mintty and modifier keys

Ryan Johnson
Thu Jul 19 20:32:00 GMT 2012

On 19/07/2012 3:06 PM, Andy Koppe wrote:
> On 19 July 2012 16:37, Ryan Johnson wrote:
>> Hi all (mostly Andy),
>> I notice that mintty 1.1 handles certain key combinations differently than
>> xterm:
>> ctrl+enter produces 0x1e (RS) vs. CR in xterm
>> alt+enter produces ESC CR vs. nothing at all in xterm
>> ctrl+shift+<letter> emits the unicode C2 control codepoints (0xc281 through
>> 0xc29a); xterm emits the C0 control value as if shift were unpressed.
>> So, two questions:
>> 1. Is there a particular reason for this behavior?
> Yes, I tried to make as many key combinations as reasonably possible
> available to applications without having to enable a special mode. I
> chose ^^ (0x1e) for Ctrl+Enter rather than a multi-character code so
> as to be able to use it in stty settings. Similarly, Ctrl+Backspace
> sends ^_ (0x1f).
... and then those get encoded with utf-8 as appropriate. Got it.

>> Perhaps rxvt or some other non-xterm terminal emulator does it?
> Nope, they're mintty-specific.
Fair enough. They seem like reasonable choices, especially compared with 
xterm (where some key combos send nothing at all!)

>> 2. Is there documentation somewhere of what convention mintty follows for
>> the various special cases?
> Yep:
> See also this on how those keycodes could be put to use in the stty settings:
Nice. I didn't know that was there. How hard would it be for me to get 
ncurses to grok these codes?

>> (these questions are partly triggered by frustration at shift+enter not
>> working, which lead to me finding a reasonably sane proposal to fix these
>> kinds of terminal woes [1]; I was surprised to find that mintty can already
>> distinguish some key presses that xterm can't)
>> [1]
> Hmm, that basically describes xterm's "modifyOtherKeys" mode, which
> mintty supports too. This can be enabled with the sequence "\e[>4;1m".
> (That's for level 1. There's also level 2, enabled with "\e[>4;2m",
> where the suggested CSI u keycodes are sent even for Ctrl+letter
> combinations.)
... except neither mode makes any visible difference in xterm-281-1: 
shift+enter and ctrl+enter both continue sending CR, and alt+enter still 
does nothing (level 1); ctrl+a still sends ^A. Mintty works as 
advertized on both counts, yet another reason to like mintty, I guess.


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