A programming guide

The following example demonstrates how to make a simple Paint-like application in Visual F#:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
open System.Drawing.Drawing2D
let drawingform = new Form(Text="Draw Objects",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let erasebutton=new Button(Text="Erase", Location=new System.Drawing.Point(120, 200))
let colorbutton=new Button(Text="Brush Color", Location=new System.Drawing.Point(40, 200))
drawingform.Controls.Add(exitbutton)
drawingform.Controls.Add(erasebutton)
drawingform.Controls.Add(colorbutton)
//creates a color dialog box
let colordlg=new ColorDialog()
//creates a colorblend object
let mutable color=new ColorBlend()

let gr=drawingform.CreateGraphics()
gr.SmoothingMode<-SmoothingMode.HighQuality
//when the form is loaded, change its color to white
drawingform.Load.Add(fun background->
//set the default brush color to indigo
color.Colors<-[|Color.Indigo|]
                        drawingform.BackColor<-Color.White)

drawingform.MouseMove.Add(fun trail->
//when the mouse button is moved and the left button is clicked

if (trail.Button=System.Windows.Forms.MouseButtons.Left)then
//draw the object assign the color seleted from the color dialog as a brush color
gr.FillRectangle(new SolidBrush(color.Colors.[0]),new Rectangle(trail.X,trail.Y,5,5))) 
//when the erase button is clicked
//erase the object drawn in the form
erasebutton.Click.Add(fun erase->gr.Clear(Color.White)) 
//when the exit button is clicked
//quit the form                                                                                                              
exitbutton.Click.Add(fun quit->drawingform.Close())
//when the brush color button is selected                                                          
colorbutton.Click.Add(fun colors->
//display the Color Dialog box
if colordlg.ShowDialog()=DialogResult.OK then
//store the value selected by the user in our colorblend object
color.Colors<-[|colordlg.Color|])
//executes our application
Application.Run(drawingform)

Click the run icon once you are done entering these codes in the code editor window. You should see the following outputs:

Obsessed with mouse trails? Try the following sample applications:
1. Line Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.DrawLine(Pens.Peru,trail.X,trail.Y,trail.X+1,trail.Y+1))                                                                                                                
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

2. Circle Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.DrawEllipse(Pens.IndianRed,new Rectangle(trail.X,trail.Y,10,10)))                                                                                                                    
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

3. Rectangle Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.DrawRectangle(Pens.Fuchsia,new Rectangle(trail.X,trail.Y,5,5)))                                                                                                                    
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

4. Arc Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.DrawArc(Pens.Violet,new Rectangle(trail.X,trail.Y,5,5),180.0f,-180.0f))                                                                                                               
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

5. Filled-Arc/FillPie Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.FillPie(Brushes.MidnightBlue,new Rectangle(trail.X,trail.Y,10,10),180.0f,180.0f))                                                                                                               
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

6. Filled Circle Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.FillEllipse(Brushes.Tomato,new Rectangle(trail.X,trail.Y,10,10)))                                                                                                               
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

7. Filled Rectangle Mouse Trail
Code:

// Learn more about F# at http://fsharp.net
//specifies the memory location of the class files
//that will be needed in our application
open System.Collections.Generic
open System
open System.Windows.Forms
open System.ComponentModel
open System.Drawing
let trailform = new Form(Text="Display Mouse Trail",AutoScaleDimensions=new System.Drawing.SizeF(60.0F, 13.0F),ClientSize=new System.Drawing.Size(300, 250),StartPosition=FormStartPosition.CenterScreen)
//creates our control
let exitbutton=new Button(Text="Exit", Location=new System.Drawing.Point(200, 200))
let gr=trailform.CreateGraphics()
trailform.Controls.Add(exitbutton)
trailform.MouseMove.Add(fun trail->gr.FillRectangle(Brushes.Indigo,new Rectangle(trail.X,trail.Y,20,20)))                                                                                                               
exitbutton.Click.Add(fun quit->trailform.Close())                                                          
//executes our application
Application.Run(trailform)

Output:

A programming guide

Paint Application in Visual F#

Mouse Trails using Basic shapes

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