Re: buffer:// under home directory

[Katsumi Yamaoka <yamaoka@xxxxxxx>]

In [emacs-w3m : No.12018] Kevin Ryde wrote:
> With recent debian i386 emacs 24.3 and the current cvs w3m, if you have
> a file foo.html in your home directory then

>     M-x find-file ~/foo.html        # into buffer foo.html
>     M-x w3m-browse-url buffer://foo.html

> gets

>     Cannot retrieve URL: file://~/foo.html

> default-directory starts with a "~" when under the home directory which
> it seems is no good for file://.

> An expand-file-name per below does the trick.

I see what the patch does, but don't see why default-directory gets
"~/":

emacs -Q -batch "~/foo.html" -eval '(message "%s" default-directory)'
 => /home/yamaoka/

Because of this, I don't get such an error.  It is of no importance,
though.

> But then I wondered if perhaps

>     (buffer-file-name (get-buffer ...))

> would help if the buffer name isn't the filename, eg. foo.html<2>.

Indeed.

> Is buffer:// a documented feature?  I suppose it could do something like
> w3m-region to take the buffer content instead of the file content in
> case you haven't saved, or for a non-file buffer.  But perhaps it's not
> that sophisticated yet.

The buffer: scheme is of emacs-w3m internal; Aota-san created it
in response to a question I posted in August 2008.  My question
was how to follow a name anchor within an html mail, that contains
a link <a href="#a">...</a> and an anchor <a name="a">...</a>.
There was no way to express the place of such an anchor, that
exists in an Emacs buffer, until then.

I haven't been taking part in the development of that feature,
so I don't know how it is now.  But I believe the door is open
for further improvements.  (Isn't it you? ;-)

> I struck this when tinkering with a way to have w3m preview html while
> editing, and perhaps rendering buffers like a tar file member if
> browsing source archive etc.  I made a copy to a temp file, but that
> loses the current directory for relative links.  Perhaps there's
> something better already which I don't know.

I usually use `M-x w3m-buffer' to preview the html source that
I'm editing.  Undo makes it revert to the source.