Protesilaos Stavrou (Prot) has another nice video on something that I was vaguely aware of but had never used: conditional abbreviations. As most Emacers know, you can define abbreviations that will expand into another, usually longer or more complicated, string. It can save a lot of time and you can set them to fire automatically or when Tab is pressed right after the abbreviation.
What’s less well known is that these abbreviations can have properties and one of those properties is to specify a function that will tell Emacs whether or not it should expand the abbreviation. Prot gives a few examples of this. In one example, he wants “Welcome” to expand to a French greeting but only if he is using one of the French input methods. Another example expands an abbreviation only if he’s in a certain directory or one of its subdirectories. A third example expands an abbreviation only if a certain minor mode is active.
Those examples might seem like they’d be complicated but they are, in fact, simple, almost trivial. In the call to define-abbrev, you simply give the name of the deciding function in the :enable-function clause. Check out Prot’s video for the details.
I use several abbreviation systems—including abbrev—but this capability in abbrev is especially nice. It’s easy to use and you can make the firing condition as simple or complex as you need it to be.
Prot’s video is 14 minutes, 33 seconds so it should be easy to find time for it. As with all of Prot’s videos, it’s worth the time.