Harlock.Render.Style (harlock v0.4.1)

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Visual attributes for a rendered cell.

%Harlock.Render.Style{fg: :cyan, bold: true}
%Harlock.Render.Style{reverse: true}
%Harlock.Render.Style{bg: {:rgb, 30, 30, 40}}

Fields:

  • :fg / :bg — foreground / background colour. Atoms for the 16 standard colours (:red, :bright_blue, …), {:color256, n} for 256-color, {:rgb, r, g, b} for truecolor, or :default for "no override."
  • :bold / :dim / :italic / :underline / :reverse — boolean attributes, all false by default.

Construct with the struct directly, or with from/1 for keyword/map input. merge/2 layers one style on top of another — useful for applying a theme :focus token to a user-set element style without losing fg/bg.

Compared by value, hashed by value — used as a key into the renderer's internal style table.

Summary

Types

color()
depth()

Color depth the terminal can display; mirrors the internal caps type.

t()

Functions

default()
downgrade(color, arg2)

Map a color to what the given terminal depth can actually emit. Exposed for tests; the renderer uses it implicitly via to_sgr/1.

from(s)
merge(under, over)

Layer over on top of under. Non-default colors in over win; boolean attributes OR (any true wins). Used to apply theme tokens on top of element-provided styles without losing user-set fg/bg.

to_sgr(s)

Emit an SGR escape sequence that fully sets the cell's attributes. Starts with \e[0m so the previous style doesn't bleed through. The diff renderer emits this once per style transition; we don't try to be clever about diffing individual attribute changes — terminals process SGR fast enough that the extra bytes are cheaper than the bookkeeping.

Types

color()

@type color() ::
  :default
  | :black
  | :red
  | :green
  | :yellow
  | :blue
  | :magenta
  | :cyan
  | :white
  | :bright_black
  | :bright_red
  | :bright_green
  | :bright_yellow
  | :bright_blue
  | :bright_magenta
  | :bright_cyan
  | :bright_white
  | {:color256, 0..255}
  | {:rgb, 0..255, 0..255, 0..255}

depth()

@type depth() :: :mono | :ansi16 | :ansi256 | :truecolor

Color depth the terminal can display; mirrors the internal caps type.

t()

@type t() :: %Harlock.Render.Style{
  bg: color(),
  bold: boolean(),
  dim: boolean(),
  fg: color(),
  italic: boolean(),
  reverse: boolean(),
  underline: boolean()
}

Functions

default()

@spec default() :: t()

downgrade(color, arg2)

@spec downgrade(color(), depth()) :: color()

Map a color to what the given terminal depth can actually emit. Exposed for tests; the renderer uses it implicitly via to_sgr/1.

from(s)

@spec from(keyword() | map() | t()) :: t()

merge(under, over)

@spec merge(t(), t()) :: t()

Layer over on top of under. Non-default colors in over win; boolean attributes OR (any true wins). Used to apply theme tokens on top of element-provided styles without losing user-set fg/bg.

to_sgr(s)

@spec to_sgr(t()) :: iodata()

Emit an SGR escape sequence that fully sets the cell's attributes. Starts with \e[0m so the previous style doesn't bleed through. The diff renderer emits this once per style transition; we don't try to be clever about diffing individual attribute changes — terminals process SGR fast enough that the extra bytes are cheaper than the bookkeeping.

Reads the active terminal color depth from the renderer's process- dictionary context (installed by the runtime around each frame) and downgrades colors that the terminal can't display:

  • :mono — fg/bg become :default (no color SGR emitted)
  • :ansi16 — {:rgb, …} and {:color256, …} collapse to the nearest standard ANSI color
  • :ansi256 — {:rgb, …} collapses into the 256-color cube
  • :truecolor — colors pass through unchanged

When no caps are installed (e.g. tests rendering through the test backend) the default is :truecolor, matching v0.3 behaviour exactly.