Tooltip sometimes does not show. Waht is wrong? How to show it programmatic

Vaadin 6 / 7 / 8
1

Hi at all,

I use a big HTML-canvas to draw a lot of thinks (squares and so on). When the mouse is moved on the canvas to “special” squares a tooltip should be raised. Therefore I I overrided in my connector method hasTooltip(), that it always returns true now. On client side I added a MouseMoveListener to my canvas and when the mousecursor moves to a position of a square, I set the description and descriptionContentMode in the connector state with the acutal tooltip string of the underlaying square and content mode. In parallel the VTooltip#TooltipEventHandler also gets a MouseMoveEvent, starts the show timer and so on. At the end, after start delay is over, I can see my tooltip.
If the mouse leaves the square I set description and descriptionContentMode to null and the tooltip disappears. So far, so good.
But in some cases it does not work. The tooltip is not visible. During debugging (and debugging mousemove-events is really annoying) it looks like, that I get my mousemove-event, but the tooltipeventhandler does not, so it does not start its show timer and so on.
So I tried to show the tooltip programmatically, but without success. First I thought to “re-fire” my mousemove-event, so the tooltipeventhandler can re-act:

final Canvas widget = myConnetor.getWidget();

// myConnetor.getConnection().getVTooltip().connectHandlersToWidget(
//					widget );

DomEvent.fireNativeEvent(
				pEvent.getNativeEvent().getNativeEvent(),
				widget,
				widget.getElement() );

The tooltiphandler recieves the event but in methode handleShowHide() it ends up in third line:

// We can ignore move event if it's handled by move or over already
if (currentElement == element && handledByFocus) {
         return;
}

I also tried to access methode showTooltip() in VTooltip directly via native access, because it is private:

private native void showMyTooltip( final VTooltip pTooltip )
/*-{
    pTooltip.showTooltip();
}-*/;

But alyways I get an error of unknown methode showTooltip() when I start Vaadin application in debug-mode. I tried to find out what could be wrong with my native call, but I am not so firm coding Vaadin client side with pure JavaScript. When I look into DevTools in Chrome I see something like this:

function com_vaadin_client_VTooltip_$showTooltip__Lcom_vaadin_client_VTooltip_2V(this$static){
    ...
}

It looks for me that there is a methode showTooltip(). So what is wrong with my call?

Does anybody has some ideas what else I could do? In my first tries I could also try to fire an blur-event first because in onBlur() handledByFocus is set to false so the condition in line 3 will fail.

But I am most interested in how to find out, why the tooltipevent-handler sometimes does not get the mousemove-events and to fix this issues. All other possibilities are a little bit stupid and not really “safe” again newer Vaadin versions and so on.
I use Vaadin framework 8.5.2 but also before I had these problems.

Thanks a lot