Ihor Radchenko <yanta...@gmail.com> writes:
> Tim Cross <theophil...@gmail.com> writes: > >> Ihor Radchenko <yanta...@gmail.com> writes: >> >>> Also, it appears to me that we may keep losing terminal-incompatible >>> keys in future unless we provide some mechanisms to check terminal >>> compatibility automatically. Any ideas? >>> >> >> No ideas on this. Problem being I don't think there is anything like a >> terminfo service which will tell you about what capabilities/bindings a >> terminal emulator has. >> >> Just some thoughts on this - >> >> I fear any such attempt is likely to end up in a game of 'wack-a-mole'. >> While it makes some sense to provide alternative key bindings for Emacs >> running under the GNU Linux console, especially given the limitations >> under the console are well defined and constant, I'm not sure >> we can provide reliable solutions or tests for different terminal >> emulators (which will often 'reserve' various key bindings for their own >> use. This is especially true for more advanced terminal emulators like >> tmux. > > We cannot even handle GNU Linux console now. Technically, man 5 terminfo > describes all the details on how to obtain terminal specs, but I am not > sure how to extract useful information for key binding purposes. Can we > do it programatically? > I probably wasn't clear enough in what I was trying to explain/suggest. I'll try to clarify. I think there are two different issues at play here. Key binding limitations in the Linux console and key handling in different terminal emulators. The first is fundamentally a limitation in the low level kernel terminal driver and not much which can be done except choose alternative key bindings when running under the linux console. The second is more about limitations within the specific terminal emulator program. Some emulators handle this better than others and it will be near impossible to find key bindings which will work across all different terminal emulators unless we restrict which key bindings we use to a much smaller subset, which will inevitably mean many difficult to use or less convenient bindings. This will just make everyone, including those using more capable terminal emulators, suffer less convenient key bindings and key bindings which are significantly different from those used when running native window/GUI version. It would make switching between GUI versions and terminal versions of Emacs even less convenient. As an example, on my Ubuntu 21.10 system, when running Emacs under the Linux console, C-c C-, completely fails. In fact,if you try to do describe key for that combination, it won't work because Emacs never sees the second key press. On the other hand, if I run Emacs inside mate-terminal, Emacs will see C-c , and not C-c C-, (but it does get both key presses). If I run Emacs under xterm, lxterm or uxterm, everything actually works just fine. Describe key will report the correct binding for C-c C-, I don't believe terminfo will be of any help here. If you look at the TERM setting for mate-terminal, uxterm, lxterm and xterm, they will all reference various versions of xterm (often xterm-color or xterm-256color etc). Looking at the terminfo definitions, I cannot see anything with would indicate whether C-, for example is supported or not. I know of no convenient and consistent way to determine if the terminal emulator being used will support things like C-, or not. For the Linux console, I think we can use the TERM environment variable to know when we are running under the Linux console if we want to provide different key bindings for some commands under the Linux console. There is also the possibility you could create a keymap for the Linux console which would configure some of the 'missing' modifier combinations to issue escape sequences which can be used to emulate the modifier behaviour under GUI environment - for example, I think you can create a keymap which will allow C-up/C-dwon/C-left/C-right etc. The question is, how useful will alternative key bindings actually be for the Linux console. I imagine the user base for people who only work under the Linux console is pretty small. For occasional use, the alternative bindings are unlikely to be that useful as it is too hard to change finger memory for occasional use and you probably won't remember the different bindings anyway (I would probably just use M-x command in these situations). For the terminal emulator situation, I believe we should do nothing except provide documentation on how to find or identify an appropriate terminal emulator which will support the key bindings used by orc, such as C-c C-,.
