Handling transparent BG color when used as FG

[Eugeny]

Nano displays its shortcuts with FG/BG colors reversed:

However, when theme BG is transparent, following happens:

The solution could be to have a separate flag that will render characters with no background as if background were transparent instead of theme.backgroundColor, but will still use the actual color for inverted elements.

[chabou]

I think it could work if alpha is forced to 1 when using background color as inverted foreground color.

[chabou]

Or do you want a new invertedForeground in theme (defaulted to backgroundColor)?

I can make a PR

[Eugeny]

I think having an invertedForeground would be a more flexible solution

[Tyriar]

I think it could work if alpha is forced to 1 when using background color as inverted foreground color.

In the interest of keeping the API simpler/slimmer I think this option would work fine, unless there's a real case where an alpha of 1 doesn't make sense (we already force alpha 1 on cells with background when background transparency is on).

[Eugeny]

@Tyriar if you mean forcing the alpha component of backgroundColor to 1 while keeping its RGB as is, I'm in.

[chabou]

@Eugeny That's what I mean :)

@Tyriar I'll try to work on a PR with this solution soon.

[sukima]

@chabou What is the status of this? How can we help? This issue is blocker for me!

[Tyriar]

@sukima we're just waiting on a PR for this if you want to work on it. The proposal above is to when the bg color is used as the fg then always force alpha to be 1 (opaque). This will need to be handled in both canvas and dom renderers:

• https://github.com/xtermjs/xterm.js/blob/master/src/renderer/TextRenderLayer.ts
• https://github.com/xtermjs/xterm.js/blob/master/src/renderer/dom/DomRendererRowFactory.ts