How switch from escaped octal character code to escaped HEX?

[Oleksandr Gavenko]

When Emacs find that byte that does
not correspond to any specific displayable character it display
octal codes instead, like: \276 (and with different color).

This is useful, but I prefer HEX base instead octal.

How can I change this behavior.

To hard find right keywords for search in manual and Google ((

[Oleksandr Gavenko]

This from manual:

As a special case, if the character lies in the range 128 (0200
octal) through 159 (0237 octal), it stands for a "raw" byte that does
not correspond to any specific displayable character. Such a
"character" lies within the `eight-bit-control' character set, and is
displayed as an escaped octal character code. In this case, `C-x ='
shows `part of display ...' instead of `file'.

I want change with behavior from octal to hex.

[Stefan Monnier]

>> When Emacs find that byte that does
>> not correspond to any specific displayable character it display
>> octal codes instead, like: \276 (and with different color).
>>
>> This is useful, but I prefer HEX base instead octal.

There is no direct/easy way to do it.
But you can do it by adding the corresponding 128 entries to the
standard-display-table.

E.g.

(setq standard-display-table (make-display-table))
(aset standard-display-table (unibyte-char-to-multibyte 131)
[?\\ ?x ?8 ?3])
(aset standard-display-table (unibyte-char-to-multibyte 132)
[?\\ ?x ?8 ?4])

Should make the bytes 131 and 132 be displayed as \x83 and \x84 rather
than \203 and \204.

Stefan

[Deniz Dogan]

2011/1/3 Stefan Monnier <mon...@iro.umontreal.ca>:

What is the reasoning behind displaying it in octal rather than
decimal or hexadecimal in the first place? I didn't know people cared
about octals anymore.

--
Deniz Dogan

[Deniz Dogan]

2011/1/3 Deniz Dogan <deniz.a...@gmail.com>:
> 2011/1/3 Stefan Monnier <mon...@iro.umontreal.ca>:

> What is the reasoning behind displaying it in octal rather than
> decimal or hexadecimal in the first place? I didn't know people cared
> about octals anymore.
>

I read on Wikipedia: "Octal representation of non-ASCII bytes may be
particularly handy with UTF-8, where any start byte has octal value
\3nn and any continuation byte has octal value \2nn."

Is this the reason perhaps?

--
Deniz Dogan

[Barry Margolin]

In article <mailman.8.1294038895...@gnu.org>,
Deniz Dogan <deniz.a...@gmail.com> wrote:

> What is the reasoning behind displaying it in octal rather than
> decimal or hexadecimal in the first place? I didn't know people cared
> about octals anymore.

I think it's historical. The original MIT developers tended to use
octal more than hex.

--
Barry Margolin, bar...@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

[Peter Dyballa]

Am 03.01.2011 um 11:13 schrieb Deniz Dogan:

> I read on Wikipedia: "Octal representation of non-ASCII bytes may be
> particularly handy with UTF-8, where any start byte has octal value
> \3nn and any continuation byte has octal value \2nn."
>
> Is this the reason perhaps?

Certainly not! GNU Emacs was octal before someone imagined "Unicode"...

It comes from sparse memory. One byte is two nibbles! (1 € is almost 2
ancient DM.) UNIX file permissions are octal. C is great in shifting
bits around.

--
Greetings

Pete

Almost anything is easier to get into than out of.
– Allen's Law

[Stefan Monnier]

> What is the reasoning behind displaying it in octal rather than
> decimal or hexadecimal in the first place?

As mentioned by someone else, this goes back to the beginning of Emacs,
so we're talking >20 years ago. IIUC octal was more common back then.

There are still some advantages to using octal: e.g., by using fewer
different chars, there is a higher likelihood that the boundary of the
\NNN sequence will be self obvious: when you see \01234, it's not
obvious that it's \012 followed by 3 and 4, but when you see \012ab the
boundary is self-evident. With hexadecimal, the cases where the
boundary is not self-evident are more common.

Stefan

[Oleksandr Gavenko]

Thanks Stefan for tips.

I read docs for 'buffer-display-table'. Here said:

For example, (aset buffer-display-table ?X [?Y]) tells Emacs
to display a capital Y instead of each X character.

So if in one encoding (cp1251) letter - й, in another (row-text) - \351.

I set:

(aset standard-display-table (unibyte-char-to-multibyte ?\xe9) [?\\ ?x
?e ?9])

but in cp1251 it properly displayed like й, in row-text - \xe9. I
afraid that it
in all case must be \xe9, but not. This is nice!

With this behavior I make I wont. Only one problem.

In GUI Emacs octal codes colorized (some thins red color,
C-u C-x = don't give font properties).

New hex values is not colorized. How make this?

PS. To make all 128 chars in hex I wrote:

(setq standard-display-table (make-display-table))
(let ( (i ?\x80) hex hi low )
(while (<= i ?\xff)
(setq hex (format "%x" i))
(setq hi (elt hex 0))
(setq low (elt hex 1))
(aset standard-display-table (unibyte-char-to-multibyte i) (vector
?\\ ?x hi low))
(setq i (+ i 1))
) )

PPS. Noel Evans send to me private mail where hi suggest:

(setq read-quoted-char-radix 16)

I already have this settings a lot of years. It allow you type byte in
hex: C-q 9 9 RET.

[Stefan Monnier]

> New hex values is not colorized. How make this?

(setq standard-display-table (make-display-table))

(let ( (i ?\x80) hex hi low )
(while (<= i ?\xff)
(setq hex (format "%x" i))
(setq hi (elt hex 0))
(setq low (elt hex 1))
(aset standard-display-table (unibyte-char-to-multibyte i)

(vector (make-glyph-code ?\\ 'escape-glyph)
(make-glyph-code ?x 'escape-glyph)
(make-glyph-code hi 'escape-glyph)
(make-glyph-code low 'escape-glyph)))
(setq i (+ i 1))))

-- Stefan

[Oleksandr Gavenko]

Oh! Very thanks!!!!!!!!

glyphs is interesting concept which I don't know.