[MacViews] Implement colored window frames.

chrome/browser/ui/cocoa/apps/titlebar_background_view.mm

+// Copyright 2015 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/apps/titlebar_background_view.h"
+
+#import "skia/ext/skia_utils_mac.h"
+
+@interface TitlebarBackgroundView ()
+- (void)setColor:(NSColor*)color inactiveColor:(NSColor*)inactiveColor;
+@end
+
+@implementation TitlebarBackgroundView
+
++ (void)addToNSWindow:(NSWindow*)window
+          activeColor:(SkColor)activeColor
+        inactiveColor:(SkColor)inactiveColor {
+  // AppKit only officially supports adding subviews to the window's
+  // contentView and not its superview (an NSNextStepFrame). The 10.10 SDK
+  // allows adding an NSTitlebarAccessoryViewController to a window, but the
+  // view can only be placed above the window control buttons, so we'd have to
+  // replicate those.
+  NSView* window_view = [[window contentView] superview];
+  CGFloat height =
+      NSHeight([window_view bounds]) - NSHeight([[window contentView] bounds]);
+  base::scoped_nsobject<TitlebarBackgroundView> titlebar_background_view(
+      [[TitlebarBackgroundView alloc]
+          initWithFrame:NSMakeRect(0, NSMaxY([window_view bounds]) - height,
+                                   NSWidth([window_view bounds]), height)]);
+  [titlebar_background_view
+      setAutoresizingMask:NSViewWidthSizable | NSViewMinYMargin];
+  [window_view addSubview:titlebar_background_view
+               positioned:NSWindowBelow
+               relativeTo:nil];
+
+  [titlebar_background_view setColor:gfx::SkColorToSRGBNSColor(activeColor)
+                       inactiveColor:gfx::SkColorToSRGBNSColor(inactiveColor)];
+}
+
+- (void)drawRect:(NSRect)rect {
+  // Only the top corners are rounded. For simplicity, round all 4 corners but
+  // draw the bottom corners outside of the visible bounds.
+  CGFloat cornerRadius = 4.0;
+  NSRect roundedRect = [self bounds];
+  roundedRect.origin.y -= cornerRadius;
+  roundedRect.size.height += cornerRadius;
+  [[NSBezierPath bezierPathWithRoundedRect:roundedRect
+                                   xRadius:cornerRadius
+                                   yRadius:cornerRadius] addClip];
+  if ([[self window] isMainWindow] || [[self window] isKeyWindow])
+    [color_ set];
+  else
+    [inactiveColor_ set];
+  NSRectFill(rect);
+}
+
+- (void)setColor:(NSColor*)color inactiveColor:(NSColor*)inactiveColor {
+  color_.reset([color retain]);
+  inactiveColor_.reset([inactiveColor retain]);
+}
+
+@end