for #410 - api is stable - unless something is missing

* documented at https://github.com/shoes/shoes3/wiki/Layout-class
* see Tests/layout/*

Tests/button/button.rb

@@ -35,7 +35,7 @@
           icon_pos: "right" do
           para "right image"
       end
-      button "top", width: 80, height: 45, icon: "#{DIR}/static/icon-info.png",
+      @b = button "top", width: 80, height: 45, icon: "#{DIR}/static/icon-info.png",
           icon_pos: "top" do
         para "top image"
       end

Tests/layout/l1.rb

@@ -1,40 +1,57 @@
 
 class MyLayout 
   attr_accessor :pos_x, :pos_y, :w, :h
-  attr_accessor :contents
+  attr_accessor :contents, :canvas
 
   def initialize()
     @pos_x = 25
     @pos_y = 25
     @contents = []
   end
 
-  def setup(attr)
+  def setup(canvas, attr)
+    @canvas = canvas
     @w = attr[:width]
     @h = attr[:height]
     puts "setup #{@w} X #{@h}"
   end
 
-  def add(widget)
+  def add(canvas, widget, attrs)
     @contents << widget
     widget.move @pos_x, @pos_y
     @pos_x += 25
     @pos_y += 25
   end
+
+  def remove(canvas, widget, pos)
+    return true
+  end
+
+  def size(canvas, pass)
+    $stderr.puts "callback: size pass=#{pass}"
+  end
+
+  def clear()
+  end
+
+  def finish()
+    @canvas.show
+  end
 end
 
 Shoes.app width: 350, height: 400, resizeable: true do
   stack do
     para "Before layout"
     @ml = MyLayout.new
-    layout manager: @ml, width: 300, height: 300 do
+    @lay = layout use: @ml, width: 300, height: 300 do
       background yellow
       p1 = para "First Para"
       a = button "one"
       b = button "two"
       p2 = para "I am #{self.class}"
     end
   end
+  @lay.start {@lay.finish}
   para "After layout"
   para "@ml is #{@ml.class}"
 end

Tests/layout/l2.rb

@@ -4,42 +4,47 @@ class MyLayout
   attr_accessor :incr_x, :incr_y, :canvas
 
   def initialize()
-    puts "initialized"
-    clear
+    $stderr.puts "initialized"
+    self.clear
   end
 
   def setup(canvas, attr)
     @canvas = canvas
     @w = attr[:width]
     @h = attr[:height]
-    puts "callback: setup #{@w} X #{@h}"
+    $stderr.puts "callback: setup #{@w} X #{@h}"
   end
 
-  def add(canvas, widget)
-    puts "callback add: #{widget.class} #{canvas.contents.size}"
-    puts "w: #{widget.width} h: #{widget.height}"
+  def add(canvas, widget, attrs)
+    $stderr.puts "callback add: #{widget.class} #{canvas.contents.size}"
     widget.move @pos_x, @pos_y
     @pos_x += @incr_x
     @pos_y += @incr_y
+    name = attrs && attrs[:name]
+    if name
+      $stderr.puts "Winner, Winner, Chicken Dinner for #{name}"
+    end
+  end
+
+  def remove(canvas, widget, pos)
+    $stderr.puts"callback: remove"
+    return true
+  end
+
+  def size(canvas, pass)
+    $stderr.puts "callback: size pass=#{pass} w: #{canvas.width} h:#{canvas.height}"
   end
 
   def clear
     @pos_x = 5
     @pos_y = 5
     @incr_x = 25
     @incr_y = 25
-    puts "callback: clear"
+    $stderr.puts "callback: clear"
   end
-
-  def refresh
-    @pos_x = 5
-    @pos_y = 5
-    @canvas.contents.each do |widget| 
-      widget.move @pos_x, @pos_y
-      @pos_x += @incr_x
-      @pos_y += @incr_y
-      puts "w: #{widget.width} h: #{widget.height}"
-    end
+
+  def finish()
+    @canvas.show
   end
 
 end
@@ -48,10 +53,10 @@ def refresh
   stack do
     @p = para "Before layout"
     @ml = MyLayout.new
-    @lay = layout manager: @ml, width: 340, height: 380  do
+    @lay = layout use: @ml, width: 340, height: 380  do
       background yellow
-      p1 = para "First Para"
-      a = button "one"
+      p1 = para "First Para", name: 'p1'
+      a = button "one", name: 'b1'
       b = button "two"
       p2 = para "I am #{self.class}"
     end

Tests/layout/l3.rb

@@ -0,0 +1,210 @@
+Shoes.setup do
+	gem 'cassowary-ruby'
+end
+require 'cassowary'
+include Cassowary
+class CassowaryLayout 
+  attr_accessor :canvas, :widgets, :solver, :attrs, :left_limit,
+	:right_limit, :top_limit, :height_limit, :right_limit_stay,
+  :canvas_set, :canvas_w, :canvas_h
+
+  def initialize()
+    #$stderr.puts "initialized"
+    @widgets = {}
+    @solver = SimplexSolver.new
+    @attrs = {}
+    @canvas_set = false
+    @canvas_x = 0
+    @canvas_y = 0
+  end
+
+
+  # canvas does not have a width or height. be careful
+  def setup(canvas, attr)
+    @canvas = canvas
+    hgt = 0
+    wid = 0
+    if (attr && attr[:width]) 
+      wid = attr[:width]
+    else
+      wid = 500
+      canvas.style width: wid
+    end
+    if (attr && attr[:height])
+      hgt = attr[:height]
+    else
+      hgt = 400
+      canvas.style height: hgt
+    end
+		@left_limit = Variable.new(name: 'left', value: 0.0)
+		@right_limit = Variable.new(name: 'width', value: wid)
+		@top_limit = Variable.new(name: "top", value: 0.0)
+		@height_limit = Variable.new(name: "height", value: hgt)
+		@solver.add_stay(@left_limit)
+		@solver.add_stay(@right_limit, Strength::WeakStrength)
+    $stderr.puts "callback: setup #{wid} X #{hgt}"
+  end
+
+  def add(canvas, widget, attrs)
+    # widget is not on-screen and allocated at this time. Pity
+    # DO NOT enumerate attrs hash - crash if you try.
+    name = attrs && attrs[:name]
+    $stderr.puts "callback add: #{name} #{widget.class} #{canvas.contents.size}"
+    self.track widget, name if name
+  end
+
+  def remove(canvas, widget, pos)
+    $stderr.puts"callback: remove"
+    return true
+  end
+
+
+  def track(obj, str)
+    @widgets[str] = obj
+    vars = {}
+    vars['left'] = Variable.new(name: 'left'+str, value: 0)
+    vars['width'] = Variable.new(name: 'width'+str, value: 0)
+    vars['top'] = Variable.new(name: 'top'+str, value: 0)
+    vars['height'] = Variable.new(name: 'height'+str, value: 0)
+    @attrs[str] = vars
+  end
+
+  # parse string like 'b1-width' and return Cassowary Variable
+  def var(str)
+     str[/(\w+)\-(\w+)/]
+     @attrs[$1][$2]
+  end
+
+  def size(canvas, pass)
+    if pass == 0
+      return
+    else
+      $stderr.puts "callback: size Change!  w: #{canvas.width} h:#{canvas.height}"
+    end
+  end
+
+  def widget_defaults
+    @canvas.show
+		@widgets.each_pair do |id, ele|
+			vh = @attrs[id]['height']
+      vh.value = ele.height
+      vw = @attrs[id]['width']
+      vw.value = ele.width
+      $stderr.puts "widget #{id} w:#{vw.value} h:#{vh.value}"
+		end
+  end
+
+  def resize(w, h)
+    @right_limit.value = w
+    @height_limit.value = h
+    #@solver.add_stay(@right_limit, Strength::RequiredStrength)
+
+    #right_limit_stay = solver.add_constraint(right_limit, strength=REQUIRED)
+    #solver.add_constraint(right_limit_stay)
+ end
+
+  def clear()
+    $stderr.puts "callback: clear"
+  end
+
+  def rules(arg)
+    $stderr.puts "callback rules #{arg}"
+  end
+
+  def finish()
+		@widgets.each_pair do |k, widget|
+			left = widget.left
+			top = widget.top
+			height = widget.height
+			width = widget.width
+			$stderr.puts "From #{left},#{top}"
+			left = @attrs[k]['left'].value.to_i
+      top = @attrs[k]['top'].value.to_i
+			width = @attrs[k]['width'].value.to_i
+      height =  @attrs[k]['height'].value.to_i
+			$stderr.puts "move to #{left}, #{top} for w:#{width} h:#{height}"
+			widget.style width: width
+			widget.move(left, top)
+		end
+  end
+
+  # send other methods to @solver
+  def method_missing(meth, *args, &block)
+    if @solver.respond_to? meth
+			@solver.send(meth, *args, &block)
+		else
+			super
+		end
+  end
+
+end
+
+Shoes.app width: 480, height: 280, resizeable: true do
+  stack do
+    flow do
+      para "Before layout  "
+      @p = para "unknown"
+    end
+    @ml = CassowaryLayout.new
+    @lay = layout use: @ml, width: 450, height: 200  do
+    #@lay = layout manager: @ml  do
+      background teal
+      a = button "one", name: 'b1'
+      b = button "two", name: 'b2'
+      para "Strings Too!", name: 'b3'
+    end
+    @lay.start do
+      # Every thing has a default h and w now. We can compute things
+      @ml.rules "foobar" # for a test
+      @ml.widget_defaults
+      # The two buttons are the same width
+      @ml.add_constraint(@ml.var('b1-width').cn_equal @ml.var('b2-width'))
+
+      # Button1 starts 50 from the left margin.
+      @ml.add_constraint(@ml.var('b1-left').cn_equal @ml.left_limit + 50)
+
+      # Button2 ends 50 from the right margin 
+      @ml.add_constraint((@ml.left_limit + @ml.right_limit).cn_equal @ml.var('b2-left') + @ml.var('b2-width') + 50)
+
+      # Button2 starts at least 50 from the end of Button1. This is the
+      # "elastic" constraint in the system that will absorb extra space
+      # in the layout.
+      @ml.add_constraint(@ml.var('b2-left').cn_equal @ml.var('b1-left') + @ml.var('b1-width') + 50)
+
+      # Button1 has a minimum width of 87
+      @ml.add_constraint(@ml.var('b1-width').cn_geq 87)
+
+      # Button1's preferred width is 87
+      @ml.add_constraint(@ml.var('b1-width').cn_equal 87, Strength::StrongStrength)
+
+      # Button2's minimum width is 113
+      @ml.add_constraint(@ml.var('b2-width').cn_geq 113)
+
+      # Button2's preferred width is 113
+      @ml.add_constraint(@ml.var('b2-width').cn_equal 113, Strength::StrongStrength)
+
+      # string b3 is at the bottom ? 
+      @ml.add_constraint(@ml.height_limit.cn_equal @ml.var('b3-top'))
+
+      @lay.finish
+      @p.text = @lay.inspect    
+    end
+  end
+  button "refresh" do
+    @lay.finish
+  end
+  button "shrink" do
+    wid = (@lay.width * 0.9).to_i
+    hgt = (@lay.height * 0.9).to_i
+    @ml.resize(wid,hgt)
+    @lay.style width: wid, height: hgt
+    @lay.finish
+  end
+  button "expand" do
+    wid = (@lay.width * 1.1).to_i
+    hgt = (@lay.height * 1.1).to_i
+    @ml.resize(wid, hgt)
+    @lay.style width: wid, height: hgt
+    @lay.finish
+  end
+end

Tests/layout/vfl1.rb

@@ -0,0 +1,16 @@
+
+Shoes.app width: 350, height: 400, resizeable: true do
+  stack do
+    para "Before layout"
+    @lay = layout use: :foobar, width: 300, height: 300 do
+      para "First Para", name: 'Label_1'
+      button "one", name: 'Button_1'
+      button "two", name: 'Button_2'
+    end
+    @lay.start {
+      @lay.rules 'foo.vfl'
+      @lay.finish
+    }
+ end
+  para "After layout"
+end

app.yaml

@@ -1,7 +1,7 @@
 name: Shoes
 major: 3
 minor: 3
-tiny: 7 
+tiny: 8 
 release: walkabout
 revision: git
 icons: