Creating a three-pane Window, using SystemWindow and LayoutFrame

window := SystemWindow labelled: 'Layout'.

redMorph := Morph new.

window 

 addMorph: redMorph

 fullFrame: (LayoutFrame 

  fractions: (0@0 corner: 1@1)   

        "in fractions: the numbers represent a value from 0 to 1  

          i.e. a decimal fraction, of 100% of the parent window's size"

  offsets: (100@0 corner: 0@50 negated)).

        "in offsets: the numerics represent absolute values, in pixels"

redMorph color: Color red.

        "there is a set of named colors.  Color objects can also be specified as RGB values

          r:g:b:  Each parameter is a number between 0 and 1.0 "

Two morphs side-by-side in a proportional layout will automagically have a grabbable, movable pane edge.

greenMorph := Morph new.

window 

 addMorph: greenMorph

 fullFrame: (LayoutFrame 

  fractions: (0@0 corner: 0@1)

  offsets: (0@0 corner: 100@50 negated)).

greenMorph color: Color green.

yellowMorph := Morph new.

window 

 addMorph: yellowMorph

 fullFrame: (LayoutFrame 

  fractions: (0@1 corner: 1@1)

  offsets: (0@50 negated corner: 0@0)).

yellowMorph color: Color yellow.

window openInWorld.  "sent to the superclass"