wpf.fs

open System
open System.Windows
open System.Windows.Controls
open System.Windows.Shapes
open System.Windows.Media

let move sh x y =
    Canvas.SetLeft(sh, x)
    Canvas.SetTop(sh, y)

let mutable canvas : Canvas = null
let mutable elem : UIElement = null
let mutable click = new Point()
let mutable orig = new Point()

let down (el : UIElement) (e : Input.MouseButtonEventArgs) =
    elem <- el
    orig <- new Point(Canvas.GetLeft(el), Canvas.GetTop(el))
    click <- e.GetPosition(canvas)
    ignore <| canvas.CaptureMouse()

[<STAThread>]
do
    let w = new Window(Title = "Test", Width = 256.0, Height = 256.0)
    w.Show()

    canvas <- new Canvas()
    w.Content <- canvas

    let r = new Rectangle(Width = 40.0, Height = 40.0)
    move r 20.0 60.0
    r.Stroke <- new SolidColorBrush(Colors.Black)
    r.Fill <- new SolidColorBrush(Colors.Yellow)
    ignore <| canvas.Children.Add(r)

    let tb = new TextBlock(Text = "abcdefg", FontSize = 24.0)
    move tb 20.0 30.0
    ignore <| canvas.Children.Add(tb)

    r.MouseDown.Add <| down r
    tb.MouseDown.Add <| down tb
    canvas.MouseMove.Add <| fun e ->
        if elem <> null then
            let p = e.GetPosition(canvas)
            move elem (orig.X + p.X - click.X) (orig.Y + p.Y - click.Y)
    canvas.MouseUp.Add <| fun _ ->
        elem <- null
        canvas.ReleaseMouseCapture()

    ignore <| (new Application()).Run(w)

Hi 7shi.
Thanks for this example of fsharp wpf mouse gui.
Have you seen Phil Treford's SL WPF Time flys ...? http://www.trelford.com/blog/?page=2
I also like Jon Harrop's Quick hull (F#.NET Journal subscription) where he uses int option ref.
"... A key aspect of the GUI is the ability to drag and drop points in the point set and watch the convex hull as it is recomputed in real time. The following drag value is the current state of the outstanding drag operation, if any, represented by the index of the point being dragged:

> let drag : int option ref = ref None;;
val drag : int option ref = {contents = null;}

This design follows the mantra "make illegal states unrepresentable". Alternative designs in languages where this cannot be so easily expressed tend to use one boolean variable to indicate whether or not a drag is in progress and another integer variable to convey the index when meaningful. Using data structures such as the option type in F# precludes the possibility of non-sensical values being created and encountered at run-time, reducing the scope for errors and the number of run-time tests. ..."

Best regards. PLH OOE Art Scott Twitter: semasiographic

Hi Art.
Thank you for your interest in my gist.
In fact, this gist is a translation from C#. https://gist.github.com/1207814
How implement drag and drop is an another problem. I like the coroutine for drag and drop. https://gist.github.com/1275258
Best regards. 7shi