Separating the views of an MDI application into different DLLs

Different views can be seperated into different dlls in an MDI application:

Advantages:

I will try to explain this using an example. In my example, I have an EXE which I call Host. It is an MDI application. Then I have 2 views inside 2 DLLs. The name of these dlls are inside an INI file called HOST.INI.

The only catch is all DLLs that the HOST application can load must export a function by called Init(). Some kind of a rudimentary COM, eh? :)

At runtime, the HOST application loads the DLL & collects information from the INI file such as its CMultiDocTemplate pointer, the handle to the image to be displayed on the menu and string to be displayed on the menu to invoke the view.

All of this information is stored in a simple CList of a struct I defined.

struct  __VIEWINFO
{
 int iImage;
 CString strLabel;
 CMultiDocTemplate *pDocTemp;	
};

 HICON hIcon;
 CString strLabel;
 CMultiDocTemplate *pDocTemplate; 
 HINSTANCE hDLL;     
 LPDLLFUNC lpfnDllFunc;   
 UINT  uReturnVal;

 m_List.SubclassDlgItem(IDC_LIST, &m_wndMyDialogBar);
 m_pImageList = new CImageList();
 m_pImageList ->Create(32, 32, TRUE,1, 4);

 int n = GetPrivateProfileInt("dll","Total",0,"host.ini");
 for (int i = 0; i < n; i++)
 {
  CString strDllName;
  strDllName.Format("dll%d",i+1);
  GetPrivateProfileString("dll",strDllName,0,strDllName.GetBuffer(15),15,"host.ini");
  strDllName.TrimRight();
  if(strDllName.IsEmpty())
   continue;
  
  hDLL = LoadLibrary(strDllName);
  lpfnDllFunc = (LPDLLFUNC)::GetProcAddress(hDLL,"Init");
  if (!lpfnDllFunc)
   FreeLibrary(hDLL);       
  else
  {
   uReturnVal = lpfnDllFunc(&hIcon,&strLabel,&pDocTemplate);
   m_pImageList ->Add(hIcon);
   __VIEWINFO *viewInfo = new __VIEWINFO;
   viewInfo->iImage = m_pImageList->GetImageCount()-1;
   viewInfo->strLabel = strLabel;
   viewInfo->pDocTemp = pDocTemplate;
   m_ViewList.AddTail(viewInfo);
  }
 }
 m_List.SetImageList(m_pImageList,LVSIL_NORMAL);
	
 POSITION pos = m_ViewList.GetHeadPosition();
 i = 0;
 while(pos != NULL)
 {
  __VIEWINFO *viewInfo = m_ViewList.GetNext(pos);
  ASSERT(viewInfo);
  int nIndex = m_List.InsertItem(i++,viewInfo->strLabel,viewInfo->iImage);
  m_List.SetItemData(nIndex,(ULONG)viewInfo->pDocTemp);
 }

{
 int nSel = m_List.GetNextItem(-1, LVNI_SELECTED);
 if(-1 == nSel)
  return;
 CMultiDocTemplate *pDocTemplate = (CMultiDocTemplate *)m_List.GetItemData(nSel);
 pDocTemplate->OpenDocumentFile(NULL); 
}

extern "C" AFX_EXT_API 
UINT Init(HICON *hIcon,CString *strLabel,CMultiDocTemplate **pDocTemplate)
{
 new CDynLinkLibrary(View1DLL);

 CWinApp* pApp = AfxGetApp();
 ASSERT(pApp != NULL);

 *pDocTemplate =  new CMultiDocTemplate(IDR_VIEW1TYPE,
  RUNTIME_CLASS(CView1Doc),
  RUNTIME_CLASS(CChildFrame),
  RUNTIME_CLASS(CView1View));

 pApp->AddDocTemplate(*pDocTemplate);
 *hIcon = pApp->LoadIcon(IDI_VIEW1ICON);
 *strLabel = "View 1";		
 return 0;
}

Download demo project - 60 KB

Date Last Updated: April 3, 1999