Re: view-read-only causes read-write

[Kevin Rodgers <ihs_4664@yahoo.com>]

Dan Jacobson wrote:

> I did
> $ emacs --no-site-file -q -nw -eval '
>   (and(setq view-read-only t) (describe-variable (quote
>   view-read-only)))'
> 
> Notes:
> 1. Ok, the help buffer says View mode in the modeline, but how about
>    turning on the -%%- marker in the modeline?


Setting that variable is not the right way to turn on View mode.  Setting
any variable is never the right the right way to turn on a mode.  Use the
mode's function.


> 2. Hey, real view-mode doesn't let me eat text with C-k etc, and then
>    you can't repair the damage with undo because no undo record is
>    kept for that buffer.


If you want the buffer in View mode, run the view-mode function.


> 3. OK, trying again without messing first with view-read-only
>    gives what one expects.
> 
>    Do I smell someone toggling read-only once too much?


No.  You don't understand that the variable is read to indicate to the user
that view mode is on, and that the view-mode function is used to invoke the
mode.


> 4. view-read-only's docstring: "*Non-nil means buffers visiting files
>    read-only, do it in view mode." (P.S. I assume the "*" means
>    "Chef's choice".)
> 
>    OK, but what about read-only buffers not visiting files? Obviously
>    you are over affecting those and at the same time not mentioning them.


M-x pick-nit


> P.S. I am no lisp pro but above I had to use an "(and ...)" or else
> only one sexp was used, without any warning to the user.


Of course.  Symbolic expressions are well-defined: (function arg ...).
In order to evaluate multiple sexps in sequence, use (progn ...) or multiple
--eval command line options.


> PSS, while we are here, let's examine this docstring:
>   toggle-read-only is an interactive compiled Lisp function in `files'.
>   (toggle-read-only &optional ARG)
> 
>   Change whether this buffer is visiting its file read-only.
>   With arg, set read-only iff arg is positive.
> 
> Ok, but it doesn't say what will happen if you give it a non positive
> arg.  One can't just assume "common sense".  E.g. me, any common sense
> and I wouldn't be hanging around this pop stand.


"iff" means "if and only if", which is a well-defined logical operator.  It
means that if arg is not positive, unset read-only.


>   If visiting file read-only and `view-read-only' is non-nil, enter view mode.
> 
> Hold on a second. We came here to toggle-read-only and like wham, we
> are sent into view mode. It's like I do "chmod -w file" and wham, "more
> file" is invoked as a free bonus.  What if I am a batch job? Anyway,
> docsting looks bad. Didn't check the code.

Then do (setq read-only t) instead of (toggle-read-only 1) to avoid the side

effects.

-- 
<a href="mailto:&lt;kevin.rodgers&#64;ihs.com&gt;">Kevin Rodgers</a>