bug#3379: Tooltip is causing crash

[Jason Rumney]

Shannon Jones wrote:
> I tried this, and I think it's not the menu that is causing the
> crash.  I think it's the tooltip that appears when you hover over
> an item on the tool-bar.
>   

Thank you for pointing us in the right direction. It is actually a 
problem with font backends on Windows. As CVS is down, I can't check in 
the immediate workaround - which is to add the uniscribe backend to 
x_create_tip_frame in w32fns.c so:

 register_font_driver (&w32font_driver, f);

becomes:

 if (uniscribe_available)
   register_font_driver (&uniscribe_font_driver, f);
 register_font_driver (&w32font_driver, f);


The bug still triggers with the same recipe if you do the following:

(add-to-list 'tooltip-frame-parameters '(font-backend . "gdi"))

but I can't reproduce the bug on GNU/Linux doing something similar 
(substituting "x" for "gdi"), so it still seems to be a Windows specific 
bug.