Windows Terminal version

1.20.3131.0

Windows build number

10.0.19045.3448

Other Software

No response

Steps to reproduce

Originally posted in #16097 (comment)

1. Set display scaling to 100%

2. Run OpenConsole or WT

3. Set font to Consolas

4. Set font size to:

   • 34 or smaller for OpenConsole, e.g. 20
   • 19 or smaller for WT, e.g. 12

5. Run something to showcase new underlines, e.g. this script

@echo off

echo 4:1 �[4:1;58:2::255:000:000mtest�[m
echo 4:2 �[4:2;58:2::255:255:000mtest�[m
echo 4:3 �[4:3;58:2::000:255:000mtest�[m
echo 4:4 �[4:4;58:2::000:255:255mtest�[m
echo 4:5 �[4:5;58:2::255:000:255mtest�[m

pause

- where � is \x1b, or whatever else you might have.

Expected Behavior

Clearly visible underline styles, curly in particular, e.g.:

Actual Behavior

Curly is rendered as single in both OpenConsole and WT:

OpenConsole also renders double underline as single, which may or may not be related.

Other terminals, e.g. wezterm, seemingly have no issues with even smaller sizes:

Technically it's not too small if the wave height is at least 2 pixels:

Additionally, OpenConsole with even smaller sizes, e.g. Consolas 15, doesn't render anything but "double" at all:

Technical limitations are understandable, but, assuming that the key selling point of this feature is spellchecking, any ugly/incorrect/clipping/overlapping rendering would be better than nothing at all.