Irreal

Marcin Borkowsi has a nice post on how to capture the current file’s location and copy it to the system clipboard. It’s just what you need for sharing information about data in a file with a colleague. By file location he means the path to the file and the line number within that file.

That doesn’t seem too hard but there are some wrinkles. First of all you want the absolute line number within the file not just the number of the line visible in the buffer. That’s pretty easy but the second problem is a bit trickier.

Sometimes, just the name of the file is not enough. It may be that two files within a project have the same name but lives under a different subdirectory. Your first thought is probably to capture the full path to the file but that isn’t optimal either. As Borkowski says, there’s no point in showing the full path on his machine. What’s needed is the path relative to the current project.

That means the path relative to the current VC repository. It’s pretty easy to get that with the vc-root-dir function. Borkowski has some code that captures the file path and line number and copies it to the system clipboard. It’s simple and can be copied and used as is or modified to meet your particular needs.

The post is definitely worth a read if only to discover how to deal with the various issues.

UPDATE [2022-06-26 Sun 14:40]: Added missing link to Borkowski’s post.

A really powerful Emacs feature for those who know a bit of Elisp in the ability to advise functions. Historically, the defadvice macro allowed the specification of code to run before, after, or around a function call. It’s really handy for modifying the action of a function without changing the function itself or getting into the details of how a function works. I have advice for 7 functions in my init.el, an indication that it’s more useful than you might think.

The defadvice macro has been obsoleted by the newer and more flexible advice-add and add-function macros. You’ll usually want to use advice-add because it works in more situations. The new macros support a finer grained specification of where the advice is to be applied.

Kaushal Modi over at A Scripter’s Notes has an excellent post that explains all the methods of specifying where the advice will operate. These methods are called “advice combinators”. Modi has what are essentially railway diagrams that illustrate the operation of each of the combinators. They’re an easy way of understanding what each of them does. He also has a summary table that describes in words how each of them works.

You should also take a look at the built-in add-function documentation that shows the new function that is created for each of the combinators.

Modi’s post is the best explanation of using advice that I’ve seen. You should definitely take a look at his post to see what’s possible.

Vivek Haldar has an observation about the expected lifetime of Emacs:

Safe to say that at this point #emacs has gone Lindy.https://t.co/HjsfWmE3ug

— Vivek Haldar (@vivekhaldar) June 12, 2022

The Lindy Effect postulates that the longer some (nonperishable) entity has existed, the more likely that it will continue to exist. It’s a bit more technical so follow the link to Wikipedia if you want the details.

Nothing lasts forever, of course, so even the mighty Emacs will eventually fade away but not, if you believe in Lindy’s law, anytime soon. It make sense if you think about it: the fact that Emacs has lasted as long as it has means that it’s meeting the needs of its users and continuing to adapt to new needs so its chances for continued support from its current users and its being embraced by new users is good.

This week there were two excellent posts on highlighting in Emacs. The first was Marcin Borkowski’s post, Highlighting and de-highlighting things. He covers most of highlighting commands but not their default keybindings.

When I first saw Borkowski’s post I thought I’d write about it if only to have a handy guide to the commands. Before I could do that, Mickey Petersen published his post on the same subject matter. That post, Highlighting by Word, Line and Regexp covers a few more commands and includes their bindings. Mickey also explains how to make a set of highlightings persist in a file.

It turns out that even Irreal has plowed this ground but it was so long ago (over a decade) that I’d forgotten all about it. One nice thing about that post is that I provided a table of keybindings at the end but I didn’t cover all the commands. Below is a new table based on Mickey’s list of bindings. The purpose of many of them is obvious from the command name but take a look at Mickey’s post for what all these commands do. If you can remember the Meta+s h part, the commands are pretty mnemonic but, of course, if you use them regularly they’ll get burned into your muscle memory.