1/*
2 * Copyright (C) 2011 Apple Inc. All Rights Reserved.
3 * Copyright (C) 2011 Google Inc. All Rights Reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27
28#include "config.h"
29#include "RuntimeEnabledFeatures.h"
30#include "platform/mac/NSScrollerImpDetails.h"
31
32namespace {
33
34// Declare notification names from the 10.7 SDK.
35#if !defined(MAC_OS_X_VERSION_10_7) || MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
36NSString* NSPreferredScrollerStyleDidChangeNotification = @"NSPreferredScrollerStyleDidChangeNotification";
37#endif
38
39// Storing the current NSScrollerStyle as a global is appreciably faster than
40// having it be a property of ScrollerStylerObserver.
41NSScrollerStyle g_scrollerStyle = NSScrollerStyleLegacy;
42
43}  // anonymous namespace
44
45@interface ScrollerStyleObserver : NSObject
46- (id)init;
47- (void)preferredScrollerStyleDidChange:(NSNotification*)notification;
48@end
49
50@implementation ScrollerStyleObserver
51- (id)init
52{
53    if ((self = [super init])) {
54        if ([NSScroller respondsToSelector:@selector(preferredScrollerStyle)]) {
55            g_scrollerStyle = [NSScroller preferredScrollerStyle];
56            NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
57            [center addObserver:self
58                       selector:@selector(preferredScrollerStyleDidChange:)
59                           name:NSPreferredScrollerStyleDidChangeNotification
60                         object:nil];
61        }
62    }
63    return self;
64}
65
66- (void)preferredScrollerStyleDidChange:(NSNotification*)notification
67{
68    g_scrollerStyle = [NSScroller preferredScrollerStyle];
69}
70@end
71
72namespace WebCore {
73
74bool isScrollbarOverlayAPIAvailable()
75{
76    static bool apiAvailable =
77        [NSClassFromString(@"NSScrollerImp") respondsToSelector:@selector(scrollerImpWithStyle:controlSize:horizontal:replacingScrollerImp:)]
78        && [NSClassFromString(@"NSScrollerImpPair") instancesRespondToSelector:@selector(scrollerStyle)];
79    return apiAvailable;
80}
81
82NSScrollerStyle recommendedScrollerStyle()
83{
84    if (RuntimeEnabledFeatures::overlayScrollbarsEnabled())
85        return NSScrollerStyleOverlay;
86
87    // The ScrollerStyleObserver will update g_scrollerStyle at init and when needed.
88    // This function is hot.
89    // http://crbug.com/303205
90    static ScrollerStyleObserver* scrollerStyleObserver = [[ScrollerStyleObserver alloc] init];
91    (void)scrollerStyleObserver;
92    return g_scrollerStyle;
93}
94
95}
96