Bind markdown-insert-list-item to M-RET rather than M-<return> #317
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This follows what e.g. org-mode and tex-mode do:
lisp/org/org.el: (org-defkey org-mode-map (kbd "M-RET") #'org-meta-return)
lisp/textmodes/tex-mode.el: (define-key map "\M-\r" 'latex-insert-item)
Long story short (but hopefully accurate):
- <return> refers to the physical "⏎" function key;
- terminals do not tell applications that a function key was pressed,
rather they send a character sequence;
- so on terminals, M-<return> cannot work;
- RET ≡ \r is not an actual key, but rather the control character
emitted by pressing Control-M in a terminal;
- on graphical displays, Emacs automatically translates <return> into
RET if there is no binding for <return>.
Using M-RET rather than M-<return> allows the following things:
1. the binding works on terminals[^1];
2. C-M-m now also works as an alternative (… which was my initial
motivation to investigate this).
Sources and gory details:
- (emacs) Keymaps
> Most modern keyboards have function keys as well as character
> keys. Function keys send input events just as character keys
> do, and keymaps can have bindings for them.
>
> …
>
> On text terminals, typing a function key actually sends the
> computer a sequence of characters; the precise details of the
> sequence depends on the function key and on the terminal type.
- (emacs) Named ASCII Chars
> Emacs can distinguish these two kinds of input if the keyboard
> does. It treats the special keys as function keys named ‘tab’,
> ‘return’, ‘backspace’, ‘linefeed’, ‘escape’, and ‘delete’.
> These function keys translate automatically into the
> corresponding ASCII characters _if_ they have no bindings of
> their own.
>
> If you do not want to distinguish between (for example) <TAB>
> and ‘C-i’, make just one binding, for the ASCII character
> <TAB> (octal code 011). If you do want to distinguish, make one
> binding for this ASCII character, and another for the function
> key ‘tab’.
>
> With an ordinary ASCII terminal, there is no way to distinguish
> between <TAB> and ‘C-i’ (and likewise for other such pairs),
> because the terminal sends the same character in both cases.
- Xah Lee:
- <http://ergoemacs.org/emacs/emacs_key_notation_return_vs_RET.html>
- <http://ergoemacs.org/emacs/keyboard_shortcuts.html>
- <http://ergoemacs.org/emacs/keystroke_rep.html>
- a *scratch* buffer:
(kbd "RET") ; "^M"
(kbd "\r") ; "^M"
(kbd "C-m") ; "^M"
(kbd "<return>") ; [return]
- on X:
C-h c ⏎ ; RET (translated from <return>) runs the command newline
- on a TTY:
C-h c ⏎ ; RET runs the command newline
[^1]: Provided the terminals send the correct character sequences.
This is not always straightforward. Here are the results of pressing
Alt-⏎ on three different terminals:
- on a TTY: M-RET
- on Terminator: C-M-j
- on XTerm: toggles fullscreen
With this .Xresources snippet:
XTerm.vt100.translations: #override \n\
Alt <Key>Return: insert-eight-bit()
XTerm also sends M-RET.
The test originally checked for M-<return> unconditionally:
(ert-deftest test-markdown-insertion/list-item-bound-keys ()
"Test that `markdown-insert-list-item' is bound to M-RET and equivalents."
(markdown-test-string "- foo"
(goto-char (point-max))
(execute-kbd-macro (read-kbd-macro "M-RET bar C-M-m baz M-<return> quux"))
(should (string-equal (buffer-string) "- foo\n- bar\n- baz\n- quux"))))
However, this failed when running make test, although it did pass when
run in a graphical Emacs:
emacs -Q
M-x load-file RET markdown-mode.el RET
M-x load-file RET tests/markdown-test.el RET
M-x ert-run-tests-interactively RET test-markdown-insertion/list-item-bound-keys RET
I'm assuming this is due to --batch running things without a window
system.
|
Thanks for the patches! I squashed these, along with an update to CHANGES.md as you suggested, and applied as c0fc524. I agree about the checkboxes–it is based on a template I found somewhere. They aren't mutually exclusive, so a first-order approximation is fine. |
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tl;dr This is consistent with org-mode and tex-mode and fixes the binding for terminals.
Description
<return>refers to the actual function key, which cannot be picked up by Emacs in a terminal. AFAIU this is because terminals translate function keys into character sequences before they tell the application what is going on. So:<return>is translated into RET ≡\r≡^MM-<return>is translated into M-RET ≡\E\r≡^[^MIn graphical frames, Emacs knows that
<return>was pressed, and translates it to RET if there is no binding specifically for<return>; in terminals, Emacs has no idea that<return>was pressed.As a side effect, this change also makes C-M-m insert new list items since C-m ≡ RET ≡ "control character 13".
(The first commit message provides additional
gory detailsexplanations)Related Issue
I did not raise an issue. Let me know if you feel this deserves more discussion; I will open one.
Type of Change
⚠ NITPICKING ⚠ Not sure about some checkboxes:
C-M-m) count as a new feature?M-RET.Checklist
<return>in the documentation; I took a look at the guide and it actually mentionsM-RET, so I guess everything works out?make test).Originally, the test checked for
M-<return>unconditionally:This does not pass when run with
make test, though it does pass when run in a graphical Emacs:I am assuming this is because
--batchdoes not load a window system; hence I added(when display-graphic-p …)before testingM-<return>.