renderlayer.cpp

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        scrollbar = 0;
    }
}

void RenderLayer::setHasHorizontalScrollbar(bool hasScrollbar)
{
    if (hasScrollbar == (m_hBar != 0))
        return;

    if (hasScrollbar)
        m_hBar = createScrollbar(HorizontalScrollbar);
    else
        destroyScrollbar(HorizontalScrollbar);

    // Destroying or creating one bar can cause our scrollbar corner to come and go.  We need to update the opposite scrollbar's style.
    if (m_hBar)
        m_hBar->styleChanged();
    if (m_vBar)
        m_vBar->styleChanged();

#if ENABLE(DASHBOARD_SUPPORT)
    // Force an update since we know the scrollbars have changed things.
    if (renderer()->document()->hasDashboardRegions())
        renderer()->document()->setDashboardRegionsDirty(true);
#endif
}

void RenderLayer::setHasVerticalScrollbar(bool hasScrollbar)
{
    if (hasScrollbar == (m_vBar != 0))
        return;

    if (hasScrollbar)
        m_vBar = createScrollbar(VerticalScrollbar);
    else
        destroyScrollbar(VerticalScrollbar);

     // Destroying or creating one bar can cause our scrollbar corner to come and go.  We need to update the opposite scrollbar's style.
    if (m_hBar)
        m_hBar->styleChanged();
    if (m_vBar)
        m_vBar->styleChanged();

#if ENABLE(DASHBOARD_SUPPORT)
    // Force an update since we know the scrollbars have changed things.
    if (renderer()->document()->hasDashboardRegions())
        renderer()->document()->setDashboardRegionsDirty(true);
#endif
}

int RenderLayer::verticalScrollbarWidth() const
{
    if (!m_vBar)
        return 0;
    return m_vBar->width();
}

int RenderLayer::horizontalScrollbarHeight() const
{
    if (!m_hBar)
        return 0;
    return m_hBar->height();
}

IntSize RenderLayer::offsetFromResizeCorner(const IntPoint& absolutePoint) const
{
    // Currently the resize corner is always the bottom right corner
    IntPoint bottomRight(width(), height());
    IntPoint localPoint = absoluteToContents(absolutePoint);
    return localPoint - bottomRight;
}

void RenderLayer::positionOverflowControls(int tx, int ty)
{
    if (!m_hBar && !m_vBar && (!renderer()->hasOverflowClip() || renderer()->style()->resize() == RESIZE_NONE))
        return;
    
    RenderBox* box = renderBox();
    if (!box)
        return;

    IntRect borderBox = box->borderBoxRect();
    IntRect scrollCorner(scrollCornerRect(this, borderBox));
    IntRect absBounds(borderBox.x() + tx, borderBox.y() + ty, borderBox.width(), borderBox.height());
    if (m_vBar)
        m_vBar->setFrameRect(IntRect(absBounds.right() - box->borderRight() - m_vBar->width(),
                                     absBounds.y() + box->borderTop(),
                                     m_vBar->width(),
                                     absBounds.height() - (box->borderTop() + box->borderBottom()) - scrollCorner.height()));

    if (m_hBar)
        m_hBar->setFrameRect(IntRect(absBounds.x() + box->borderLeft(),
                                     absBounds.bottom() - box->borderBottom() - m_hBar->height(),
                                     absBounds.width() - (box->borderLeft() + box->borderRight()) - scrollCorner.width(),
                                     m_hBar->height()));
    
    if (m_scrollCorner)
        m_scrollCorner->setFrameRect(scrollCorner);
    if (m_resizer)
        m_resizer->setFrameRect(resizerCornerRect(this, borderBox));
}

int RenderLayer::scrollWidth()
{
    if (m_scrollDimensionsDirty)
        computeScrollDimensions();
    return m_scrollWidth;
}

int RenderLayer::scrollHeight()
{
    if (m_scrollDimensionsDirty)
        computeScrollDimensions();
    return m_scrollHeight;
}

void RenderLayer::computeScrollDimensions(bool* needHBar, bool* needVBar)
{
    RenderBox* box = renderBox();
    ASSERT(box);
    
    m_scrollDimensionsDirty = false;
    
    bool ltr = renderer()->style()->direction() == LTR;

    int clientWidth = box->clientWidth();
    int clientHeight = box->clientHeight();

    m_scrollLeftOverflow = ltr ? 0 : min(0, box->leftmostPosition(true, false) - box->borderLeft());

    int rightPos = ltr ?
                    box->rightmostPosition(true, false) - box->borderLeft() :
                    clientWidth - m_scrollLeftOverflow;
    int bottomPos = box->lowestPosition(true, false) - box->borderTop();

    m_scrollWidth = max(rightPos, clientWidth);
    m_scrollHeight = max(bottomPos, clientHeight);
    
    m_scrollOriginX = ltr ? 0 : m_scrollWidth - clientWidth;

    if (needHBar)
        *needHBar = rightPos > clientWidth;
    if (needVBar)
        *needVBar = bottomPos > clientHeight;
}

void RenderLayer::updateOverflowStatus(bool horizontalOverflow, bool verticalOverflow)
{
    if (m_overflowStatusDirty) {
        m_horizontalOverflow = horizontalOverflow;
        m_verticalOverflow = verticalOverflow;
        m_overflowStatusDirty = false;
        
        return;
    }
    
    bool horizontalOverflowChanged = (m_horizontalOverflow != horizontalOverflow);
    bool verticalOverflowChanged = (m_verticalOverflow != verticalOverflow);
    
    if (horizontalOverflowChanged || verticalOverflowChanged) {
        m_horizontalOverflow = horizontalOverflow;
        m_verticalOverflow = verticalOverflow;
        
        if (FrameView* frameView = renderer()->document()->view()) {
            frameView->scheduleEvent(OverflowEvent::create(horizontalOverflowChanged, horizontalOverflow, verticalOverflowChanged, verticalOverflow),
                renderer()->node());
        }
    }
}

void
RenderLayer::updateScrollInfoAfterLayout()
{
    RenderBox* box = renderBox();
    if (!box)
        return;

    m_scrollDimensionsDirty = true;

    bool horizontalOverflow, verticalOverflow;
    computeScrollDimensions(&horizontalOverflow, &verticalOverflow);

    if (box->style()->overflowX() != OMARQUEE) {
        // Layout may cause us to be in an invalid scroll position.  In this case we need
        // to pull our scroll offsets back to the max (or push them up to the min).
        int newX = max(0, min(scrollXOffset(), scrollWidth() - box->clientWidth()));
        int newY = max(0, min(m_scrollY, scrollHeight() - box->clientHeight()));
        if (newX != scrollXOffset() || newY != m_scrollY) {
            RenderView* view = renderer()->view();
            ASSERT(view);
            // scrollToOffset() may call updateLayerPositions(), which doesn't work
            // with LayoutState.
            // FIXME: Remove the disableLayoutState/enableLayoutState if the above changes.
            if (view)
                view->disableLayoutState();
            scrollToOffset(newX, newY);
            if (view)
                view->enableLayoutState();
        }
    }

    bool haveHorizontalBar = m_hBar;
    bool haveVerticalBar = m_vBar;
    
    // overflow:scroll should just enable/disable.
    if (renderer()->style()->overflowX() == OSCROLL)
        m_hBar->setEnabled(horizontalOverflow);
    if (renderer()->style()->overflowY() == OSCROLL)
        m_vBar->setEnabled(verticalOverflow);

    // A dynamic change from a scrolling overflow to overflow:hidden means we need to get rid of any
    // scrollbars that may be present.
    if (renderer()->style()->overflowX() == OHIDDEN && haveHorizontalBar)
        setHasHorizontalScrollbar(false);
    if (renderer()->style()->overflowY() == OHIDDEN && haveVerticalBar)
        setHasVerticalScrollbar(false);
    
    // overflow:auto may need to lay out again if scrollbars got added/removed.
    bool scrollbarsChanged = (box->hasAutoHorizontalScrollbar() && haveHorizontalBar != horizontalOverflow) || 
                             (box->hasAutoVerticalScrollbar() && haveVerticalBar != verticalOverflow);    
    if (scrollbarsChanged) {
        if (box->hasAutoHorizontalScrollbar())
            setHasHorizontalScrollbar(horizontalOverflow);
        if (box->hasAutoVerticalScrollbar())
            setHasVerticalScrollbar(verticalOverflow);

#if ENABLE(DASHBOARD_SUPPORT)
        // Force an update since we know the scrollbars have changed things.
        if (renderer()->document()->hasDashboardRegions())
            renderer()->document()->setDashboardRegionsDirty(true);
#endif

        renderer()->repaint();

        if (renderer()->style()->overflowX() == OAUTO || renderer()->style()->overflowY() == OAUTO) {
            if (!m_inOverflowRelayout) {
                // Our proprietary overflow: overlay value doesn't trigger a layout.
                m_inOverflowRelayout = true;
                renderer()->setNeedsLayout(true, false);
                if (renderer()->isRenderBlock())
                    toRenderBlock(renderer())->layoutBlock(true);
                else
                    renderer()->layout();
                m_inOverflowRelayout = false;
            }
        }
    }
    
    // If overflow:scroll is turned into overflow:auto a bar might still be disabled (Bug 11985).
    if (m_hBar && box->hasAutoHorizontalScrollbar())
        m_hBar->setEnabled(true);
    if (m_vBar && box->hasAutoVerticalScrollbar())
        m_vBar->setEnabled(true);

    // Set up the range (and page step/line step).
    if (m_hBar) {
        int clientWidth = box->clientWidth();
        int pageStep = (clientWidth - cAmountToKeepWhenPaging);
        if (pageStep < 0) pageStep = clientWidth;
        m_hBar->setSteps(cScrollbarPixelsPerLineStep, pageStep);
        m_hBar->setProportion(clientWidth, m_scrollWidth);
        m_hBar->setValue(scrollXOffset());
    }
    if (m_vBar) {
        int clientHeight = box->clientHeight();
        int pageStep = (clientHeight - cAmountToKeepWhenPaging);
        if (pageStep < 0) pageStep = clientHeight;
        m_vBar->setSteps(cScrollbarPixelsPerLineStep, pageStep);
        m_vBar->setProportion(clientHeight, m_scrollHeight);
    }
 
    if (renderer()->node() && renderer()->document()->hasListenerType(Document::OVERFLOWCHANGED_LISTENER))
        updateOverflowStatus(horizontalOverflow, verticalOverflow);
}

void RenderLayer::paintOverflowControls(GraphicsContext* context, int tx, int ty, const IntRect& damageRect)
{
    // Don't do anything if we have no overflow.
    if (!renderer()->hasOverflowClip())
        return;
    
    // Move the scrollbar widgets if necessary.  We normally move and resize widgets during layout, but sometimes
    // widgets can move without layout occurring (most notably when you scroll a document that
    // contains fixed positioned elements).
    positionOverflowControls(tx, ty);

    // Now that we're sure the scrollbars are in the right place, paint them.
    if (m_hBar)
        m_hBar->paint(context, damageRect);
    if (m_vBar)
        m_vBar->paint(context, damageRect);

    // We fill our scroll corner with white if we have a scrollbar that doesn't run all the way up to the
    // edge of the box.
    paintScrollCorner(context, tx, ty, damageRect);
    
    // Paint our resizer last, since it sits on top of the scroll corner.
    paintResizer(context, tx, ty, damageRect);
}

void RenderLayer::paintScrollCorner(GraphicsContext* context, int tx, int ty, const IntRect& damageRect)
{
    RenderBox* box = renderBox();
    ASSERT(box);

    IntRect cornerRect = scrollCornerRect(this, box->borderBoxRect());
    IntRect absRect = IntRect(cornerRect.x() + tx, cornerRect.y() + ty, cornerRect.width(), cornerRect.height());
    if (!absRect.intersects(damageRect))
        return;

    if (context->updatingControlTints()) {
        updateScrollCornerStyle();
        return;
    }

    if (m_scrollCorner) {
        m_scrollCorner->paintIntoRect(context, tx, ty, absRect);
        return;
    }
    
    context->fillRect(absRect, Color::white);
}

void RenderLayer::paintResizer(GraphicsContext* context, int tx, int ty, const IntRect& damageRect)
{
    if (renderer()->style()->resize() == RESIZE_NONE)
        return;

    RenderBox* box = renderBox();
    ASSERT(box);

    IntRect cornerRect = resizerCornerRect(this, box->borderBoxRect());
    IntRect absRect = IntRect(cornerRect.x() + tx, cornerRect.y() + ty, cornerRect.width(), cornerRect.height());
    if (!absRect.intersects(damageRect))
        return;

    if (context->updatingControlTints()) {
        updateResizerStyle();
        return;
    }
    
    if (m_resizer) {
        m_resizer->paintIntoRect(context, tx, ty, absRect);
        return;
    }

    // Paint the resizer control.
    DEFINE_STATIC_LOCAL(RefPtr<Image>, resizeCornerImage, (Image::loadPlatformResource("textAreaResizeCorner")));
    IntPoint imagePoint(absRect.right() - resizeCornerImage->width(), absRect.bottom() - resizeCornerImage->height());
    context->drawImage(resizeCornerImage.get(), imagePoint);

    // Draw a frame around the resizer (1px grey line) if there are any scrollbars present.
    // Clipping will exclude the right and bottom edges of this frame.
    if (m_hBar || m_vBar) {
        context->save();
        context->clip(absRect)