+        constraintEqualToAnchor:[stackView centerXAnchor]]
+  ]];
+}
+
+@end