I'm once again an Emacs convert (spoken multiple times since this was first posted). I used Emacs a fair bit back in 2011 as my main editor (when
vimpulse was becoming a viable alternative to native Vim and I forced Emacs upon myself for as long as I could), I even wrote a few posts about extending it. But eventually it was starting to feel sluggish with everything I was throwing at it and I had to give it up (looking back, it was probably a bad minor-mode or two).
However in the time I was away from Emacs the eco-system has really modernized. There are various starter kits for getting up and running quickly with sane defaults in CURRENTYEAR, we have
package.el since Emacs 24, along with MELPA as a maintained repository of elisp packages, and even a set of decent color themes! And of course I can't leave out evil (the extensible vi layer) which I can't do without.
There were a mountain of features I missed from Emacs while in Vim-land (although there are plenty of ports both ways), but I want to share the killer feature for me since picking it up again: narrowing, and indirect buffers.
Emacs has a concept of narrowing buffers, which restricts your view of a buffer to an area that you specify, which is great for focusing on a particular method or for running commands that operate on the entire buffer. You can also change your major mode while in a narrow buffer, which is great for editing code in the middle of an email (for example).
I begin by opening the HTML file, and split Emacs into three windows. Then in each window I select the appropriate code and run the
narrow-to-region command, but oh no! This actually narrows all three of the editor windows at once, when I only wanted to narrow one…
This is where indirect buffers come in. From the docs:
"An indirect buffer shares the text of some other buffer, which is called the base buffer of the indirect buffer. In some ways it is a buffer analogue of a symbolic link between files."
By turning each window view into an indirect buffer, we will be able to narrow them separately, all we need to do is run
clone-indirect-buffer on each window to create an indirect buffer from the underlying buffer. Then we can use the
narrow-to-region command again, only this time each window will remain separated as intended. Once the panes are narrowed they can each have their own major-mode set too. When done you can simply kill the buffer like you would with a regular file.
A Handy Shortcut
Of course this wouldn't be much of an Emacs post without some lisp, so here is a shortcut command that combines the cloning and narrowing:
(defun narrow-to-region-indirect (start end) "Restrict editing in this buffer to the current region, indirectly." (interactive "r") (deactivate-mark) (let ((buf (clone-indirect-buffer nil nil))) (with-current-buffer buf (narrow-to-region start end)) (switch-to-buffer buf)))