MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/cocoa/views_scrollbar_bridge.mm

Index: ui/views/cocoa/views_scrollbar_bridge.mm
diff --git a/ui/views/cocoa/views_scrollbar_bridge.mm b/ui/views/cocoa/views_scrollbar_bridge.mm
new file mode 100644
index 0000000000000000000000000000000000000000..22d0f06b34953a2cb9af61bc996b81c52e8bd84c
--- /dev/null
+++ b/ui/views/cocoa/views_scrollbar_bridge.mm
@@ -0,0 +1,52 @@
+// Copyright 2016 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 "ui/views/cocoa/views_scrollbar_bridge.h"
+
+#include "base/mac/mac_util.h"
+#include "base/mac/sdk_forward_declarations.h"

[tapted, 2016/02/11 08:46:17]

nit: import

[spqchan, 2016/02/13 01:39:23]

Done.

+
+@interface ViewsScrollbarBridge ()
+
+// Called when we receive a NSPreferredScrollerStyleDidChangeNotification.
+- (void)onScrollerStyleChanged:(NSNotification*)notification;
+
+@end
+
+@implementation ViewsScrollbarBridge
+
+- (void)setDelegate:(ViewsScrollbarBridgeDelegate*)delegate {
+  DCHECK_NE(delegate, delegate_);
+  if (!delegate_) {
+    [[NSNotificationCenter defaultCenter]
+        removeObserver:self

[tapted, 2016/02/11 08:46:17]

i think we can omit the name and object arguments -- that seems more
conventional in chrome

[spqchan, 2016/02/13 01:39:23]

Done.

+                  name:NSPreferredScrollerStyleDidChangeNotification
+                object:nil];
+    return;
+  }
+  [[NSNotificationCenter defaultCenter]
+      addObserver:self
+         selector:@selector(onScrollerStyleChanged:)
+             name:NSPreferredScrollerStyleDidChangeNotification
+             object:nil];
+}
+
+- (void)dealloc {
+  DCHECK(!delegate_);
+  [super dealloc];
+}
+
+- (void)onScrollerStyleChanged:(NSNotification*)notification {
+  delegate_->OnScrollerStyleChanged();

[tapted, 2016/02/11 08:46:17]

this should check for a null delegate (which is fine - it's the usual way we
solve the different lifetime models)

[spqchan, 2016/02/13 01:39:23]

Done.

+}
+
+- (NSScrollerStyle)getPreferredScrollerStyle {
+  if (![NSScroller respondsToSelector:@selector(preferredScrollerStyle)]) {
+    DCHECK(base::mac::IsOSSnowLeopard());
+    return NSScrollerStyleLegacy;
+  }
+  return [NSScroller preferredScrollerStyle];
+}
+
+@end