/core/externals/google-toolbox-for-mac/iPhone/GTMFadeTruncatingLabel.m

  1//
  2//  GTMFadeTruncatingLabel.m
  3//
  4//  Copyright 2012 Google Inc.
  5//
  6//  Licensed under the Apache License, Version 2.0 (the "License"); you may not
  7//  use this file except in compliance with the License.  You may obtain a copy
  8//  of the License at
  9//
 10//  http://www.apache.org/licenses/LICENSE-2.0
 11//
 12//  Unless required by applicable law or agreed to in writing, software
 13//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 14//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 15//  License for the specific language governing permissions and limitations under
 16//  the License.
 17//
 18#import "GTMFadeTruncatingLabel.h"
 19
 20@interface GTMFadeTruncatingLabel ()
 21- (void)setup;
 22@end
 23
 24@implementation GTMFadeTruncatingLabel
 25
 26@synthesize truncateMode = truncateMode_;
 27
 28- (void)setup {
 29  self.backgroundColor = [UIColor clearColor];
 30  truncateMode_ = GTMFadeTruncatingTail;
 31}
 32
 33- (id)initWithFrame:(CGRect)frame {
 34  self = [super initWithFrame:frame];
 35  if (self) {
 36    // Use clip as a default value.
 37    self.lineBreakMode = NSLineBreakByClipping;
 38    [self setup];
 39  }
 40  return self;
 41}
 42
 43- (void)awakeFromNib {
 44  [self setup];
 45}
 46
 47// Draw fade gradient mask if text is wider than rect.
 48- (void)drawTextInRect:(CGRect)requestedRect {
 49  CGContextRef context = UIGraphicsGetCurrentContext();
 50  CGContextSaveGState(context);
 51
 52  CGSize size = [self.text sizeWithFont:self.font];
 53  if (size.width > requestedRect.size.width) {
 54    UIImage* image = [[self class]
 55        getLinearGradient:requestedRect
 56                 fadeHead:((self.truncateMode & GTMFadeTruncatingHead) > 0)
 57                 fadeTail:((self.truncateMode & GTMFadeTruncatingTail) > 0)];
 58    CGContextClipToMask(context, self.bounds, image.CGImage);
 59  }
 60
 61  if (self.shadowColor) {
 62    CGContextSetFillColorWithColor(context, self.shadowColor.CGColor);
 63    CGRect shadowRect = CGRectOffset(requestedRect, self.shadowOffset.width,
 64                                     self.shadowOffset.height);
 65    [self.text drawInRect:shadowRect
 66                 withFont:self.font
 67            lineBreakMode:self.lineBreakMode
 68                alignment:self.textAlignment];
 69  }
 70
 71  CGContextSetFillColorWithColor(context, self.textColor.CGColor);
 72  [self.text drawInRect:requestedRect
 73               withFont:self.font
 74          lineBreakMode:self.lineBreakMode
 75              alignment:self.textAlignment];
 76
 77  CGContextRestoreGState(context);
 78}
 79
 80// Create gradient opacity mask based on direction.
 81+ (UIImage*)getLinearGradient:(CGRect)rect
 82                     fadeHead:(BOOL)fadeHead
 83                     fadeTail:(BOOL)fadeTail {
 84  // Create an opaque context.
 85  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
 86  CGContextRef context = CGBitmapContextCreate(NULL,
 87                                               rect.size.width,
 88                                               rect.size.height,
 89                                               8,
 90                                               4*rect.size.width,
 91                                               colorSpace,
 92                                               (CGBitmapInfo)kCGImageAlphaNone);
 93
 94  // White background will mask opaque, black gradient will mask transparent.
 95  CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
 96  CGContextFillRect(context, rect);
 97
 98  // Create gradient from white to black.
 99  CGFloat locs[2] = { 0.0f, 1.0f };
100  CGFloat components[4] = { 1.0f, 1.0f, 0.0f, 1.0f };
101  CGGradientRef gradient =
102      CGGradientCreateWithColorComponents(colorSpace, components, locs, 2);
103  CGColorSpaceRelease(colorSpace);
104
105  // Draw head and/or tail gradient.
106  CGFloat fadeWidth = MIN(rect.size.height * 2, floor(rect.size.width / 4));
107  CGFloat minX = CGRectGetMinX(rect);
108  CGFloat maxX = CGRectGetMaxX(rect);
109  if (fadeTail) {
110    CGFloat startX = maxX - fadeWidth;
111    CGPoint startPoint = CGPointMake(startX, CGRectGetMidY(rect));
112    CGPoint endPoint = CGPointMake(maxX, CGRectGetMidY(rect));
113    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
114  }
115  if (fadeHead) {
116    CGFloat startX = minX + fadeWidth;
117    CGPoint startPoint = CGPointMake(startX, CGRectGetMidY(rect));
118    CGPoint endPoint = CGPointMake(minX, CGRectGetMidY(rect));
119    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
120  }
121  CGGradientRelease(gradient);
122
123  // Clean up, return image.
124  CGImageRef ref = CGBitmapContextCreateImage(context);
125  UIImage* image = [UIImage imageWithCGImage:ref];
126  CGImageRelease(ref);
127  CGContextRelease(context);
128  return image;
129}
130
131@end