render_layer.cpp

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    if (beforeChild) {
        beforeChild->setPreviousSibling(child);
        child->setNextSibling(beforeChild);
    }
    else
        setLastChild(child);

    child->setParent(this);

    // Dirty the z-order list in which we are contained.  The stackingContext() can be null in the
    // case where we're building up generated content layers.  This is ok, since the lists will start
    // off dirty in that case anyway.
    RenderLayer* stackingContext = child->stackingContext();
    if (stackingContext)
        stackingContext->dirtyZOrderLists();
}

RenderLayer* RenderLayer::removeChild(RenderLayer* oldChild)
{
    // remove the child
    if (oldChild->previousSibling())
        oldChild->previousSibling()->setNextSibling(oldChild->nextSibling());
    if (oldChild->nextSibling())
        oldChild->nextSibling()->setPreviousSibling(oldChild->previousSibling());

    if (m_first == oldChild)
        m_first = oldChild->nextSibling();
    if (m_last == oldChild)
        m_last = oldChild->previousSibling();

    // Dirty the z-order list in which we are contained.  When called via the
    // reattachment process in removeOnlyThisLayer, the layer may already be disconnected
    // from the main layer tree, so we need to null-check the |stackingContext| value.
    RenderLayer* stackingContext = oldChild->stackingContext();
    if (stackingContext)
        oldChild->stackingContext()->dirtyZOrderLists();

    oldChild->setPreviousSibling(0);
    oldChild->setNextSibling(0);
    oldChild->setParent(0);

    return oldChild;
}

void RenderLayer::removeOnlyThisLayer()
{
    if (!m_parent)
        return;

    // Dirty the clip rects.
    clearClipRects();

    // Remove us from the parent.
    RenderLayer* parent = m_parent;
    RenderLayer* nextSib = nextSibling();
    parent->removeChild(this);

    // Now walk our kids and reattach them to our parent.
    RenderLayer* current = m_first;
    while (current) {
        RenderLayer* next = current->nextSibling();
        removeChild(current);
        parent->addChild(current, nextSib);
        current = next;
    }

    detach(renderer()->renderArena());
}

void RenderLayer::insertOnlyThisLayer()
{
    if (!m_parent && renderer()->parent()) {
        // We need to connect ourselves when our renderer() has a parent.
        // Find our enclosingLayer and add ourselves.
        RenderLayer* parentLayer = renderer()->parent()->enclosingLayer();
        if (parentLayer)
            parentLayer->addChild(this,
                                  renderer()->parent()->findNextLayer(parentLayer, renderer()));
    }

    // Remove all descendant layers from the hierarchy and add them to the new position.
    for (RenderObject* curr = renderer()->firstChild(); curr; curr = curr->nextSibling())
        curr->moveLayers(m_parent, this);

    // Clear out all the clip rects.
    clearClipRects();
}

void
RenderLayer::convertToLayerCoords(const RenderLayer* ancestorLayer, int& x, int& y) const
{
    if (ancestorLayer == this)
        return;

    if (m_object->style()->position() == FIXED) {
        // Add in the offset of the view.  We can obtain this by calling
        // absolutePosition() on the RenderCanvas.
        int xOff, yOff;
        m_object->absolutePosition(xOff, yOff, true);
        x += xOff;
        y += yOff;
        return;
    }

    RenderLayer* parentLayer;
    if (m_object->style()->position() == ABSOLUTE)
        parentLayer = enclosingPositionedAncestor();
    else
        parentLayer = parent();

    if (!parentLayer) return;

    parentLayer->convertToLayerCoords(ancestorLayer, x, y);

    x += xPos();
    y += yPos();
}

void
RenderLayer::scrollOffset(int& x, int& y)
{
    x += scrollXOffset();
    y += scrollYOffset();
}

void
RenderLayer::subtractScrollOffset(int& x, int& y)
{
    x -= scrollXOffset();
    y -= scrollYOffset();
}

void
RenderLayer::scrollToOffset(int x, int y, bool updateScrollbars, bool repaint)
{
    if (renderer()->style()->overflow() != OMARQUEE) {
        if (x < 0) x = 0;
        if (y < 0) y = 0;

        // Call the scrollWidth/Height functions so that the dimensions will be computed if they need
        // to be (for overflow:hidden blocks).
        int maxX = scrollWidth() - m_object->clientWidth();
        int maxY = scrollHeight() - m_object->clientHeight();

        if (x > maxX) x = maxX;
        if (y > maxY) y = maxY;
    }

    // FIXME: Eventually, we will want to perform a blit.  For now never
    // blit, since the check for blitting is going to be very
    // complicated (since it will involve testing whether our layer
    // is either occluded by another layer or clipped by an enclosing
    // layer or contains fixed backgrounds, etc.).
    m_scrollX = x;
    m_scrollY = y;

    // Update the positions of our child layers.
    for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
        child->updateLayerPositions(false, false);

#if APPLE_CHANGES
    // Move our widgets.
    m_object->updateWidgetPositions();

    // Update dashboard regions, scrolling may change the clip of a
    // particular region.
    RenderCanvas *canvas = renderer()->canvas();
    if (canvas)
        canvas->view()->updateDashboardRegions();
#endif

    // Fire the scroll DOM event.
    m_object->element()->dispatchHTMLEvent(EventImpl::SCROLL_EVENT, true, false);

    // Just schedule a full repaint of our object.
    if (repaint)
        m_object->repaint();

    if (updateScrollbars) {
        if (m_hBar)
            m_hBar->setValue(m_scrollX);
        if (m_vBar)
            m_vBar->setValue(m_scrollY);
    }
}

void
RenderLayer::updateScrollPositionFromScrollbars()
{
    bool needUpdate = false;
    int newX = m_scrollX;
    int newY = m_scrollY;

    if (m_hBar) {
        newX = m_hBar->value();
        if (newX != m_scrollX)
           needUpdate = true;
    }

    if (m_vBar) {
        newY = m_vBar->value();
        if (newY != m_scrollY)
           needUpdate = true;
    }

    if (needUpdate)
        scrollToOffset(newX, newY, false);
}

void
RenderLayer::setHasHorizontalScrollbar(bool hasScrollbar)
{
    if (hasScrollbar && !m_hBar) {
        QScrollView* scrollView = m_object->element()->getDocument()->view();
        m_hBar = new QScrollBar(Qt::Horizontal, 0);
        scrollView->addChild(m_hBar, 0, -50000);
        if (!m_scrollMediator)
            m_scrollMediator = new RenderScrollMediator(this);
        m_scrollMediator->connect(m_hBar, SIGNAL(valueChanged(int)), SLOT(slotValueChanged(int)));
    }
    else if (!hasScrollbar && m_hBar) {
        QScrollView* scrollView = m_object->element()->getDocument()->view();
        scrollView->removeChild (m_hBar);

        m_scrollMediator->disconnect(m_hBar, SIGNAL(valueChanged(int)),
                                     m_scrollMediator, SLOT(slotValueChanged(int)));
        delete m_hBar;
        m_hBar = 0;
    }
}

void
RenderLayer::setHasVerticalScrollbar(bool hasScrollbar)
{
    if (hasScrollbar && !m_vBar) {
        QScrollView* scrollView = m_object->element()->getDocument()->view();
        m_vBar = new QScrollBar(Qt::Vertical, 0);
        scrollView->addChild(m_vBar, 0, -50000);
        if (!m_scrollMediator)
            m_scrollMediator = new RenderScrollMediator(this);
        m_scrollMediator->connect(m_vBar, SIGNAL(valueChanged(int)), SLOT(slotValueChanged(int)));
    }
    else if (!hasScrollbar && m_vBar) {
        QScrollView* scrollView = m_object->element()->getDocument()->view();
        scrollView->removeChild (m_vBar);

        m_scrollMediator->disconnect(m_vBar, SIGNAL(valueChanged(int)),
                                     m_scrollMediator, SLOT(slotValueChanged(int)));
        delete m_vBar;
        m_vBar = 0;
    }
}

int
RenderLayer::verticalScrollbarWidth()
{
    if (!m_vBar)
        return 0;

    return m_vBar->width();
}

int
RenderLayer::horizontalScrollbarHeight()
{
    if (!m_hBar)
        return 0;

    return m_hBar->height();
}

void
RenderLayer::moveScrollbarsAside()
{
    if (m_hBar)
        m_hBar->move(0, -50000);
    if (m_vBar)
        m_vBar->move(0, -50000);
}

void
RenderLayer::positionScrollbars(const QRect& absBounds)
{
    if (m_vBar) {
        m_vBar->move(absBounds.x()+absBounds.width()-m_object->borderRight()-m_vBar->width(),
                     absBounds.y()+m_object->borderTop());
        m_vBar->resize(m_vBar->width(), absBounds.height() -
                       (m_object->borderTop()+m_object->borderBottom()) -
                       (m_hBar ? m_hBar->height()-1 : 0));
    }

    if (m_hBar) {
        m_hBar->move(absBounds.x()+m_object->borderLeft(),
                     absBounds.y()+absBounds.height()-m_object->borderBottom()-m_hBar->height());
        m_hBar->resize(absBounds.width() - (m_object->borderLeft()+m_object->borderRight()) -
                       (m_vBar ? m_vBar->width()-1 : 0),
                       m_hBar->height());
    }
}

#define LINE_STEP   10
#define PAGE_KEEP   40

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)
{
    m_scrollDimensionsDirty = false;

    int rightPos = m_object->rightmostPosition(true, false) - m_object->borderLeft();
    int bottomPos = m_object->lowestPosition(true, false) - m_object->borderTop();

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

    m_scrollWidth = kMax(rightPos, clientWidth);
    m_scrollHeight = kMax(bottomPos, clientHeight);

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

void
RenderLayer::updateScrollInfoAfterLayout()
{
    m_scrollDimensionsDirty = true;
    if (m_object->style()->overflow() == OHIDDEN)
        return; // All we had to do was dirty.

    bool needHorizontalBar, needVerticalBar;
    computeScrollDimensions(&needHorizontalBar, &needVerticalBar);

    if (m_object->style()->overflow() != 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 = kMax(0, kMin(m_scrollX, scrollWidth() - m_object->clientWidth()));
        int newY = kMax(0, kMin(m_scrollY, scrollHeight() - m_object->clientHeight()));
        if (newX != m_scrollX || newY != m_scrollY)
            scrollToOffset(newX, newY);
    }

    bool haveHorizontalBar = m_hBar;
    bool haveVerticalBar = m_vBar;