I think I've figured it out - with a textual cell (e.g. author name) the tooltip will continue to display as long as the mouse hovers.
But with a long text column that contains multiple links to large images the first image is displayed for about half a second, then the second one for about half a second, and so on. It has nothing to do with the icon or my mouse pointer valet because I tried removing both.
But something has changed - not sure when. In version 1.48 when I hover the mouse pointer over the cell where I have the Kris Swindle image, that you can see my earlier post, I see this:-
IMO that's adequate as a
tooltip for something that contains image links (the two white squares). In my case the images are local links (file:///blah blah) so they're fast, but if they were web links (http://blah blah) then... zzz.
I'm guessing this a Qt issue - and that it could go back as far as the change to version 5. Of late I've been doing some 'work' on the library where I have lots of embedded links to large images so the 'tooltip image popups' are particularly irritating - I can workaround by disabling the tooltips when working on that library.
BR