cline.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

'直线段类

Imports System.Math

Public Class CLine
    Inherits CGElement

    Private m_Begin, m_End As PointF

    '直线段的起点属性
    Public Property LBegin() As PointF
        Get
            Return m_Begin
        End Get
        Set(ByVal Value As PointF)
            m_Begin = Value
        End Set
    End Property

    '直线段的终点属性
    Public Property LEnd() As PointF
        Get
            Return m_End
        End Get
        Set(ByVal Value As PointF)
            m_End = Value
        End Set
    End Property

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

    '构造函数，用已知的两点构造直线段
    Public Sub New(ByVal pBegin As PointF, ByVal pEnd As PointF)
        Init()
        m_Begin = pBegin
        m_End = pEnd
    End Sub

    '构造函数，用已知的直线段构造直线段
    Public Sub New(ByVal aline As CLine)
        m_Begin = aline.LBegin
        m_End = aline.LEnd
    End Sub

    '初始化直线段
    Private Shadows Sub Init()
        MyBase.Init()
        With m_Begin
            .X = 0
            .Y = 0
        End With
        m_End = m_Begin
    End Sub

    '绘直线段
    Public Overrides Sub Draw(ByVal g As Graphics, ByVal aDrawMode As geDrawMode)

        '将直线段的起点和终点坐标转换为页面坐标
        Dim eb As PointF = WorldtoPage(m_Begin)
        Dim ee As PointF = WorldtoPage(m_End)

        '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)
        '把画笔移动到直线段的起点处
        Win32API.MoveToEx(hdc, eb.X, eb.Y, Nothing)
        '绘直线段到终点
        Win32API.LineTo(hdc, 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