bool ScrollbarThemeComposite::paint(ScrollbarThemeClient* scrollbar, GraphicsContext* graphicsContext, const IntRect& damageRect)
{
    // Create the ScrollbarControlPartMask based on the damageRect
    ScrollbarControlPartMask scrollMask = NoPart;

    IntRect backButtonStartPaintRect;
    IntRect backButtonEndPaintRect;
    IntRect forwardButtonStartPaintRect;
    IntRect forwardButtonEndPaintRect;
    if (hasButtons(scrollbar)) {
        backButtonStartPaintRect = backButtonRect(scrollbar, BackButtonStartPart, true);
        if (damageRect.intersects(backButtonStartPaintRect))
            scrollMask |= BackButtonStartPart;
        backButtonEndPaintRect = backButtonRect(scrollbar, BackButtonEndPart, true);
        if (damageRect.intersects(backButtonEndPaintRect))
            scrollMask |= BackButtonEndPart;
        forwardButtonStartPaintRect = forwardButtonRect(scrollbar, ForwardButtonStartPart, true);
        if (damageRect.intersects(forwardButtonStartPaintRect))
            scrollMask |= ForwardButtonStartPart;
        forwardButtonEndPaintRect = forwardButtonRect(scrollbar, ForwardButtonEndPart, true);
        if (damageRect.intersects(forwardButtonEndPaintRect))
            scrollMask |= ForwardButtonEndPart;
    }

    IntRect startTrackRect;
    IntRect thumbRect;
    IntRect endTrackRect;
    IntRect trackPaintRect = trackRect(scrollbar, true);
    if (damageRect.intersects(trackPaintRect))
        scrollMask |= TrackBGPart;
    bool thumbPresent = hasThumb(scrollbar);
    if (thumbPresent) {
        IntRect track = trackRect(scrollbar);
        splitTrack(scrollbar, track, startTrackRect, thumbRect, endTrackRect);
        if (damageRect.intersects(thumbRect))
            scrollMask |= ThumbPart;
        if (damageRect.intersects(startTrackRect))
            scrollMask |= BackTrackPart;
        if (damageRect.intersects(endTrackRect))
            scrollMask |= ForwardTrackPart;
    }

    // Paint the scrollbar background (only used by custom CSS scrollbars).
    paintScrollbarBackground(graphicsContext, scrollbar);

    // Paint the back and forward buttons.
    if (scrollMask & BackButtonStartPart)
        paintButton(graphicsContext, scrollbar, backButtonStartPaintRect, BackButtonStartPart);
    if (scrollMask & BackButtonEndPart)
        paintButton(graphicsContext, scrollbar, backButtonEndPaintRect, BackButtonEndPart);
    if (scrollMask & ForwardButtonStartPart)
        paintButton(graphicsContext, scrollbar, forwardButtonStartPaintRect, ForwardButtonStartPart);
    if (scrollMask & ForwardButtonEndPart)
        paintButton(graphicsContext, scrollbar, forwardButtonEndPaintRect, ForwardButtonEndPart);
    
    if (scrollMask & TrackBGPart)
        paintTrackBackground(graphicsContext, scrollbar, trackPaintRect);
    
    if ((scrollMask & ForwardTrackPart) || (scrollMask & BackTrackPart)) {
        // Paint the track pieces above and below the thumb.
        if (scrollMask & BackTrackPart)
            paintTrackPiece(graphicsContext, scrollbar, startTrackRect, BackTrackPart);
        if (scrollMask & ForwardTrackPart)
            paintTrackPiece(graphicsContext, scrollbar, endTrackRect, ForwardTrackPart);

        paintTickmarks(graphicsContext, scrollbar, trackPaintRect);
    }

    // Paint the thumb.
    if (scrollMask & ThumbPart)
        paintThumb(graphicsContext, scrollbar, thumbRect);

    return true;
}
bool ScrollbarThemeGtk::paint(ScrollbarThemeClient* scrollbar, GraphicsContext* graphicsContext, const IntRect& damageRect)
{
    if (graphicsContext->paintingDisabled())
        return false;

    // Create the ScrollbarControlPartMask based on the damageRect
    ScrollbarControlPartMask scrollMask = NoPart;

    IntRect backButtonStartPaintRect;
    IntRect backButtonEndPaintRect;
    IntRect forwardButtonStartPaintRect;
    IntRect forwardButtonEndPaintRect;
    if (hasButtons(scrollbar)) {
        backButtonStartPaintRect = backButtonRect(scrollbar, BackButtonStartPart, true);
        if (damageRect.intersects(backButtonStartPaintRect))
            scrollMask |= BackButtonStartPart;
        backButtonEndPaintRect = backButtonRect(scrollbar, BackButtonEndPart, true);
        if (damageRect.intersects(backButtonEndPaintRect))
            scrollMask |= BackButtonEndPart;
        forwardButtonStartPaintRect = forwardButtonRect(scrollbar, ForwardButtonStartPart, true);
        if (damageRect.intersects(forwardButtonStartPaintRect))
            scrollMask |= ForwardButtonStartPart;
        forwardButtonEndPaintRect = forwardButtonRect(scrollbar, ForwardButtonEndPart, true);
        if (damageRect.intersects(forwardButtonEndPaintRect))
            scrollMask |= ForwardButtonEndPart;
    }

    IntRect trackPaintRect = trackRect(scrollbar, true);
    if (damageRect.intersects(trackPaintRect))
        scrollMask |= TrackBGPart;

    if (m_troughUnderSteppers && (scrollMask & BackButtonStartPart
            || scrollMask & BackButtonEndPart
            || scrollMask & ForwardButtonStartPart
            || scrollMask & ForwardButtonEndPart))
        scrollMask |= TrackBGPart;

    bool thumbPresent = hasThumb(scrollbar);
    IntRect currentThumbRect;
    if (thumbPresent) {
        IntRect track = trackRect(scrollbar, false);
        currentThumbRect = thumbRect(scrollbar, track);
        if (damageRect.intersects(currentThumbRect))
            scrollMask |= ThumbPart;
    }

    ScrollbarControlPartMask allButtons = BackButtonStartPart | BackButtonEndPart | ForwardButtonStartPart | ForwardButtonEndPart;
    if (scrollMask & TrackBGPart || scrollMask & ThumbPart || scrollMask & allButtons)
        paintScrollbarBackground(graphicsContext, scrollbar);
        paintTrackBackground(graphicsContext, scrollbar, trackPaintRect);

    // Paint the back and forward buttons.
    if (scrollMask & BackButtonStartPart)
        paintButton(graphicsContext, scrollbar, backButtonStartPaintRect, BackButtonStartPart);
    if (scrollMask & BackButtonEndPart)
        paintButton(graphicsContext, scrollbar, backButtonEndPaintRect, BackButtonEndPart);
    if (scrollMask & ForwardButtonStartPart)
        paintButton(graphicsContext, scrollbar, forwardButtonStartPaintRect, ForwardButtonStartPart);
    if (scrollMask & ForwardButtonEndPart)
        paintButton(graphicsContext, scrollbar, forwardButtonEndPaintRect, ForwardButtonEndPart);

    // Paint the thumb.
    if (scrollMask & ThumbPart)
        paintThumb(graphicsContext, scrollbar, currentThumbRect);

    return true;
}
bool ScrollbarThemeComposite::paint(Scrollbar* scrollbar, GraphicsContext* graphicsContext, const IntRect& damageRect)
{
    // Create the ScrollbarControlPartMask based on the damageRect
    ScrollbarControlPartMask scrollMask = NoPart;

    IntRect backButtonStartPaintRect;
    IntRect backButtonEndPaintRect;
    IntRect forwardButtonStartPaintRect;
    IntRect forwardButtonEndPaintRect;
    if (hasButtons(scrollbar)) {
        backButtonStartPaintRect = backButtonRect(scrollbar, BackButtonStartPart, true);
        if (damageRect.intersects(backButtonStartPaintRect))
            scrollMask |= BackButtonStartPart;
        backButtonEndPaintRect = backButtonRect(scrollbar, BackButtonEndPart, true);
        if (damageRect.intersects(backButtonEndPaintRect))
            scrollMask |= BackButtonEndPart;
        forwardButtonStartPaintRect = forwardButtonRect(scrollbar, ForwardButtonStartPart, true);
        if (damageRect.intersects(forwardButtonStartPaintRect))
            scrollMask |= ForwardButtonStartPart;
        forwardButtonEndPaintRect = forwardButtonRect(scrollbar, ForwardButtonEndPart, true);
        if (damageRect.intersects(forwardButtonEndPaintRect))
            scrollMask |= ForwardButtonEndPart;
    }

    IntRect startTrackRect;
    IntRect thumbRect;
    IntRect endTrackRect;
    IntRect trackPaintRect = trackRect(scrollbar, true);
    if (damageRect.intersects(trackPaintRect))
        scrollMask |= TrackBGPart;
    bool thumbPresent = hasThumb(scrollbar);
    if (thumbPresent) {
        IntRect track = trackRect(scrollbar);
        splitTrack(scrollbar, track, startTrackRect, thumbRect, endTrackRect);
        if (damageRect.intersects(thumbRect))
            scrollMask |= ThumbPart;
        if (damageRect.intersects(startTrackRect))
            scrollMask |= BackTrackPart;
        if (damageRect.intersects(endTrackRect))
            scrollMask |= ForwardTrackPart;
    } 

#if PLATFORM(WIN)
    // FIXME: This API makes the assumption that the custom scrollbar's metrics will match
    // the theme's metrics.  This is not a valid assumption.  The ability for a client to paint
    // custom scrollbars should be removed once scrollbars can be styled via CSS.
    if (Page* page = pageForScrollView(scrollbar->parent())) {
        if (page->settings()->shouldPaintCustomScrollbars()) {
            float proportion = static_cast<float>(scrollbar->visibleSize()) / scrollbar->totalSize();
            float value = scrollbar->currentPos() / static_cast<float>(scrollbar->maximum());
            ScrollbarControlState s = 0;
            if (scrollbar->client()->isActive())
                s |= ActiveScrollbarState;
            if (scrollbar->enabled())
                s |= EnabledScrollbarState;
            if (scrollbar->pressedPart() != NoPart)
                s |= PressedScrollbarState;
            if (page->chrome()->client()->paintCustomScrollbar(graphicsContext,
                                                               scrollbar->frameRect(), 
                                                               scrollbar->controlSize(),
                                                               s, 
                                                               scrollbar->pressedPart(), 
                                                               scrollbar->orientation() == VerticalScrollbar,
                                                               value,
                                                               proportion,
                                                               scrollMask))
                return true;
        }
    }
#endif

    // Paint the scrollbar background (only used by custom CSS scrollbars).
    paintScrollbarBackground(graphicsContext, scrollbar);

    // Paint the back and forward buttons.
    if (scrollMask & BackButtonStartPart)
        paintButton(graphicsContext, scrollbar, backButtonStartPaintRect, BackButtonStartPart);
    if (scrollMask & BackButtonEndPart)
        paintButton(graphicsContext, scrollbar, backButtonEndPaintRect, BackButtonEndPart);
    if (scrollMask & ForwardButtonStartPart)
        paintButton(graphicsContext, scrollbar, forwardButtonStartPaintRect, ForwardButtonStartPart);
    if (scrollMask & ForwardButtonEndPart)
        paintButton(graphicsContext, scrollbar, forwardButtonEndPaintRect, ForwardButtonEndPart);
    
    if (scrollMask & TrackBGPart)
        paintTrackBackground(graphicsContext, scrollbar, trackPaintRect);
    
    if ((scrollMask & ForwardTrackPart) || (scrollMask & BackTrackPart)) {
        // Paint the track pieces above and below the thumb.
        if (scrollMask & BackTrackPart)
            paintTrackPiece(graphicsContext, scrollbar, startTrackRect, BackTrackPart);
        if (scrollMask & ForwardTrackPart)
            paintTrackPiece(graphicsContext, scrollbar, endTrackRect, ForwardTrackPart);

        paintTickmarks(graphicsContext, scrollbar, trackPaintRect);
    }

    // Paint the thumb.
    if (scrollMask & ThumbPart)
        paintThumb(graphicsContext, scrollbar, thumbRect);

    return true;
}