DLL Registration / Unregistration using a Shell Extension

This time is about shell extensions. Because I am tired to open a console every time when I want to register the Debug dll as shell extension, I was thinking that's a good idea to right-click the dll to register/unregister.

So here we are! (as stupid Dexters's sister, DeeDee, said once). You will find here few things you cannot find in MSDN or in other articles.

1. GUID. You can obtain this sinister number running one of the uuidgen or guidgen tools. This is CLSID_DLLRegisterer.

2. The main file, where the DLL's entry point DllMain resides, is dllregshex.cpp. I prefer to load resources at start and free them at end, especially when are in little number. So, the routines _LoadResources and _UnloadResources do this. The other two interesting routines are DllRegisterServer and DllUnregisterServer. If you use one, be polite to the user and use the twin (I have seen may Reg, but few Unreg). That's when you did not choose another way (as a .reg file, for example, or separate install/uninstall programs).

So, what's happening registering a dll as shell context extension? You have to create the entry in CLSID key and to create under this the 'samename' key and the thread model key (I read somewhere that only 'Apartment' is accepted for context extensions - is really true?).

STDAPI 
DllRegisterServer(void)
{
  HINSTANCE hInst = g_hmodThisDll;

  int      i;
  HKEY     hKey;
  LRESULT  lResult;
  DWORD    dwDisp;
  TCHAR    szSubKey[MAX_PATH];
  TCHAR    szCLSID[MAX_PATH];
  TCHAR    szModule[MAX_PATH];
  LPWSTR   pwszShellExt;

  StringFromIID(CLSID_DLLRegisterer, &pwszShellExt);

  if (pwszShellExt) 
  {
    WideCharToLocal(szCLSID, pwszShellExt, ARRAYSIZE(szCLSID));

    LPMALLOC pMalloc;
    CoGetMalloc(1, &pMalloc);
    if(pMalloc)
    {
      pMalloc->Free(pwszShellExt);
      pMalloc->Release();
    }
  }                                                

  GetModuleFileName(hInst, szModule, ARRAYSIZE(szModule));
  REGSTRUCT ShExClsidEntries[] = 
  {
    HKEY_CLASSES_ROOT, TEXT("CLSID\\%s"), NULL, TEXT(DLLREGUNREGNAME),
    HKEY_CLASSES_ROOT, TEXT("CLSID\\%s\\InProcServer32"), NULL, TEXT("%s"),
    HKEY_CLASSES_ROOT, TEXT("CLSID\\%s\\InProcServer32"),
	  TEXT("ThreadingModel"), TEXT("Apartment"), NULL, NULL, NULL, NULL
  };

  for(i = 0; ShExClsidEntries[i].hRootKey; i++) 
  {
    wsprintf(szSubKey, ShExClsidEntries[i].lpszSubKey, szCLSID);
    lResult = RegCreateKeyEx(ShExClsidEntries[i].hRootKey, szSubKey, 0, NULL,
      REG_OPTION_NON_VOLATILE,  KEY_WRITE, NULL,
      &hKey, &dwDisp);

    if(NOERROR == lResult) 
    {
      TCHAR szData[MAX_PATH];
      wsprintf(szData, ShExClsidEntries[i].lpszData, szModule);
      lResult = RegSetValueEx(hKey, ShExClsidEntries[i].lpszValueName, 0,
        REG_SZ, 
        (LPBYTE)szData, lstrlen(szData) + 1);
      RegCloseKey(hKey);
    } 
    else
      return SELFREG_E_CLASS;
    }

  REGSTRUCT OtherShExEntries[] = 
  {
    HKEY_LOCAL_MACHINE, TEXT("software\\classes\\clsid\\"DLLREGUNREGNAME),
    NULL,   TEXT("%s"),
    HKEY_CLASSES_ROOT,
	TEXT("dllfile\\shellex\\ContextMenuHandlers\\"DLLREGUNREGNAME),
	NULL, TEXT("%s"), NULL, NULL, NULL, NULL
  };

  for (i = 0; OtherShExEntries[i].hRootKey; i++) 
  {
    wsprintf(szSubKey, OtherShExEntries[i].lpszSubKey, szCLSID);
    lResult = RegCreateKeyEx(OtherShExEntries[i].hRootKey, szSubKey, 0, NULL, 
      REG_OPTION_NON_VOLATILE, KEY_WRITE, NULL, &hKey, &dwDisp);

    if(NOERROR == lResult) 
    {
      TCHAR szData[MAX_PATH];
      wsprintf(szData, OtherShExEntries[i].lpszData, szCLSID);
      lResult = RegSetValueEx(hKey, OtherShExEntries[i].lpszValueName, 0,
	  REG_SZ,
        (LPBYTE)szData, lstrlen(szData) + 1);
      RegCloseKey(hKey);
    } 
    else
      return SELFREG_E_CLASS;
  }

  OSVERSIONINFO  osvi;
  osvi.dwOSVersionInfoSize = sizeof(osvi);
  GetVersionEx(&osvi);
  if (VER_PLATFORM_WIN32_NT == osvi.dwPlatformId)  
  {
    lstrcpy( szSubKey,
    TEXT(
      "Software\\Microsoft\\Windows\\CurrentVersion\\Shell Extensions\\Approved"
	));
    lResult = RegCreateKeyEx(HKEY_LOCAL_MACHINE, szSubKey, 0, NULL,
      REG_OPTION_NON_VOLATILE, KEY_WRITE,
      NULL, &hKey, &dwDisp);
    if(NOERROR == lResult) 
    {
      TCHAR szData[MAX_PATH];
      lstrcpy(szData, DLLREGUNREGNAME);
      lResult = RegSetValueEx(hKey, szCLSID, 0, REG_SZ, (LPBYTE)szData,
	  lstrlen(szData) + 1);
      RegCloseKey(hKey);
    } 
    else
      return SELFREG_E_CLASS;
  }

  return S_OK;
}

#include "dllreg_xhdr.h"
#include "dllregshex.h"
#include "dllreg_util.h"
#include "resource.h"

extern UINT      g_cRefThisDll;
extern HINSTANCE   g_hmodThisDll;

extern HBITMAP      hBmp_Install;
extern HBITMAP      hBmp_Uninstall;
extern HBITMAP      hBmp_About;
extern HMENU      hSubMenu;

// IContextMenu
STDMETHODIMP 
CShellExt::QueryContextMenu(HMENU hMenu, UINT indexMenu, UINT idCmdFirst,
  UINT idCmdLast, UINT uFlags)
{
  _UNUSED_PARAMETER(idCmdLast);
  UINT idCmd = idCmdFirst;

  char *szMenuText_Popup   = "Shell e&xtension";
  char *szMenuText_Install   = "&Install";
  char *szMenuText_Uninstall   = "&Uninstall";
  char *szMenuText_About   = "&About...";

  BOOL bAppendItems = TRUE;

  if((uFlags & 0x000F) == CMF_NORMAL)
    bAppendItems = TRUE;
  else if (uFlags & CMF_VERBSONLY)
    bAppendItems = TRUE;
  else if (uFlags & CMF_EXPLORE)
    bAppendItems = TRUE;
  else
    bAppendItems = FALSE;

  if(bAppendItems)
  {
    InsertMenu(hMenu, indexMenu++, MF_SEPARATOR | MF_BYPOSITION, 0, NULL);  

    HMENU hSubMenu = CreateMenu();
    if(hSubMenu)
    {
      InsertMenu(hSubMenu, 0, MF_STRING    | MF_BYPOSITION, idCmd++,
	    szMenuText_Install);
      SetMenuItemBitmaps(hSubMenu, 0, MF_BYPOSITION, hBmp_Install,
	    hBmp_Install);
      InsertMenu(hSubMenu, 1, MF_STRING | MF_BYPOSITION, idCmd++,
	    szMenuText_Uninstall);
      SetMenuItemBitmaps(hSubMenu, 1, MF_BYPOSITION, hBmp_Uninstall,
	    hBmp_Uninstall);

      InsertMenu(hSubMenu, 2, MF_SEPARATOR | MF_BYPOSITION, 0, NULL);

      InsertMenu(hSubMenu, 3, MF_STRING    | MF_BYPOSITION, idCmd++,
	    szMenuText_About);
      SetMenuItemBitmaps(hSubMenu, 3, MF_BYPOSITION, hBmp_About, hBmp_About);
    }
     
    InsertMenu(hMenu, indexMenu++, MF_STRING | MF_POPUP | MF_BYPOSITION, 
      (UINT_PTR)hSubMenu, szMenuText_Popup);
    InsertMenu(hMenu, indexMenu++, MF_SEPARATOR | MF_BYPOSITION, 0, NULL);

    return ResultFromShort(idCmd - idCmdFirst);
  }
  
  return NOERROR;
}

STDMETHODIMP 
CShellExt::InvokeCommand(LPCMINVOKECOMMANDINFO lpcmi)
{
  HRESULT hr = E_INVALIDARG;
  if (!HIWORD(lpcmi->lpVerb))
  {
    UINT idCmd = LOWORD(lpcmi->lpVerb);
    switch (idCmd)
    {
      case 0:
        hr = DoInstall(lpcmi->hwnd, lpcmi->lpDirectory,
		  lpcmi->lpVerb, lpcmi->lpParameters, lpcmi->nShow);
        break;
      case 1:
        hr = DoUninstall(lpcmi->hwnd, lpcmi->lpDirectory,
		  lpcmi->lpVerb, lpcmi->lpParameters, lpcmi->nShow);
        break;
      case 2:
        hr = DoAbout(lpcmi->hwnd, lpcmi->lpDirectory,
		  lpcmi->lpVerb, lpcmi->lpParameters, lpcmi->nShow);
        break;
      default:
        break;
    }
  }
  return hr;
}

STDMETHODIMP 
CShellExt::GetCommandString(UINT idCmd, UINT uFlags, UINT FAR *reserved,
  LPSTR pszName, UINT cchMax)
{
  _UNUSED_PARAMETER(reserved);
  _UNUSED_PARAMETER(uFlags);

  *pszName = 0;
  cchMax   = 40;
  char psz[40];

  switch (idCmd)
  {
    case 0:
      LoadString(g_hmodThisDll, IDCMD_INSTALL, psz, cchMax);
      break;
    case 1:
      LoadString(g_hmodThisDll, IDCMD_UNINSTALL, psz, cchMax);
      break;
    case 2:
      LoadString(g_hmodThisDll, IDCMD_ABOUT, psz, cchMax);
      break;
    default:
      break;
  }
  wcscpy((unsigned short *)pszName, _WCSTR(psz));
  return NOERROR;
}

STDMETHODIMP 
CShellExt::_GetFullFileName()
{
  HRESULT hr = S_FALSE;

  //
  // IEnumFORMATETC. Needed for format enumeration.
  //
  IEnumFORMATETC *pefEtc = 0;
  hr = m_pDataObj->EnumFormatEtc(DATADIR_GET, &pefEtc);
  if(SUCCEEDED(hr))
  {
    hr = pefEtc->Reset();   //   Reset enumeration.

    if(SUCCEEDED(hr))
    {
      //
      //   FORMATETC. Needed for get data about object.
      //
      FORMATETC fEtc;
      ULONG ulFetched = 0L;

      while(TRUE)
      {
        hr = pefEtc->Next(1, &fEtc, &ulFetched);
        if(FAILED(hr) || (ulFetched <= 0))
          break;

        //
        //   'Arm' format and 'launch' to obtain STGMEDIUM...
        //
        fEtc.cfFormat   = CF_HDROP;
        fEtc.dwAspect   = DVASPECT_CONTENT;
        fEtc.lindex      = -1;
        fEtc.ptd      = NULL;
        fEtc.tymed      = TYMED_HGLOBAL;
        //
        //   IDataObject : GetData. Returned as TYMED_HGLOBAL.
        //
        STGMEDIUM stgM;
        hr = m_pDataObj->GetData(&fEtc, &stgM);
        if(SUCCEEDED(hr))
        {
          if(stgM.tymed == TYMED_HGLOBAL)
          {
            m_ppszFileUserClickedOn[0] = '\0';

            UINT nFileCount = DragQueryFile((HDROP)stgM.hGlobal,
              (UINT)INVALID_HANDLE_VALUE, NULL, 0);
            if(nFileCount >= 1)
            {
              if(m_ppszFileUserClickedOn)
              {
                DeleteFileData();
              }

              m_ppszFileUserClickedOn = new LPTSTR[nFileCount];

              for(register UINT x = 0; x < nFileCount; x++)
              {
                m_ppszFileUserClickedOn[x] = new TCHAR[_MAX_PATH + 1];
                // one file only; eliminate this and improve code to allow
                //  multiple-DLL file (un)registering
                DragQueryFile((HDROP)stgM.hGlobal, x,
                  m_ppszFileUserClickedOn[x], _MAX_PATH + 1);
              }

              m_xFileCount = nFileCount;
            }
          }
        }
      }
    }
  }

  if(pefEtc)
    pefEtc->Release();
  return hr;
}