Upstream Chrome on iOS source code [6/11].

ios/chrome/browser/ui/omnibox/truncating_attributed_label.mm

+// Copyright (c) 2012 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/omnibox/truncating_attributed_label.h"
+
+#include <algorithm>
+
+#include "base/mac/objc_property_releaser.h"
+#include "base/mac/scoped_cftyperef.h"
+
+@interface OmniboxPopupTruncatingLabel ()
+- (void)setup;
+- (UIImage*)getLinearGradient:(CGRect)rect;
+@end
+
+@implementation OmniboxPopupTruncatingLabel {
+  // Attributed text.
+  base::scoped_nsobject<CATextLayer> textLayer_;
+  // Gradient used to create fade effect. Changes based on view.frame size.
+  base::scoped_nsobject<UIImage> gradient_;
+
+  base::mac::ObjCPropertyReleaser propertyReleaser_OmniboxPopupTruncatingLabel_;
+}
+
+@synthesize truncateMode = truncateMode_;
+@synthesize attributedText = attributedText_;
+@synthesize highlighted = highlighted_;
+@synthesize highlightedText = highlightedText_;
+@synthesize textAlignment = textAlignment_;
+
+- (void)setup {
+  self.backgroundColor = [UIColor clearColor];
+  self.contentMode = UIViewContentModeRedraw;
+  truncateMode_ = OmniboxPopupTruncatingTail;
+
+  // Disable animations in CATextLayer.
+  textLayer_.reset([[CATextLayer layer] retain]);
+  base::scoped_nsobject<NSDictionary> actions([[NSDictionary alloc]
+      initWithObjectsAndKeys:[NSNull null], @"contents", nil]);
+  [textLayer_ setActions:actions];
+  [textLayer_ setFrame:self.bounds];
+  [textLayer_ setContentsScale:[[UIScreen mainScreen] scale]];
+}
+
+- (id)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    propertyReleaser_OmniboxPopupTruncatingLabel_.Init(
+        self, [OmniboxPopupTruncatingLabel class]);
+    [self setup];
+  }
+  return self;
+}
+
+- (void)awakeFromNib {
+  [super awakeFromNib];
+  [self setup];
+}
+
+- (void)setFrame:(CGRect)frame {
+  [super setFrame:frame];
+  [textLayer_ setFrame:self.bounds];
+
+  // Cache the fade gradient when the frame changes.
+  if (!CGRectIsEmpty(frame) &&
+      (!gradient_.get() || !CGSizeEqualToSize([gradient_ size], frame.size))) {
+    CGRect rect = CGRectMake(0, 0, frame.size.width, frame.size.height);
+    gradient_.reset([[self getLinearGradient:rect] retain]);
+  }
+}
+
+- (void)drawRect:(CGRect)rect {
+  if ([attributedText_ length] == 0)
+    return;
+
+  CGContextRef context = UIGraphicsGetCurrentContext();
+  CGContextSaveGState(context);
+  [textLayer_ setString:highlighted_ ? highlightedText_ : attributedText_];
+  CGContextClipToMask(context, self.bounds, [gradient_ CGImage]);
+  [textLayer_ renderInContext:context];
+
+  CGContextRestoreGState(context);
+}
+
+- (void)setTextAlignment:(NSTextAlignment)textAlignment {
+  if (textAlignment == NSTextAlignmentLeft) {
+    [textLayer_ setAlignmentMode:kCAAlignmentLeft];
+    self.truncateMode = OmniboxPopupTruncatingTail;
+  } else if (textAlignment == NSTextAlignmentRight) {
+    [textLayer_ setAlignmentMode:kCAAlignmentRight];
+    self.truncateMode = OmniboxPopupTruncatingHead;
+  } else if (textAlignment == NSTextAlignmentNatural) {
+    [textLayer_ setAlignmentMode:kCAAlignmentNatural];
+    self.truncateMode = OmniboxPopupTruncatingTail;
+  } else {
+    NOTREACHED();
+  }
+  if (textAlignment != textAlignment_)
+    gradient_.reset();
+  textAlignment_ = textAlignment;
+}
+
+// Create gradient opacity mask based on direction.
+- (UIImage*)getLinearGradient:(CGRect)rect {
+  // Create an opaque context.
+  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
+  CGContextRef context =
+      CGBitmapContextCreate(NULL, rect.size.width, rect.size.height, 8,
+                            4 * rect.size.width, colorSpace, kCGImageAlphaNone);
+
+  // White background will mask opaque, black gradient will mask transparent.
+  CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
+  CGContextFillRect(context, rect);
+
+  // Create gradient from white to black.
+  CGFloat locs[2] = {0.0f, 1.0f};
+  CGFloat components[4] = {1.0f, 1.0f, 0.0f, 1.0f};
+  CGGradientRef gradient =
+      CGGradientCreateWithColorComponents(colorSpace, components, locs, 2);
+  CGColorSpaceRelease(colorSpace);
+
+  // Draw head and/or tail gradient.
+  CGFloat fadeWidth =
+      std::min(rect.size.height * 2, (CGFloat)floor(rect.size.width / 4));
+  CGFloat minX = CGRectGetMinX(rect);
+  CGFloat maxX = CGRectGetMaxX(rect);
+  if (self.truncateMode & OmniboxPopupTruncatingTail) {
+    CGFloat startX = maxX - fadeWidth;
+    CGPoint startPoint = CGPointMake(startX, CGRectGetMidY(rect));
+    CGPoint endPoint = CGPointMake(maxX, CGRectGetMidY(rect));
+    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
+  }
+  if (self.truncateMode & OmniboxPopupTruncatingHead) {
+    CGFloat startX = minX + fadeWidth;
+    CGPoint startPoint = CGPointMake(startX, CGRectGetMidY(rect));
+    CGPoint endPoint = CGPointMake(minX, CGRectGetMidY(rect));
+    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
+  }
+  CGGradientRelease(gradient);
+
+  // Clean up, return image.
+  CGImageRef ref = CGBitmapContextCreateImage(context);
+  UIImage* image = [UIImage imageWithCGImage:ref];
+  CGImageRelease(ref);
+  CGContextRelease(context);
+  return image;
+}
+
+@end