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4.1.2.6 iTerm Wiki for Emacs

iTerm Wiki for Emacs — Super and Hyper Keys

1. Why getting Super and Hyper working in a terminal is not straightforward

   The reason for this has to do a lot with DEC terminal history and the keys that were available in some of the earliest possible terminals. The DEC terminal became the default basis of emulation for most software.

   Contrast this with the Space-cadet keyboard that influenced the design of Emacs, made for MIT Lisp machines. It included several modifier keys which allowed multiple character sets as well as a large macro space for binding commands to key combinations. Two modifier keys to the left of the space bar on the Space-cadet keyboard include the Super and Hyper keys.

   While insanely useful for the experienced user, fewer people worked on Lisp machines compared to the widespread availability of VT-series character terminals. All command line and serial-terminal interaction you’ll ever find supports VT-100.

   In GUI mode most emacsen will bind the Windows or Option key to Super*U. Or if you’re a Mac user, you might have swapped *Alt and ⌘ so the Meta key is closest to the spacebar and easier to reach.

   When you press a key on your keyboard your terminal emulator will send a character or an escape sequence down the connection. For DEC or xterm terminals, some keys may not send signals. iTerm2 can make use of any key that OSX will respond to and you can customize it to run commands locally, remotely or send signals down the terminal connection to the remote machine.

2. Testing escape codes

   First, connect your remote machine and issue the cat command with no parameters. Depending on your OS, termcap on the remote and the codepage your keyboard is set to, you’ll see either a character or an escape sequence when you type something.

   Let’s see how the Latin letter O works when pressed with modifier keys.

   • When I press o, I get an o.
   • But when I press ALT+o, I get ^[o
   • When I press CTRL+ALT+o, I get ^[^O
   • And when I press SHIFT+ALT+o, I get ^[O

   These combos are being read by the remote machine and being fed to STDIN to cat (and cat is reading them back as output). They’re also the most basic escape sequences, as ^ is the code for COMMAND, and ^[ is for ALT/META, known as the escape sequence ^[ . For terminals and IBM PCs, the ^[ signifies some sort of terminal code, signifying a keypress or some action to be taken on the terminal or the remote. If your keyboard has a D-pad, try hitting <up> <down> <right> and <left>. Usually these will be ^[[A, ^[[B, ^[[C and ^[[D, respectively.

   You can press C-c to get out of cat

   Now let’s try sending a more complicated escape sequence using some keys on your keyboard and fool Emacs on the remote into thinking you pressed a Hyper key combo.

   • Go into your iTerm2 settings for your connection profile.
   • In the Keys panel, let’s set a key combo for Ctrl+⌘+Option+A, which is the three leftmost keys next to the space bar plus the letter A.
   • I’m pretty confident your remote termcap probably does not have an entry for ^[[1;P9, so let’s start off with that code.
   • Your setting should look like this:

     Keyboard Shortcut

     ^+Option+Control+a

     Action

     Send Escape Sequence

     Escape

     [1;P9

   • Let’s get Emacs to listen for this key. Evaluate the following Lisp code in an Emacs session (I took the liberty of adding escapes for the rest of the keys):
   • Now we can bind Hyper to something. Let’s try this:
     • (global-set-key (kbd "H-a") 'dired)
   • Now when you press Ctrl+⌘+Option+A, dired should pop up. Proceed with adding the rest of the keys and escape codes in your iTerm2 setup. Also, you can use the cat command to check your work and ensure that the proper escape sequences are reaching the remote machine.
   • You can also make combinations with Control and META such as C-c H-o with this technique. For C-c H-o you would hit C-c and then release the keys, then Ctrl+⌘+Option+o for the H-o part.
   • Now you can make loads more keybindings for all your favorite Emacs commands.