ccircle.vb

苏金明编写的《用VB.NET和VC#.NET开发交互式CAD系统》一书的源代码

Imports System.Drawing.Drawing2D
Imports System.Math

Public Class CCircle
    Inherits GESelecter

    Private m_Center, m_pCircle As PointF

    '圆心
    Public Property Center() As PointF
        Get
            Return m_Center
        End Get
        Set(ByVal newValue As PointF)
            m_Center = newValue
        End Set
    End Property

    '圆上一点
    Public Property pCircle() As PointF
        Get
            Return m_pCircle
        End Get
        Set(ByVal newValue As PointF)
            m_pCircle = newValue
        End Set
    End Property

    '半径属性，只读
    Public ReadOnly Property Radius() As Single
        Get
            Dim r As Single
            r = DistPtoP(m_Center, m_pCircle)
            Return r
        End Get
    End Property

    '计算点与点之间的距离
    Private Function DistPtoP(ByVal p1 As PointF, _
                   ByVal p2 As PointF) As Single
        Dim dx As Single
        Dim dy As Single
        dx = p2.X - p1.X
        dy = p2.Y - p1.Y
        Return Sqrt((dx * dx) + (dy * dy))
    End Function

    '无参构造函数
    Public Sub New()
    End Sub

    '构造函数，用已知的两点构造圆
    Public Sub New(ByVal pCenter As PointF, ByVal pCir As PointF)
        m_Center = pCenter
        m_pCircle = pCir
    End Sub

    '绘圆
    Public Overrides Sub Draw(ByVal g As Graphics, _
                               ByVal aDrawMode As geDrawMode)
        Dim pen As Pen = DrawSettings(aDrawMode)
        g.DrawEllipse(pen, m_Center.X - Radius, _
              m_Center.X - Radius, Radius * 2, Radius * 2)
    End Sub

    '拾取圆
    Public Overrides Function Pick(ByVal aPos As PointF) As Boolean
        Dim gp As New GraphicsPath()
        gp.AddEllipse(m_Center.X - Radius, m_Center.X - Radius, _
                      Radius * 2, Radius * 2)
        If gp.GetBounds.Contains(aPos) Then
            If gp.IsOutlineVisible(aPos, Pens.Black) Then
                gp.Dispose()
                Return True
            Else
                gp.Dispose()
                Return False
            End If
        Else
            gp.Dispose()
            Return False
        End If
    End Function
End Class