Create CollectionViewTextCell

ios/chrome/browser/ui/collection_view/cells/collection_view_text_cell.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.
+
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_text_cell.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+const CGFloat kMargin = 16;
+const CGFloat kMinimalHeight = 48;
+}
+
+@implementation CollectionViewTextCell
+
+@synthesize textLabel = _textLabel;
+@synthesize detailTextLabel = _detailTextLabel;
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    UIView* containerView = [[UIView alloc] initWithFrame:CGRectZero];
+    containerView.translatesAutoresizingMaskIntoConstraints = NO;
+    [self.contentView addSubview:containerView];
+
+    _textLabel = [[UILabel alloc] initWithFrame:CGRectZero];
+    _textLabel.translatesAutoresizingMaskIntoConstraints = NO;
+    [containerView addSubview:_textLabel];
+
+    _detailTextLabel = [[UILabel alloc] initWithFrame:CGRectZero];
+    _detailTextLabel.translatesAutoresizingMaskIntoConstraints = NO;
+    [containerView addSubview:_detailTextLabel];
+
+    [NSLayoutConstraint activateConstraints:@[
+      // Total height.
+      [self.contentView.heightAnchor
+          constraintGreaterThanOrEqualToConstant:kMinimalHeight],

[lpromero, 2017/03/22 15:51:47]

Why? Material spec?

[gambard, 2017/03/23 09:41:29]

Yes.

+
+      // Container.
+      [containerView.leadingAnchor

[lpromero, 2017/03/22 15:51:47]

Why do you need the container? I'd remove it.

[gambard, 2017/03/23 09:41:29]

The container is needed to center the labels in case the font is too small and
the sum margins+fontSize is smaller than the minimal height.

+          constraintEqualToAnchor:self.contentView.leadingAnchor
+                         constant:kMargin],
+      [containerView.trailingAnchor
+          constraintEqualToAnchor:self.contentView.trailingAnchor
+                         constant:-kMargin],
+      [containerView.topAnchor
+          constraintGreaterThanOrEqualToAnchor:self.contentView.topAnchor
+                                      constant:kMargin],
+      [containerView.bottomAnchor
+          constraintLessThanOrEqualToAnchor:self.contentView.bottomAnchor
+                                   constant:-kMargin],
+      [containerView.centerYAnchor
+          constraintEqualToAnchor:self.contentView.centerYAnchor],

[lpromero, 2017/03/22 15:51:47]

You already set top and bottom, why do you need this one?

[gambard, 2017/03/23 09:41:29]

Same as above.

[lpromero, 2017/03/23 12:23:35]

I see. And I didn't notice that the top/bottom where inequalities. So it's not
over-constrained.

+
+      // Labels.
+      [_textLabel.leadingAnchor
+          constraintEqualToAnchor:containerView.leadingAnchor],
+      [_textLabel.trailingAnchor
+          constraintLessThanOrEqualToAnchor:containerView.trailingAnchor],

[lpromero, 2017/03/22 15:51:47]

Why not going all the way to the trailing edge?

[gambard, 2017/03/23 09:41:29]

We had some problem with RTL + editing when the label is taking all the width.
See crbug.com/698379

+      [_textLabel.topAnchor constraintEqualToAnchor:containerView.topAnchor],
+      [_textLabel.bottomAnchor
+          constraintEqualToAnchor:_detailTextLabel.topAnchor],
+      [_detailTextLabel.leadingAnchor
+          constraintEqualToAnchor:_textLabel.leadingAnchor],
+      [_detailTextLabel.trailingAnchor
+          constraintLessThanOrEqualToAnchor:containerView.trailingAnchor],
+      [_detailTextLabel.bottomAnchor
+          constraintLessThanOrEqualToAnchor:containerView.bottomAnchor],
+    ]];
+  }
+  return self;
+}
+
+// Implement -layoutSubviews as per instructions in documentation for
+// +[MDCCollectionViewCell cr_preferredHeightForWidth:forItem:].
+- (void)layoutSubviews {
+  [super layoutSubviews];
+  // Adjust the text and detailText label preferredMaxLayoutWidth when the
+  // parent's width changes, for instance on screen rotation.
+  CGFloat prefferedMaxLayoutWidth =

[lpromero, 2017/03/23 12:23:35]

preferred

[gambard, 2017/03/23 15:32:28]

Done.

+      CGRectGetWidth(self.contentView.frame) - 2 * kMargin;
+  _textLabel.preferredMaxLayoutWidth = prefferedMaxLayoutWidth;
+  _detailTextLabel.preferredMaxLayoutWidth = prefferedMaxLayoutWidth;
+
+  // Re-layout with the new preferred width to allow the label to adjust its
+  // height.
+  [super layoutSubviews];
+}

[lpromero, 2017/03/22 15:51:47]

Can you add prepareForReuse?

[gambard, 2017/03/23 09:41:29]

Done.
I am not sure about what to reset in prepareForReuse. I cannot reset everything
in the labels.

[lpromero, 2017/03/23 12:23:35]

I guess we'll have to do incrementally.

[gambard, 2017/03/23 15:32:28]

Acknowledged.

+

[lpromero, 2017/03/22 15:51:47]

Can you add proper accessibility? I think it's just a matter of setting
isAccessibilityElement to self (check other cells), and implementing
accessibilityLabel to concatenate the two labels strings.

[gambard, 2017/03/23 09:41:29]

The accessibility is done in the item.

[lpromero, 2017/03/23 12:23:35]

Acknowledged.

+@end