Canvas.vb

Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Windows.Forms
Imports System.Runtime.InteropServices

Public Class Canvas : Implements IDisposable

    Private Const DEFAULT_BACKGROUND_COLOR As UInteger = &H7F7F7F

    Private memBmp As Bitmap        'Memory bitmap
    Private hMemBmp As IntPtr       'Bitmap handle
    Private memDC As Graphics       'Device context
    Private hMemDC As IntPtr        'Context handle
    Private hOld As IntPtr          'Last selected GDI object
    Private _target As PictureBox   'Render target
    Private _disposed As Boolean = False

    Public Sub New(ByRef Target As PictureBox)
        _target = Target
        CreateContext()
    End Sub
    Friend Sub CreateContext()
        Try
            CleanUp()

            Dim clientDC As Graphics = _target.CreateGraphics()
            Dim hdc As IntPtr = clientDC.GetHdc()
            hMemDC = Win32API.CreateCompatibleDC(hdc)
            memDC = Graphics.FromHdc(hMemDC)

            memBmp = New Bitmap(_target.ClientSize.Width, _target.ClientSize.Height, PixelFormat.Format16bppRgb555)
            hMemBmp = memBmp.GetHbitmap()
            hOld = [Select](hMemBmp)
            Clear()

            clientDC.ReleaseHdc(hdc)
            clientDC.Dispose()
            _disposed = False
        Catch
        End Try
    End Sub
    Friend Function [Select](ByRef hObject As IntPtr) As IntPtr
        Return Win32API.SelectObject(hMemDC, hObject)
    End Function
    Public Sub Resize()
        CreateContext()
    End Sub
    Public Sub Clear(Optional ByVal Color As Integer = DEFAULT_BACKGROUND_COLOR)
        Dim rc As Win32API.STRUCT_RECT
        With rc
            .top = 0
            .left = 0
            .right = _target.ClientSize.Width
            .bottom = _target.ClientSize.Height
        End With
        Dim _brush As New SolidBrush(Color)
        FillRect(hMemDC, rc, _brush.Handle)
        _brush.Dispose()
    End Sub
    Public Sub Render(ByVal e As PaintEventArgs)
        Try
            Dim hdc As IntPtr = e.Graphics.GetHdc()
            Win32API.BitBlt(hdc, e.ClipRectangle.X, e.ClipRectangle.Y, e.ClipRectangle.Width, e.ClipRectangle.Height, hMemDC, e.ClipRectangle.X, e.ClipRectangle.Y, TernaryRasterOperations.SRCCOPY)
            e.Graphics.ReleaseHdc(hdc)
        Catch
        End Try
    End Sub
    Public Sub Copy(ByRef source As Canvas)
        Try
            Dim hdc As IntPtr = source.Buffer.GetHdc()
            Win32API.BitBlt(hMemDC, 0, 0, source.Target.ClientSize.Width, source.Target.ClientSize.Height, hdc, 0, 0, TernaryRasterOperations.SRCCOPY)
            source.Buffer.ReleaseHdc(hdc)
        Catch
        End Try
    End Sub

    Public ReadOnly Property Graphics As Graphics
        Get
            Return memDC
        End Get
    End Property
    Friend ReadOnly Property Handle As IntPtr
        Get
            Return hMemDC
        End Get
    End Property
    Friend ReadOnly Property Target As PictureBox
        Get
            Return _target
        End Get
    End Property

    Public Overloads Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub
    Protected Overridable Overloads Sub Dispose(ByVal disposing As Boolean)
        If Not _disposed Then
            If disposing Then
                'Clear managed resources
                memBmp.Dispose()
                memDC.Dispose()
            End If
            'Clear unmanaged resources
            CleanUp(disposing)
            _disposed = True
        End If
    End Sub
    Private Sub CleanUp(Optional ByVal disposing As Boolean = False)
        If hOld.ToInt32 <> 0 Then [Select](hOld)
        If hMemBmp.ToInt32 <> 0 Then Win32API.DeleteObject(hMemBmp)
        If hMemDC.ToInt32 <> 0 Then Win32API.DeleteDC(hMemDC)
        hOld = 0
        hMemBmp = 0
        hMemDC = 0
        If Not disposing Then
            If Not memBmp Is Nothing Then memBmp.Dispose()
            If Not memDC Is Nothing Then memDC.Dispose()
            memDC = Nothing
            memBmp = Nothing
        End If
    End Sub

End Class