Terminal: ConPTY Passthrough mode

Created on 16 Jul 2019 · 3Comments · Source: microsoft/terminal

I've discussed this a couple times on different threads before, but I think I never made a real issue for it.

The idea of conpty passthrough mode is that a commandline client application that _knows_ it's only going to use VT sequences (and __not__ the API) to modify the console could set a special mode, ENABLE_PASSTHROUGH_MODE. If conpty is active, the console would then _stop_ rendering itself over conpty, and anything that was written to the console would go straight to the terminal.

This would work especially well for something like wsl, where it's only ever going to be talking VT.
It would _not_ work for cmd.exe, because of cmd.exe's heavy reliance on the API.
Windows Powershell again needs the API pretty heavily, but maybe Powershell Core, which is cross-platform, could make use of it.

This has some rough edges that need to be sorted out.

[ ] What happens when the app exits, and passthrough mode is turned off? The terminal and conpty's buffers would not be equivalent anymore!
- I've been toying with the idea of having conpty both pass the sequences through, and also process them itself, so that the terminal and conpty stay in sync.
[ ] What happens when someone tries to call Console API's in passthrough mode?
- I'm thinking we just cause them to fail. All save for Get/SetConsoleMode and reading input / writing output.
- We'll also probably need to be able to read resize events.

This needs a real spec written, but it probably needs prototyping done before that.

Area-Server Issue-Feature Needs-Triage Product-Conpty Resolution-Duplicate

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