Sleep blocks whole program (Smalltalk Squeak)

Question

I'm making a N*N queens problem with gui. I want the gui to stop for x seconds each move of every queen, problem is, the program just stacks all the waits together and then runs everything at speed. I'm giving the code here: http://pastebin.com/s2VT0E49

EDIT: This is my workspace:

board := MyBoard new initializeWithStart: 8.
Transcript show:'something'.
3 seconds asDelay wait.
board solve.
3 seconds asDelay wait.
board closeBoard.

This is where i want the wait to happen

canAttack: testRow x: testColumn
    | columnDifference  squareMark |
    columnDifference := testColumn - column.
    ((row = testRow
        or: [row + columnDifference = testRow])
        or: [row - columnDifference = testRow]) ifTrue: [
            squareDraw := squareDraw
            color: Color red.
            0.2 seconds asDelay wait.           
            ^ true ].

  squareDraw := squareDraw color: Color black.
  ^ neighbor canAttack: testRow x: testColumn

Answer 1

To make your workspace code work insert this before the delay:

World doOneCycle.

This will cause the Morphic world to be redisplayed.

Note that this is quick-and-very-dirty hack and not the proper way to do it (see my other answer). Delays block the whole UI process, whereas the whole point of Morphic is that you can do many things simultaneously while your code is executing.