Emacs M- (Alt) key not working for some combinations inside the terminal

[Themistoklis]

Environment

Windows build number: 10.0.18362
Windows Terminal version (if applicable): 0.11.1251.0

Any other software?

• emacs
• wsl (I haven't tried emacs for Windows inside the Windows Terminal)

Reproduce

1. Open emacs in WSL using Windows Terminal.
2. Use the describe key (C-h k or M-x describe-key)
   • M-left
   • M-right

I think there might be other combinations that do not work but I didn't try them all.

Expected result

Using the normal terminal with WSL or MinTTY for WSL:

• M-left -> emacs detects it and displays M-left and the function attached
• M-right -> emacs detects it and displays M-right and the function attached

Result inside the Windows Terminal

• M-left -> nothing happens
• M-right -> nothing happens

Note

C-right or C-left work correctly for example.

Wheel scroll don't work either, it is not captured and passed to emacs. The terminal scrolls normally (which it shouldn't) and you get out of emacs boundaries. See other xterm related issues.

[DHowett-MSFT]

Thanks for the report! There's two things here.

1. I believe this is caused by the default pane motion bindings on alt+arrow. You can unbind them in your local settings file.
   • (we know that keyboards are tight real estate. I'm sorry about us stomping on inputs that some applications care about!)
2. This sounds like "alternate scroll" mode (DECSET 1007). Conhost supports it, and so does Terminal, but we're missing one critical bit of infrastructure. Terminal doesn't know that an "alternate buffer" is in use, and so will not use alternate scroll. That'll be ConPTY: pass through requests for the alt buffer #381.

[Themistoklis]

Thanks for the input.

1. Unbinding alt+up/down/left/right worked fine (I didn't even realize they were bound to something)
   • Suggestion 1: put all unbound-able keybindings inside the settings file
   • Suggestion 2: like for the scroll, redirect keybindings to the buffer instead of using them in Terminal under the "alternate buffer" mode
2. //

[DHowett-MSFT]

Good idea in number 2 for the alternate buffer. We'd need to spec that, because it'll be a big departure from how other terminals work.

All of the unbindable keys actually are available in the settings file. We've unfortunately failed to document it appropriately:

[jiucenglou]

It seems that <Alt>-<Shift>-<Enter> does not work with Windows Terminal. Could you suggest the solution ?