Re: emacs -Q not documented

[storm@cua.dk (Kim F. Storm)]

Richard Stallman <rms@gnu.org> writes:

>     It is intended to be an option turn off all "extra features".
>
> On what criterion are these features "extra"?

They are various "decorations" to the basic Emacs frame or
functionality.  

Turning them off, skips over a fairly big (and complex) part of
internal redisplay code (e.g. building menu and tool bars which may
run quite a deal of lisp code).

>
>     But most important, running emacs -Q when debugging redisplay problems
>     makes it much easier to know what's going on.
>
> Why does the blinking cursor relate to this?

It means running timers and async Lisp code, and triggers redisplay
which may influense how a bug in redisplay manifests itself on the
screen.

Furthermore, it means you cannot just put a breakpoint on (or anywhere
inside) redisplay_internal and then execute some code to generate a
specific error...  The blinking cursor timer will trigger that
breakpoint every second, making it practically impossible to
debug such problems.

The -Q option has saved me many hours debugging rediplay problems!

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk