Unified Interface for Switching Contexts - Switch to Thing

Now I have ditched save-desktop for recentf which gives me a faster startup time but still being able to quickly access my most common files (i.e. those I have most recently opened) I have realised that I would like to have quick access to other Emacs resources after a startup.

This has led me to creating a unified interface of sorts to switch to different contexts through a single keybinding. If you think that sounds vague, well you are correct!, I shall try and explain myself.

save-desktop has served me well for many many years as a quick method to call up my last session including recreating buffers in their last positions and thus repopulating the ibuffer list and re-enabling the default Emacs switch-to-buffer mechanism.

Unfortunately as I am now fiddling around with elisp it means that restarting Emacs has become much more commonplace and I don’t really want to wait around for save-desktop to recreate itself after each reload. In addition there were the odd peculiarities that I could never seem to resolve.

Out of the box recentf has its own basic opening mechanism not tied into anything particularly modern with a list of files populated for selection in a separate buffer, but consult-recent-file solves this by giving me a nice completing-read experience.

So now I can recall my most recent files in a nice completing-read way how about preserving a familiar switching experience, I could bind consult-recent-file to C-x b, hence switch-to-buffer for continuity, but then of course I can’t switch to buffer! should I have separate keybinding for consult-recent-file?, well maybe, but what else would I like to quickly switch to?

Well of course buffers! I shouldn’t get carried away without forgetting the Emacs staple switching mechanism and in fact switch-to-buffer is perfectly fine and is completing-read enabled (I could also use consult-buffer)

Bookmarks! (can I start a sentence like that?). This is a very underrated feature that I have become more accustomed to using and of course the USP being that a bookmark can reference a file, info page, directory, or pretty much anything you would want to access in Emacs. Well that has a separate selection mechanism too via bookmark-bmenu-list which displays a list of existing bookmarks in a separate buffer. Again the brilliant consult-bookmark comes to the rescue converting the bookmark mechanism into a completing-read, but how do I access this list?, another keybinding?, well maybe.

I am also one of those people that switches themes very often, like several times a day, well how do I do this?, load-theme, customize-themes?. Out of the box theme selecting has a separate selection mechanism too which displays a list of existing themes in a separate buffer. Again the brilliant consult-theme comes to the rescue giving a nice completing-read selection mechanism, but how do I access this list?, another keybinding?, well maybe.

So I have four contexts to switch to and I don’t want a single keybinding for each one so can I merge all of these contexts into a single completing-read under a single keybinding, with the completion mechanism of choice performing the heavy lifting to give me a fast unified method of quick switching? (and breathe! 😵‍💫), the answer of course is - “this is Emacs dummy, of course you can!”.

I thought this would also be a perfect opportunity to further my understanding of elisp by tackling this problem myself, which is how I came up with my/switch-to-thing, which is described below:

my/switch-to-thing

The provided Emacs Lisp function `my/switch-to-thing` offers a unified interface within Emacs to quickly switch contexts. It enables a user to perform one of several actions based on the user’s selection from a prompted completion list. The specific actions that can be taken are:

1. Switching to an Open Buffer: If the selection matches the name of an open buffer, the function switches the current window to display that buffer.

2. Opening a Recent File: If the selection matches an entry in the list of recently opened files, that file is opened in the current window.

3. Jumping to a Bookmark: If the selection matches a bookmark’s name, Emacs navigates to that bookmark.

4. Changing the Emacs Theme: If the selection starts with the prefix “Theme: “, the function interprets the rest of the selection as the name of a theme. It then loads and applies that theme.

Here is a break down of its behavior:

• Initialization: It first creates lists of current buffer names (`buffers`), recent files (`recent-files`), bookmark names (`bookmarks`), and available themes formatted with a “Theme: " prefix (`themes`). These lists are then concatenated into `all-options`, forming a comprehensive list of choices for the user.

• User Input: It prompts the user with a “`Switch to:`” message using `completing-read`, offering autocomplete functionality based on the `all-options` list. This prompt also integrates with Emacs’ `file-name-history` for enhanced usability.

• Action Selection: Based on the user’s choice (`selection`), the function uses `pcase` to pattern-match and decide the action:

  • If the selection is an open buffer, it switches to that buffer (`switch-to-buffer`).
  • If the selection is a bookmark, it jumps to that bookmark (`bookmark-jump`).
  • If the selection is prefixed with “Theme: “, it extracts the theme name, converts it back to a symbol, and loads that theme (`load-theme`).
  • If none of the above conditions are met, it interprets the selection as a file path/name and attempts to open it (`find-file`).

This function effectively encapsulates multiple navigation and customization actions within Emacs into a single command, streamlining the user’s workflow by providing a centralized interface for common tasks.

(defun my/switch-to-thing ()
  "Switch to a buffer, open a recent file, jump to a bookmark, or change the theme from a unified interface."
  (interactive)
  (let* ((buffers (mapcar #'buffer-name (buffer-list)))
          (recent-files recentf-list)
          (bookmarks (bookmark-all-names))
          (themes (custom-available-themes))
          (all-options (append buffers recent-files bookmarks
                         (mapcar (lambda (theme) (concat "Theme: " (symbol-name theme))) themes)))
          (selection (completing-read "Switch to: "
                       (lambda (str pred action)
                         (if (eq action 'metadata)
                           '(metadata . ((category . file)))
                           (complete-with-action action all-options str pred)))
                       nil t nil 'file-name-history)))
    (pcase selection
      ((pred (lambda (sel) (member sel buffers))) (switch-to-buffer selection))
      ((pred (lambda (sel) (member sel bookmarks))) (bookmark-jump selection))
      ((pred (lambda (sel) (string-prefix-p "Theme: " sel)))
        (load-theme (intern (substring selection (length "Theme: "))) t))
      (_ (find-file selection)))))