REBOL [Title: "Arc Angle Draw Test" Author: "DideC"]

begin: angle: 178
lines?: 'closed

plot-red: [
	'fill-pen red 'pen black 'line-width 5
	'arc 100x100 90x90 begin angle lines?
]
plot-green: [
	'fill-pen green 'pen black 'line-width 5
	'arc 100x100 90x90 360 - begin 360 - angle lines?
]

update: does [
	res-r/text: remold at plot-red 7
	res-g/text: remold at plot-green 7
	bxg/effect/draw: reduce plot-green
	show [bxr bxg res-r res-g]
]

view center-face layout [
	across
	style vt vtext 55 right
	style sc scroller 392x16 with [data: 0.5]
	bxr: box 200x200 effect [draw plot-red]
	bxg: box 200x200 effect reduce ['draw reduce plot-green] return
	;vt "Draw cmd:"
	vt res-r: vtext bold red 400 (remold at plot-red 7) return
	vt res-g: vtext bold green 400 (remold at plot-green 7) return
	vt "Start:" sc [angle: round face/data * 360 update] return
	vt "Angle:" sc [begin: round face/data * 360 update] return
	vt "Closed:" toggle "yes" "no" [
		either face/data [lines?: false] [lines?: 'closed] update
	] return
]