Learning WPF with F# - The Dock and the Grid and Problems with Static Readonly Fields

Working through Chapter 8 of Petzold's "Applications = Code + Markup: A Guide to the Microsoft Windows Presentation Foundation" book.

Working on the SpaceButton examples forced me to work with static members and static constructors in F#. Unfortunately, I'm completely stumped. In the SpaceButton example, I don't know how to setup a static readonly field in F# and I don't know how to initialize SpaceProperty outside of SpaceButton class due to initialization dependency with SpaceButton. The closest thing that I can find on the web is the following blog entry by Lewis Bruck which indicates that F# and SQL2005 CLR has problems because F# does not generate static readonly fields. Don Syme apparently has thought about this subject as he has published an article An Alternative Approach to Initializing Mutually Referential Objects". But it wasn't obvious to me how to resolve my problem with initializing SpaceProperty field. I post the code I have so far, but it's nonfunctional. If anyone else knows a solution, please let me know!

SetFontSizeProperty
#light 
#I @"C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.0"
#r @"WindowsBase.dll"
#r @"PresentationCore.dll"
#r @"PresentationFramework.dll"

open System
open System.Windows
open System.Windows.Controls
open System.Windows.Documents
open System.Windows.Input
open System.Windows.Media  


(* From Chap 8 - SetFontSizeProperty.cs *)
type SetFontSizeProperty = class
   inherit Window as base 

   
   new () as this = {} then
      this.Title <- "Set FontSize Property";
      this.SizeToContent <- SizeToContent.WidthAndHeight;
      this.ResizeMode <- ResizeMode.CanMinimize;
      this.FontSize <- 16.0
      let fntsizes = [|8.0;16.0;32.0|]
      
      // Create Grid Panel
      let grid = new Grid()
      this.Content <- grid
      
      // Define row and columns
      for i in [0..1] do
         let row = new RowDefinition()
         row.Height <- GridLength.Auto
         grid.RowDefinitions.Add(row)
      
      for i in [0..(fntsizes.Length-1)] do
         let col = new ColumnDefinition()
         col.Width <- GridLength.Auto
         grid.ColumnDefinitions.Add(col)
         
      // Create six buttons
      for i in [0..(fntsizes.Length-1)] do
         let btn = new Button()
         btn.Content <- new TextBlock
            (new Run("Set window FontSize to " + Float.to_string(fntsizes.[i])))
         btn.Tag <- fntsizes.[i]
         btn.HorizontalAlignment <- HorizontalAlignment.Center
         btn.VerticalAlignment <- VerticalAlignment.Center
         // Implement WindowFontSizeOnClick
         btn.Click.Add
            (fun _ -> this.FontSize <- (btn.Tag :?> double))
         grid.Children.Add(btn) |> ignore
         Grid.SetRow(btn,0)
         Grid.SetColumn(btn,i)
         
         let btn = new Button()
         btn.Content <- new TextBlock
            (new Run("Set button FontSize to " + Float.to_string(fntsizes.[i])))
         btn.Tag <- fntsizes.[i]
         btn.HorizontalAlignment <- HorizontalAlignment.Center
         btn.VerticalAlignment <- VerticalAlignment.Center
         // Implement ButtonFontSizeOnClick
         btn.Click.Add
            (fun _ -> btn.FontSize <- (btn.Tag :?> double))
         grid.Children.Add(btn) |> ignore
         Grid.SetRow(btn,1)
         Grid.SetColumn(btn,i)
      ()
end

#if COMPILED
[<STAThread()>]
do 
    let app =  new Application() in
    app.Run(new SetFontSizeProperty()) |> ignore
#endif

SetSpaceProperty Example - broken
#light 
#I @"C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.0"
#r @"WindowsBase.dll"
#r @"PresentationCore.dll"
#r @"PresentationFramework.dll"

open System
open System.Text
open System.Windows
open System.Windows.Controls
open System.Windows.Input
open System.Windows.Media  
// 
(* From Chap 8 - SetSpaceProperty example with DependencyProperty *)
// 
(* From Chap 8 - SpaceButton.cs *)
type SpaceButton =   class
   inherit Button as base 

   val mutable txt: string

   new () as this = {txt = null}

   
   static member initSpaceProperty =
      let metadata = new FrameworkPropertyMetadata()
      metadata.DefaultValue <- 1
      metadata.AffectsMeasure <- true
      metadata.Inherits <- true
      metadata.PropertyChangedCallback <- new PropertyChangedCallback(SpaceButton.OnSpacePropertyChanged)
      DependencyProperty.Register("Space", 
                                   typeof<int>,
                                   typeof<SpaceButton>, 
                                   metadata, 
                                   // callback method for value validation
                                   (fun obj -> let i = (obj :?> int) in (i >= 0)))
   
   // I'm completely stumped...I don't know how to setup a static readonly property
   // in F# and I don't know how to initialize SpaceProperty outside of SpaceButton
   // class due to initialization dependency with SpaceButton.
   // The closest thing I can find on the web is the following blog by Lewis Bruck
   // http://blogs.msdn.com/lbruck/archive/2006/05/24/606653.aspx which also indicates
   // that F# and SQL2005 CLR has problems because F# does not generate static readonly
   // fields.  Don Syme apparently has thought about this subject as he has published an
   // article "An Alternative Approach to Initializing Mutually Referential Objects"
   // to be found http://research.microsoft.com/~dsyme/papers/valrec-tr.pdf
   static member SpaceProperty = SpaceButton.initSpaceProperty
     
   static member OnSpacePropertyChanged (obj:DependencyObject) (args:DependencyPropertyChangedEventArgs) =
      let btn = obj :?> SpaceButton
      btn.Content <- btn.SpaceOutText btn.txt
      
   member this.Text 
      with get() = this.txt
      and set value = 
         this.txt <- value
         this.Content <- this.SpaceOutText(this.txt)
         
   member this.Space
      with get() = 
        let value = this.GetValue(SpaceButton.SpaceProperty)
        (value :?> int)
      and set (value:int) = this.SetValue(SpaceButton.SpaceProperty,value)
         
   member this.SpaceOutText (str:string) =
     
     if (str <> null) then
        let appendSpace c = String.of_char(c) + new string(' ',this.Space)
        let build = String.map_concat  appendSpace str
        build
     else 
       null
   
end   

   
(* From Chap 8 - SpaceWindow.cs *)

type SpaceWindow = class
   inherit Window as base 
   
   new () as this = {}

   // A static DependencyProperty 
   static member SpaceProperty = 
      let metadata = new FrameworkPropertyMetadata()
      metadata.Inherits <- true
      
      // Add owner to SpaceProeprty & override metadata
      let prop = SpaceButton.SpaceProperty.AddOwner(typeof<SpaceWindow>)
      prop.OverrideMetadata(typeof<SpaceWindow>,metadata)
      prop      
   
   member this.Space
      with get() = (this.GetValue(SpaceWindow.SpaceProperty) :?> int)
      and set (value:int) = this.SetValue(SpaceWindow.SpaceProperty,value)
   
end

(* From Chap 8 - SetSpaceProperty.cs *)

type SetSpaceProperty  = class
   inherit SpaceWindow as base 

   new () as this = {} then
      this.Title <- "Set Space Property"
      this.SizeToContent <- SizeToContent.WidthAndHeight
      this.ResizeMode <- ResizeMode.CanMinimize
      let iSpaces = [|0;1;2|]
      
      let grid = new Grid()
      this.Content <- grid
      
      for i in [0..2] do
         let row = new RowDefinition()
         row.Height <- GridLength.Auto
         grid.RowDefinitions.Add(row)
      
      for i in [0..(iSpaces.Length-1)] do
         let col = new ColumnDefinition()
         col.Width <- GridLength.Auto
         grid.ColumnDefinitions.Add(col)
         
      for i in [0..(iSpaces.Length-1)] do
         let btn = new SpaceButton();
         btn.Text <- "Set window Space to " + Int32.to_string(iSpaces.[i])
         btn.Tag <- iSpaces.[i];
         btn.HorizontalAlignment <- HorizontalAlignment.Center
         btn.VerticalAlignment <- VerticalAlignment.Center

         //btn.Click += WindowPropertyOnClick;         
         btn.Click.Add(fun _ -> this.Space <- (btn.Tag :?> int))
         grid.Children.Add(btn)|>ignore
         Grid.SetRow(btn, 0)
         Grid.SetColumn(btn, i)
         

         let btn = new SpaceButton()
         btn.Text <- "Set button Space to " + Int32.to_string(iSpaces.[i])
         btn.Tag <- iSpaces.[i];
         btn.HorizontalAlignment <- HorizontalAlignment.Center
         btn.VerticalAlignment <- VerticalAlignment.Center
         
         //btn.Click += ButtonPropertyOnClick
         btn.Click.Add(fun _ -> btn.Space <- (btn.Tag :?> int))
         grid.Children.Add(btn) |> ignore
         Grid.SetRow(btn, 1)
         Grid.SetColumn(btn, i)

end


#if COMPILED
[<STAThread()>]
do 
    let app =  new Application() in
    app.Run(new SetSpaceProperty()) |> ignore
#endif