Problem: Default color scheme is suboptimal.
Solution: Start using new color scheme. Introduce new `vim` color scheme
for opt-in backward compatibility.
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Main design ideas
- Be "Neovim branded".
- Be minimal for 256 colors with a bit more shades for true colors.
- Be accessible through high enough contrast ratios.
- Be suitable for dark and light backgrounds via exchange of dark and
light palettes.
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Palettes
- Have dark and light variants. Implemented through exporeted
`NvimDark*` and `NvimLight*` hex colors.
- Palettes have 4 shades of grey for UI elements and 6 colors (red,
yellow, green, cyan, blue, magenta).
- Actual values are computed procedurally in Oklch color space based on
a handful of hyperparameters.
- Each color has a 256 colors variant with perceptually closest color.
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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, `DiffAdd` (as background), `DiagnosticOk`, and some
minor text UI elements.
- Cyan as main syntax color, i.e. for function usage (`Function`
highlight group), `DiffText`, `DiagnosticInfo`, and some minor text UI
elements.
- Red to generally mean high user attention, i.e. errors; in particular
for `ErrorMsg`, `DiffDelete`, `DiagnosticError`.
- Yellow very sparingly only with true colors to mean mild user
attention, i.e. warnings. That is, `DiagnosticWarn` and `WarningMsg`.
- Blue very sparingly only with true colors as `DiagnosticHint` and some
additional important syntax group (like `Identifier`).
- Magenta very carefully (if at all).
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Notes
- To make tests work without relatively larege updates, each one is
prepended with an equivalent of the call `:colorscheme vim`.
Plus some tests which spawn new Neovim instances also now use 'vim'
color scheme.
In some cases tests are updated to fit new default color scheme.
Extend the capabilities of is_os to detect more platforms such as
freebsd and openbsd. Also remove `iswin()` helper function as it can be
replaced by `is_os("win")`.
This is essentially a convenience wrapper around the `pending()`
function, similar to `skip_fragile()` but more general-purpose.
Also remove `pending_win32` function as it can be replaced by
`skip(iswin())`.
Ref: #9342
Adds the option to have a single global statusline for the current window at the bottom of the screen instead of a statusline at the bottom of every window. Enabled by setting `laststatus = 3`.
Due to the fact that statuslines at the bottom of windows are removed when global statusline is enabled, horizontal separators are used instead to separate horizontal splits. The horizontal separator character is configurable through the`horiz` item in `'fillchars'`. Separator connector characters are also used to connect the horizontal and vertical separators together, which are also configurable through the `horizup`, `horizdown`, `vertleft`, `vertright` and `verthoriz` items in `fillchars`.
The window separators are highlighted using the `WinSeparator` highlight group, which supersedes `VertSplit` and is linked to `VertSplit` by default in order to maintain backwards compatibility.
PR #8221 took a short-cut when implementing the tests: screen.lua would
translate the linegrid highlight ids back into the old per-cell
attribute description.
Apart from cleaning up technical debt, this enables to check both rgb
and cterm colors in the same expect(), which previously was needlessly
restricted to ext_hlstate tests only.
