Custom Tabs do not have enough contrast while using certain themes

[s-daveb]

Hello!

Since making the switch to Neovim, I've been thoroughly enjoying VimR over MacVim!

One nagging issue I've had, however, is that the theme I enjoy (everforest) uses a very light color for visual select. Upon switching to VimR, I noticed the custom tabs were much lighter than the built-in neovim tabs.

After looking through issues I discovered that VimR is using selection text color to theme its tabs, rather than the colorscheme's TablineSel highlight group, which was what I expected as a long-time vimmer.

There's probably two ways to solve this:

• Add logic to the Tab view so that for light colors, a darker text is selected
• Match Vim's native behavior and use the tab colors defined in the colorscheme. (The theme authors probably chose contrasting colors. )

As an experiment, and as someone who hasn't worked with a lot of Swift, I decided to try solution 2, not wanting to try to add code to predict good text contrast for every possible vim color scheme.

I will submit a PR in addition to this issue.