Tooltip for disabled controls

Tooltip Handler (located in TooltipHandler.h/cpp) is a utility function
that handles MFC bug – disabled controls don’t show tooltip. All that the programmer has to do is overwrite PreTranslateMessage() of the dialog box class, and to pass to the handler an array of the controls that may be disabled, a number of controls in the array and a pointer to the tooltip
class – and it works !

Header file

#ifndef _TOOLTIP_HANDLER_H
#define _TOOLTIP_HANDLER_H

#include <afxcmn.h>

// This function is a patch that overcomes MFC bug of
// tooltips that don't show up on in disabled controls 
// if modal dialogs. Call this function in your overidable of
// PreTranslateMessage, before calling the inherited one.
void HandleTooltipsActivation(MSG *pMsg, CWnd *This, CWnd *disabledCtrls[], int numOfCtrls, CToolTipCtrl *pTooltip);

#endif

CPP file

#include "TooltipHandler.h"

void HandleTooltipsActivation(MSG *pMsg, CWnd *This, CWnd *disabledCtrls[], int numOfCtrls, CToolTipCtrl *pTooltip)
{
      CRect  rect;
      POINT  pt;

      HWND   hWnd     = pMsg->hwnd;
      LPARAM lParam   = pMsg->lParam;

      //---------------------------------------------------------------------------
      //      Disabled control do not show tool tips, in modal dialog
      //
      //
      //      The hwnd of the WM_MOUSEMOVE above a disabled control
      //      is the hWnd of the Dialog itself, this confuse the tooltip
      //
      //      To correct this, if we get WM_MOUSEMOVE and the hwnd is the dialog's hwnd
      //
      //      We check on all the controls that are Visible, but disabled if the point is in their
      //  rectangle.
      //
      // In this case we alter the msg to the controls hWnd and coordinates before
      // Relaying it to the toolTip control
      //----------------------------------------


      if( (pMsg->message == WM_MOUSEMOVE) && (pMsg->hwnd == This->m_hWnd)) {

              //---------------------------
              // The point is in the dialog 
              // client coordinates
              //---------------------------
              pt.x = LOWORD(pMsg->lParam);  // horizontal position of cursor 
              pt.y = HIWORD(pMsg->lParam);  // vertical position of cursor 

              for (int i = 0; i < numOfCtrls; i++) {

                              //---------------------------------
                              // rect is the control rectangel in
                              // Dialog client coordinates
                              //----------------------------------
                              disabledCtrls[i]->GetWindowRect(&rect);
                              This->ScreenToClient(&rect);

                              if(rect.PtInRect(pt) ) {
                                      //----------------------------------------------------------------
                                      // The mouse is inside the control
                                      //
                                      // 1. We change the Msg hwnd    to the controls hWnd
                                      // 2. We change the Msg lParam  to the controls client coordinates
                                      //
                                      //----------------------------------------------------------------

                                      pMsg->hwnd = disabledCtrls[i]->m_hWnd;

                                      This->ClientToScreen(&pt);
                                      disabledCtrls[i]->ScreenToClient(&pt);
                                      pMsg->lParam = MAKELPARAM(pt.x, pt.y);
                                      break;
                              }
                      }
              }


      //---------------------------------------
      //      Relay the msg to the tool tip control
      //---------------------------------------
      pTooltip->RelayEvent(pMsg);
      pTooltip->Activate(TRUE);

      //--------------------------------------
      //      Restore the original msg
      //--------------------------------------
      pMsg->hwnd = hWnd;
      pMsg->lParam = lParam;
}