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

ios/chrome/browser/ui/collection_view/cells/collection_view_detail_item.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/cells/collection_view_detail_item.h"
+
+#include <algorithm>
+
+#import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
+#import "ios/third_party/material_roboto_font_loader_ios/src/src/MaterialRobotoFontLoader.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+
+// Padding used on the leading and trailing edges of the cell and between the
+// two labels.
+const CGFloat kHorizontalPadding = 16;
+
+// Minimum proportion of the available width to guarantee to the main and detail
+// labels.
+const CGFloat kMinTextWidthRatio = 0.75f;
+const CGFloat kMinDetailTextWidthRatio = 0.25f;
+}
+
+@implementation CollectionViewDetailItem
+
+@synthesize accessoryType = _accessoryType;
+@synthesize text = _text;
+@synthesize detailText = _detailText;
+
+- (instancetype)initWithType:(NSInteger)type {
+  self = [super initWithType:type];
+  if (self) {
+    self.cellClass = [CollectionViewDetailCell class];
+  }
+  return self;
+}
+
+#pragma mark CollectionViewItem
+
+- (void)configureCell:(CollectionViewDetailCell*)cell {
+  [super configureCell:cell];
+  cell.accessoryType = self.accessoryType;
+  cell.textLabel.text = self.text;
+  cell.detailTextLabel.text = self.detailText;
+}
+
+@end
+
+@implementation CollectionViewDetailCell {
+  NSLayoutConstraint* _textLabelWidthConstraint;
+  NSLayoutConstraint* _detailTextLabelWidthConstraint;
+}
+
+@synthesize textLabel = _textLabel;
+@synthesize detailTextLabel = _detailTextLabel;
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    self.isAccessibilityElement = YES;
+    UIView* contentView = self.contentView;
+
+    _textLabel = [[UILabel alloc] init];
+    _textLabel.translatesAutoresizingMaskIntoConstraints = NO;
+    _textLabel.backgroundColor = [UIColor clearColor];
+    [contentView addSubview:_textLabel];
+
+    _textLabel.font =
+        [[MDFRobotoFontLoader sharedInstance] mediumFontOfSize:14];
+    _textLabel.textColor = [[MDCPalette greyPalette] tint900];
+
+    _detailTextLabel = [[UILabel alloc] init];
+    _detailTextLabel.translatesAutoresizingMaskIntoConstraints = NO;
+    _detailTextLabel.backgroundColor = [UIColor clearColor];
+    [contentView addSubview:_detailTextLabel];
+
+    _detailTextLabel.font =
+        [[MDFRobotoFontLoader sharedInstance] regularFontOfSize:14];
+    _detailTextLabel.textColor = [[MDCPalette greyPalette] tint500];
+
+    // Set up the width constraints. They are activated here and updated in
+    // layoutSubviews.
+    _textLabelWidthConstraint =
+        [_textLabel.widthAnchor constraintEqualToConstant:0];
+    _detailTextLabelWidthConstraint =
+        [_detailTextLabel.widthAnchor constraintEqualToConstant:0];
+
+    [NSLayoutConstraint activateConstraints:@[
+      // Fix the leading and trailing edges of the text labels.
+      [_textLabel.leadingAnchor
+          constraintEqualToAnchor:contentView.leadingAnchor
+                         constant:kHorizontalPadding],
+      [_detailTextLabel.trailingAnchor
+          constraintEqualToAnchor:contentView.trailingAnchor
+                         constant:-kHorizontalPadding],
+
+      // Center the text label vertically and align the baselines of the two
+      // text labels.
+      [_textLabel.centerYAnchor
+          constraintEqualToAnchor:contentView.centerYAnchor],
+      [_detailTextLabel.firstBaselineAnchor
+          constraintEqualToAnchor:_textLabel.firstBaselineAnchor],
+
+      _textLabelWidthConstraint,
+      _detailTextLabelWidthConstraint,
+    ]];
+  }
+  return self;
+}
+
+// Updates the layout constraints of the text labels and then calls the
+// superclass's implementation of layoutSubviews which can then take account of
+// the new constraints.
+- (void)layoutSubviews {
+  [super layoutSubviews];
+
+  // Size the labels in order to determine how much width they want.
+  [self.textLabel sizeToFit];
+  [self.detailTextLabel sizeToFit];
+
+  // Update the width constraints.
+  _textLabelWidthConstraint.constant = self.textLabelTargetWidth;
+  _detailTextLabelWidthConstraint.constant = self.detailTextLabelTargetWidth;
+
+  // Now invoke the layout.
+  [super layoutSubviews];
+}
+
+- (CGFloat)textLabelTargetWidth {
+  CGFloat availableWidth =
+      self.contentView.bounds.size.width - (3 * kHorizontalPadding);
+  CGFloat textLabelWidth = self.textLabel.frame.size.width;
+  CGFloat detailTextLabelWidth = self.detailTextLabel.frame.size.width;
+
+  if (textLabelWidth + detailTextLabelWidth <= availableWidth)
+    return textLabelWidth;
+
+  return std::max(
+      availableWidth - detailTextLabelWidth,
+      std::min(availableWidth * kMinTextWidthRatio, textLabelWidth));
+}
+
+- (CGFloat)detailTextLabelTargetWidth {
+  CGFloat availableWidth =
+      self.contentView.bounds.size.width - (3 * kHorizontalPadding);
+  CGFloat textLabelWidth = self.textLabel.frame.size.width;
+  CGFloat detailTextLabelWidth = self.detailTextLabel.frame.size.width;
+
+  if (textLabelWidth + detailTextLabelWidth <= availableWidth)
+    return detailTextLabelWidth;
+
+  return std::max(availableWidth - textLabelWidth,
+                  std::min(availableWidth * kMinDetailTextWidthRatio,
+                           detailTextLabelWidth));
+}
+
+- (NSString*)accessibilityLabel {
+  return self.textLabel.text;
+}
+
+- (NSString*)accessibilityValue {
+  return self.detailTextLabel.text;
+}
+
+@end