vscode: Black blocks in terminal at every underscore

I was seeing this earlier in the week doing TPIs on Linux… but now I don’t today so seems fixed.

Found the issue. This https://github.com/xtermjs/xterm.js/blob/b68f82078b5f6fb336afd39a98685e489cca7c79/addons/xterm-addon-webgl/src/atlas/WebglCharAtlas.ts#L563 clearRect ends up drawing a #000000FF background instead of the natural color, so the full temp canvas texture is used which explains the odd size of the rectangle.

I think I can confirm the conclusion reached by @yume-chan. When using the desktop app in Ubuntu 22.04, the font Droid Sans Mono presents the same behavior. Using other fonts the underscore is rendered correctly.

It’s called “DejaVu Sans Mono” version 2.37

I’m using macOS at the moment but I asked a couple of colleagues to test.

• Both Firefox 100.0.2 (64-bit) and Chrome 103.0.5060.53 (Official Build) (64-bit) are affected.
• The VSCode desktop app is not affected.
• This happens both on Fedora 34 using X11 and KDE, and Ubuntu 20.04 with a standard GNOME desktop.
• Disabling acceleration in Firefox (i.e. setting layers.acceleration.disabled to true) doesn’t help.
• Turning terminal.integrated.gpuAcceleration off or setting it to canvas fixes the issue.

This is on Lenovo laptops with Intel graphics. lspci reports this on the Fedora machine:

00:02.0 VGA compatible controller: Intel Corporation WhiskeyLake-U GT2 [UHD Graphics 620]

And this on the Ubuntu one:

00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (Whiskey Lake)

This is a snippet from glxinfo’s output:

OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) UHD Graphics 620 (WHL GT2)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 21.2.6
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

Hope this helps!