About `char' in momentary-string-display

About `char' in momentary-string-display

[Xue Fuqiao]

Hi,

In (info "(elisp) Temporary Displays"):

 -- Function: momentary-string-display string position &optional char
          message
[...]
     Thus, typing CHAR will simply remove the string from the display,
     while typing (say) `C-f' will remove the string from the display
     and later (presumably) move point forward.  The argument CHAR is a
     space by default.

I tried evaluating ‘(momentary-string-display "foo" 1)’ in the *scratch*
buffer and typed ‘C-f’, but the point didn't move forward.  Instead, a
‘[6]’ is echoed in the *Messages* buffer.  I don't know what the ‘[6]’
stands for, but the codepoint for ^F is #x6 (ACK).  So I think there may
be a link between them.

But anyway, why didn't the point move forward (the point wasn't at eob)?
Can anyone point me in the right direction?

(I searched the archives, but didn't get anything that looked promising.)

-- 
Best regards, Xue Fuqiao.
http://www.gnu.org/software/emacs/

Re: About `char' in momentary-string-display

[Kevin Rodgers]

On 10/17/13 7:06 AM, Xue Fuqiao wrote:
> Hi,
>
> In (info "(elisp) Temporary Displays"):
>
>   -- Function: momentary-string-display string position&optional char
>            message
> [...]
>       Thus, typing CHAR will simply remove the string from the display,
>       while typing (say) `C-f' will remove the string from the display
>       and later (presumably) move point forward.  The argument CHAR is a
>       space by default.
>
> I tried evaluating ‘(momentary-string-display "foo" 1)’ in the *scratch*
> buffer and typed ‘C-f’, but the point didn't move forward.  Instead, a
> ‘[6]’ is echoed in the *Messages* buffer.  I don't know what the ‘[6]’
> stands for, but the codepoint for ^F is #x6 (ACK).  So I think there may
> be a link between them.
>
> But anyway, why didn't the point move forward (the point wasn't at eob)?
> Can anyone point me in the right direction?


CHAR defaults to SPC, but you typed C-f.  What happens if you type SPC?

What happens if you specify C-f as CHAR:
(momentary-string-display "foo" 1 ?\C-f)

-- 
Kevin Rodgers
Denver, Colorado, USA

Re: About `char' in momentary-string-display

[Xue Fuqiao]

On Thu, Oct 17, 2013 at 9:17 PM, Kevin Rodgers
<kevin.d.rodgers@gmail.com> wrote:
> On 10/17/13 7:06 AM, Xue Fuqiao wrote:
>> In (info "(elisp) Temporary Displays"):
>>
>>   -- Function: momentary-string-display string position&optional char
>>
>>            message
>> [...]
>>       Thus, typing CHAR will simply remove the string from the display,
>>       while typing (say) `C-f' will remove the string from the display
>>       and later (presumably) move point forward.  The argument CHAR is a
>>       space by default.
>>
>> I tried evaluating ‘(momentary-string-display "foo" 1)’ in the *scratch*
>> buffer and typed ‘C-f’, but the point didn't move forward.  Instead, a
>> ‘[6]’ is echoed in the *Messages* buffer.  I don't know what the ‘[6]’
>> stands for, but the codepoint for ^F is #x6 (ACK).  So I think there may
>> be a link between them.
>>
>> But anyway, why didn't the point move forward (the point wasn't at eob)?
>> Can anyone point me in the right direction?
>
> CHAR defaults to SPC, but you typed C-f.  What happens if you type SPC?

Thanks for your attention.  If I type SPC, Emacs (as expected) ignores
it.  But what I'm asking is about the case when CHAR ≠ the-character-i-press.

> What happens if you specify C-f as CHAR:
> (momentary-string-display "foo" 1 ?\C-f)

It doesn't make sense, I think.  Emacs will simply remove "foo" from the
display, and ignore the "C-f".  It is the same as pressing SPC with
‘(momentary-string-display "foo" 1)’.

-- 
Best regards, Xue Fuqiao.
http://www.gnu.org/software/emacs/

Re: About `char' in momentary-string-display

[Kai Großjohann]

Xue Fuqiao wrote:
> I tried evaluating ‘(momentary-string-display "foo" 1)’ in the *scratch*
> buffer and typed ‘C-f’, but the point didn't move forward.

I think it's related to evaluation in the *scratch* buffer.  Try typing
M-: and then eval the expession there -- it works as advertised.

But how exactly the *scratch* buffer makes it fail, I'm not sure.  I
tried to eval (previous-line 3) in the scratch buffer, and it dutifully
went up some lines before inserting "nil" (the return value).

Kai

Re: About `char' in momentary-string-display

[Xue Fuqiao]

On Fri, Oct 18, 2013 at 4:12 AM, Kai Großjohann <kai.grossjohann@gmx.net> wrote:
> Xue Fuqiao wrote:
>> I tried evaluating ‘(momentary-string-display "foo" 1)’ in the *scratch*
>> buffer and typed ‘C-f’, but point didn't move forward.
>
> I think it's related to evaluation in the *scratch* buffer.  Try typing
> M-: and then eval the expession there -- it works as advertised.
>
> But how exactly the *scratch* buffer makes it fail, I'm not sure.  I
> tried to eval (previous-line 3) in the scratch buffer, and it dutifully
> went up some lines before inserting "nil" (the return value).

Thanks.  But in fact I didn't use eval-print-last-sexp (which is bound
to C-j in lisp-interaction-mode by default).  I was using eval-last-sexp
(C-x C-e).  I also tried ‘load’ and ‘eval-expression’, but neither of
them worked as I expected.

Maybe we are using different versions of Emacs?  I'm using 24.3.50
(114635 eliz@gnu.org-20131012090021-bau450cmd6gk61ag) on Ubuntu 13.04.

-- 
Best regards, Xue Fuqiao.
http://www.gnu.org/software/emacs/

Re: About `char' in momentary-string-display

[Kai Großjohann]

Xue Fuqiao wrote:
> 
> Thanks.  But in fact I didn't use eval-print-last-sexp (which is bound
> to C-j in lisp-interaction-mode by default).  I was using eval-last-sexp
> (C-x C-e).  I also tried ‘load’ and ‘eval-expression’, but neither of
> them worked as I expected.

C-x C-e worked beautifully for me:

GNU Emacs 24.3.1 (x86_64-apple-darwin12.3.0, NS apple-appkit-1187.37) of
2013-04-01 on teneight-slave.macports.org

Kai