Don't change background color of selected terminal text

[akbyrd]

Type: Bug

Text selection in the terminal seems to render by changing the background color of text. While that seems reasonable on the surface, it does weird things with powerline type features and other highlighting that might be built into the shell. Notice in the second screenshot below that different parts of the powerline are no longer visible nor are the highlights on directories.

Contrast this with Windows Terminal

Perhaps vscode could blend the selection background and foreground colors with the existing colors instead of overwriting them. Or render selection as an overlay.

VS Code version: Code - Insiders 1.86.0-insider (02b9071, 2023-12-08T11:53:10.286Z)
OS version: Windows_NT x64 10.0.19045
Modes:

System Info

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GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	undefined
Memory (System)	31.92GB (20.17GB free)
Process Argv	--crash-reporter-id 22cf4e37-a96e-4ad9-82f0-8715f8e2bf6e
Screen Reader	no
VM	0%

Extensions: none

A/B Experiments

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[Tyriar]

It was actually a pretty big feature to get the behavior working that you're saying you want changed 😅. The overlay option was how it worked before (and actually how it still worked with "terminal.integrated.gpuAcceleration": "canvas") and it was trivial to add as it's simply rectangles drawn on top of the content. Unfortunately it has big accessibility issues as it does nothing to ensure contrast is sufficient, making the text quite unreadable.

The powerline specific "problem" is happening due to the fact that powerline is essentially a hack where it alternates between the background color (which changes with selection) and special characters (which changes to ensure minimum contrast ratio). I have considered making it a little nicer, perhaps by just hiding the powerline symbols completely, but its not clear what the right behavior is here.

We could quite easily make the above do this:

But anything more clever than that may be a little too complex, I'm hesitant to try to track "powerline" state in the cells that simply change their background color.

FWIW I also hit this problem, this is what mine looks like:

[akbyrd]

I would make the case that if background colors in terminal output are supported then having the terminal ever overwrite those background colors is necessarily a problem.

I wouldn't call powerline a hack any more than I would call highlighting directories using a background color a hack. Color conveys information in the same way glyphs do. If I choose to output something in a particular way I don't want that information arbitrarily erased by the terminal.

Either the background color is reserved for selection highlighting or it's not. If it's not reserved and users are allowed to choose background colors to convey information, then the terminal does not have the authority to erase that entirely. Munge based on user settings yes, erase no.

As far as solutions, I can think of a few possibilities:

1. Modify existing background colors instead of overwriting them. This is what other terminals seem to do and seems like a happy middle ground.

2. Blend the selection background color and the existing background color. It may not meet the desired contrast though.

3. Allow the overlay approach to be used. Between my vscode theme and my terminal configuration I have enough control to maintain the level of contrast I need.

4. Treat "terminal.integrated.minimumContrastRatio": 1 as an opt-out and don't overwrite background colors.

[Tyriar]

Thanks for taking the time to put forward the proposals. I'm leaning towards 2 and blending with the selection color @ 50% opacity. Contrast is less of a problem as the foreground changes dynamically due to minimumContrastRatio.

Plus we can have some special logic on the powerline glyphs to also be included in the blending, they already do something similar in how they ignore the minimumContrastRatio requirements as they are seen as background by the user.

[Tyriar]

WIP:

[andreamah]

Tried to verify using the quick-term ohmyposh theme. Not sure if this is the expected result.

[VSCodeTriageBot]

This bug has been fixed in the latest release of VS Code Insiders!

@akbyrd, you can help us out by commenting /verified if things are now working as expected.

If things still don't seem right, please ensure you're on version 3dea5cb of Insiders (today's or later - you can use Help: About in the command palette to check), and leave a comment letting us know what isn't working as expected.

Happy Coding!

[akbyrd]

The behavior on insiders doesn't quite match @Tyriar's WIP screenshot, which matches my desired behavior. In practice powerline background colors are still being overwritten.

[Tyriar]

@akbyrd @andreamah can you share your settings file? Still seems to work as expected for me 🤔

[akbyrd]

I'm able to repro in latest insiders (5d34400) with no VS Settings, no pwsh config (except loading oh-my-posh), and default oh-my-posh config. Maybe related to oh-my-posh if you're using a different powerline implementation?

pwsh config

oh-my-posh init pwsh | Invoke-Expression

[Tyriar]

Can repro with oh-my-posh, looking into it

[andreamah]

Looks like it works 👍