Windows Terminal version

1.19.2682.0

Windows build number

10.0.19045.3448

Other Software

No response

Steps to reproduce

1. Download the VT220 soft font from this gist.
2. Open a cmd shell in Windows Terminal.
3. TYPE the soft font file downloaded in step 1.

Expected Behavior

The next prompt that is output should be rendered with that low-res VT220 font, looking something like this:

Actual Behavior

It appears that some of the characters are only partially downloaded, and some haven't been downloaded at all, so I'm seeing this:

If you look at the contents of the font file, you'll see that it's defined as a series of DECDLD sequences, so it's downloading 24 sets of 4 characters, rather than a single 94 character set. I think that's part of the reason for the failure, because fonts that aren't chunked like that don't seem to have the problem.

I also noticed that it only happens in a cmd shell, but not in PowerShell or a WSL bash shell. My guess is that the other shells are buffering their output in a way that hides the problem. It's also possible there is a timing factor, but the cmd shell failure is easily reproducible for me.

And as far as I can tell, the problem was introduced in PR #15991. The commit prior to 41f7ed7 was working as expected.