components/TextFields/src/MDCTextInputUnderlineView.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 "MDCTextInputUnderlineView.h"

#import "MaterialPalettes.h"

static const CGFloat MDCTextInputUnderlineDefaultHeight = 1;

// TODO: (larche): Make disabled color parameterized?
static inline UIColor *MDCTextInputUnderlineColor() {
  return [UIColor lightGrayColor];
}

@interface MDCTextInputUnderlineView ()

@property(nonatomic, strong) CAShapeLayer *disabledUnderline;
@property(nonatomic, strong) CAShapeLayer *underline;

@end

@implementation MDCTextInputUnderlineView

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

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

- (void)commonMDCUnderlineViewInit {
  _color = MDCTextInputUnderlineColor();
  _disabledColor = MDCTextInputUnderlineColor();
  _enabled = YES;
  _lineHeight = MDCTextInputUnderlineDefaultHeight;

  [self setContentHuggingPriority:UILayoutPriorityDefaultHigh
                          forAxis:UILayoutConstraintAxisVertical];
  [self setClipsToBounds:NO];
  [self updateUnderline];
}

- (instancetype)copyWithZone:(__unused NSZone *)zone {
  MDCTextInputUnderlineView *copy = [[[self class] alloc] initWithFrame:self.frame];

  copy.color = self.color;
  copy.disabledColor = self.disabledColor;
  copy.enabled = self.enabled;
  copy.lineHeight = self.lineHeight;

  return copy;
}

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

- (CGSize)intrinsicContentSize {
  return CGSizeMake(UIViewNoIntrinsicMetric, self.lineHeight);
}

- (void)updateUnderlinePath {
  CGRect bounds = [self bounds];
  CGMutablePathRef path = CGPathCreateMutable();
  CGFloat offSet = 1 / [UIScreen mainScreen].scale;
  CGPathMoveToPoint(path, NULL, CGRectGetMinX(bounds), CGRectGetMidY(bounds) + offSet);
  CGPathAddLineToPoint(path, NULL, CGRectGetMaxX(bounds), CGRectGetMidY(bounds) + offSet);

  if (_underline) {
    _underline.frame = bounds;
    _underline.path = path;
  }

  if (_disabledUnderline) {
    _disabledUnderline.frame = bounds;
    _disabledUnderline.path = path;
  }
  CGPathRelease(path);
}

- (void)updateUnderline {
  if (_enabled) {
    if (!_underline) {
      _underline = [CAShapeLayer layer];
      _underline.contentsScale = [UIScreen mainScreen].scale;
      _underline.frame = CGRectZero;
      _underline.lineWidth = self.lineHeight;
      _underline.strokeColor = _color.CGColor;

      [self.layer addSublayer:_underline];
    }

    _disabledUnderline.opacity = 0;
  } else {
    if (!_disabledUnderline) {
      _disabledUnderline = [CAShapeLayer layer];
      _disabledUnderline.contentsScale = [UIScreen mainScreen].scale;
      _disabledUnderline.frame = CGRectZero;
      _disabledUnderline.lineJoin = kCALineJoinMiter;
      _disabledUnderline.lineDashPattern = @[ @1.5, @1.5 ];
      _disabledUnderline.lineWidth = 1.0;
      _disabledUnderline.opaque = NO;
      _disabledUnderline.strokeColor = _disabledColor.CGColor;
      [self.layer addSublayer:_disabledUnderline];
    }

    _disabledUnderline.opacity = 1;
  }

  _underline.lineWidth = self.lineHeight;

  [self updateUnderlinePath];
  [self updateColor];
}

- (void)updateColor {
  BOOL showUnderline = self.enabled;
  UIColor *strokeColor = [UIColor clearColor];
  if (showUnderline) {
    strokeColor = _color;
  }

  self.disabledUnderline.strokeColor = self.disabledColor.CGColor;
  self.underline.strokeColor = strokeColor.CGColor;
  self.opaque = showUnderline;
}

#pragma mark - Property implementation

- (void)setColor:(UIColor *)color {
  _color = color;
  [self updateColor];
}

- (void)setEnabled:(BOOL)enabled {
  if (_enabled != enabled) {
    _enabled = enabled;
    [self updateUnderline];
    [self updateColor];
  }
}

- (void)setLineHeight:(CGFloat)lineHeight {
  if (_lineHeight != lineHeight) {
    _lineHeight = lineHeight;
  }
  [self updateUnderline];
}

@end