Re: help.vim's syntax

On 2019-05-15, Mathieu Roux wrote:
> On mar., 2019-05-14 at 13:17 -0700, Gary Johnson wrote:
> > On 2019-05-14, Mathieu Roux wrote:
> > > Hi everybody,
> > >
> > > I have understood that for vim's help, the syntax file used is
> > > help.vim
> > > (in the directory /usr/share/vim/vim80/syntax).
> > >
> > > I can use it with:
> > > :so help.vim
> > > (if it is in the same directory of the file i open)
> > >
> > > But i still don't understand why, when i open one file in
> > > /usr/share/vim/vim80/doc
> > > EVEN A NEW FILE
> > > it automatically uses the syntax of help.vim, whereas i do
> > > nothing...
> > > Maybe someone can explain me.
> >
> > This is explained in
> >
> > :help syntax
> >
> > In short, when you enable syntax highlighting by executing
> >
> > :syntax enable
> >
> > in your vimrc, you source $VIMRUNTIME/filetype.vim, which contains:
> >
> > " Vim help file
> > au BufNewFile,BufRead $VIMRUNTIME/doc/*.txt setf help
> >
> > Whenever you open a file matching that pattern, Vim sets the
> > 'filetype' to "help" and (with the aid of a few other scripts)
> > sources $VIMRUNTIME/syntax/help.vim.
> >
> >
> > You wrote above that you opened a new file in
> > /usr/share/vim/vim80/doc. Do not create new syntax files in that
> > directory. Do not create new files or modify any files anywhere
> > under /usr/share/vim/vim80. Those directories are for files
> > included with the Vim package. Any files in those directories may
> > be overwritten by an update to the Vim package and will not be
> > accessed when you upgrade to a version later than 8.0.
> >
> > Instead, put any files you create for you own use under ~/.vim or
> > any that you want to share with other users under
> > /usr/share/vim/vimfiles. Then they will be safe from any changes to
> > your distribution's Vim package and will continue to be used even if
> > you build Vim yourself.
> >
> > Regards,
> > Gary
> >
> > --
>
> I think i don't understand...
>
> In fact, i don't want to modify /usr/share/vim/vim80/. i just tried,
> and i see that a new file automatically uses help.vim syntax.

I inferred too much from your comment in your earlier post about
opening a new file in /usr/share/vim/vim80/doc. Newcomers to Vim
often do not understand the problems with modifying or adding files
under $VIMRUNTIME (in your case, /user/share/vim/vim80) and I wanted
to help you avoid those problems.

> In my ~/.vimrc, i don't see where i source filetype.vim. Should i have
> a lign so filetype.vim?

No, you don't need a line in your ~/.vimrc to source filetype.vim.
Vim automatically sources filetype.vim when it executes the ":syntax
on" or ":filetype on" commands. Those commands are usually in the
system vimrc provided by your Linux distribution's vim package.

> /usr/share/vim/vim80/ has a subdirectory called syntax, but it contains
> many .vim files with many syntaxes. I don't understand why file in doc
> directory uses help.vim.

The files in /usr/share/vim/vim80/doc use help.vim because of the
line I quoted earlier from $VIMRUNTIME/filetype.vim:

au BufNewFile,BufRead $VIMRUNTIME/doc/*.txt setf help

That is an autocommand that sets the 'filetype' to help for every
file opened whose path name matches the pattern

$VIMRUNTIME/doc/*.txt

Vim also uses modelines in help files to set the filetype to "help".
Look at the last line of any file in $VIMRUNTIME/doc. It will look
like this example from $VIMRUNTIME/doc/workshop.txt:

vim:tw=78:ts=8:noet:ft=help:norl:

If you put that line as the last line of your files, their filetype
will be set to "help" when they are opened.

> As for me, in my directory, say ~/mathieu, i want that every .txt file
> that i create uses help.vim syntax.

The easiest way to do that is to put that modeline at the bottom of
every .txt file in that directory. Another way to do that is to
create an autocommand to set the filetype to "help" for any file
whose path name matches the pattern

~/mathieu/*.txt

If you want to use that second method, read

:help new-filetype

I know that you're not adding a new filetype, you're adding a new
pattern to detect an existing filetype, but in this case, the
solution is the same.

> I copied help.vim file in ~/mathieu and in ~/mathieu/syntax. I tried
> :syntax on
> But it does not work.
>
> The only solution for me is to do :so help.vim
> But when i close my .txt file and open it again, i have to do :so
> help.vim again.
>
> I am sorry, i am quite a beginner in vim, but i really don't understand
> your explanation.

I hope the explanation above is better.

Regards,
Gary

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