Graphics.EnumerateMetafile Method (Metafile, Point, Graphics.EnumerateMetafileProc)

 

Sends the records in the specified Metafile, one at a time, to a callback method for display at a specified point.

Namespace:   System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

Public Sub EnumerateMetafile (
	metafile As Metafile,
	destPoint As Point,
	callback As Graphics.EnumerateMetafileProc
)

Parameters

metafile
Type: System.Drawing.Imaging.Metafile

Metafile to enumerate.

destPoint
Type: System.Drawing.Point

Point structure that specifies the location of the upper-left corner of the drawn metafile.

callback
Type: System.Drawing.Graphics.EnumerateMetafileProc

Graphics.EnumerateMetafileProc delegate that specifies the method to which the metafile records are sent.

This method enumerates the records contained in the specified metafile. Each record is individually sent to a callback method specified by the callback parameter. Typically, the callback method calls the PlayRecord method to "play back", or draw, the record.

If the callback method calls PlayRecord, it must do so by calling the PlayRecord method of the specific Metafile that is being enumerated.

The following code example creates a form that has a Metafile as one of its private members. The OnPaint method calls EnumerateMetafile, which calls the form's MetafileCallback method for each record in the metafile. The MetafileCallback method calls the PlayRecord method. Notice that the MetafileCallback method receives the record data as an IntPtr, but the PlayRecord method expects the record data to be a byte array. The call to Copy copies the record data to a byte array so that it can be passed to PlayRecord.

Imports System
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Windows.Forms
' for Marshal.Copy
Imports System.Runtime.InteropServices


Public Class Form1
    Inherits Form
    Private metafile1 As Metafile
    Private metafileDelegate As Graphics.EnumerateMetafileProc
    Private destPoint As Point

    Public Sub New() 
        metafile1 = New Metafile("C:\test.wmf")
        metafileDelegate = New Graphics.EnumerateMetafileProc(AddressOf MetafileCallback)
        destPoint = New Point(20, 10)

    End Sub

    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) 
        e.Graphics.EnumerateMetafile(metafile1, destPoint, metafileDelegate)

    End Sub

    Private Function MetafileCallback(ByVal recordType As _
        EmfPlusRecordType, ByVal flags As Integer, ByVal dataSize As Integer, _
        ByVal data As IntPtr, ByVal callbackData As PlayRecordCallback) As Boolean

        Dim dataArray As Byte() = Nothing
        If data <> IntPtr.Zero Then

            ' Copy the unmanaged record to a managed byte buffer 
            ' that can be used by PlayRecord.
            dataArray = New Byte(dataSize) {}
            Marshal.Copy(data, dataArray, 0, dataSize)
        End If

        metafile1.PlayRecord(recordType, flags, dataSize, dataArray)
        Return True

    End Function

    Shared Sub Main() 
        Application.Run(New Form1())
    End Sub

End Class

.NET Framework
Available since 1.1
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