Finding Display Size of Dialog From Resource

This article explains how to find display size of the dialog from it’s resource handle.
It will be helpful, if you need to arrange position and size of other windows based upon
the dialog size before the dialog gets displayed.

There is no MFC support to find the display size of dialog from it’s resource and
it becomes even more painful to implement if dialog resides in a DLL and contains
some ActiveX controls.

Here is the function to find it :

CRect CalcDialogSize(INT nResourceId,
                     const char* strDllName=NULL)
{
 CRect rectSize;
 // if the dialog resource resides in a DLL …
 //	
 HINSTANCE hExeResourceHandle;
 HINSTANCE hModule;
 if(strDllName != NULL)
 {
  hExeResourceHandle = AfxGetResourceHandle();
  hModule= ::LoadLibrary(strDllName);
  ASSERT(hModule);
  AfxSetResourceHandle(hModule);
 }
 HINSTANCE hInst =
  AfxFindResourceHandle(MAKEINTRESOURCE(nResourceId),
                        RT_DIALOG);
 ASSERT(hInst != NULL);
 HRSRC hRsrc = ::FindResource(hInst,
                              MAKEINTRESOURCE(nResourceId),
                              RT_DIALOG);
 ASSERT(hRsrc != NULL);
 HGLOBAL hTemplate = ::LoadResource(hInst, hRsrc);
 ASSERT(hTemplate != NULL);
 DLGTEMPLATE* pTemplate = (DLGTEMPLATE*)::LockResource(hTemplate);
 //Load coresponding DLGINIT resource 
 //(if we have any ActiveX components)
 //
 void* lpDlgInit;
 HGLOBAL hDlgInit = NULL;
 CDialog dlg;
 HRSRC hsDlgInit = ::FindResource(hInst,
                                  MAKEINTRESOURCE(nResourceId),
                                  RT_DLGINIT);
 if (hsDlgInit != NULL)
 {
  // load it
  hDlgInit = ::LoadResource(hInst, hsDlgInit);
  ASSERT(hDlgInit != NULL);
  // lock it
  lpDlgInit = ::LockResource(hDlgInit);
  ASSERT(lpDlgInit != NULL);
  dlg.CreateIndirect(pTemplate, NULL, lpDlgInit);
 }
 else
 {
  dlg.CreateIndirect(pTemplate, NULL);
 }
 CRect rect;
 dlg.GetClientRect(rectSize);
 dlg.DestroyWindow();
 ::UnlockResource(hTemplate);
 ::FreeResource(hTemplate);
 if (hDlgInit)
 {
  ::UnlockResource(hDlgInit);
  ::FreeResource(hDlgInit);
 }
 if(strDllName != NULL)
 {
  AfxSetResourceHandle(hExeResourceHandle);
  ::FreeLibrary(hModule);
 }
 return rectSize;
}