Physical layout

Layout of components can be done in countless number of ways, but the simplest and perhaps the most useful is the boxes-and-glue style of layout. A set of DisplayHandles are combined together in a box, tiling them either horisontally or vertically:

module Main(main) where

import Haggis
import Random (randomInts)

main =
 mkDC ["*title: BoxORama"] >>= \ env ->
 let
  rs = take 64 (map (`mod` 40) (randomInts 17 57))
 in
 zipWithIO
   (\ sz ix ->
      button (text (show ix)) ix env >>= \ (btn,dh) ->
      return (btn, augmentNatSize (sz,0) dh))
   rs
   [1..64]     >>= \ ls ->
 realiseDH env (layout True (map (snd) ls)) >>
 return ()
 
{-
 Constructs a tiling layout that changes orientation of
 box used at each level. Assumes n>=2 and power of 2, where
 n is initial length of list.
-}
layout :: Bool -> [DisplayHandle] -> DisplayHandle
layout flg [x,y] = (if flg then vbox else hbox) [x,y]
layout flg ls  = 
 let
  (as,bs) = splitAt (length ls `div` 2) ls
 in
 (if flg then vbox else hbox) [layout (not flg) as,layout (not flg) bs]