问Graphics.DrawLine，AccessViolation，Visual

EN

Public Class Form1
Public Sub DrawLineInt2(ByVal e As PaintEventArgs)
    'Misc
    Dim Ret As GpStatus

    ' Create pen. 
    Dim blackPen As IntPtr = IntPtr.Zero
    Dim blackbrush As IntPtr = IntPtr.Zero
    Dim c As Int32 = &HFF000000

    Ret = GdipCreateSolidFill(c, blackbrush)
    'Ret = GdipCreatePen1(c, 10, GpUnit.UnitPixel, blackPen)
    Ret = GdipCreatePen2(blackbrush, 10, GpUnit.UnitPixel, blackPen)

    ' Create coordinates of points that define line. 
    Dim x1 As Integer = 100
    Dim y1 As Integer = 100
    Dim x2 As Integer = 500
    Dim y2 As Integer = 125

    ' Draw line to screen.
    Dim graphics As IntPtr = IntPtr.Zero

    'Ret = GdipCreateFromHDC(e.Graphics.GetHdc, graphics)
    Ret = GdipCreateFromHWND(Me.Handle, graphics)

    'System.AccessViolationException here
    Ret = GdipDrawLineI(graphics, blackPen, x1, y1, x2, y2)

    'Here Also
    'Ret = GdipDrawRectangleI(graphics, blackPen, x1, y1, x2, y2)

    'Here as well
    'Ret = GdipDrawArcI(graphics, blackPen, x1, y1, x2, y2, 15, 20)

    'No problems with this line
    'Ret = GdipFillRectangleI(graphics, blackbrush, x1, y1, x2, y2)


    Ret = GdipDeletePen(blackPen)
    Ret = GdipDeleteBrush(blackbrush)
    Ret = GdipDeleteGraphics(graphics)

    'e.Graphics.ReleaseHdc()
End Sub

Public Sub DrawLineInt(ByVal e As PaintEventArgs)
    ' Create pen. 
    Dim blackPen As New Pen(Color.Black, 3)
    ' Create coordinates of points that define line. 
    Dim x1 As Integer = 100
    Dim y1 As Integer = 100
    Dim x2 As Integer = 500
    Dim y2 As Integer = 100

    ' Draw line to screen.
    Try
        e.Graphics.DrawLine(blackPen, x1, y1, x2, y2)
    Catch
    End Try
    blackPen.Dispose()
End Sub
Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
    'DrawLineInt(e)
    DrawLineInt2(e)
End Sub


Private Enum GpStatus As Int32
    Ok = 0
    GenericError = 1
    InvalidParameter = 2
    OutOfMemory = 3
    ObjectBusy = 4
    InsufficientBuffer = 5
    NotImplemented = 6
    Win32Error = 7
    WrongState = 8
    Aborted = 9
    FileNotFound = 10
    ValueOverflow = 11
    AccessDenied = 12
    UnknownImageFormat = 13
    FontFamilyNotFound = 14
    FontStyleNotFound = 15
    NotTrueTypeFont = 16
    UnsupportedGdiplusVersion = 17
    GdiplusNotInitialized = 18
    PropertyNotFound = 19
    PropertyNotSupported = 20
End Enum

Private Enum GpUnit As Int32  ' aka Unit
    UnitWorld      ' 0 -- World coordinate (non-physical unit)
    UnitDisplay    ' 1 -- Variable -- for PageTransform only
    UnitPixel      ' 2 -- Each unit is one device pixel.
    UnitPoint      ' 3 -- Each unit is a printer's point, or 1/72 inch.
    UnitInch       ' 4 -- Each unit is 1 inch.
    UnitDocument   ' 5 -- Each unit is 1/300 inch.
    UnitMillimeter ' 6 -- Each unit is 1 millimeter.
End Enum

Private Declare Function GdipDrawLine Lib "gdiplus.dll" (ByVal graphics As IntPtr, ByVal pen As IntPtr, ByVal x1 As Single, ByVal y1 As Single, ByVal x2 As Single, ByVal y2 As Single) As GpStatus
Private Declare Function GdipDrawLineI Lib "gdiplus.dll" (ByVal graphics As IntPtr, ByVal pen As IntPtr, ByVal x1 As Int32, ByVal y1 As Int32, ByVal x2 As Int32, ByVal y2 As Int32) As GpStatus

Private Declare Function GdipCreatePen1 Lib "gdiplus.dll" (ByVal color As Int32, ByVal Width As Single, ByVal unit As GpUnit, ByRef pen As IntPtr) As GpStatus
Private Declare Function GdipCreatePen2 Lib "gdiplus.dll" (ByVal brush As IntPtr, ByVal Width As Single, ByVal unit As GpUnit, ByRef pen As IntPtr) As GpStatus
Private Declare Function GdipDeletePen Lib "gdiplus.dll" (ByVal pen As Int32) As GpStatus

Private Declare Function GdipCreateSolidFill Lib "gdiplus" (ByVal argb As Int32, ByRef brush As IntPtr) As GpStatus
Private Declare Function GdipDeleteBrush Lib "gdiplus" (ByVal brush As IntPtr) As GpStatus

Private Declare Function GdipFillRectangleI Lib "gdiplus" (ByVal graphics As IntPtr, ByVal brush As IntPtr, ByVal x As Int32, ByVal y As Int32, ByVal Width As Int32, ByVal Height As Int32) As GpStatus
Private Declare Function GdipDrawRectangleI Lib "gdiplus" (ByVal graphics As IntPtr, ByVal pen As IntPtr, ByVal x As Int32, ByVal y As Int32, ByVal Width As Int32, ByVal Height As Int32) As GpStatus

Private Declare Function GdipDrawArcI Lib "gdiplus" (ByVal graphics As IntPtr, ByVal pen As IntPtr, ByVal x As Int32, ByVal y As Int32, ByVal Width As Int32, ByVal Height As Int32, ByVal startAngle As Single, ByVal sweepAngle As Single) As GpStatus


Private Declare Function GdipCreateFromHDC Lib "gdiplus.dll" (ByVal hdc As IntPtr, ByRef graphics As IntPtr) As GpStatus
Private Declare Function GdipCreateFromHWND Lib "gdiplus.dll" (ByVal hwnd As IntPtr, ByRef graphics As IntPtr) As GpStatus
Private Declare Function GdipDeleteGraphics Lib "gdiplus" (ByVal graphics As IntPtr) As GpStatus