How to set the Picture property of an ActiveX control in Visual C++

MORE INFORMATION

Using the Grid Control (Grid32.ocx is shipped with Visual C++ 4.x) as an example, you can implement the SetPicture() and GetPicture() methods in the control classes provided by the Component Gallery by using this code:

   void CGridCtrl::SetPicture(LPDISPATCH propVal)
   {
        SetProperty(0x15, VT_DISPATCH, propVal);
   }

   CPicture CGridCtrl::GetPicture()
   {
        LPDISPATCH pDispatch;
        GetProperty(0x15, VT_DISPATCH, (void*)&pDispatch);
        return CPicture(pDispatch);
   }
				

It is not intuitively clear how to use these methods to get or set the picture property. The following steps show how to set the picture property of an ActiveX control successfully in an AppWizard-generated application. The particular control used in this example is the Microsoft Grid Control, and its picture property is being set to the toolbar bitmap provided by AppWizard.

1. Generate a new non-dialog based AppWizard application. Be sure to select both Container and Control support in AppWizard Step 3.
2. Add the Grid Control from the OLE Controls tab (or Registered ActiveX Controls in VC++ 5.0) in the Component Gallery.
3. Add Afxctl.h to the list of pre-compiled header files in Stdafx.h.
4. Add a Grid Control object to the About Dialog box in the dialog editor.
5. Using ClassWizard, add a control member variable called m_grid to the Grid Control in the About Dialog box.
6. Override the container's initialization routine to create and initialize a CPictureHolder object. Call the SetPicture() method for the control, passing in the CPictureHolder's dispatch pointer. SetPicture calls SetProperty() for the control. Here's an example:

         BOOL CAboutDlg::OnInitDialog()
         {
             CDialog::OnInitDialog();
   
             // Create and Initialize the CPictureHolder variable with the
             // toolbar resource
             CPictureHolder pictholder;
             pictholder.CreateFromBitmap(IDR_MAINFRAME);
   
             //Pass dispatch pointer to CPictureHolder
             m_grid.SetPicture(pictholder.GetPictureDispatch());
   
             // NOTE: GetPictureDispatch() QI()'s for the IPictureDisp
             // interface, so the picture object will remain alive until
             // the property is reset or the control is destroyed. When
             // pictholder goes out of scope, it calls Release() on the
             // picture object, but the previously mentioned QI() will have
             // bumped the ref count, allowing it to remain alive until the
             // control itself releases the picture object.
   
           return TRUE;
         }