feat: unified diff colors for legacy colors

[habamax]

Closes #121

[habamax]

Every colorscheme has

;;; "Standard" diff colors
Include: _diff

At the end of template.

Feel free to suggest adjustments to bg colors.

[habamax]

Ah!

@romainl I didn't touch 2 colorschemes: blue and darkblue.

They both have quite nice colors (at least in 256c :) )

I can convert them too if you don't mind or we can leave them as is.

[habamax]

And darkblue is actually also converted :) sorry.

[romainl]

We may have a problem with bold Statement:

[habamax]

I don't have it...

[romainl]

OK, it's a terminal emulator setting.

[habamax]

soften colors a bit:

[habamax]

darkblue

And I am still not sure about blue as of now:

Might be

PS, although it also looks good...

[habamax]

Anyway, I don't mind any other color selection ...

[romainl]

My comments…

• 235/#262626 is not distinct enough from black for the difference to matter so I would simply use ctermbg=16 (256c) and guibg=#000000 (GUI).

• DiffDelete and DiffAdd are way too close too each other in 256c/GUI.

• "green" and "yellow" work relatively well for people with normal vision but they are basically indistinguishable for people with deuteranopia (the most common form of color blindness):

  

• funnily enough, it's "blue" and "green" that are confusing in case of tritanopia (which is very rare):

  

I'm still not sure about how much attention we should give to color blindness since there are relatively inexpensive glasses that supposedly correct that issue. But the lack of contrast between DiffDelete and DiffAdd is bothering.

[habamax]

How about this?

[romainl]

That works very well for normal vision. Great!

[habamax]

Blue difftext clashes with visual of my own colorscheme :(, but that is ok.

[habamax]

@romainl I wanted to propose this kind of change too

[romainl]

Yeah, :qa! was tiring.

[romainl]

FWIW, I just spent some time in master in 16c and the diffs in this branch are a hell of a lot better.

The only slight issue I have is the lack of contrast of black on blue for DiffChange.

I tried with white on blue and sure enough the contrast is stronger, but now it sort of doesn't fit :-(:

@habamax what do you think?

[habamax]

we can have white fg on 16c and black for the rest

[romainl]

The problem is indeed worse on white bg. That's a good idea.

[habamax]

ctermbg=14

[habamax]

On the other hand black on blue is still readable for me on default xterm16

[habamax]

nice, what about white for diffadd?

[habamax]

btw, we could have a single _diff with 2 definitions depending on background

[romainl]

Maybe. I tried it but colortemplate reported a bunch of errors so I opted for a different file.

[habamax]

I will fix it later, once we agree on colors

[habamax]

White fg is actually quite readable on dark bg too:

[habamax]

nice!