Reduce integer-output-format to print-integers-as-characters

The variable now only controls whether characters are printed, not
the radix.  Control chars are printed in human-readable syntax
only when special escapes such as ?\n are available.  Spaces,
formatting and combining chars are excluded (bug#44155).
Done in collaboration with Juri Linkov.

* src/character.c (graphic_base_p):
* src/print.c (named_escape): New functions.
(print_object): Change semantics as described above.
(syms_of_print): Rename integer-output-format.  Update doc string.
* doc/lispref/streams.texi (Output Variables):
* etc/NEWS:
* test/src/print-tests.el (print-integers-as-characters):
Rename and update according to new semantics.  The test now passes.

1 files changed, 12 insertions, 6 deletions

diff --git a/doc/lispref/streams.texi b/doc/lispref/streams.texi
index f171f137790..0534afb67fa 100644
--- a/doc/lispref/streams.texi
+++ b/doc/lispref/streams.texi
@@ -903,10 +903,16 @@ in the C function @code{sprintf}.  For further restrictions on what
 you can use, see the variable's documentation string.
 @end defvar
 
-@defvar integer-output-format
-This variable specifies how to print integer numbers.  The default is
-@code{nil}, meaning use the decimal format.  When bound to @code{t},
-print integers as characters when an integer represents a character
-(@pxref{Basic Char Syntax}).  When bound to the number @code{16},
-print non-negative integers in the hexadecimal format.
+@defvar print-integers-as-characters
+When this variable is non-@code{nil}, integers that represent
+graphic base characters will be printed using Lisp character syntax
+(@pxref{Basic Char Syntax}). Other numbers are printed the usual way.
+For example, the list @code{(4 65 -1 10)} would be printed as
+@samp{(4 ?A -1 ?\n)}.
+
+More precisely, values printed in character syntax are those
+representing characters belonging to the Unicode general categories
+Letter, Number, Punctuation, Symbol and Private-use
+(@pxref{Character Properties}), as well as the control characters
+having their own escape syntax such as newline.
 @end defvar