mac: Add overscroll animator slider

content/browser/web_contents/web_contents_view_overscroll_animator_mac.h

+// Copyright 2014 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.
+
+#ifndef CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_OVERSCROLL_ANIMATOR_MAC_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_OVERSCROLL_ANIMATOR_MAC_H_
+
+#import <Cocoa/Cocoa.h>
+
+namespace content {
+class WebContentsImpl;
+
+// The direction of the overscroll animations. Backwards means that the user
+// wants to navigate backwards in the navigation history. The opposite applies
+// to forwards.
+enum OverscrollAnimatorDirection {
+  OVERSCROLL_ANIMATOR_DIRECTION_BACKWARDS,
+  OVERSCROLL_ANIMATOR_DIRECTION_FORWARDS,
+};
+}  // namespace content
+
+// NSViews that intend to manage the animation associated with an overscroll
+// must implement this protocol.
+@protocol WebContentsOverscrollAnimator
+// Some implementations require the WebContentsView to supply a snapshot of a
+// previous navigation state. This method determines whether the snapshot passed
+// to the overscroll animator is expected to be non-nil.
+- (BOOL)needsNavigationSnapshot;
+
+// Begin an overscroll animation. The method -needsNavigationSnapshot determines
+// whether |snapshot| can be nil.
+- (void)beginOverscrollInDirection:
+            (content::OverscrollAnimatorDirection)direction
+                navigationSnapshot:(NSImage*)snapshot;
+
+// Due to the nature of some of the overscroll animations, implementators of
+// this protocol must have control over the layout of the RenderWidgetHost's
+// NativeView. When there is no overscroll animation in progress, the
+// implementor must guarantee that the frame of the RenderWidgetHost's
+// NativeView in screen coordinates is the same as its own frame in screen
+// coordinates.
+// Due to the odd ownership cycles of the RenderWidgetHost's NativeView, it is
+// important that its presence in the NSView hierarchy is the only strong
+// reference, and that when it gets removed from the NSView hierarchy, it will
+// be dealloc'ed shortly thereafter.
+- (void)addRenderWidgetHostNativeView:(NSView*)view;
+
+// During an overscroll animation, |progress| ranges from 0 to 2, and indicates
+// how close the overscroll is to completing. If the overscroll ends with
+// |progress| >= 1, then the overscroll is considered completed.
+- (void)updateOverscrollProgress:(CGFloat)progress;
+
+// Animate the finish of the overscroll and perform a navigation. The navigation
+// may not happen synchronously, but is guaranteed to eventually occur.
+- (void)completeOverscroll:(content::WebContentsImpl*)webContents;
+
+// Animate the cancellation of the overscroll.
+- (void)cancelOverscroll;
+@end
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_WEB_CONTENTS_VIEW_OVERSCROLL_ANIMATOR_MAC_H_