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Subject: |
display-raw-bytes-as-hex generates ambiguous output for Emacs strings |
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Date: |
Tue, 6 Jun 2017 20:57:51 -0700 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 |
With the default octal display format one can copy text out of a terminal window
and into an Emacs string, reliably. With the new hex display this doesn't work
any more, unfortunately. For example, if I run this shell script:
printf 'x\2205y\n' >foo.txt
LC_ALL=C emacs -nw --color=no --eval '(progn (setq display-raw-bytes-as-hex t)
(find-file-literally "foo.txt"))'
then on the terminal display I see:
x\x905y
If I cut and paste this (using my windowing system) into an Emacs string, like
this:
"x\x905y"
and then evaluate the string, the result is the string "xअy", that is, a
3-character string with the characters "x", "अ", and "y", where the middle
character is U+090F DEVANAGARI LETTER A. This is an incorrect representation, as
the buffer actually contains the four characters "x", "\x90", "5", and "y". The
problem is that the string has glued together the representation of the
character "\x90" to the representation of the character "5", resulting in the
representation of the character "\x905" which is not accurate.
Please change the behavior of display-raw-bytes-as-hex so that it is not
ambiguous in this way.
A simple solution would be to display this instead:
x\x90\x35y
though that is awkward because it means the ASCII 0-9, a-f, A-F would be
displayed as hexadecimal escapes when they follow another hexadecimal escape.
Perhaps we can think of a better approach. One possibility would be to define
and use a new string escape \Xxx that contains at most two hex digits.
By the way, I expected display-raw-bytes-as-hex to affect how Emacs displays
Emacs strings, too. Shouldn't it?
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--- Begin Message ---
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Subject: |
Re: bug#27270: display-raw-bytes-as-hex generates ambiguous output for Emacs strings |
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Date: |
Thu, 28 Apr 2022 10:58:33 -0700 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 |
On 4/27/22 10:22, Lars Ingebrigtsen wrote:
Paul Eggert <eggert@cs.ucla.edu> writes:
Could you explain what you mean by "change the output"? (Sorry, I'm
not seeing it.)
I said earlier:
display-raw-bytes-as-hex is a display setting. You want to change it so
that the data output will be different
Still not quite following, as I had been thinking more recently of
changing only how display-raw-bytes-as-hex displays.
That being said, I looked into the code and found that what I was asking
for would be quite a pain to implement - more trouble than it's worth,
anyway - so I withdraw the suggestion and am closing the bug report.
I installed the attached, which documents the situation.
0001-Document-807-etc.-in-raw-byte-display.patch
Description: Text Data
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