Halogen.Widgets.DoubleKnob

Package

purescript-halogen-widgets

Repository

afcondon/purescript-halogen-widgets

A concentric two-layer knob — the Strymon / Chase Bliss pattern where one physical control hosts two parameters: an outer ring (primary, more visible) and an inner ring (secondary, more subtle). Each layer has its own value, its own range, and its own drag — both report through a single Output ADT tagged by which layer changed.

This is "DoubleKnob" in the producing-with-your-feet sense: concentric layers, not a 2D-drag (one axis per parameter). A 2D-drag variant could be a future DoubleKnob2D.

Geometry, SVG primitives, and drag-tracking machinery share the same conventions as Knob (300° sweep, 140 px = full range, document-level mousemove/mouseup subscription on mousedown).

type Layer = { color :: String, max :: Number, min :: Number, value :: Number }

type Input = { debounce :: Milliseconds, disabled :: Boolean, inner :: Layer, label :: Maybe String, outer :: Layer, size :: Number }

data Output

data Query a

type Slot = Slot Query Output

component :: forall m. MonadAff m => Component Query Input Output m

defaultInput :: Number -> Number -> Input