New console screen buffer contains scroll from main buffer

[2trvl]

Windows Terminal version

1.20.11781.0

Windows build number

10.0.19045.4651

Other Software

hAlternateConsoleOutput = create_console_screen_buffer(
    GENERIC_READ | GENERIC_WRITE,
    FILE_SHARE_READ | FILE_SHARE_WRITE,
    CONSOLE_TEXTMODE_BUFFER
)

Steps to reproduce

Enter commands in the main buffer until scrolling appears. Create a new console screen buffer.

Expected Behavior

Empty console screen without scrollback

Actual Behavior

Scroll up to the top and see the commands you entered in the main buffer.

In some cases, the last command also goes to a new screen buffer.

[DHowett]

This may have been addressed by #17510; Can you try the Canary version of Terminal?

[2trvl]

In this case I see full compliance between virtual codes and console API methods, good job.