MDCBottomAppBarLayer.m

// Copyright 2017-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 "MDCBottomAppBarLayer.h"

#import "MaterialMath.h"
#import "MDCBottomAppBarAttributes.h"

@implementation MDCBottomAppBarLayer

+ (instancetype)layer {
  MDCBottomAppBarLayer *layer = [super layer];
  layer.fillColor = [UIColor whiteColor].CGColor;
  layer.shadowColor = [UIColor blackColor].CGColor;

  // TODO(#2018): These shadow attributes will be updated once specs are finalized.
  CGFloat scale = UIScreen.mainScreen.scale;
  layer.shadowOpacity = 0.4f;
  layer.shadowRadius = 4.f;
  layer.shadowOffset = CGSizeMake(0, 2.f);
  layer.needsDisplayOnBoundsChange = YES;
  layer.contentsScale = scale;
  layer.rasterizationScale = scale;
  layer.shouldRasterize = YES;
  return layer;
}

- (CGPathRef)pathWithCutFromRect:(CGRect)rect
          floatingButtonPosition:(MDCBottomAppBarFloatingButtonPosition)floatingButtonPosition
                 layoutDirection:(UIUserInterfaceLayoutDirection)layoutDirection {
  UIBezierPath *bottomBarPath = [UIBezierPath bezierPath];

  static CGFloat kStartAngle;
  static CGFloat kEndAngle;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    // Since we know the hypotenuse (radius) and opposite side (height above the line) we can
    // compute the angle.
    // sin( θ ) = opposite / hypotenuse
    // θ = arcsin( opposite / hypotenuse )
    // More reading: https://www.mathsisfun.com/algebra/trig-finding-angle-right-triangle.html
    kEndAngle = (CGFloat)asin(kMDCBottomAppBarFloatingButtonPositionY /
                              kMDCBottomAppBarFloatingButtonRadius);
    kStartAngle = (CGFloat)(M_PI - kEndAngle);
  });

  CGFloat width = CGRectGetWidth(rect);
  CGFloat height = CGRectGetHeight(rect);
  CGFloat midX = CGRectGetMidX(rect);

  // Paths generated below differ based on the placement of the floating button.
  switch (floatingButtonPosition) {
    case MDCBottomAppBarFloatingButtonPositionLeading: {
      if (layoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
        [self pathWithCutRight:bottomBarPath
                         width:width
                        height:height
                    startAngle:kStartAngle
                      endAngle:kEndAngle];
      } else {
        [self pathWithCutLeft:bottomBarPath
                        width:width
                       height:height
                   startAngle:kStartAngle
                     endAngle:kEndAngle];
      }
      break;
    }
    case MDCBottomAppBarFloatingButtonPositionCenter: {
      [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
      CGPoint centerPath = CGPointMake(midX,
                                       kMDCBottomAppBarYOffset -
                                       kMDCBottomAppBarFloatingButtonPositionY);
      [bottomBarPath addArcWithCenter:centerPath
                               radius:kMDCBottomAppBarFloatingButtonRadius
                           startAngle:kStartAngle
                             endAngle:kEndAngle
                            clockwise:NO];
      [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(width, height * 2)];
      [bottomBarPath addLineToPoint:CGPointMake(0, height * 2)];
      [bottomBarPath closePath];
      break;
    }
    case MDCBottomAppBarFloatingButtonPositionTrailing: {
      if (layoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
        [self pathWithCutLeft:bottomBarPath
                        width:width
                       height:height
                   startAngle:kStartAngle
                     endAngle:kEndAngle];
      } else {
        [self pathWithCutRight:bottomBarPath
                         width:width
                        height:height
                    startAngle:kStartAngle
                      endAngle:kEndAngle];
      }
      break;
    }
    default: {

      // The default path does not contain a cut for the floating button. However, it is necessary
      // to include the same number of points as the cut path version so there is a smooth
      // transition between cut and without cut paths.
      [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(height, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(height,
                                                height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath closePath];
      break;
    }
  }
  return bottomBarPath.CGPath;
}

- (UIBezierPath *)pathWithCutLeft:(UIBezierPath *)bottomBarPath
                            width:(CGFloat)width
                           height:(CGFloat)height
                       startAngle:(CGFloat)startAngle
                         endAngle:(CGFloat)endAngle {
  [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
  CGPoint centerPath = CGPointMake(kMDCBottomAppBarFloatingButtonPositionX,
                                   kMDCBottomAppBarYOffset -
                                   kMDCBottomAppBarFloatingButtonPositionY);
  [bottomBarPath addArcWithCenter:centerPath
                           radius:kMDCBottomAppBarFloatingButtonRadius
                       startAngle:startAngle
                         endAngle:endAngle
                        clockwise:NO];
  [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width,
                                            height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath closePath];
  return bottomBarPath;
}

- (UIBezierPath *)pathWithCutRight:(UIBezierPath *)bottomBarPath
                             width:(CGFloat)width
                            height:(CGFloat)height
                        startAngle:(CGFloat)startAngle
                          endAngle:(CGFloat)endAngle {
  [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
  CGPoint centerPath = CGPointMake(width - kMDCBottomAppBarFloatingButtonPositionX,
                                   kMDCBottomAppBarYOffset -
                                   kMDCBottomAppBarFloatingButtonPositionY);
  [bottomBarPath addArcWithCenter:centerPath
                           radius:kMDCBottomAppBarFloatingButtonRadius
                       startAngle:startAngle
                         endAngle:endAngle
                        clockwise:NO];
  [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath closePath];
  return bottomBarPath;
}

- (CGPathRef)pathWithoutCutFromRect:(CGRect)rect
             floatingButtonPosition:(MDCBottomAppBarFloatingButtonPosition)floatingButtonPosition
                    layoutDirection:(UIUserInterfaceLayoutDirection)layoutDirection {

  CGFloat height = CGRectGetHeight(rect);
  CGFloat width = CGRectGetWidth(rect);
  CGFloat midX = CGRectGetMidX(rect);

  UIBezierPath *bottomBarPath = [UIBezierPath bezierPath];
  switch (floatingButtonPosition) {
    case MDCBottomAppBarFloatingButtonPositionLeading: {
      if (layoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
        [self pathWithoutCutRight:bottomBarPath width:width height:height];
      } else {
        [self pathWithoutCutLeft:bottomBarPath width:width height:height];
      }
      break;
    }
    case MDCBottomAppBarFloatingButtonPositionCenter: {
      CGFloat offsetRadiusDiff = kMDCBottomAppBarYOffset - kMDCBottomAppBarFloatingButtonRadius;
      [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(midX - offsetRadiusDiff,
                                                kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(midX, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(midX + offsetRadiusDiff,
                                                kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(width, height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath closePath];
      break;
    }
    case MDCBottomAppBarFloatingButtonPositionTrailing: {
      if (layoutDirection == UIUserInterfaceLayoutDirectionRightToLeft) {
        [self pathWithoutCutLeft:bottomBarPath width:width height:height];
      } else {
        [self pathWithoutCutRight:bottomBarPath width:width height:height];
      }
      break;
    }
    default: {
      [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(height, kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(height,
                                                height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
      [bottomBarPath closePath];
      break;
    }
  }
  return bottomBarPath.CGPath;
}

- (UIBezierPath *)pathWithoutCutLeft:(UIBezierPath *)bottomBarPath
                               width:(CGFloat)width
                              height:(CGFloat)height {
  CGFloat offsetRadiusDiff = kMDCBottomAppBarYOffset - kMDCBottomAppBarFloatingButtonRadius;
  [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(kMDCBottomAppBarFloatingButtonPositionX -
                                            offsetRadiusDiff,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(kMDCBottomAppBarFloatingButtonPositionX,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(kMDCBottomAppBarFloatingButtonPositionX +
                                            offsetRadiusDiff,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath closePath];
  return bottomBarPath;
}

- (UIBezierPath *)pathWithoutCutRight:(UIBezierPath *)bottomBarPath
                                width:(CGFloat)width
                               height:(CGFloat)height {
  CGFloat offsetRadiusDiff = kMDCBottomAppBarYOffset - kMDCBottomAppBarFloatingButtonRadius;
  [bottomBarPath moveToPoint:CGPointMake(0, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width - kMDCBottomAppBarFloatingButtonPositionX -
                                            offsetRadiusDiff,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width - kMDCBottomAppBarFloatingButtonPositionX,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width - kMDCBottomAppBarFloatingButtonPositionX +
                                            offsetRadiusDiff,
                                            kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width, kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(width, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath addLineToPoint:CGPointMake(0, height * 2 + kMDCBottomAppBarYOffset)];
  [bottomBarPath closePath];
  return bottomBarPath;
}

@end