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[REBOL] Re: PREZ dialect

From: jeff:rebol at: 6-Jun-2001 9:14

Thanks for the reminder, Allen.. The Prez dialect is up on my reb page: There is a simple test script that the viewer will fetch from my site as well. I don't have it doc'd really, but below is the test example, with a little explaination: First the main function PRESENT expects to receive a block, sort of like LAYOUT. At the beginning of the block you can define some preset effects. These effects can be based on the built in effects with overrides for your needs (sort of like stylize). So for example, we have a slow-fade-red, below, which is a fade that starts immediately (0:0:0) and fades to red in 0:0:10 seconds. GO is an effect which says to move to an absolute place. GROW is an effect which affects the element's size, positive or negative (shrinking). (there's also an effect MOVE which will just move some item in a given direction, usually given a small pair, like 1x1, move up 1 over 1 etc..) Each new preset can be built out of a number of different builtin effects. ;-- Test-prez.r ------------------------------------------------------ effects [ slow-fade-red fade [start: 0:0:0 fade-to: red duration: 0:0:10] go-c-slow go [xy: 250x250 duration: :0:5] go-c-fast go [xy: 250x250 duration: :0:1] go-c-med-fade go [xy: 250x250 duration: :0:3] fade [ start: :0:1 fade-to: green duration: :0:3 ] slow-grow-fade grow [start: :0:1 xy: 150x150 duration: :0:10 ] fade [ start: :0:1 fade-to: 10.20.200 duration: :0:10 ] slow-shrink grow [start :0:1 xy: 5x5 duration: :0:10] ] size 500x500 [ backdrop 200.150.130 h1 "Testing presentation engine" across button "8" :0:0 slow-grow-fade tab button "9" :0:0 slow-shrink below txt "1" :0:0 go-c-slow txt "2" :0:1 go-c-fast h1 "3" :0:2 go-c-med-fade at 480x400 guide h1 "4" :0:0 go-c-fast h2 "5" :0:1 go-c-slow h3 "6" :0:2 go-c-med-fade ] ;------------------------------------------------------------------ Okay, so the actual presentation portion has the required format of size pair! [prez-block]. The size must be set because the things may be flying all over the place and there'll be no way to figure out the bounds of the presentation. So then the presentation block is a lot like a layout. You can specify any number of styles and then provide effects that apply to the preceding style. Above we are using presents, but they are shorthand for the more generic approach where you place the effect info right after the affect. This is the format: style appear-time [effect-block] For example: button "Hello" 0:0:1 [ fade :0:0 green :0:02 fade :0:2 yellow :0:04 fade :0:4 black :0:06 ] The button, specified above, will appear 1 second after the presentation begins (the first time after "Hello"). It will immediately fade to green taking 2 seconds to complete (specified by the first line). At 2 seconds after the button's effects have started (right after the green fade completed) the button will fade to yellow for 2 seconds-- finally, 4 seconds after the effects have begun, the button fades to black in 2 seconds. Green yellow and black fade, like some crazy rasta man stuff, a'rite! A preset works basically by replacing that big block with the effects block that it represents. This is handy if you are applying the same effect repeatedly to a number of elements. You can, of course, use any VID style, including images -- but there are some odd bugs with some of VID that may appear. Images don't have a proper fading ability, just fade to a color-- not fade to transparent.. The way the system works is it basically takes the presentation, runs through and makes absolute time calculations for everything in the presentation. Then there's a central player loop that says "hmm, is there anything that needs to appear now? yes-- appear and start your effects... hmm are there any effects that need updating? Yes.. go update yourselves.." etc.. The code might seem a little hairy if you look at it, but do feel free to modify and/or improve it!! :-) -jeff