bug#14838: 24.3.50; repeating next-line or previous-line is broken

[Stephen Berman]

On Fri, 12 Jul 2013 12:48:41 +0300 Eli Zaretskii <eliz@gnu.org> wrote:

>> Date: Thu, 11 Jul 2013 23:25:05 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: 14838@debbugs.gnu.org
>> 
>> > From: Stephen Berman <stephen.berman@gmx.net>
>> > Cc: jan.h.d@swipnet.se,  14838@debbugs.gnu.org
>> > Date: Thu, 11 Jul 2013 22:04:07 +0200
>> > 
>> > > I don't believe the aref part.  I think the real culprit is font-info.
>> > > Let's conduct an experiment: if you modify default-font-height so that
>> > > it always just calls frame-char-height, does the problem go away?
>> > 
>> > Yep, that it does.  And no trace messages are emitted.
>> 
>> Thanks, I will come up with a change that will refrain from calling
>> font-info unless it's strictly necessary.
>
> I'm unsure what test(s) to use to detect reliably the situation where
> the font of the default face is different from the frame's default.
> The two candidates I thought about are:
>
>   . See if face-remapping-alist is non-nil and includes an association
>     for the 'default' face
>
>   . Compare
>
>       (frame-parameter 'font)
>
>     with
>
>       (face-font 'default)
>
> Regarding the 1st candidate, I'm not sure the condition will always
> hold whenever the font of the default face was modified in some way.
>
> Regarding the 2nd candidate, I'm not sure (frame-parameter 'font) will
> always return a non-trivial value.  Can it return nil, for example?
>
> Any other suggestions?
>
> Stephen, can you test both of the above in your case?

With emacs -Q, where the problem with holding down C-n does not happen
(when I have no ~/.Xresources file):

face-remapping-alist => nil
(frame-parameter nil 'font) =>
"-unknown-DejaVu Sans Mono-normal-normal-normal-*-15-*-*-*-m-0-iso10646-1"
(face-font 'default) =>
"-unknown-DejaVu Sans Mono-normal-normal-normal-*-15-*-*-*-m-0-iso10646-1"

and after setting the default font to one that does cause the problem:

face-remapping-alist => nil
(frame-parameter nil 'font) =>
"-Adobe-Adobe Courier-normal-normal-normal-*-14-*-*-*-m-90-iso10646-1"
(face-font 'default) =>
"-Adobe-Adobe Courier-normal-normal-normal-*-14-*-*-*-m-90-iso10646-1"

I guess that's not very helpful :-(

Steve Berman