Is the QToolTip::showText Bug？

[cspp]

Now I want to show some tips when my mouse hovered on some QTreeWidgetItem in QTreeWidget.

but the tips sometimes show and change well,but sometimes it does not changed,although
I have to change the position.
The porblem is:
when the mouse hovered on the first item,it should be show like "TipA";
and the second third item also show the tip "TipA".but the position should be changed!

but now,it didn't changed!

In QTooltip::showText,I find this code:

else if (!QTipLabel::instance->fadingOut){
            // If the tip has changed, reuse the one
            // that is showing (removes flickering)
            if (QTipLabel::instance->tipChanged(pos, text, w)){
                QTipLabel::instance->reuseTip(text);
                QTipLabel::instance->setTipRect(w, rect);
                QTipLabel::instance->placeTip(pos, w);
            }
            return;
        }

else if (!QTipLabel::instance->fadingOut){
            // If the tip has changed, reuse the one
            // that is showing (removes flickering)
            if (QTipLabel::instance->tipChanged(pos, text, w)){
                QTipLabel::instance->reuseTip(text);
                QTipLabel::instance->setTipRect(w, rect);
                QTipLabel::instance->placeTip(pos, w);
            }
            return;
        }

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if my tip contents didnot changed,it will be returned direct when I use QToolTip::showText();

so in function tipChanged,should add some judgement like pos!