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

'圆类
Imports System.Math
Imports System.Drawing.Drawing2D

Public Class CCircle
    Inherits CGElement

    Private m_Center As PointF
    Private m_PCircle As PointF

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

    '圆上一点属性
    Public Property PCircle() As PointF
        Get
            Return m_PCircle
        End Get
        Set(ByVal Value As PointF)
            m_PCircle = Value
        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

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

    '构造函数，用已知的两个点构造圆
    Public Sub New(ByVal pCenter As PointF, ByVal pCircle As PointF)
        Init()
        m_Center = pCenter
        m_PCircle = pCircle
    End Sub

    '构造函数，用已知的圆构造圆
    Public Sub New(ByVal aCircle As CCircle)
        With aCircle
            m_Center = .Center
            m_PCircle = .PCircle
        End With
    End Sub

    '初始化圆
    Private Shadows Sub Init()
        MyBase.Init()
        With m_Center
            .X = 0
            .Y = 0
        End With
        m_PCircle = m_Center
    End Sub

    '绘圆
    Public Overrides Sub Draw(ByVal g As Graphics, ByVal aDrawMode As geDrawMode)

        '将控制点的坐标转换为页面坐标
        Dim ec As PointF = WorldtoPage(m_Center)
        Dim ep As PointF = WorldtoPage(m_PCircle)

        '获取绘图环境的句柄
        Dim hdc As IntPtr
        hdc = g.GetHdc()
        '设置画笔参数
        Dim penPara As Integer() = DrawSettings(hdc, aDrawMode)
        '创建画笔
        Dim aPen As Long = Win32API.CreatePen(penPara(0), penPara(1), penPara(2))
        '把画笔选入绘图环境，并返回原来的画笔
        Dim oldP As Long = Win32API.SelectObject(hdc, aPen)
        '把空刷子选入绘图环境
        Win32API.SelectObject(hdc, Win32API.GetStockObject(5))
        '绘圆
        Win32API.Ellipse(hdc, ec.X - Radius, ec.Y + Radius, _
           ec.X + Radius, ec.Y - Radius)
        '把原来的画笔选入绘图环境
        Win32API.SelectObject(hdc, oldP)
        '删除新创建的画笔
        Win32API.DeleteObject(aPen)
        '释放绘图环境句柄
        g.ReleaseHdc(hdc)
    End Sub

End Class