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// Reference WPF dlls
#r "PresentationCore.dll"
#r "PresentationFramework.dll"
#r "WindowsBase.dll"

open System
open System.Windows
open System.Windows.Media

type Axis (low:double, high:double) =
    member this.Min = low
    member this.Max = high
    member this.Length = high - low

    static member Create (values:seq<float>) =
        let f (l,h) x = min l x, max h x
        Axis(values |> Seq.fold f (0.0,0.0))        

    static member CreateTransform(rect:Rect,xAxis:Axis,yAxis:Axis) =        
        let transform = Matrix.Identity
        transform.Translate(rect.Left, rect.Bottom)        
        transform.ScaleAtPrepend(
            rect.Width / xAxis.Length, 
            -rect.Height / yAxis.Length,
            xAxis.Min, 
            yAxis.Min)
        transform               

type Plot (f:float -> float, xs:seq<float>) =
    inherit System.Windows.Controls.ItemsControl ()    

    /// Creates formatted text
    let CreateText =
        let typeface = new Typeface("Verdana")               
        fun (s, emSize) ->
            new FormattedText(
                s,
                System.Globalization.CultureInfo.InvariantCulture,
                FlowDirection.LeftToRight,
                typeface,
                emSize,
                Brushes.Black)

    /// Renders plot               
    override this.OnRender (context) =
        /// Plot area               
        let rect = 
            let width, height =             
                this.ActualWidth-this.Margin.Left+this.Margin.Right),        
                this.ActualHeight-(this.Margin.Top+this.Margin.Bottom) 
            new Rect(
                this.Margin.Left, 
                this.Margin.Top, 
                max 0.0 width, 
                max 0.0 height)

        // Render background
        let bg = LinearGradientBrush(Colors.White,Colors.LightGray, 90.0)
        context.DrawRectangle(bg, new Pen(Brushes.Black, 1.0), rect)

        /// Calculated values        
        let ys = xs |> Seq.map (fun x -> f x)

        let xAxis, yAxis = Axis.Create xs, Axis.Create ys        

        let transform = Axis.CreateTransform (rect, xAxis, yAxis)

        let DrawXLabel x = 
            let label = CreateText(x.ToString(), 9.0)
            let p1 = Point(x, yAxis.Min) * transform
            let p2 = Point(x, yAxis.Max) * transform
            context.DrawText(label, 
                new Point(p1.X-(label.Width/2.0), p1.Y+4.0))
            context.DrawText(label,
                new Point(p2.X-(label.Width/2.0), p2.Y-label.Height-4.0))

        let DrawYLabel y = 
            let label = CreateText(y.ToString(), 9.0)
            let p1 = Point(xAxis.Min, y) * transform
            let p2 = Point(xAxis.Max, y) * transform
            context.DrawText(label, 
                new Point(p1.X-label.Width-4.0, p2.Y-(label.Height/2.0)))
            context.DrawText(label, 
                new Point(p2.X+4.0, p2.Y-(label.Height/2.0)))        

        DrawXLabel xAxis.Min; DrawXLabel xAxis.Max        
        DrawYLabel yAxis.Min; DrawYLabel yAxis.Max

        // Render lines                        
        let pen = new Pen(Brushes.Red, 1.0)        
        Seq.zip xs ys
        |> Seq.pairwise 
        |> Seq.iter (fun ((x0,y0),(x1,y1)) -> 
            context.DrawLine(pen, 
                new Point(x0,y0) * transform, 
                new Point(x1,y1) * transform)
        )                               

let PlotWindow (f:(float -> float), xs:seq<float>) =
    let plot = new Plot(f, xs, Margin=Thickness(16.0))
    new Window(Title="Plot",Width=640.0,Height=480.0,Content=plot)           

do  let f x = 3.0 * x * x + 2.0 * x + 2.0

let win = PlotWindow (f, seq {-2.0..0.01..2.0})

do win.Show() |> ignore