Mac: Optimize TabView drawing.

chrome/browser/ui/cocoa/tabs/tab_view.mm

Index: chrome/browser/ui/cocoa/tabs/tab_view.mm
diff --git a/chrome/browser/ui/cocoa/tabs/tab_view.mm b/chrome/browser/ui/cocoa/tabs/tab_view.mm
index cad76744d3ea0f3e22403f3653185a39d494e10a..bd5b053e29234616eecb871ae3edf81d6198cd21 100644
--- a/chrome/browser/ui/cocoa/tabs/tab_view.mm
+++ b/chrome/browser/ui/cocoa/tabs/tab_view.mm
@@ -19,12 +19,12 @@
 #import "third_party/google_toolbox_for_mac/src/AppKit/GTMFadeTruncatingTextFieldCell.h"
 #import "ui/base/cocoa/nsgraphics_context_additions.h"
 #import "ui/base/cocoa/nsview_additions.h"
+#include "ui/base/cocoa/three_part_image.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 
 
-const int kMaskHeight = 29;  // Height of the mask bitmap.
 const int kFillHeight = 25;  // Height of the "mask on" part of the mask bitmap.
 
 // The amount of time in seconds during which each type of glow increases, holds
@@ -44,12 +44,30 @@ const NSTimeInterval kGlowUpdateInterval = 0.025;
 // has moved less than the threshold, we want to close the tab.
 const CGFloat kRapidCloseDist = 2.5;
 
+namespace {
+
+ui::ThreePartImage* GetMaskImage() {
+  static ui::ThreePartImage* mask =
+      new ui::ThreePartImage(IDR_TAB_ALPHA_LEFT, 0, IDR_TAB_ALPHA_RIGHT);
+  return mask;
+}
+
+ui::ThreePartImage* GetStrokeImage(bool active) {
+  static ui::ThreePartImage* activeStroke = new ui::ThreePartImage(
+      IDR_TAB_ACTIVE_LEFT, IDR_TAB_ACTIVE_CENTER, IDR_TAB_ACTIVE_RIGHT);
+  static ui::ThreePartImage* inactiveStroke = new ui::ThreePartImage(
+      IDR_TAB_INACTIVE_LEFT, IDR_TAB_INACTIVE_CENTER, IDR_TAB_INACTIVE_RIGHT);
+
+  return active ? activeStroke : inactiveStroke;
+}
+
+}  // namespace
+
 @interface TabView(Private)
 
 - (void)resetLastGlowUpdateTime;
 - (NSTimeInterval)timeElapsedSinceLastGlowUpdate;
 - (void)adjustGlowValue;
-- (CGImageRef)tabClippingMask;
 
 @end  // TabView(Private)
 
@@ -82,6 +100,8 @@ const CGFloat kRapidCloseDist = 2.5;
     [labelCell setFont:font];
     [titleView_ setCell:labelCell];
     titleViewCell_ = labelCell;
+
+    [self setWantsLayer:YES];  // -drawFill: needs a layer.
   }
   return self;
 }
@@ -157,34 +177,9 @@ const CGFloat kRapidCloseDist = 2.5;
     return defaultHitTestResult;
 
   NSPoint viewPoint = [self convertPoint:aPoint fromView:[self superview]];
-  NSRect pointRect = NSMakeRect(viewPoint.x, viewPoint.y, 1, 1);
-
-  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-  NSImage* left = rb.GetNativeImageNamed(IDR_TAB_ALPHA_LEFT).ToNSImage();
-  if (viewPoint.x < [left size].width) {
-    NSRect imageRect = NSMakeRect(0, 0, [left size].width, [left size].height);
-    if ([left hitTestRect:pointRect withImageDestinationRect:imageRect
-          context:nil hints:nil flipped:NO]) {
-      return self;
-    }
-    return nil;
-  }
-
-  NSImage* right = rb.GetNativeImageNamed(IDR_TAB_ALPHA_RIGHT).ToNSImage();
-  CGFloat rightX = NSWidth([self bounds]) - [right size].width;
-  if (viewPoint.x > rightX) {
-    NSRect imageRect = NSMakeRect(
-        rightX, 0, [right size].width, [right size].height);
-    if ([right hitTestRect:pointRect withImageDestinationRect:imageRect
-          context:nil hints:nil flipped:NO]) {
-      return self;
-    }
-    return nil;
-  }
-
-  if (viewPoint.y < kFillHeight)
-    return self;
-  return nil;
+  NSRect maskRect = [self bounds];
+  maskRect.size.height = kFillHeight;
+  return GetMaskImage()->HitTest(viewPoint, maskRect) ? self : nil;
 }
 
 // Returns |YES| if this tab can be torn away into a new window.
@@ -312,74 +307,48 @@ const CGFloat kRapidCloseDist = 2.5;
   return themeProvider->GetNSImageColorNamed(bitmapResources[active][selected]);
 }
 
-// Draws the active tab background.
-- (void)drawFillForActiveTab:(NSRect)dirtyRect {
-  NSColor* backgroundImageColor = [self backgroundColorForSelected:YES];
-  [backgroundImageColor set];
-
-  // Themes can have partially transparent images. NSRectFill() is measurably
-  // faster though, so call it for the known-safe default theme.
-  ThemeService* themeProvider =
-      static_cast<ThemeService*>([[self window] themeProvider]);
-  if (themeProvider && themeProvider->UsingDefaultTheme())
-    NSRectFill(dirtyRect);
-  else
-    NSRectFillUsingOperation(dirtyRect, NSCompositeSourceOver);
-}
-
 // Draws the tab background.
 - (void)drawFill:(NSRect)dirtyRect {
   gfx::ScopedNSGraphicsContextSaveGState scopedGState;
-  NSGraphicsContext* context = [NSGraphicsContext currentContext];
-  CGContextRef cgContext = static_cast<CGContextRef>([context graphicsPort]);
+  NSRect bounds = [self bounds];
+
+  NSRect clippingRect = bounds;
+  clippingRect.size.height = kFillHeight;
+  if (state_ != NSOnState) {
+    // Background tabs should not paint over the tab strip separator, which is
+    // two pixels high in both lodpi and hidpi.
+    clippingRect.origin.y = 2 * [self cr_lineWidth];
+    clippingRect.size.height -= clippingRect.origin.y;
+  }
+  NSRectClip(clippingRect);
 
-  ThemeService* themeProvider =
-      static_cast<ThemeService*>([[self window] themeProvider]);
   NSPoint position = [[self window]
-      themeImagePositionForAlignment: THEME_IMAGE_ALIGN_WITH_TAB_STRIP];
-  [context cr_setPatternPhase:position forView:self];
+      themeImagePositionForAlignment:THEME_IMAGE_ALIGN_WITH_TAB_STRIP];
+  [[NSGraphicsContext currentContext] cr_setPatternPhase:position forView:self];
 
-  CGImageRef mask([self tabClippingMask]);
-  CGRect maskBounds = CGRectMake(0, 0, maskCacheWidth_, kMaskHeight);
-  CGContextClipToMask(cgContext, maskBounds, mask);
+  [[self backgroundColorForSelected:(state_ != NSOffState)] set];
+  NSRectFill(dirtyRect);
 
-  // There is only 1 active tab at a time.
-  // It has a different fill color which draws over the separator line.
-  if (state_ == NSOnState) {
-    [self drawFillForActiveTab:dirtyRect];
-    return;
-  }
-
-  // Background tabs should not paint over the tab strip separator, which is
-  // two pixels high in both lodpi and hidpi.
-  if (dirtyRect.origin.y < 1)
-    dirtyRect.origin.y = 2 * [self cr_lineWidth];
+  if (state_ == NSOffState)
+    [self drawGlow:dirtyRect];
 
-  // There can be multiple selected tabs.
-  // They have the same fill color as the active tab, but do not draw over
-  // the separator.
-  if (state_ == NSMixedState) {
-    [self drawFillForActiveTab:dirtyRect];
-    return;
+  // If we filled outside the middle rect, we need to erase what we filled
+  // outside the tab's shape.
+  // This only works if we are drawing to our own backing layer.
+  if (!NSContainsRect(GetMaskImage()->GetMiddleRect(bounds), dirtyRect)) {
+    DCHECK([self layer]);
+    GetMaskImage()->DrawInRect(bounds, NSCompositeDestinationIn, 1.0);
   }
+}
 
-  // Draw the tab background.
-  NSColor* backgroundImageColor = [self backgroundColorForSelected:NO];
-  [backgroundImageColor set];
-
-  // Themes can have partially transparent images. NSRectFill() is measurably
-  // faster though, so call it for the known-safe default theme.
-  bool usingDefaultTheme = themeProvider && themeProvider->UsingDefaultTheme();
-  if (usingDefaultTheme)
-    NSRectFill(dirtyRect);
-  else
-    NSRectFillUsingOperation(dirtyRect, NSCompositeSourceOver);
+// Draw the glow for hover and the overlay for alerts.
+- (void)drawGlow:(NSRect)dirtyRect {
+  NSGraphicsContext* context = [NSGraphicsContext currentContext];
+  CGContextRef cgContext = static_cast<CGContextRef>([context graphicsPort]);
 
-  // Draw the glow for hover and the overlay for alerts.
   CGFloat hoverAlpha = [self hoverAlpha];
   CGFloat alertAlpha = [self alertAlpha];
   if (hoverAlpha > 0 || alertAlpha > 0) {
-    gfx::ScopedNSGraphicsContextSaveGState contextSave;
     CGContextBeginTransparencyLayer(cgContext, 0);
 
     // The alert glow overlay is like the selected state but at most at most 80%
@@ -388,12 +357,14 @@ const CGFloat kRapidCloseDist = 2.5;
     backgroundAlpha += (1 - backgroundAlpha) * 0.5 * hoverAlpha;
     CGContextSetAlpha(cgContext, backgroundAlpha);
 
-    [self drawFillForActiveTab:dirtyRect];
+    [[self backgroundColorForSelected:YES] set];
+    NSRectFill(dirtyRect);
 
     // ui::ThemeProvider::HasCustomImage is true only if the theme provides the
     // image. However, even if the theme doesn't provide a tab background, the
     // theme machinery will make one if given a frame image. See
     // BrowserThemePack::GenerateTabBackgroundImages for details.
+    ui::ThemeProvider* themeProvider = [[self window] themeProvider];
     BOOL hasCustomTheme = themeProvider &&
         (themeProvider->HasCustomImage(IDR_THEME_TAB_BACKGROUND) ||
          themeProvider->HasCustomImage(IDR_THEME_FRAME));
@@ -422,35 +393,12 @@ const CGFloat kRapidCloseDist = 2.5;
 
 // Draws the tab outline.
 - (void)drawStroke:(NSRect)dirtyRect {
-  BOOL focused = [[self window] isMainWindow];
-  CGFloat alpha = focused ? 1.0 : tabs::kImageNoFocusAlpha;
-
-  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-  float height =
-      [rb.GetNativeImageNamed(IDR_TAB_ACTIVE_LEFT).ToNSImage() size].height;
-  if (state_ == NSOnState) {
-    NSDrawThreePartImage(NSMakeRect(0, 0, NSWidth([self bounds]), height),
-        rb.GetNativeImageNamed(IDR_TAB_ACTIVE_LEFT).ToNSImage(),
-        rb.GetNativeImageNamed(IDR_TAB_ACTIVE_CENTER).ToNSImage(),
-        rb.GetNativeImageNamed(IDR_TAB_ACTIVE_RIGHT).ToNSImage(),
-        /*vertical=*/NO,
-        NSCompositeSourceOver,
-        alpha,
-        /*flipped=*/NO);
-  } else {
-    NSDrawThreePartImage(NSMakeRect(0, 0, NSWidth([self bounds]), height),
-        rb.GetNativeImageNamed(IDR_TAB_INACTIVE_LEFT).ToNSImage(),
-        rb.GetNativeImageNamed(IDR_TAB_INACTIVE_CENTER).ToNSImage(),
-        rb.GetNativeImageNamed(IDR_TAB_INACTIVE_RIGHT).ToNSImage(),
-        /*vertical=*/NO,
-        NSCompositeSourceOver,
-        alpha,
-        /*flipped=*/NO);
-  }
+  CGFloat alpha = [[self window] isMainWindow] ? 1.0 : tabs::kImageNoFocusAlpha;
+  GetStrokeImage(state_ == NSOnState)
+      ->DrawInRect([self bounds], NSCompositeSourceOver, alpha);
 }
 
 - (void)drawRect:(NSRect)dirtyRect {
-  // Close button and image are drawn by subviews.
   [self drawFill:dirtyRect];
   [self drawStroke:dirtyRect];
 
@@ -749,57 +697,4 @@ const CGFloat kRapidCloseDist = 2.5;
   [self setNeedsDisplay:YES];
 }
 
-- (CGImageRef)tabClippingMask {
-  // NOTE: NSHeight([self bounds]) doesn't match the height of the bitmaps.
-  CGFloat scale = 1;
-  if ([[self window] respondsToSelector:@selector(backingScaleFactor)])
-    scale = [[self window] backingScaleFactor];
-
-  NSRect bounds = [self bounds];
-  CGFloat tabWidth = NSWidth(bounds);
-  if (tabWidth == maskCacheWidth_ && scale == maskCacheScale_)
-    return maskCache_.get();
-
-  maskCacheWidth_ = tabWidth;
-  maskCacheScale_ = scale;
-
-  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-  NSImage* leftMask = rb.GetNativeImageNamed(IDR_TAB_ALPHA_LEFT).ToNSImage();
-  NSImage* rightMask = rb.GetNativeImageNamed(IDR_TAB_ALPHA_RIGHT).ToNSImage();
-
-  CGFloat leftWidth = leftMask.size.width;
-  CGFloat rightWidth = rightMask.size.width;
-
-  // Image masks must be in the DeviceGray colorspace. Create a context and
-  // draw the mask into it.
-  base::ScopedCFTypeRef<CGColorSpaceRef> colorspace(
-      CGColorSpaceCreateDeviceGray());
-  base::ScopedCFTypeRef<CGContextRef> maskContext(
-      CGBitmapContextCreate(NULL, tabWidth * scale, kMaskHeight * scale,
-                            8, tabWidth * scale, colorspace, 0));
-  CGContextScaleCTM(maskContext, scale, scale);
-  NSGraphicsContext* maskGraphicsContext =
-      [NSGraphicsContext graphicsContextWithGraphicsPort:maskContext
-                                                 flipped:NO];
-
-  gfx::ScopedNSGraphicsContextSaveGState scopedGState;
-  [NSGraphicsContext setCurrentContext:maskGraphicsContext];
-
-  // Draw mask image.
-  [[NSColor blackColor] setFill];
-  CGContextFillRect(maskContext, CGRectMake(0, 0, tabWidth, kMaskHeight));
-
-  NSDrawThreePartImage(NSMakeRect(0, 0, tabWidth, kMaskHeight),
-      leftMask, nil, rightMask, /*vertical=*/NO, NSCompositeSourceOver, 1.0,
-      /*flipped=*/NO);
-
-  CGFloat middleWidth = tabWidth - leftWidth - rightWidth;
-  NSRect middleRect = NSMakeRect(leftWidth, 0, middleWidth, kFillHeight);
-  [[NSColor whiteColor] setFill];
-  NSRectFill(middleRect);
-
-  maskCache_.reset(CGBitmapContextCreateImage(maskContext));
-  return maskCache_;
-}
-
 @end  // @implementation TabView(Private)