Sunday, September 18, 2011

Re: Remembering syntax when moving in and out of buffers

On 19/09/11 00:14, Benjamin R. Haskell wrote:
> On Sun, 18 Sep 2011, Spiros Bousbouras wrote:
>
>> On Sep 18, 5:45 pm, "Benjamin R. Haskell" wrote:
>>> On Sun, 18 Sep 2011, Spiros Bousbouras wrote:
>>>
>>> The problem is that the filetype is being detected again every time
>>> you switch buffers. Apparently Debian (like most distros) has a bunch
>>> of auto-detection on filetypes. With your:
>>>
>>> :let &verbose=20
>>>
>>> You can see there's an autocmd on BufRead that gets triggered every
>>> time. It's conditioned on:
>>>
>>> if !did_filetype()
>>>
>>> And, since your filetype isn't set up the way Debian expects it
>>> (which may or may not be the way Vim normally does it),
>>> did_filetype() returns 0.
>>
>> I'm afraid I don't follow your explanation. Don't the Debian specific
>> stuff become irrelevant when I do vim -u NONE ? Or do you mean that
>> Debian have modified the source of vim before compiling so that even
>> when I start vim with -u NONE some filetype detection stuff still
>> happens ? In the experiment with vim -u NONE a b I described why is it
>> that when I return to a then issuing only the syntax command (but not
>> the highlight command) turns on highlighting ? And I didn't see any
>> autocommands being executed either , the output was exactly as I
>> described it.
>
> I wasn't using -u NONE, sorry. I was explaining what goes wrong without
> it. In the -u NONE case that you present, it gets cleared because syntax
> starts fresh prior to loading each new buffer, so that filetype
> detection can detect the file and load the proper syntax without having
> to worry about clearing out the syntax of whatever other file or files
> are open.
>
> There are a few ways to avoid having Vim load the buffer from scratch
> each time you switch to it. One way is to set the 'hidden' option.
> Another is to set bufhidden=hide. Both of those alter how buffer
> management works slightly. (You can switch away from a buffer that
> contains unsaved changes, for example, though Vim will prompt you about
> that if you try to exit.)
>
>
>>>> Here's a version of the problem with no simplifications:
>>>> File a contains
>>>> This is a special line
>>>
>>>> File b is empty. I do
>>>> vim -u NONE a b
>>>> :let &verbose=20
>>>> :syntax match special /special/
>>>> :highlight special term=bold cterm=bold
>>>
>>>> The word "special" gets highlighted.
>>>> 2Ctrl-^
>>>> "b" 0 lines, 0 characters
>>>> Ctrl-^
>>>> "a" 1 line, 23 characters
>>>
>>>> Now "special" is no longer highlighted.
>>>> :syntax
>>>> No Syntax items defined for this buffer
>>>> :syntax match special /special/
>>>
>>>> The word "special" gets highlighted again. Note that this time I
>>>> didn't have to enter the highlight command to get the highlighting.
>>>
>>>> I would be especially interested if anyone who runs Debian Lenny would
>>>> try the above test.
>>>
>>> Is Debian Lenny the same as Debian 6? I don't use Debian, but I have
>>> VM's of Debian 5 and 6 for testing things. Under 6 is where I observed
>>> the BufRead problem.
>>
>> Debian 6 is squeeze , Debian 5 is lenny.
>
> Works the same on Lenny for me as it did on Squeeze.
>
>
>>> I'm not sure which parts of this are necessary, but the following
>>> works for me. Using your example with the 'a' and 'b' files, but
>>> moving 'a' to 'a.myfile' (so it can be detected by extension):
>>>
>>> 1. Change your autocmd for detection from:
>>>
>>> (old:) autocmd BufReadPost,BufNewFile *.myfile source ~/myfile.vim
>>>
>>> to, either:
>>>
>>> i. if you *really* want to keep it in vimrc (for some reason -- not
>>> recommended, but it worked fine in testing):
>>>
>>> aug filetypedetect
>>> autocmd BufReadPost,BufNewFile *.myfile setf myfile
>>> aug END
>>>
>>> ii. or just put it in ~/.vim/ftdetect/myfile.vim (where you don't
>>> need the augroup wrapper):
>>>
>>> au BufReadPost,BufNewFile *.myfile setf myfile
>>>
>>> " au is short for :autocmd
>>> " setf is short for :setfiletype
>>>
>>> 2. And create a file ~/.vim/syntax/myfile.vim containing just the
>>> following two lines:
>>>
>>> syn match special /special/
>>> hi special term=bold cterm=bold
>>>
>>> Then it's properly detected for me under Debian 6.
>>
>> Thanks but if these are the alternatives then it's simpler just to
>> reexecute the syntax commands every time the buffer is loaded.
>
> Maybe I'm missing something, but my suggestion is simpler than (or at
> worst "as simple as") what you're already doing. And it has the benefit
> of being better-contained: All your Vim-related settings are in your
> ~/.vimrc file and ~/.vim directory (and its subdirs).
>
>
> = What you said you were doing: =
>
> 1. in your .vimrc (1 line):
>
> autocmd BufReadPost,BufNewFile *.myfile source ~/myfile.vim
>
> 2. in ~/myfile.vim (6 lines of code):
>
> if exists("b:myfile")
> finish
> endif
>
> let b:myfile = 1
> syntax match special /special/
> highlight special term=bold cterm=bold
>
>
> = What you could be doing (one version): =
>
> 1. in your .vimrc (3 lines):

these 3 lines actually belong in ~/.vim/filetype.vim (for Unix) or in
~/vimfiles/filetype.vim (for Windows) or in $VIM/vimfiles/filetype.vim
(for access by any user, on any OS) — in all cases, create missing
directories as you go along. The "other version" below (replacing
filetype.vim by ftdetect/myfile.vim and doing away with the augroup,
which Vim sets before sourcing everything in the ftdetect directory)
would also work.

This way this autocommand will be correctly forgotten and remembered
back if ever you do ":filetype off" and later ":filetype on".

See ":help new-filetype".

>
> aug filetypedetect
> au BufReadPost,BufNewFile *.myfile setf myfile
> aug END
>
> " The aug[roup] might not be necessary, but it makes management easier
>
> 2. put ~/myfile.vim into a different directory ( ~/.vim/syntax/ ) and
> remove all but the last two lines (2 lines):
>
> syntax match special /special/
> highlight special term=bold cterm=bold
>
>
> = What you could be doing (the other version): =
>
> 1. in ~/.vim/ftdetect/myfile.vim (1 line):
>
> au BufReadPost,BufNewFile *.myfile setf myfile
>
> 2. put the last two lines of ~/myfile.vim into ~/.vim/syntax/myfile.vim
> (2 lines):
>
> syn match special /special/
> hi special term=bold cterm=bold
>

Best regards,
Tony.
--
"When I get real bored, I like to drive downtown and get a great
parking spot, then sit in my car and count how many people ask me if
I'm leaving."
-- Steven Wright

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