Re: Cannot Identify header line text at mouse pointer after mouse drag to different frame

[Eli Zaretskii <eliz@gnu.org>]

> From: Marc Munro <marc@bloodnok.com>
> Date: Sun, 01 Aug 2021 16:38:23 -0700
> 
> If I drag from a header line to the same header line, or to another
> header line in the same frame, all is well, but if I drag to a header
> line in a different frame the posn-xxx functions appear to not realise
> the windows in that frame have header lines.
> 
> My header lines contain a number of buttons, and I'm trying to
> implement drag and drop functionality between them.
> 
> Interestingly, during a drag operation when I mouse over the buttons in
> windows within my start frame, all of the tooltips and face changes
> associated with the buttons work just as they do outside of drag
> operations, but in other frames the header line appears inert.  If I
> continue dragging back to the source frame, the header line buttons
> that I mouse over continue to interact normally.
> 
> It looks like emacs is unwilling to acknowledge the header lines of any
> but the source window while mouse dragging is under way.
> 
> Any ideas?  Is this a deficiency, a philosophical issue (ie, it has to
> be like this because...), or am I missing something?

It's hard to say, since you didn't show any code.  A simple recipe to
reproduce the problem would go a long way towards understanding the
reasons for what you see.