webkit中hover的幾個小知識

1。每個元素都有一個hover狀態，通過hovered和setHover來控制，該函數在WebCore::Node上：

bool hovered() const { return getFlag(IsHoveredFlag); }

....

virtual void setHovered(bool f = true) { setFlag(f, IsHoveredFlag); }

 

2. setHover是個虛函數，WebCore::ContainerNode重載了它，並且能夠更新界面

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. 參照上面的代碼，判斷一個節點是否有Hover的CSS關聯方法：renderer()->style()->affectedByHoverRules()

 

4. WebCore::Document元素保存一個當前的hover指針：

void Document::setHoverNode(PassRefPtr<Node> newHoverNode)

{

    m_hoverNode = newHoverNode;

}

 

5. 重新設置一個hover節點完整的方法：

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: 產生一個假的鼠標移動事件，在窗口位置、狀態變化後重新hover，但實際上用戶並沒有移動鼠標：

  1) 定義

class EventHandler {

....

Timer<EventHandler> m_fakeMouseMoveEventTimer;

....

};

  2) 初始化

EventHandler::EventHandler(Frame* frame)

    : m_frame(frame)

    ....

    , m_fakeMouseMoveEventTimer(this, &EventHandler::fakeMouseMoveEventTimerFired)

......