webkit中hover的几个小知识

1。每个元素都有一个hover状态，通过hovered和setHover来控制，该函数在WebCore::Node上：

bool hovered() const { return getFlag(IsHoveredFlag); }
....
virtual void setHovered( bool f = true ) { setFlag(f, IsHoveredFlag); }

 

2. setHover是个虚函数，WebCore::ContainerNode重载了它，并且能够更新界面

void ContainerNode::setHovered( bool over)
{
    if (over == hovered()) return ;
    Node::setHovered(over);
    // note that we need to recalc the style
    // FIXME: Move to Element
    if (renderer()) {
        if (renderer()->style()->affectedByHoverRules())
            setNeedsStyleRecalc();
        if (renderer() && renderer()->style()->hasAppearance())
            renderer()->theme()->stateChanged(renderer(), HoverState);
    }
}

3. 参照上面的代码，判断一个节点是否有Hover的CSS关联方法：renderer()->style()->affectedByHoverRules()

 

4. WebCore::Document元素保存一个当前的hover指针：

void Document::setHoverNode(PassRefPtr<Node> newHoverNode)
{
    m_hoverNode = newHoverNode;
}

 

5. 重新设置一个hover节点完整的方法：

static RenderObject* commonAncestor(RenderObject* obj1, RenderObject* obj2)
{
    if (!obj1 || !obj2)
        return 0;
    for (RenderObject* currObj1 = obj1; currObj1; currObj1 = currObj1->hoverAncestor())
        for (RenderObject* currObj2 = obj2; currObj2; currObj2 = currObj2->hoverAncestor())
            if (currObj1 == currObj2)
                return currObj1;
    return 0;
}
static void switchHover(Document *document, Node* oldHoveredNode, Node* newHoveredNode)
{
    RenderObject *ancestor = commonAncestor(oldHoveredNode ? oldHoveredNode->renderer(): NULL, newHoveredNode ? newHoveredNode->renderer() : NULL);
    if (oldHoveredNode){
        oldHoveredNode->setHovered( false );
        for (RenderObject* curr = oldHoveredNode->renderer(); curr && curr != ancestor; curr = curr->hoverAncestor()) {
            if (curr->node() && !curr->isText() /*&& curr->node()->inActiveChain()*/ )
                curr->node()->setHovered( false );
        }
    }
    document->setHoverNode(newHoveredNode);
    if (newHoveredNode)
    {
        for (RenderObject* curr = newHoveredNode->renderer(); curr; curr = curr->hoverAncestor()) {
            if (curr->node() && !curr->isText() /*&& curr->node()->inActiveChain()*/ )
                curr->node()->setHovered( true );
        }
        newHoveredNode->setHovered( true );
    }
}

 

6. EventHandler的fakeMouseMoveEvent: 产生一个假的鼠标移动事件，在窗口位置、状态变化后重新hover，但实际上用户并没有移动鼠标：

  1) 定义

class EventHandler {
....
Timer<EventHandler> m_fakeMouseMoveEventTimer;
....
};

  2) 初始化

EventHandler::EventHandler(Frame* frame)
    : m_frame(frame)
    ....
    , m_fakeMouseMoveEventTimer( this , &EventHandler::fakeMouseMoveEventTimerFired)
......