Lesson 30: Drawing Polygon & Pie in VB2022

Private Sub BtnDrawTriangle_Click(sender As Object, e As EventArgs) Handles BtnDrawTriangle.Click
    ' Create graphics object
    Dim g As Graphics = Me.CreateGraphics()
    
    ' Define triangle vertices
    Dim point1 As New Point(100, 50)
    Dim point2 As New Point(50, 150)
    Dim point3 As New Point(150, 150)
    
    ' Create point array
    Dim trianglePoints As Point() = {point1, point2, point3}
    
    ' Create a pen
    Dim myPen As New Pen(Color.DarkBlue, 3)
    
    ' Draw the triangle
    g.DrawPolygon(myPen, trianglePoints)
    
    ' Clean up resources
    myPen.Dispose()
    g.Dispose()
End Sub

Private Sub BtnDrawPentagon_Click(sender As Object, e As EventArgs) Handles BtnDrawPentagon.Click
    Dim g As Graphics = Me.CreateGraphics()
    Dim centerX As Integer = 150
    Dim centerY As Integer = 150
    Dim radius As Integer = 100
    Dim sides As Integer = 5
    Dim points(sides - 1) As Point
    
    ' Calculate vertices
    For i As Integer = 0 To sides - 1
        Dim angle As Double = Math.PI / 2 + i * 2 * Math.PI / sides
        points(i) = New Point(
            centerX + radius * Math.Cos(angle),
            centerY + radius * Math.Sin(angle)
        )
    Next
    
    ' Draw pentagon
    Dim myPen As New Pen(Color.DarkGreen, 3)
    g.DrawPolygon(myPen, points)
    
    ' Clean up
    myPen.Dispose()
    g.Dispose()
End Sub

Private Sub BtnDrawPie_Click(sender As Object, e As EventArgs) Handles BtnDrawPie.Click
    Dim g As Graphics = Me.CreateGraphics()
    
    ' Define bounding rectangle
    Dim rect As New Rectangle(50, 50, 200, 200)
    
    ' Start angle (0° = east direction)
    Dim startAngle As Single = 0
    
    ' Sweep angle (90° clockwise)
    Dim sweepAngle As Single = 90
    
    ' Create pen
    Dim myPen As New Pen(Color.DarkBlue, 3)
    
    ' Draw pie segment
    g.DrawPie(myPen, rect, startAngle, sweepAngle)
    
    ' Clean up
    myPen.Dispose()
    g.Dispose()
End Sub

Private Sub BtnDrawPieChart_Click(sender As Object, e As EventArgs) Handles BtnDrawPieChart.Click
    Dim g As Graphics = Me.CreateGraphics()
    Dim rect As New Rectangle(50, 50, 200, 200)
    Dim startAngle As Single = 0
    
    ' Segment 1: 40% - Blue
    Dim sweep1 As Single = 360 * 0.4
    g.DrawPie(New Pen(Color.Blue, 2), rect, startAngle, sweep1)
    startAngle += sweep1
    
    ' Segment 2: 25% - Green
    Dim sweep2 As Single = 360 * 0.25
    g.DrawPie(New Pen(Color.Green, 2), rect, startAngle, sweep2)
    startAngle += sweep2
    
    ' Segment 3: 20% - Red
    Dim sweep3 As Single = 360 * 0.2
    g.DrawPie(New Pen(Color.Red, 2), rect, startAngle, sweep3)
    startAngle += sweep3
    
    ' Segment 4: 15% - Orange
    Dim sweep4 As Single = 360 * 0.15
    g.DrawPie(New Pen(Color.Orange, 2), rect, startAngle, sweep4)
    
    ' Clean up
    g.Dispose()
End Sub

Private progressValue As Integer = 0
Private progressTimer As New Timer()

Private Sub BtnStartProgress_Click(sender As Object, e As EventArgs) Handles BtnStartProgress.Click
    progressValue = 0
    progressTimer.Interval = 100 ' 100 ms
    AddHandler progressTimer.Tick, AddressOf UpdateProgress
    progressTimer.Start()
End Sub

Private Sub UpdateProgress(sender As Object, e As EventArgs)
    If progressValue >= 100 Then
        progressTimer.Stop()
        RemoveHandler progressTimer.Tick, AddressOf UpdateProgress
        Return
    End If
    
    progressValue += 1
    Me.Invalidate() ' Force redraw
End Sub

Private Sub MainForm_Paint(sender As Object, e As PaintEventArgs) Handles MyBase.Paint
    Dim g As Graphics = e.Graphics
    Dim rect As New Rectangle(50, 50, 200, 200)
    
    ' Draw background circle
    g.DrawEllipse(Pens.LightGray, rect)
    
    ' Draw progress pie
    Dim sweepAngle As Single = 360 * (progressValue / 100)
    g.DrawPie(New Pen(Color.Blue, 3), rect, -90, sweepAngle)
    
    ' Draw progress text
    Dim text As String = $"{progressValue}%"
    Dim font As New Font("Arial", 24, FontStyle.Bold)
    Dim textSize As SizeF = g.MeasureString(text, font)
    Dim textX As Single = rect.X + (rect.Width - textSize.Width) / 2
    Dim textY As Single = rect.Y + (rect.Height - textSize.Height) / 2
    g.DrawString(text, font, Brushes.Black, textX, textY)
    
    font.Dispose()
End Sub