#	@(#)README	8.4 (Berkeley) 11/22/94

Generally, all non-system error and informational messages in nvi are
catalog messages, i.e. they can be tailored to a specific langauge.
Command strings, usage strings, system errors and other "known text"
are not.  It would certainly be possible to internationalize all the
text strings in nvi, but it's unclear that it's the right thing to do.

First, there's no portable way to do message catalogs.  The System V
scheme is a reasonable choice, but none of the 4BSD derived systems
support it.  So, catalogs are completely implemented within nvi, and
don't require any library support.

Message catalogs in nvi are fairly simple.  Every catalog message
consists of two parts -- an initial number followed by a pipe (`|')
character, followed by the English text for the message.  For example:

	msgq(sp, M_ERR, "001|This is an error message");

would be a typical message.

When the msgq() routine is called, if the user has specified a message
catalog and the format string (the third argument) has a leading number,
then it is converted to a record number, and that record is retrieved
from the message catalog and used as a replacement format string.  If
the record can't be retrieved for any reason, the English text is displayed
instead.

Each message format string MUST map into the English format string, i.e.
it can't display more or different arguments than the English one.

For example:

	msgq(sp, M_ERR, "002|Error: %d %x", arg1, arg2);

is a format string that displays two arguments.  It is possible, however,
to reorder the arguments or to not display all of them.  The convention
nvi uses is the System V printf(3) convention, i.e. "%[0-9]*$" is the name
of a specific, numbered argument.  For example:

	msgq(sp, M_ERR, "002|Error: %2$d %1$x", arg1, arg2);

displays the arguments in reverse order.

If the system supports this convention in its library printf routines
(as specified by the test #define NL_ARGMAX), nvi uses those routines.
Otherwise, there is some serious magic going on in common/msg.c to make
this all work.

Arguments to the msgq function are required to contain ONLY printable
characters.  No further translation is done by the msgq routine before
displaying the message on the screen.  For example, in the msgq call:

	msgq(sp, M_ERR, "003|File: %s", file_name);

"file_name" must contain only printable characters.  The routine
msg_print() returns a printable version of a string in allocated
memory.  For example:

	char *p;

	p = msg_print(sp, file_name);
	msgq(sp, M_ERR, M("003", "File: %s"), p);
	FREE_SPACE(sp, p, 0);

makes sure that "file_name" is printable before calling the msgq
routine.

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The message catalogs themselves are maintained in two files.  The first
is the "base file" which contains two fields, a record number and the
message itself.  All base files are named using the convention
"vi_<language>.base", e.g. the English one is "vi_english.base".  For
example:

	002 "Unable to create temporary file"
	003 "Warning: %s is not a regular file"
	004 "%s already locked, session is read-only"
	005 "%s: remove"
	006 "%s: close"
	007 "%s: remove"
	008 "%s: remove"
	009 "Read-only file, not written; use ! to override"
	010 "Read-only file, not written"

are the first few lines of the current vi_english.base file.  Note that
message #1 is missing -- the first message of each catalog is a special
one, so that nvi can recognize message catalog files.  It's added by the
Makefile script that creates the second version of the message catalog.

The second file is the file used by nvi to access messages, and is a list
of the messages, one per line:

	VI_MESSAGE_CATALOG
	Unable to create temporary fileX
	Warning: %s is not a regular fileX
	%s already locked, session is read-onlyX
	%s: removeX
	%s: closeX
	%s: removeX
	%s: removeX
	Read-only file, not written; use ! to overrideX
	Read-only file, not writtenX

Note that all messages have had a trailing 'X' character appended.  This
is to provide nvi a place to store a trailing nul for the message so that
C library routines that expect one won't be disappointed.

These files are named for their language, e.g. "vi_english".  The second
files are automatically created from the first files.

To create a new catalog for nvi:

Copy the file vi_english.base to a file that you can modify , e.g.  "cp
vi_english.base vi_german.base".  For each of the messages in the file,
replace the message with the string that you want to use.  To find out
what the arguments to a message are, I'm afraid you'll have to search
the source code for the message number.  You can find them fairly quickly
by doing:

	cd ..; egrep '123\|' */*.[chys]

I'm sorry that there's not an easier way, but I couldn't think of
anything that wasn't a lot of work.

If, for some reason, you don't have the file vi_english.base, or you
have new sources for which you want to create a new base catalog, you
can create it by running the command "make english" in the catalog
directory.

Once you've translated all of the strings, then add your catalog to the
"CAT=" line of the Makefile, and run the command "make catalog".  This
will create the second (and corresponding) file for each file named
<language>.base.

Don't worry about missing line numbers, i.e. base files that look like:

	005	Message number 5.
	007	Message number 7.

This simply means that a message was deleted during the course of nvi's
development.  It will be taken care of automatically when you create
the second form of the file.

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If you add new messages to the nvi sources, you can check your work by
doing "make english; make check".  The "make check" target lists unused
message numbers, duplicate message numbers, and duplicate messages.
Unused message numbers are only useful if you are condensing messages.
Duplicate message numbers are a serious problem and have to be fixed.
Duplicate messages are only interesting if a message appears often enough
that it's worth creating a routine so that the string is only need in
a single place.

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To select a catalog when running nvi, set the "msgcat" option.  If the
value of this option ends with a '/', it is treated as the name of a
directory that contains a message catalog "vi_XXXX", where XXXX is the
value of the LANG environmental variable, if it's set, or the value of
the LC_MESSAGES environmental variable if it's not.  If neither of those
environmental variables are set, or if the option doesn't end in a '/',
the option is treated as the full path name of the message catalog to use.

If any messages are missing from the catalog, the backup text (English)
is used instead.
