Question

I need to determine the size of a dialog client area as defined in the resource file.

GetClientRect clips the design size by the size of the desktop. I need the size as designed in screen units. I found this which purports to retrieve the size form the dialog resource but sadly it uses MFC.

I have the dialog open and have its HWND and it’s ID. How can I get the dsign size in screen units without using MFC stuff?

Answer 1

SIZE GetDialogSize(INT nResourceId, BOOL bApproximateCalcMethod = FALSE, LPCTSTR strDllName = NULL)
{

    SIZE dlgSize = {0}; 
    HINSTANCE hModule = 0;

    if(strDllName != NULL)   
        hModule= ::LoadLibrary(strDllName);              
    else
        hModule = ::GetModuleHandle(NULL);   

    HRSRC hRsrc = ::FindResource(hModule, MAKEINTRESOURCE(nResourceId), RT_DIALOG);  

    HGLOBAL hTemplate = ::LoadResource(hModule, hRsrc);  

    DLGTEMPLATE* pTemplate = (DLGTEMPLATE*)::LockResource(hTemplate);

    if (bApproximateCalcMethod) // the approximate method of calculating
    {
        LONG dlgBaseUnits = GetDialogBaseUnits();
        int baseunitX = LOWORD(dlgBaseUnits), baseunitY = HIWORD(dlgBaseUnits);
        dlgSize.cx = MulDiv(pTemplate->cx, baseunitX, 4);
        dlgSize.cy = MulDiv(pTemplate->cy, baseunitY, 8);
    }
    else // the accurate method of calculation
    {
        HWND hDlg = ::CreateDialogIndirect(0, pTemplate, NULL, DialogProc);         
        RECT rc = {0};
        ::GetWindowRect(hDlg, &rc);
        ::DestroyWindow(hDlg);

        dlgSize.cx = rc.right - rc.left;
        dlgSize.cy = rc.bottom - rc.top;
    }

    UnlockResource(hTemplate);
    ::FreeResource(hTemplate);

    if(strDllName != NULL)
        ::FreeLibrary(hModule);

    return dlgSize;
}