carc.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

'圆弧类
Imports System.Drawing.Drawing2D
Imports System.Math

Public Class CArc
    Inherits CGElement

    Private m_Center, m_Begin, m_End 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

    '圆弧起点属性
    Public Property ABegin() As PointF
        Get
            Return m_Begin
        End Get
        Set(ByVal Value As PointF)
            m_Begin = Value
        End Set
    End Property

    '圆弧终点属性
    Public Property AEnd() As PointF
        Get
            Return m_End
        End Get
        Set(ByVal Value As PointF)
            m_End = Value
        End Set
    End Property

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

    '圆弧起点的方位角
    Public ReadOnly Property AngleBegin() As Single
        Get
            Dim aAngle As Single
            aAngle = GetAngle(m_Center, m_Begin)
            Return aAngle
        End Get
    End Property

    '圆弧终点的方位角
    Public ReadOnly Property AngleEnd() As Single
        Get
            Dim aAngle As Single
            aAngle = GetAngle(m_Center, m_End)
            Return aAngle
        End Get
    End Property

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

    '构造函数，用已知的圆心、起点和另一点进行构造
    Public Sub New(ByVal pCenter As PointF, ByVal p1 As PointF, ByVal p2 As PointF)
        Init()
        m_Center = pCenter
        m_Begin = p1
        Dim r As Single = DistPtoP(m_Center, m_Begin)
        Dim angle2 As Single = GetAngle(m_Center, p2)
        m_End.X = r * Cos(angle2) + m_Center.X
        m_End.Y = r * Sin(angle2) + m_Center.Y
    End Sub

    '构造函数，用已知的一个圆弧进行构造
    Public Sub New(ByVal aArc As CArc)
        With aArc
            m_Center = .Center
            m_Begin = .ABegin
            m_End = .AEnd
        End With
    End Sub

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

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

        '将控制点的坐标由世界坐标转换为页面坐标
        Dim ec As PointF = WorldtoPage(m_Center)
        Dim eb As PointF = WorldtoPage(m_Begin)
        Dim ee As PointF = WorldtoPage(m_End)

        '获得当前绘图环境的句柄
        Dim hdc As IntPtr
        hdc = g.GetHdc()

        '得到圆弧终点的坐标
        Dim X As Single = Radius * Cos(AngleEnd) + m_Center.X
        Dim Y As Single = Radius * Sin(AngleEnd) + m_Center.Y
        Dim pEnd As New PointF(X, Y)
        '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)
        '用刚刚创建的画笔绘圆弧
        Win32API.Arc(hdc, ec.X - Radius, ec.Y + Radius, _
            ec.X + Radius, ec.Y - Radius, eb.X, _
            eb.Y, ee.X, ee.Y)
        '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