components/CollectionCells/src/MDCCollectionViewTextCell.m

// Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#import "MDCCollectionViewTextCell.h"

#import <MDFInternationalization/MDFInternationalization.h>
#import "MaterialMath.h"
#import "MaterialTypography.h"

#include <tgmath.h>

// Default cell heights.
const CGFloat MDCCellDefaultOneLineHeight = 48;
const CGFloat MDCCellDefaultOneLineWithAvatarHeight = 56;
const CGFloat MDCCellDefaultTwoLineHeight = 72;
const CGFloat MDCCellDefaultThreeLineHeight = 88;

// Default cell fonts.
static inline UIFont *CellDefaultTextFont(void) {
  return [MDCTypography subheadFont];
}

static inline UIFont *CellDefaultDetailTextFont(void) {
  return [MDCTypography body1Font];
}

// Default cell font opacity.
static inline CGFloat CellDefaultTextOpacity(void) {
  return [MDCTypography subheadFontOpacity];
}

static inline CGFloat CellDefaultDetailTextFontOpacity(void) {
  return [MDCTypography captionFontOpacity];
}

// Image size.
static const CGFloat kImageSize = 40;
// Cell image view padding.
static const CGFloat kCellImagePaddingLeading = 16;
// Cell padding top/bottom.
static const CGFloat kCellTwoLinePaddingTop = 20;
static const CGFloat kCellTwoLinePaddingBottom = 20;
static const CGFloat kCellThreeLinePaddingTop = 16;
static const CGFloat kCellThreeLinePaddingBottom = 20;
// Cell padding leading/trailing.
static const CGFloat kCellTextNoImagePaddingLeading = 16;
static const CGFloat kCellTextNoImagePaddingTrailing = 16;
static const CGFloat kCellTextWithImagePaddingLeading = kCellImagePaddingLeading + kImageSize +
  kCellTextNoImagePaddingLeading;

// Returns the closest pixel-aligned value higher than |value|, taking the scale factor into
// account. At a scale of 1, equivalent to Ceil().
static inline CGFloat AlignValueToUpperPixel(CGFloat value) {
  CGFloat scale = [[UIScreen mainScreen] scale];
  return (CGFloat)MDCCeil(value * scale) / scale;
}

// Returns the closest pixel-aligned value lower than |value|, taking the scale factor into
// account. At a scale of 1, equivalent to Floor().
static inline CGFloat AlignValueToLowerPixel(CGFloat value) {
  CGFloat scale = [[UIScreen mainScreen] scale];
  return (CGFloat)MDCFloor(value * scale) / scale;
}

// Returns the rect resulting from applying AlignSizeToUpperPixel to the rect size.
static inline CGRect AlignRectToUpperPixel(CGRect rect) {
  rect = CGRectStandardize(rect);
  return CGRectMake(AlignValueToLowerPixel(rect.origin.x), AlignValueToLowerPixel(rect.origin.y),
                    AlignValueToUpperPixel(rect.size.width),
                    AlignValueToUpperPixel(rect.size.height));
}

@implementation MDCCollectionViewTextCell {
  UIView *_contentWrapper;
}

- (instancetype)initWithFrame:(CGRect)frame {
  self = [super initWithFrame:frame];
  if (self) {
    [self commonMDCCollectionViewTextCellInit];
  }
  return self;
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
  self = [super initWithCoder:aDecoder];
  if (self) {
    [self commonMDCCollectionViewTextCellInit];
  }
  return self;
}

- (void)resetMDCCollectionViewTextCellLabelProperties {
  _textLabel.font = CellDefaultTextFont();
  _textLabel.textColor = [UIColor colorWithWhite:0 alpha:CellDefaultTextOpacity()];
  _textLabel.shadowColor = nil;
  _textLabel.shadowOffset = CGSizeZero;
  _textLabel.textAlignment = NSTextAlignmentNatural;
  _textLabel.lineBreakMode = NSLineBreakByTruncatingTail;
  _textLabel.numberOfLines = 1;

  _detailTextLabel.font = CellDefaultDetailTextFont();
  _detailTextLabel.textColor = [UIColor colorWithWhite:0 alpha:CellDefaultDetailTextFontOpacity()];
  _detailTextLabel.shadowColor = nil;
  _detailTextLabel.shadowOffset = CGSizeZero;
  _detailTextLabel.textAlignment = NSTextAlignmentNatural;
  _detailTextLabel.lineBreakMode = NSLineBreakByTruncatingTail;
  _detailTextLabel.numberOfLines = 1;
}

- (void)commonMDCCollectionViewTextCellInit {
  _contentWrapper = [[UIView alloc] initWithFrame:self.contentView.bounds];
  _contentWrapper.autoresizingMask =
      UIViewAutoresizingFlexibleWidth |
      MDFTrailingMarginAutoresizingMaskForLayoutDirection(
          self.mdf_effectiveUserInterfaceLayoutDirection);
  _contentWrapper.clipsToBounds = YES;
  [self.contentView addSubview:_contentWrapper];

  // Text label.
  _textLabel = [[UILabel alloc] initWithFrame:CGRectZero];
  _textLabel.autoresizingMask = MDFTrailingMarginAutoresizingMaskForLayoutDirection(
      self.mdf_effectiveUserInterfaceLayoutDirection);

  // Detail text label.
  _detailTextLabel = [[UILabel alloc] initWithFrame:CGRectZero];
  _detailTextLabel.autoresizingMask = MDFTrailingMarginAutoresizingMaskForLayoutDirection(
      self.mdf_effectiveUserInterfaceLayoutDirection);

  [self resetMDCCollectionViewTextCellLabelProperties];

  [_contentWrapper addSubview:_textLabel];
  [_contentWrapper addSubview:_detailTextLabel];

  // Image view.
  _imageView = [[UIImageView alloc] initWithFrame:CGRectZero];
  _imageView.autoresizingMask = MDFTrailingMarginAutoresizingMaskForLayoutDirection(
      self.mdf_effectiveUserInterfaceLayoutDirection);
  [self.contentView addSubview:_imageView];
}

#pragma mark - Layout

- (void)prepareForReuse {
  self.imageView.image = nil;
  self.textLabel.text = nil;
  self.detailTextLabel.text = nil;

  [self resetMDCCollectionViewTextCellLabelProperties];

  [super prepareForReuse];
  [self setNeedsLayout];
}

- (void)layoutSubviews {
  [super layoutSubviews];
  [self applyMetrics];
}

- (CGRect)contentWrapperFrame {
  CGFloat leadingPadding =
      _imageView.image ? kCellTextWithImagePaddingLeading : kCellTextNoImagePaddingLeading;
  CGFloat trailingPadding = kCellTextNoImagePaddingTrailing;
  UIEdgeInsets insets = MDFInsetsMakeWithLayoutDirection(
      0, leadingPadding, 0, trailingPadding, self.mdf_effectiveUserInterfaceLayoutDirection);
  return UIEdgeInsetsInsetRect(self.contentView.bounds, insets);
}

- (void)applyMetrics {
  // Set content wrapper frame.
  _contentWrapper.frame = [self contentWrapperFrame];
  CGFloat boundsHeight = CGRectGetHeight(_contentWrapper.bounds);

  // Image layout.
  CGRect imageFrame = CGRectZero;
  imageFrame.size.width = MIN(_imageView.image.size.width, kImageSize);
  imageFrame.size.height = MIN(_imageView.image.size.height, kImageSize);
  imageFrame.origin.x = kCellImagePaddingLeading;
  imageFrame.origin.y =
      (CGRectGetHeight(self.contentView.frame) / 2) - (imageFrame.size.height / 2);

  // Text layout and line count
  CGRect textFrame = CGRectZero;
  textFrame.size = [self frameSizeForLabel:_textLabel];
  NSInteger textLines = (NSInteger)floor(textFrame.size.height / _textLabel.font.lineHeight);
  CGRect detailFrame = CGRectZero;
  detailFrame.size = [self frameSizeForLabel:_detailTextLabel];
  NSInteger detailsLines =
      (NSInteger)floor(detailFrame.size.height / _detailTextLabel.font.lineHeight);
  NSInteger numberOfAllVisibleTextLines = textLines + detailsLines;

  // Adjust the labels X origin.
  textFrame.origin.x = 0;
  detailFrame.origin.x = 0;

  // Adjust the labels Y origin.
  if (numberOfAllVisibleTextLines == 1) {
    // Alignment for single line.
    textFrame.origin.y = (boundsHeight / 2) - (textFrame.size.height / 2);
    detailFrame.origin.y = (boundsHeight / 2) - (detailFrame.size.height / 2);

  } else if (numberOfAllVisibleTextLines == 2) {
    if (!CGRectIsEmpty(textFrame) && !CGRectIsEmpty(detailFrame)) {
      // Alignment for two lines.
      textFrame.origin.y =
          kCellTwoLinePaddingTop + _textLabel.font.ascender - textFrame.size.height;
      detailFrame.origin.y = boundsHeight - kCellTwoLinePaddingBottom - detailFrame.size.height -
                             _detailTextLabel.font.descender;
    } else {
      // Since single wrapped label, just center.
      textFrame.origin.y = (boundsHeight / 2) - (textFrame.size.height / 2);
      detailFrame.origin.y = (boundsHeight / 2) - (detailFrame.size.height / 2);
    }

  } else if (numberOfAllVisibleTextLines >= 3) {
    if (!CGRectIsEmpty(textFrame) && !CGRectIsEmpty(detailFrame)) {
      // Alignment for three lines.
      textFrame.origin.y =
          kCellThreeLinePaddingTop + _textLabel.font.ascender - _textLabel.font.lineHeight;
      detailFrame.origin.y = boundsHeight - kCellThreeLinePaddingBottom - detailFrame.size.height -
                             _detailTextLabel.font.descender;
      imageFrame.origin.y = kCellThreeLinePaddingTop;
    } else {
      // Since single wrapped label, just center.
      textFrame.origin.y = (boundsHeight / 2) - (textFrame.size.height / 2);
      detailFrame.origin.y = (boundsHeight / 2) - (detailFrame.size.height / 2);
    }
  }
  textFrame = AlignRectToUpperPixel(textFrame);
  detailFrame = AlignRectToUpperPixel(detailFrame);
  imageFrame = AlignRectToUpperPixel(imageFrame);

  if (self.mdf_effectiveUserInterfaceLayoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
    textFrame = MDFRectFlippedHorizontally(textFrame, CGRectGetWidth(_contentWrapper.bounds));
    detailFrame = MDFRectFlippedHorizontally(detailFrame, CGRectGetWidth(_contentWrapper.bounds));
    imageFrame = MDFRectFlippedHorizontally(imageFrame, CGRectGetWidth(self.contentView.bounds));
  }

  _textLabel.frame = textFrame;
  _detailTextLabel.frame = detailFrame;
  _imageView.frame = imageFrame;
}

- (CGSize)frameSizeForLabel:(UILabel *)label {
  CGFloat width = CGRectGetWidth(_contentWrapper.bounds);
  CGFloat height =
      [label textRectForBounds:_contentWrapper.bounds limitedToNumberOfLines:label.numberOfLines]
          .size.height;
  return CGSizeMake(width, height);
}

@end