QuickInfo for text out of view, then scrolled in doesn't wor

Hi,
again I hope for your appreciated help:
According to your sample for a QuickInfoProvider (IntelliPrompt-QuickStarts-QuickInfo) I implemented the same for my purpose.
The text in the editor is very long and therefore, not all text is shown, part of the line has to be scrolled in.
Now the problem:

For all the text that is shown at the first glance I got a quick info. Those text to which I first have to scroll and then try to get a quick info - I didn't get any. There will be no RequestSession triggered.

You can try it with your own example: (IntelliPrompt-QuickStarts-QuickInfo)
You have the line:
"function displayScreenPixelCount(screenWidth, screenHeight)"
Make the editor so small, that yo can see only the part
"function displayScreenPixelCount(screenWidth,"
Switch to another sample then again to this view.
Try to get QuickInfo for "screenWidth" and other words seen. That works.
Then scroll to the word "screenHeight" and try to get a QuickInfo: you will not get one.
Only when you make the editor window as large as you can see the whole text, then quick infos will be provided for all of the text.
Is that a bug or how can I fix this?

Thanks!