HOWTO: Call Clipboard API from Visual Basic 4.0
Last reviewed: August 13, 1997
Article ID: Q159823
The information in this article applies to:
Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0
SUMMARY
This article contains sample code that illustrates how to call Windows Clipboard API to copy a disk metafile to the Windows Clipboard using the 16-bit and 32-bit versions of Visual Basic 4.0. The code in the article can also be used to work around a bug in the SetData method of the Visual Basic Clipboard object. The workaround replaces the SetData method you use when you copy a disk metafile to clipboard.
MORE INFORMATION
The following statement loads a metafile from a disk and copies it to the Windows Clipboard:
'DiskMetaFileName is the path to a WMF file on the disk.
Clipboard.SetData LoadPicture(DiskMetaFileName), vbCFMetafile
The metafile is successfully copied to the Clipboard. However, the metafile size in the y dimension suggested in the disk metafile is ignored, and is set to match the suggested size in the x dimension. You can reproduce the bug by using the following code fragment with an Image control (Image1) on the form:
Clipboard.Clear ' Clear Clipboard.
Clipboard.SetData LoadPicture(DiskMetaFileName), vbCFMetafile
Image1.Stretch = False 'Resize the control to fit the graphics
Image1.Picture = Clipboard.GetData(vbCFMetafile) 'Copy from Clipboard
Debug.Print Image1.Width, Image1.Height
NOTE: Image1.Width is always the same as Image1.Height.
The sample code in this article provides a subroutine, SetMetaToClp, that works around the bug by directly calling Windows API.
Step-by-Step Example
Start Visual Basic 4.0. If it is already running, choose New Project from the File menu. Form1 is created by default.
Add two CommandButtons, Command1 and Command2, to Form1.
Add one Image control, Image1, to Form1.
Clear all the code for Form1, and then paste the following code to the code window of Form1:
'Please change the path so that it points to a valid metafile.
Private Const strFileName = "d:\vb4\metafile\arrows\Smallarw.wmf"
Private Sub Command1_Click()
Clipboard.Clear ' Clear Clipboard.
Clipboard.SetData LoadPicture(strFileName), vbCFMetafile
Image1.Stretch = False
Image1.Picture = Clipboard.GetData(vbCFMetafile) 'Copy from Clipboard
Debug.Print Image1.Width, Image1.Height
'Image1.Width is always the same as Image1.Height. Bug!
End Sub
Private Sub Command2_Click()
Clipboard.Clear ' Clear Clipboard.
SetMetaToClp strFileName
Image1.Stretch = False
Image1.Picture = Clipboard.GetData(vbCFMetafile) 'Copy from Clipboard
Debug.Print Image1.Width, Image1.Height
'Image1.Width and Image1.Height now display the metafile size suggested
'in the disk metafile
End Sub
Insert a module, Module1, into the project. Copy and paste the following code to Module1:
Public Const OFS_MAXPATHNAME = 128 Public Const OF_READ = &H0 Public Const GMEM_SHARE = &H2000 Public Const GMEM_MOVEABLE = &H2 Public Const GMEM_ZEROINIT = &H40 Public Const GHND = (GMEM_MOVEABLE Or GMEM_ZEROINIT) Public Const HFILE_ERROR = &HFFFF
Type OFSTRUCT
cBytes As Byte
fFixedDisk As Byte
nErrCode As Integer
Reserved1 As Integer
Reserved2 As Integer
szPathName(OFS_MAXPATHNAME) As Byte
End Type
Type RECT
Left As Integer
Top As Integer
Right As Integer
Bottom As Integer
End Type
Type APMFILEHEADER
key As Long
hmf As Integer
bbox As RECT
inch As Integer
reserved As Long
checksum As Integer
End Type
#If Win16 Then
Type METAHEADER
mtType As Integer
mtHeaderSize As Integer
mtVersion As Integer
dummy1 As Integer
mtSize As Long
mtjects As Integer
dummy2 As Integer
mtMaxRecord As Long
mtNoParameters As Integer
End Type
Type METAFILEPICT
mm As Integer
xExt As Integer
yExt As Integer
hmf As Integer
End Type
#Else
Type METAHEADER
mtType As Integer
mtHeaderSize As Integer
mtVersion As Integer
mtSize As Long
mtjects As Integer
mtMaxRecord As Long
mtNoParameters As Integer
End Type
Type METAFILEPICT
mm As Long
xExt As Long
yExt As Long
hmf As Long
End Type
#End If
#If Win16 Then
Declare Function OpenClipboard Lib "User" (ByVal hwnd As Integer) _
As Integer
Declare Function CloseClipboard Lib "User" () As Integer
Declare Function EmptyClipboard Lib "User" () As Integer
Declare Function SetClipboardData Lib "User" (ByVal wFormat As _
Integer, ByVal hMem As Integer) As Integer
Declare Function GlobalAlloc Lib "Kernel" (ByVal wFlags As Integer, _
ByVal dwBytes As Long) As Integer
Declare Function GlobalLock Lib "Kernel" (ByVal hMem As Integer) As Long
Declare Function GlobalUnlock Lib "Kernel" (ByVal hMem As _
Integer) As Integer
Declare Function GlobalFree Lib "Kernel" (ByVal hMem As Integer) _
As Integer
Declare Sub CopyMemory Lib "Kernel" Alias "hmemcpy" (hpvDest As Any, _
ByVal hpvSource As Long, ByVal cbCopy As Long)
Declare Sub CopyMemory2 Lib "Kernel" Alias "hmemcpy" (ByVal hpvDest _
As Long, hpvSource As Any, ByVal cbCopy As Long)
Declare Function OpenFile Lib "Kernel" (ByVal lpFileName As String, _
lpReOpenBuff As OFSTRUCT, ByVal wStyle As Integer) As Integer
Declare Function llseek Lib "Kernel" Alias "_llseek" (ByVal hFile As _
Integer, ByVal lOffset As Long, ByVal iOrigin As Integer) As Long
Declare Function lread Lib "Kernel" Alias "_lread" (ByVal hFile As _
Integer, lpBuffer As Any, ByVal wBytes As Integer) As Integer
Declare Function lread2 Lib "Kernel" Alias "_lread" (ByVal hFile As _
Integer, ByVal lpBuffer As Long, ByVal wBytes As Integer) As Integer
Declare Function hread2 Lib "Kernel" Alias "_hread" (ByVal hFile As _
Integer, ByVal lpBuffer As Long, ByVal wBytes As Long) As Long
Declare Function lclose Lib "Kernel" Alias "_lclose" (ByVal hFile As _
Integer) As Integer
Declare Function SetMetaFileBits Lib "GDI" (ByVal hMem As _
Integer) As Integer #Else
Declare Function OpenClipboard Lib "user32" (ByVal hwnd As Long) As Long
Declare Function CloseClipboard Lib "user32" () As Long
Declare Function EmptyClipboard Lib "user32" () As Long
Declare Function SetClipboardData Lib "user32" (ByVal wFormat As Long, _
ByVal hMem As Long) As Long
Declare Function GlobalAlloc Lib "Kernel32" (ByVal wFlags As Long, _
ByVal dwBytes As Long) As Long
Declare Function GlobalLock Lib "Kernel32" (ByVal hMem As Long) As Long
Declare Function GlobalUnlock Lib "Kernel32" (ByVal hMem As Long) As Long
Declare Function GlobalFree Lib "Kernel32" (ByVal hMem As Long) As Long
Declare Sub CopyMemory Lib "Kernel32" Alias "RtlMoveMemory" ( _
hpvDest As Any, ByVal hpvSource As Long, ByVal cbCopy As Long)
Declare Sub CopyMemory2 Lib "Kernel32" Alias "RtlMoveMemory" (ByVal _
hpvDest As Long, hpvSource As Any, ByVal cbCopy As Long)
Declare Function OpenFile Lib "Kernel32" (ByVal lpFileName As String, _
lpReOpenBuff As OFSTRUCT, ByVal wStyle As Long) As Long
Declare Function llseek Lib "Kernel32" Alias "_llseek" (ByVal hFile As _
Long, ByVal lOffset As Long, ByVal iOrigin As Long) As Long
Declare Function lread Lib "Kernel32" Alias "_lread" (ByVal hFile _
As Long, lpBuffer As Any, ByVal wBytes As Long) As Long
Declare Function lread2 Lib "Kernel32" Alias "_lread" (ByVal hFile _
As Long, ByVal lpBuffer As Long, ByVal wBytes As Long) As Long
Declare Function lclose Lib "Kernel32" Alias "_lclose" (ByVal hFile _
As Long) As Long
Declare Function SetMetaFileBitsEx Lib "gdi32" (ByVal nSize As Long, _
ByVal lpData As Long) As Long
#End If
Public Const CF_METAFILEPICT = 3
Public Const MM_ANISOTROPIC = 8 Public Const MM_ISOTROPIC = 7 Public Const MM_TWIPS = 6 Public Const MM_HIENGLISH = 5 Public Const MM_HIMETRIC = 3 Public Const MM_LOENGLISH = 4 Public Const MM_LOMETRIC = 2 Public Const MM_TEXT = 1
Public Sub SetMetaToClp(szFileName As String)
Dim inof As OFSTRUCT
Dim APMHeader As APMFILEHEADER
Dim mfHeader As METAHEADER
#If Win16 Then
Dim fh As Integer
Dim hData As Integer
Dim hmf As Integer
Dim hGlobal As Integer
#Else
Dim fh As Long
Dim hData As Long
Dim hmf As Long
Dim hGlobal As Long
#End If
fh = OpenFile(szFileName, inof, OF_READ)
If fh = HFILE_ERROR Then
Debug.Print "openfile fails"
Exit Sub
End If
llseek fh, 0, 0
lread fh, APMHeader, LenB(APMHeader)
llseek fh, LenB(APMHeader), 0
lread fh, mfHeader, LenB(mfHeader)
hData = GlobalAlloc(GHND, (mfHeader.mtSize * 2))
If hData = 0 Then
Debug.Print "fail to allocate memory"
lclose fh
Exit Sub
End If
Dim lpData As Long
lpData = GlobalLock(hData)
llseek fh, LenB(APMHeader), 0
#If Win16 Then
hread2 fh, lpData, mfHeader.mtSize * 2
GlobalUnlock (hData)
hmf = SetMetaFileBits(hData)
#Else
lread2 fh, lpData, mfHeader.mtSize * 2
hmf = SetMetaFileBitsEx(mfHeader.mtSize * 2, lpData)
#End If
lclose fh
'if any above file op's fail, hmf will be 0
'or you can check each file op return to see if it is HFILE_ERROR
'but that will be a big waste of code
If hmf = 0 Then
Debug.Print "openfile or SetMetaFile fails"
GlobalFree hData
Exit Sub
End If
Dim myMetaFilePict As METAFILEPICT
myMetaFilePict.mm = MM_ANISOTROPIC
myMetaFilePict.xExt = 2540& * (APMHeader.bbox.Right - _
APMHeader.bbox.Left) / APMHeader.inch
myMetaFilePict.yExt = 2540& * (APMHeader.bbox.Bottom - _
APMHeader.bbox.Top) / APMHeader.inch
myMetaFilePict.hmf = hmf
'cannot directly put myMetaFilePict to clipboard
'memory block for clipboard has to have the flag GMEM_SHARE
hGlobal = GlobalAlloc(GMEM_SHARE, LenB(myMetaFilePict))
Dim lpPict As Long
lpPict = GlobalLock(hGlobal)
CopyMemory2 lpPict, myMetaFilePict, LenB(myMetaFilePict)
GlobalUnlock hGlobal
OpenClipboard 0
EmptyClipboard
SetClipboardData CF_METAFILEPICT, hGlobal
CloseClipboard
End Sub
(c) Microsoft Corporation 1996, All Rights Reserved. Contributions by Wei Hua, Microsoft Corporation
Keywords : APrgWindow VB4ALL VB4WIN kbcode kbhowto
Version : 4.0
Platform : NT WINDOWS
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Last reviewed: August 13, 1997
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