Terminal: ConPTY does not translate arrow keys with +ENHANCED_KEY in their modifiers

[SummerLife]

Today I updated Windows to 1903 and found that a python program I had written earlier ran incorrectly.

The brief test code is as follows:

import msvcrt
ch1 = msvcrt.getch()
ch2 = msvcrt.getch()
print(ch1)
print(ch2)

When I run the above code in native powershell, press ← key when collecting characters, and it will print b'\xe0' B 'K', and the same code running in the terminal returns b'\x00' b'K'.
This problem didn't appear in the last version of Windows (18.xx).

• OS Version: windows 10 1903
• terminal version : preview

Steps to Reproduce:

1. Run this code on the powershell terminal of vscode using Python3
2. press ← key，record print information
3. Run this code directly from your powershell on Windows using Python3
4. press ← key，record print information
5. Look at different outputs

A related issue on vscode：

https://github.com/microsoft/vscode/issues/78682

Thank you for your attention.

[SummerLife]

Any help?

[zadjii-msft]

We believe this is a bug, but we're not really sure what the root cause is. Presumably something about how ConPTY builds INPUT_RECORDs compared to how we build them from window input directly.

We're also _very_ confused that ch1 in the above sample is b'\xe0' b'K' - we _really_ didn't expect that. So we just need someone to really debug into this.

[SummerLife]

Before the 1903 version of Windows, the return value was b'\xe0' b'K', which became b'\x00' b'K' when upgraded to 1903, causing some programs to fail.

[DHowett-MSFT]

Eureka!

Under normal circumstances:

• ↓ wch:0x0000 '\0' mod:EnhancedKey (0x00000100) repeat:0x0001 vk:0x0025 vsc:0x004b

Under ConPTY:

• ↓ wch:0x0000 '\0' mod:None (0x00000000) repeat:0x0001 vk:0x0025 vsc:0x004b

Critical here is mod:EnhancedKey. ConPTY isn't setting it. I'm not sure how it could know _to_ set it, because we usually derive its value from the Win32 window proc...
ConPTY only sets it if there's a modifier _on_ the arrow key.

The documentation on ENHANCED_KEY says:

Enhanced keys for the IBM® 101- and 102-key keyboards are the INS, DEL, HOME, END, PAGE UP, PAGE DOWN, and direction keys in the clusters to the left of the keypad; and the divide (/) and ENTER keys in the keypad.

[DHowett-MSFT]

And now that we have a root cause, I'm finally renaming this issue.

[DHowett-MSFT]

Yanking the triage tag after a discussion with @carlos-zamora and @zadjii-msft. Carlos is down to look at this :smile:

[wmcbrine]

This also prevents PDCurses from recognizing the cursor keys, as I just discovered.

[SummerLife]

This also prevents PDCurses from recognizing the cursor keys, as I just discovered.

So, the program written before runs unnormal.

[msftbot[bot]]

:tada:This issue was addressed in #5021, which has now been successfully released as Windows Terminal Preview v0.11.1121.0.:tada:

Handy links:

• Release Notes
• Store Download

[thomthom]

Thank you! I can finally get rid of cmder now and switch to Terminal full time! 🎉

[DHowett-MSFT]

Great!