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*dev_theme.txt* Nvim
NVIM REFERENCE MANUAL
Nvim theme style guide *dev-theme*
This is style guide for developers working on Nvim's default color scheme.
License: CC-By 3.0 https://creativecommons.org/licenses/by/3.0/
Type |gO| to see the table of contents.
==============================================================================
Design
- Be "Neovim branded", i.e. have mostly "green-blue" feel plus one or two
colors reserved for very occasional user attention.
- Be oriented for 'termguicolors' (true colors) while being extra minimal for
'notermguicolors' (16 colors) as fallback.
- Be accessible, i.e. have high enough contrast ratio (as defined in
https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef).
This means to have value at least 7 for |hl-Normal| and 4.5 for some common
cases (|hl-Visual|, `Comment` with set 'cursorline', colored syntax, `Diff*`,
|hl-Search|).
- Be suitable for dark and light backgrounds via exchange of dark and light
palettes.
- Be usable, i.e. provide enough visual feedback for common objects.
==============================================================================
Palettes
- There are two separate palettes: dark and light. They all contain the same
set of colors exported as `NvimDark*` and `NvimLight*` colors respectively.
- The dark palette is used for background in the dark color scheme and for
foreground in the light color scheme; and vice versa. This introduces
recognizable visual system without too standing out.
- Actual computation of palettes should be done in a perceptually uniform
color space. Oklch is a good choice.
- Each palette has the following colors (descriptions are for dark background;
reverse for light one):
- Four shades of colored "cold" greys for general UI.
- Dark ones (from darkest to lightest) are reserved as background for
|hl-NormalFloat| (considered as "black"), |hl-Normal| (background),
|hl-CursorLine|, |hl-Visual|.
- Light ones (also from darkest to lightest) are reserved for
`Comment`, |hl-StatusLine|/|hl-TabLine|, |hl-Normal| (foreground),
and color considered as "white".
- Six colors to provide enough terminal colors: red, yellow, green, cyan,
blue, magenta.
They should have (reasonably) similar lightness and chroma to make them
visually coherent. Lightness should be as equal to the palette's basic grey
(which is used for |hl-Normal|) as possible. They should have (reasonably)
different hues to make them visually separable.
- For 16 colors:
- Greys are not used and are replaced with the foreground and background
colors of the terminal emulator.
- Non-grey colors fall back to terminal colors as ordered in ANSI codes
(https://en.wikipedia.org/wiki/ANSI_escape_code#3-bit_and_4-bit),
that is red (1, 9), green (2, 10), yellow (3, 11), blue (4, 12),
magenta (5, 13), cyan (6, 14).
To increase contrast, colors 1-6 are used for light background and 9-14
for dark background.
==============================================================================
Highlight groups
Use:
- Grey shades for general UI according to their design.
- Bold text for keywords (`Statement` highlight group). This is an important
choice to increase accessibility for people with color deficiencies, as it
doesn't rely on actual color.
- Green for strings, |hl-DiffAdd| (as background), |hl-DiagnosticOk|, and some
minor text UI elements.
- Cyan as main syntax color, i.e. for function usage (`Function` highlight
group), |hl-DiffText|, |hl-DiagnosticInfo|, and some minor text UI elements.
- Red to generally mean high user attention, i.e. errors; in particular for
|hl-ErrorMsg|, |hl-DiffDelete|, |hl-DiagnosticError|.
- Yellow very sparingly to mean mild user attention, i.e. warnings. That is,
|hl-DiagnosticWarn| and |hl-WarningMsg|.
- Blue very sparingly as |hl-DiagnosticHint| and some additional important
syntax group (like `Identifier`).
- Magenta very carefully (if at all).
In case of 16 colors:
- Rely on the assumption "Background color can be used as background; other
colors can be used as foreground". This means that in any
foreground/background combination there should be background and one
non-background color.
- Use 0 (black) or 15 (bright white) as foreground for non-grey background,
depending on whether normal background is light or dark.
vim:tw=78:ts=8:et:ft=help:norl:
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