RE: list-buffers by buffer type

[Drew Adams]

> I'd like to have several buffer lists, each dedicated to a 
> file type, e.g., an "org-list," an "el-list," etc., to tidy
> up and better navigate the buffer ring.
> 
> Wondering if anything like this already exists before diving into
> development myself.

Here are two things that might help, depending on what you really want to do.
Others will no doubt offer more suggestions.

1. Ibuffer (command `ibuffer') can list buffers in groups according to type, and
let you operate on them etc.  Ibuffer comes with Emacs out of the box.

2. The buffer commands in Icicles (visiting/switching, killing, whatever) let
you access buffers by type in various ways: files only, same-mode,
same-or-derived-mode, same-frame.  In addition, they let you use on-the-fly keys
to remove buffers in given modes etc. from the list of completion candidates.

http://www.emacswiki.org/cgi-bin/wiki/Icicles


Here is the (long) doc string for `icicle-buffer' (`C-x b' in Icicle mode), for
more info.  This command happens to be a multi-command (you can do things to
multiple buffers in the same invocation) that allows multi-completion input (in
this case, match the buffer name and/or buffer content).

,---- icicle-buffer ---
|
| Switch to a different buffer, whose content contains a regexp match.
|
| By default, Icicle mode remaps all key sequences that are normally
| bound to `switch-to-buffer' to `icicle-buffer'.  If you do not want
| this remapping, then customize option `icicle-top-level-key-bindings'.
| 
| Completion candidates are two-part multi-completions, with the second
| part optional.  If both parts are present they are separated by
| `icicle-list-join-string' ("^G^J", by default).
| 
| The first part is matched as a regexp against a buffer name.
| The second part is matched as a regexp against buffer content.
| Candidates that do not match are filtered out.
| 
| Your minibuffer input can match a buffer name or buffer content, or
| both.  Use `C-M-j' (equivalent here to `C-q C-g C-j') to input the
| default separator.
| 
| For example:
| 
| To match `foo' against buffer names, use input `foo'.
| To match `bar' against buffer contents, use input `C-M-j bar'.
| To match both, use input `foo C-M-j bar'.
| 
| Only the matching buffer names are shown in *Completions*, and only
| the chosen buffer name is returned.  The actual content matches are
| unimportant anyway: content matching is used only to filter
| candidates.
| 
| This is a buffer-switching command.  If you instead want to navigate
| to text searched for in buffers then use `icicle-search'.
| 
| The buffer-name portion of completion candidates is as follows,
| depending on the prefix arg:
| 
| * No prefix arg: all buffers
| * Numeric arg > 0: buffers visiting files or directories (Dired)
| * Numeric arg < 0: buffers associated with the selected frame
| * Numeric arg = 0: buffers with the same mode as the current buffer
| * Plain prefix arg (`C-u'): buffers with the same mode as current, or
|   with a mode that the current mode is derived from
| 
| For Emacs 23 and later, the default values (via `M-n') are the
| (buffer-name components of the) first four completion candidates
| (respecting the prefix argument).
| 
| You can use these additional keys during completion:
| 
| * `C-x m'     Visit a bookmarked buffer (only if you use Bookmark+).
| * `C-x C-m -' Remove candidate buffers whose mode is derived from a
|               given mode.  Repeatable.  (`C-m' = `RET'.)
| * `C-x M -'   Remove buffers in a given mode.  Repeatable.
| * `C-x C-m +' Keep only buffers in a mode derived from a given mode.
| * `C-x M +'   Keep only buffers in a given mode.
| * `S-delete'  Kill the buffer named by a completion candidate.
| 
| These options, when non-nil, control candidate matching and filtering:
| 
|  `icicle-buffer-ignore-space-prefix-flag' - Ignore space-prefix names
|  `icicle-buffer-extras'             - Extra buffers to display
|  `icicle-buffer-match-regexp'       - Regexp that buffers must match
|  `icicle-buffer-no-match-regexp'    - Regexp buffers must not match
|  `icicle-buffer-predicate'          - Predicate buffer names satisfy
|  `icicle-buffer-sort'               - Sort function for candidates
| 
| For example, to show only buffers that are associated with files, set
| `icicle-buffer-predicate' to (lambda (buf) (buffer-file-name buf)).
| 
| Option `icicle-buffer-require-match-flag' can be used to override
| option `icicle-require-match-flag'.
| 
| Option `icicle-buffers-ido-like' non-nil gives this command a more
| Ido-like behavior.
| 
| See also command `icicle-buffer-no-search', which is `icicle-buffer'
| without the multi-completion behavior that searches buffer content.
| 
| See also command `icicle-buffer-config', which lets you choose a
| configuration of user options for commands such as `icicle-buffer'.
| 
| Note: The prefix arg is tested, even when this is called
| noninteractively.  Lisp code can bind `current-prefix-arg' to control
| the behavior.
| 
| Read input, then call `switch-to-buffer' to act on it.
| 
| Input-candidate completion and cycling are available.  While cycling,
| these keys with prefix `C-' are active:
| 
| `C-mouse-2', `C-return' - Act on current completion candidate only
| `C-down', `C-wheel-down' - Move to next completion candidate and act
| `C-up', `C-wheel-up' - Move to previous completion candidate and act
| `C-next'  - Move to next apropos-completion candidate and act
| `C-prior' - Move to previous apropos-completion candidate and act
| `C-end'   - Move to next prefix-completion candidate and act
| `C-home'  - Move to previous prefix-completion candidate and act
| `C-!'     - Act on *all* candidates, successively (careful!)
| 
| When candidate action and cycling are combined (e.g. `C-next'), user
| option `icicle-act-before-cycle-flag' determines which occurs first.
| 
| With prefix `C-M-' instead of `C-', the same keys (`C-M-mouse-2',
| `C-M-RET', `C-M-down', and so on) provide help about candidates.
| 
| Use `mouse-2', `RET', or `S-RET' to finally choose a candidate, or
| `C-g' to quit.
`----

What that does not mention is that you can also sort buffer candidates in
multiple ways on the fly (cycle sort orders with `C-,'), which can be helpful
when cycling among them.  This includes sorting by:

. last access
. size
. major-mode name
. mode-line major-mode name
. file name or process name
. previous use alphabetically
. last use as input
. alphabetical by content-part match
  (the multi-completion second part)

HTH.