@spec braille_strips(
  map(),
  {pos_integer(), pos_integer()}
) :: [Drafter.Draw.Strip.t()] | nil

Renders spec as rows strips of cols braille cells, or nil when it cannot be drawn. Labels the chart places in cells are written over the braille.

@spec cell_sets() :: [atom()]

The glyph sets accepted as modes, each drawing through cells_strips/3.

@spec cells_strips(
  map(),
  {pos_integer(), pos_integer()},
  FrenchCurve.Backend.Cells.set()
) ::
  [Drafter.Draw.Strip.t()] | nil

Renders spec as rows strips of cols cells in the glyph set set, or nil when it cannot be drawn. Labels the chart places in cells are written over the glyphs.

@spec modes() :: [atom()]

The list of mode atoms accepted by :renderer, DRAFTER_MODE, and the mode: run option: [:auto, :pixel, :kitty, :iterm2, :sixel, :braille, :text, :half, :quad, :sextant, :octant].

@spec picture(map(), atom() | nil, {pos_integer(), pos_integer()}) ::
  Drafter.Render.Picture.t() | nil

Draws spec as a Drafter.Render.Picture filling a cols by rows cell box at the widget's top left, to be drawn with protocol.

The image has the terminal's own pixel size per cell: :cell_size in spec, else the size the session's terminal reported (Drafter.Session.Context.cell_size/0), else :scale pixels across (default 4) and twice that down. :overlay cells in spec, {col, row, text, fg, bg}, are drawn over the chart, and :marker, a {col, color} pair, shades that column behind it. Returns nil when protocol is nil or the chart cannot be drawn.

@spec protocol(atom() | nil) :: atom() | nil

The graphics protocol to draw with, or nil when the terminal has none.

A renderer naming a protocol (:kitty, :iterm2, :sixel) is used as given; any mode that is not :auto or :pixel has no protocol and returns nil.

:auto and :pixel take what the terminal answered when it was probed at startup — see Drafter.Terminal.Probe. A terminal that was never probed, or that answered the probe without naming a protocol, is guessed at from its environment instead, through FrenchCurve.Capability.detect/1.

Either way the terminal in question is the one this session is attached to, which for a session served over ssh or telnet is the connecting client's rather than the host's.

@spec resolve(atom() | nil) :: atom()

Resolve an effective mode from precedence: the DRAFTER_MODE env var forces and wins over everything; otherwise an explicit per-widget renderer (any mode atom), then the runtime :drafter :render_mode application env, then :text.

@spec terminal() :: atom() | nil

The graphics protocol of this session's terminal, whatever mode is in force.

What the terminal answered when it was probed at startup, or, when it was never probed or named no protocol, what its environment suggests through FrenchCurve.Capability.detect/1. nil when neither names one. An iTerm2 session is always judged by its environment, whatever it answered: :iterm2, or :kitty when FRENCH_CURVE_ITERM2=kitty is set (see FrenchCurve.Capability).

@spec value_range(
  map(),
  {pos_integer(), pos_integer()}
) :: {number(), number()} | nil

The value range spec is drawn against in a cols by rows box, {low, high}, or nil when it cannot be drawn. Axis labels read it.