REBOL [ File: %list-supply-how-to.r Date: 2006-04-19 Title: "List How-To" Purpose: "How-To use a list and the 'supply block" library: [ level: 'beginner platform: 'all type: [how-to] domain: [gui] tested-under: [winxp] license: [bsd] support: none ] Comment: { I just extracted this out of a script, in answer to a question on the ml. Thats why the names may seem a little odd ;-) I myself got it from one of Carls scripts once. The slider is not updated when the list-data changes, this is left as an exercise to the reader :-) } ] comm-list-data: [ ["first 1" "first 2"] ["second 1" "second 1"] ["third 1" "third 3"] ] comm-sld-cnt: 0 ; needed to connect the slider to the list view layout [ across comm-list: list 280x200 [ across t1: text 100 t2: text 100 ] supply [ ; supply block is the body of a function that is called like this: ; supply: func [face count index] ; face the current face, thus either t1 or t2 ; count like the "linenumber" in the display ; index for every "line" it is called twice, once for t1, once for t2 ; (and so on for more elements), index tells you which face in ; the current "line" it is ; add the slider offset (comm-sld-cnt) to the "linenumber" (count) ; to find the position in your data count: count + comm-sld-cnt ;comm-sld-cnt is from the slider ... ; if we're out of data, we can set everything to none, and exit if none? v: pick comm-list-data count [ ; set color to background color, otherwise the last color would be used face/color: snow ; set face/text to none, otherwise last text would be used face/text: none ; nothing else to do, exit exit ] ; color the lines in alternating colors face/color: either even? count [ivory - 50.50.50][ivory] ; now set the text ... face/text: pick v index ] comm-sld: slider 16x200 [ comm-sld-c: max 0 to-integer (length? comm-list-data) * value if comm-sld-c <> comm-sld-cnt [comm-sld-cnt: comm-sld-c show comm-list] ] return button "Add" [ append/only comm-list-data reduce [form random 1000 form random 1000] show comm-list ] button "Remove" [ remove back tail comm-list-data show comm-list ] ]