Adjust new tab button path to get crisp line along top edge (Mac).

chrome/browser/ui/cocoa/new_tab_button.mm

 // Copyright (c) 2011 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 "chrome/browser/ui/cocoa/new_tab_button.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/sdk_forward_declarations.h"
 #import "chrome/browser/ui/cocoa/image_button_cell.h"
 #include "chrome/browser/ui/cocoa/tabs/tab_view.h"
@@ skipping 342 matching lines @@
   [imageRep setRenderingOption:renderingOption];
 
   NSImage* newTabButtonImage =
       [[[NSImage alloc] initWithSize:NSMakeSize(34, 17)] autorelease];
   [newTabButtonImage setCacheMode:NSImageCacheAlways];
   [newTabButtonImage addRepresentation:imageRep];
 
   return newTabButtonImage;
 }
 
-+ (NSBezierPath*)newTabButtonBezierPathWithInset:(CGFloat)inset {
++ (NSBezierPath*)newTabButtonBezierPathWithInset:(int)inset
+                                       lineWidth:(CGFloat)lineWidth {
   NSBezierPath* bezierPath = [NSBezierPath bezierPath];
 
   // Bottom edge.
   [bezierPath moveToPoint:NSMakePoint(19 - inset, 1.2825 + inset)];
   [bezierPath lineToPoint:NSMakePoint(10.45 + inset, 1.2825 + inset)];
 
   // Lower-left corner.
   [bezierPath curveToPoint:NSMakePoint(6.08 + inset, 2.85 + inset)
              controlPoint1:NSMakePoint(10.1664 + inset, 1.3965 + inset)
              controlPoint2:NSMakePoint(7.89222 + inset, 0.787708 + inset)];
 
   // Left side.
   [bezierPath lineToPoint:NSMakePoint(0.7125 + inset, 14.25 - inset)];
 
   // Upper-left corner.
-  [bezierPath curveToPoint:NSMakePoint(1.71 + inset, 16.2688 - inset)
+  const float topEdgeY = 16.2688;
+  [bezierPath curveToPoint:NSMakePoint(1.71 + inset, topEdgeY - inset)
              controlPoint1:NSMakePoint(0.246496 + inset, 15.2613 - inset)
              controlPoint2:NSMakePoint(0.916972 + inset, 16.3489 - inset)];
 
   // Top edge.
-  [bezierPath lineToPoint:NSMakePoint(23.275 - inset, 16.2688 - inset)];
+  [bezierPath lineToPoint:NSMakePoint(23.275 - inset, topEdgeY - inset)];
 
   // Upper right corner.
   [bezierPath curveToPoint:NSMakePoint(27.645 - inset, 14.7012 - inset)
              controlPoint1:NSMakePoint(26.4376 - inset, 16.3305 - inset)
              controlPoint2:NSMakePoint(26.9257 - inset, 15.8059 - inset)];
 
   // Right side.
   [bezierPath lineToPoint:NSMakePoint(32.9543 - inset, 3.62561 + inset)];
 
   // Lower right corner.
   [bezierPath curveToPoint:NSMakePoint(32.015 - inset, 1.2825 + inset)
              controlPoint1:NSMakePoint(34.069 - inset, 1.45303 + inset)
              controlPoint2:NSMakePoint(31.0348 - inset, 1.31455 + inset)];
 
   [bezierPath closePath];
 
+  // On non-Retina machines, adjust the path so that the top line rests along
+  // a pixel line (to get a crisp line on the display).
+  if (lineWidth == 1) {
+    NSAffineTransform* translateTransform = [NSAffineTransform transform];
+    [translateTransform translateXBy:0
+                                 yBy:0.5 - (topEdgeY - trunc(topEdgeY))];
+    [bezierPath transformUsingAffineTransform:translateTransform];
+  }
+
+  [bezierPath setLineWidth:lineWidth];
+
   return bezierPath;
 }
 
 + (void)drawNewTabButtonImage:(NewTabButtonCustomImageRep*)imageRep {
   [[NSGraphicsContext currentContext]
       cr_setPatternPhase:[imageRep patternPhasePosition]
       forView:[imageRep destView]];
 
-  NSBezierPath* bezierPath = [self newTabButtonBezierPathWithInset:0];
   CGContextRef context = static_cast<CGContextRef>(
       [[NSGraphicsContext currentContext] graphicsPort]);
   CGFloat lineWidth = LineWidthFromContext(context);
-  [bezierPath setLineWidth:lineWidth];
+  NSBezierPath* bezierPath = [self newTabButtonBezierPathWithInset:0
+                                                         lineWidth:lineWidth];
 
   if ([imageRep fillColor]) {
     [[imageRep fillColor] set];
     [bezierPath fill];
   }
 
   static NSColor* strokeColor =
       [[NSColor colorWithCalibratedWhite:0 alpha:0.4] retain];
   [strokeColor set];
   [bezierPath stroke];
@@ skipping 44 matching lines @@
 
     case RenderingOption::INLAY_LIGHTEN:
       [lightColor set];
       inset = 1;
       break;
 
     case RenderingOption::NORMAL:
       break;
   }
   if (inset != -1) {
-    bezierPath = [self newTabButtonBezierPathWithInset:inset];
-    [bezierPath setLineWidth:lineWidth];
+    bezierPath = [self newTabButtonBezierPathWithInset:inset
+                                             lineWidth:lineWidth];
     [bezierPath fill];
   }
 }
 
 - (NSImage*)imageWithFillColor:(NSColor*)fillColor {
   NSImage* image =
       [[[NSImage alloc] initWithSize:NSMakeSize(34, 17)] autorelease];
 
   [image lockFocus];
   [fillColor set];
-  [[NewTabButton newTabButtonBezierPathWithInset:0] fill];
+  CGContextRef context = static_cast<CGContextRef>(
+      [[NSGraphicsContext currentContext] graphicsPort]);
+  CGFloat lineWidth = LineWidthFromContext(context);
+  [[NewTabButton newTabButtonBezierPathWithInset:0 lineWidth:lineWidth] fill];
   [image unlockFocus];
   return image;
 }
 
 @end