Source/WebKit/UIProcess/ios/WebMemoryPressureHandlerIOS.mm

/*
 * Copyright (C) 2014 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#import "config.h"
#import "WebMemoryPressureHandlerIOS.h"

#if PLATFORM(IOS)

#import "ViewSnapshotStore.h"

namespace WebKit {

void installMemoryPressureHandler()
{
    static bool installed = false;
    if (installed)
        return;
    installed = true;

    // FIXME: This should be able to share code with WebCore's MemoryPressureHandler (and be platform independent).
    // Right now it cannot because WebKit1 and WebKit2 need to be able to coexist in the UI process,
    // and you can only have one WebCore::MemoryPressureHandler.

    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"WebKitSuppressMemoryPressureHandler"])
        return;

    // Use a static here so the intentionally immortal dispatch source does not show up as a storage leak.
    static auto source = dispatch_source_create(DISPATCH_SOURCE_TYPE_MEMORYPRESSURE, 0, DISPATCH_MEMORYPRESSURE_WARN, dispatch_get_main_queue());
    dispatch_source_set_event_handler(source, ^ {
        ViewSnapshotStore::singleton().discardSnapshotImages();
    });
    dispatch_resume(source);
}

} // namespace WebKit

#endif