TermBuf::Gradient

Stability: stable — changes only in a major release.

A colour ramp across a rectangle, handed to a draw call as a Blend.

A gradient is not a field of Style: styles are interned by value, so everything in one has to hash and compare, and a colour that depends on where the cell is cannot. It is a position-aware blend instead — the one thing in the drawing API that already takes a cell's coordinates.

ramp = TermBuf::Gradient.new Color.rgb(0x101820), Color.rgb(0x2060C0),
  screen.bounds, :vertical
screen.clear TermBuf::Style::DEFAULT, blend: ramp.background

A view can carry one instead, in which case the gradient is built against View#bounds and the view translates each cell into its own coordinates before asking. See View#blend.

The colours it answers with are always Color.rgb, whatever the endpoints were: the encoder narrows a 24 bit colour to the 256 colour cube or to the sixteen system colours against the terminal's mask, so one gradient renders everywhere and only the banding differs.

Each cell's colour is a separate Style, and StyleTable only grows. A gradient painted once, or repainted in the same colours, costs a style per cell it covers and no more. One whose endpoints move every frame interns a fresh set each time; an animation wanting that should step through a fixed palette instead.