Re: header-line and mode-line leave residue with certain fonts

[Jan D.]

> Start Emacs under X11 with -q -no-site-file, then type `M-x
> set-frame-font RET' and at the prompt type
> `-misc-fixed-medium-r-normal--13-120-75-75-c-70-iso8859-1 RET'.  Now
> type `M-x ruler-mode' twice, first to display and then hide the ruler.
> You will now see a vertical line the height of the ruler in the upper
> left margin, between the scroll bar and the fringe.  Similarly, typing
> `M-: (setq mode-line-format nil)' leaves a vertical line the height of
> the mode line in the lower left margin, between the scroll bar and the
> fringe.  Further observations:
>
> - These residues of the mode line and header line (if that's what they
>   are) disappear when the frame is redisplayed (e.g. by typing `C-l').
> - Unsplitting a vertically split frame also leaves such residues.
> - I've also observed residues of the header lines in tabbar-mode and
>   w3m-mode, but the Info header line appears to leave either a very
>   faint residue or none, on my monitor with the default colors.
> - The residues appear only with certain fontsets.  I haven't tried all
>   the fonts on my system, but I've only observed the residues with
>   fonts with a width field of 70.
> - The residues appear only when the scroll bar is on the left.

Not really, I can get then on both sides.

> - The residues appear whether or not there is a left fringe.
> - The residues don't appear in the released Emacs 21.3.1, nor do I
>   recall seeing them in CVS Emacs with the Xaw3d scroll bars
>   (currently I only have the GTK build of CVS Emacs available).

This is a bad interaction between GTK and X and occur because Emacs 
can't
use the GTK event loop and scroll bars need to be double buffered to
avoid flicker.  It is a GTK only problem.  I have this on my todo list
(actually been there since GTK first made it into Emacs), I'll try to
give it more priority.

Thanks,

        Jan D.