create a draggable button - working version

dragbutton.r3

Rebol [
	file: %dragndrop.r3
	title: "DragNdrop example"
	author: "Graham Chiu"
	date: 22-may-2013
	purpose: "show how drag and drop works"
]

update-field-data: func [arg] [
	set-face offset arg/delta + arg/base
	set-face base arg/base
	set-face delta arg/delta
]

stylize [
	dragbutton: button [
		about: "draggable button"
		facets: [original-position: none]
		actors: [
			on-click: [; arg: event
				focus face
				; update info fields at top
				set-face goboff face/gob/offset
				if arg/type = 'down [
					; save the starting positiong in our custom facet
					set-facet face 'original-position face/gob/offset
					; return the drag object which is then passed to the on-drag actor
					return init-drag/only face arg/offset
				]
				do-face face
				; docs says none needs to be returned but seems to work without it
				none
			]
			on-offset: [ ; arg: offset
				if all [arg get-facet face 'original-position] [
					face/gob/offset: arg + get-facet face 'original-position
				]
			]
			on-drag: [; arg: drag-object
				; update our info fields
				update-field-data arg
				;show face/gob				
				do-actor face 'on-offset arg/delta ; arg/delta + arg/base
				; update the face to show the new position
				draw-face face
				do-attached face
				do-face face
			]
			on-drop: [	
				print "==========on drop"
				probe arg
			]
		]
	]
]

view [
	hpanel [
		label "Current: " current: field
		label "Gob Offset: " goboff: field
		label "Offset:" offset: field
		label "Base: " base: field
		label "Delta: " delta: field
	]
	scroll-panel [
		pad 10x200
		button "Where is dragbutton" on-action [set-face current db/gob/offset]
		button "Send Dragbutton to home" on-action [db/gob/offset: 0x0 draw-face db]
		db: dragbutton "DragMe" options [ show-mode: 'fixed ]
	]
]

New version does not send button back to original position by preventing resizing with show-mode: 'fixed