Toomasv's Rich Text Scroller

RTDScroller.red

context [
    rt: scr: i2: none
    select-line: function [line][
        pos: rt/text
        loop line - 1 [pos: find/tail pos newline]
        i1: index? pos
        if not i2: find next pos lf [i2: tail rt/text]
        i2: index? i2
        rt/data/1: as-pair i1 i2 - i1
    ]
    view [
        rt: rich-text 100x150 "one^/two^/three^/four^/five^/six^/seven^/eight" 
        with [flags: 'scrollable] 
        on-created [
            put get-scroller face 'horizontal 'visible? no 
            scr: get-scroller face 'vertical 
            scr/max-size: rich-text/line-count? face
            scr/page-size: 1
            i2: index? find face/text newline 
            face/data: compose [(as-pair 1 i2) 255.255.255 backdrop 0.120.215 ]
        ] 
        on-scroll [
            unless event/key = 'end [
                select-line scr/position: min max 1 switch event/key [
                    track [event/picked]
                    up page-up [scr/position - 1]
                    down page-down [scr/position + 1]
                ] scr/max-size
            ]
        ]
    ]
]