Source/WebCore/platform/ScrollbarTheme.h

/*
 * Copyright (C) 2008 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. ``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
 * 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. 
 */

#ifndef ScrollbarTheme_h
#define ScrollbarTheme_h

#include "GraphicsContext.h"
#include "IntRect.h"
#include "ScrollTypes.h"

namespace WebCore {

class PlatformMouseEvent;
class Scrollbar;
class ScrollView;

#if ENABLE(RUBBER_BANDING)
class GraphicsLayer;
#endif

class ScrollbarTheme {
    WTF_MAKE_NONCOPYABLE(ScrollbarTheme); WTF_MAKE_FAST_ALLOCATED;
public:
    ScrollbarTheme() = default;
    virtual ~ScrollbarTheme() {};

    virtual void updateEnabledState(Scrollbar&) { }

    virtual bool paint(Scrollbar&, GraphicsContext&, const IntRect& /*damageRect*/) { return false; }
    virtual ScrollbarPart hitTest(Scrollbar&, const IntPoint&) { return NoPart; }
    
    virtual int scrollbarThickness(ScrollbarControlSize = RegularScrollbar, ScrollbarExpansionState = ScrollbarExpansionState::Expanded) { return 0; }

    virtual ScrollbarButtonsPlacement buttonsPlacement() const { return ScrollbarButtonsSingle; }

    virtual bool supportsControlTints() const { return false; }
    virtual bool usesOverlayScrollbars() const { return false; }
    virtual void usesOverlayScrollbarsChanged() { }
    virtual void updateScrollbarOverlayStyle(Scrollbar&) { }

    virtual void themeChanged() {}
    
    virtual bool invalidateOnMouseEnterExit() { return false; }

    void invalidateParts(Scrollbar& scrollbar, ScrollbarControlPartMask mask)
    {
        if (mask & BackButtonStartPart)
            invalidatePart(scrollbar, BackButtonStartPart);
        if (mask & ForwardButtonStartPart)
            invalidatePart(scrollbar, ForwardButtonStartPart);
        if (mask & BackTrackPart)
            invalidatePart(scrollbar, BackTrackPart);
        if (mask & ThumbPart)
            invalidatePart(scrollbar, ThumbPart);
        if (mask & ForwardTrackPart)
            invalidatePart(scrollbar, ForwardTrackPart);
        if (mask & BackButtonEndPart)
            invalidatePart(scrollbar, BackButtonEndPart);
        if (mask & ForwardButtonEndPart)
            invalidatePart(scrollbar, ForwardButtonEndPart);
    }

    virtual void invalidatePart(Scrollbar&, ScrollbarPart) { }

    virtual void paintScrollCorner(GraphicsContext& context, const IntRect& cornerRect) { defaultPaintScrollCorner(context, cornerRect); }
    static void defaultPaintScrollCorner(GraphicsContext& context, const IntRect& cornerRect) { context.fillRect(cornerRect, Color::white); }

    virtual void paintTickmarks(GraphicsContext&, Scrollbar&, const IntRect&) { }
    virtual void paintOverhangAreas(ScrollView&, GraphicsContext&, const IntRect&, const IntRect&, const IntRect&) { }

#if ENABLE(RUBBER_BANDING)
    virtual void setUpOverhangAreasLayerContents(GraphicsLayer*, const Color&) { }
    virtual void setUpContentShadowLayer(GraphicsLayer*) { }
#endif

    virtual ScrollbarButtonPressAction handleMousePressEvent(Scrollbar&, const PlatformMouseEvent&, ScrollbarPart);
    virtual bool shouldSnapBackToDragOrigin(Scrollbar&, const PlatformMouseEvent&) { return false; }
    virtual bool shouldDragDocumentInsteadOfThumb(Scrollbar&, const PlatformMouseEvent&) { return false; }
    virtual int thumbPosition(Scrollbar&) { return 0; } // The position of the thumb relative to the track.
    virtual int thumbLength(Scrollbar&) { return 0; } // The length of the thumb along the axis of the scrollbar.
    virtual int trackPosition(Scrollbar&) { return 0; } // The position of the track relative to the scrollbar.
    virtual int trackLength(Scrollbar&) { return 0; } // The length of the track along the axis of the scrollbar.

    virtual int maxOverlapBetweenPages() { return std::numeric_limits<int>::max(); }

    virtual Seconds initialAutoscrollTimerDelay() { return 250_ms; }
    virtual Seconds autoscrollTimerDelay() { return 50_ms; }

    virtual void registerScrollbar(Scrollbar&) { }
    virtual void unregisterScrollbar(Scrollbar&) { }

    virtual bool isMockTheme() const { return false; }

    WEBCORE_EXPORT static ScrollbarTheme& theme();

private:
    static ScrollbarTheme& nativeTheme(); // Must be implemented to return the correct theme subclass.
};

}
#endif