FIX: When You Use SendMessage with TB_GETIMAGELIST to Get an ImageList Handle on Windows XP, You Do Not Get the Correct Handle

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You can use SendMessage to get the image handle from various controls in Microsoft Windows Common Controls 6.0 (Mscomctl.ocx). By using SendMessage, you can pass TB_GETIMAGELIST, LVM_GETIMAGELIST, TVM_GETIMAGELIST, or TCM_GETIMAGELIST to get the imagelist handle for the Toolbar, ListView, TreeView, and TabStrip controls.

However, when you do this on a computer running Windows XP, the wrong handle is returned. If you call any other APIs, and then pass this handle, those API calls will not function correctly.
This problem occurs because Windows XP and Mscomctl.ocx load two different versions of Comctl32.dll that are not compatible.
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Visual Studio 6.0 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
   Date         Time   Version   Size       File name   -----------------------------------------------------   13-Dec-2002  00:18  1,062,160  Mscomctl.ocx
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

Steps to Reproduce the Behavior

To reproduce the problem by using the Toolbar control, follow these steps:
  1. Start a new Visual Basic 6.0 Standard EXE project. By default, Form1 is created.
  2. On the Projects menu, click Components. In the Components dialog box, add a reference to Microsoft Windows Common Controls 6.0.
  3. Add an ImageList (ImageList1) control, a Toolbar (Toolbar1) control, and a CommandButton (Command1) to Form1.
  4. Right-click the ImageList control, and then click the Images tab. Add two images to the ImageList control.
  5. Add the following code to Form1:
    Option ExplicitPrivate Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByRef lParam As Any) As LongPrivate Declare Function GetImageCount Lib "comctl32" Alias "ImageList_GetImageCount" (ByVal p As Long) As LongPrivate Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal cmd As Long) As LongPrivate Const WM_USER = &H400Private Const TB_GETIMAGELIST = WM_USER + 49Private Const GW_CHILD = 5Private Sub Command1_Click()    Dim hImageList As Long, hChild As Long        hChild = GetWindow(Toolbar1.hwnd, GW_CHILD)        hImageList = SendMessage(hChild, TB_GETIMAGELIST, 0, 0)    MsgBox "Image Count = " & GetImageCount(hImageList)End SubPrivate Sub Form_Load()    Set Toolbar1.ImageList = ImageList1    Toolbar1.Buttons.Add , , "Button 1"    Toolbar1.Buttons.Add , , "Button 2"    Toolbar1.Buttons(1).Image = 1    Toolbar1.Buttons(2).Image = 2End Sub
  6. Run the application, and then click Command1. The Image Count text box contains 0. After you apply the hotfix, the image count correctly returns as 2.

Article ID: 811415 - Last Review: 02/27/2014 21:16:13 - Revision: 2.3

Microsoft Visual Basic 6.0 Enterprise Edition, Microsoft Visual Basic 6.0 Learning Edition, the operating system: Microsoft Windows XP

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