Fader

In plain words

A fader is the slider of a mixing desk: one per channel, usually for the volume. Drag the cap, click anywhere on the track to jump there, or scroll over it.

ui.audio.Fader(value=self.volume, caption="Master", level=engine.level()[1],
               on_change=lambda e: engine.set(out, "volume", e.value))

How it works

• Drag the cap to move it; Shift makes the movement ten times finer.
• Click on the track (not on the cap) to jump to that point.
• Scroll to nudge it, double-click to reset it to default.
• level (0..1) draws a small meter beside the track: pass the channel’s peak every frame and the fader doubles as a meter, like on a real console.

Looks

variant	Looks like
"console"	A grooved metal cap, like an analog mixing desk.
"fl"	FL Studio’s dark cap with a colored line, the track filled up to it in color.
"flat"	A round handle on a filled track, matching the rest of the theme.

vertical=False lays it out horizontally (a crossfader). ticks sets how many marks are drawn along the track (0 for none) and length its size in pixels.

Properties

Property	Default	What it does
value, min, max	0.75, 0, 1	The value and its range.
default, step, curve	None, None, "lin"	As on the knob.
caption, unit, decimals		Text under it and how the value is written.
length	160	Length of the track in pixels.
vertical	True	False for a horizontal fader.
variant	"console"	"console", "fl" or "flat".
ticks	11	Marks along the track.
level	None	A 0..1 level drawn as a meter next to the track.
color	"accent"	The fill and the line on the cap.
show_value, disabled	True, False

Event: on_change with the new value.

Tip

A mixer channel is a column: a knob for pan, two LED buttons for mute and solo and a fader with its level. The MIDI controller demo puts eight of them side by side.