Mac: Optimize HistoryOverlayView using layer.

chrome/browser/ui/cocoa/history_overlay_controller.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 "chrome/browser/ui/cocoa/history_overlay_controller.h"
 
 #include "base/logging.h"
+#include "base/mac/scoped_cftyperef.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #include "grit/theme_resources.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
 
 // Constants ///////////////////////////////////////////////////////////////////
@@ skipping 11 matching lines @@
 // considered complete.
 const CGFloat kShieldHeightCompletionAdjust = 10;
 
 // HistoryOverlayView //////////////////////////////////////////////////////////
 
 // The content view that draws the semicircle and the arrow.
 @interface HistoryOverlayView : NSView {
  @private
   HistoryOverlayMode mode_;
   CGFloat shieldAlpha_;
+  base::scoped_nsobject<CAShapeLayer> shapeLayer_;
 }
 @property(nonatomic) CGFloat shieldAlpha;
 - (id)initWithMode:(HistoryOverlayMode)mode
              image:(NSImage*)image;
 @end
 
 @implementation HistoryOverlayView
 
 @synthesize shieldAlpha = shieldAlpha_;
 
 - (id)initWithMode:(HistoryOverlayMode)mode
              image:(NSImage*)image {
   NSRect frame = NSMakeRect(0, 0, kShieldWidth, kShieldHeight);
   if ((self = [super initWithFrame:frame])) {
     mode_ = mode;
+    shieldAlpha_ = 1.0;  // CAShapeLayer's fillColor defaults to opaque black.
+
+    // A layer-hosting view.
+    shapeLayer_.reset([[CAShapeLayer alloc] init]);
+    [self setLayer:shapeLayer_];
+    [self setWantsLayer:YES];
 
     // If going backward, the arrow needs to be in the right half of the circle,
     // so offset the X position.
     CGFloat offset = mode_ == kHistoryOverlayModeBack ? kShieldRadius : 0;
     NSRect arrowRect = NSMakeRect(offset, 0, kShieldRadius, kShieldHeight);
     arrowRect = NSInsetRect(arrowRect, 10, 0);  // Give a little padding.
 
     base::scoped_nsobject<NSImageView> imageView(
         [[NSImageView alloc] initWithFrame:arrowRect]);
     [imageView setImage:image];
     [imageView setAutoresizingMask:NSViewMinYMargin | NSViewMaxYMargin];
     [self addSubview:imageView];
   }
   return self;
 }
 
-- (void)drawRect:(NSRect)dirtyRect {
-  NSBezierPath* path = [NSBezierPath bezierPathWithOvalInRect:self.bounds];
-  NSColor* fillColor = [NSColor colorWithCalibratedWhite:0 alpha:shieldAlpha_];
-  [fillColor set];
-  [path fill];
+- (void)setFrameSize:(CGSize)newSize {
+  NSSize oldSize = [self frame].size;
+  [super setFrameSize:newSize];
+
+  if (![shapeLayer_ path] || !NSEqualSizes(oldSize, newSize))  {
+    base::ScopedCFTypeRef<CGMutablePathRef> oval(CGPathCreateMutable());
+    CGRect ovalRect = CGRectMake(0, 0, newSize.width, newSize.height);
+    CGPathAddEllipseInRect(oval, nullptr, ovalRect);
+    [shapeLayer_ setPath:oval];
+  }
+}
+
+- (void)setShieldAlpha:(CGFloat)shieldAlpha {
+  if (shieldAlpha != shieldAlpha_) {
+    shieldAlpha_ = shieldAlpha;
+    base::ScopedCFTypeRef<CGColorRef> fillColor(
+      CGColorCreateGenericGray(0, shieldAlpha));

[Robert Sesek, 2015/02/04 16:08:20]

nit: indent +2

[Andre, 2015/02/04 16:38:19]

Oops, done.

+    [shapeLayer_ setFillColor:fillColor];
+  }
 }
 
 @end
 
 // HistoryOverlayController ////////////////////////////////////////////////////
 
 @implementation HistoryOverlayController
 
 - (id)initForMode:(HistoryOverlayMode)mode {
   if ((self = [super init])) {
@@ skipping 37 matching lines @@
   frame.origin.y = (NSHeight(parentFrame) / 2) - (height / 2);
 
   CGFloat width = std::min(kShieldRadius * gestureAmount, kShieldRadius);
   if (mode_ == kHistoryOverlayModeForward)
     frame.origin.x = NSMaxX(parentFrame) - width;
   else if (mode_ == kHistoryOverlayModeBack)
     frame.origin.x = NSMinX(parentFrame) - kShieldWidth + width;
 
   self.view.frame = frame;
   [contentView_ setShieldAlpha:shieldAlpha];
-  [contentView_ setNeedsDisplay:YES];
 }
 
 - (void)showPanelForView:(NSView*)view {
   parent_.reset([view retain]);
   [self setProgress:0 finished:NO];  // Set initial view position.
   [parent_  addSubview:self.view];
 }
 
 - (void)dismiss {
   const CGFloat kFadeOutDurationSeconds = 0.4;
@@ skipping 15 matching lines @@
 }
 
 - (void)animationDidStop:(CAAnimation*)theAnimation finished:(BOOL)finished {
   [self.view removeFromSuperview];
   // Destroy the CAAnimation and its strong reference to its delegate (this
   // class).
   [self.view setAnimations:nil];
 }
 
 @end