Trying to create original StackLayout class and FlowLayout class for Shoes 4 inherited from Swt::Widgets::Layout class.

stack_and_flow_layout.rb

require 'java'
require 'swt'

module Swt::Widgets
  import org.eclipse.swt.widgets.Layout
end

display = Swt::Widgets::Display.new
shell = Swt::Widgets::Shell.new display, Swt::SWT::SHELL_TRIM
shell.setLayout Swt::Layout::RowLayout.new
shell.set_background display.getSystemColor Swt::SWT::COLOR_WHITE
shell.background_mode = Swt::SWT::INHERIT_DEFAULT
shell.addListener Swt::SWT::Close, proc{Swt.display.dispose}

class ShoesLayout < Swt::Widgets::Layout
  def initialize *args
    opts = args.last.class == Hash ? args.pop : {}
    @width, @height = opts[:width], opts[:height]
    super *args
  end
end

class StackLayout < ShoesLayout
  def computeSize *args
    eles = args[0].getChildren
    @width ||= eles.map{|e| e.is_a?(Swt::Custom::StyledText) ? 0 : get_size(e).x}.max
    @height ||= eles.map{|e| get_size(e).y}.inject(:+)
    Swt::Graphics::Point.new @width, @height
  end
  
  def layout *args
    eles = args[0].getChildren
    x, y = 0, 0
    eles.each do |e|
      size = get_size e
      e.setBounds x, y, size.x, size.y
      y += size.y
    end
  end
  
  def get_size e
    w = e.is_a?(Swt::Custom::StyledText) ? @width : Swt::SWT::DEFAULT
    e.computeSize w, Swt::SWT::DEFAULT
  end
end

class FlowLayout < ShoesLayout
  def computeSize *args
    eles = args[0].getChildren
    @width ||= eles.map{|e| 0}.max            # not yet
    @height ||= eles.map{|e| 0}.inject(:+)   # not yet
    Swt::Graphics::Point.new @width, @height
  end
  def layout *args
    # not yet
  end
end

def button cs, name
  b = Swt::Widgets::Button.new cs, Swt::SWT::PUSH
  b.setText name
end

def para cs, str
  st = Swt::Custom::StyledText.new cs, Swt::SWT::WRAP
  st.setText str
end

def stack parent, opts={}, &blk
  cs = Swt::Widgets::Composite.new parent, Swt::SWT::NULL
  cs.setLayout StackLayout.new opts
  blk[cs]
end

def flow parent, opts={}, &blk
  cs = Swt::Widgets::Composite.new parent, Swt::SWT::NULL
  cs.setLayout FlowLayout.new opts
  blk[cs]
end

stack shell do |cs| 
  2.times{|i| button cs, "Button #{i}"}
  stack cs do |cs1|
  #flow cs, width: 300, height: 100 do |cs1|
    button cs1, 'long ' * 5
    para cs1, 'hello ' * 28
    button cs1, 'short'
  end
  2.times{|i| button cs, "Button #{i}"}
end

shell.pack
shell.open
Swt.event_loop{Swt.display.isDisposed}