Displaying Context-Sensitive Help

Context-sensitive help, for the purpose of this discussion, refers to help support for the controls in a dialog box that users access:

• By pressing the F1 key.

• By right-clicking a control (What's This? Help).

• By using the question-mark pointer (the What's This? Help pointer).

For each control that you want to support context-sensitive help, set the HelpID property to True.

If necessary, add htmlhelp.lib to the Additional Dependencies property, which is in the Input property page of the Linker folder in your project's Property Pages dialog box.

The source information for context-sensitive help is stored in a .txt file that you include in your HTML Help project.

To create the context-sensitive help text file

1. Use a text editor to create a .txt file.

2. Format the topics as follows:

   .topic 1

   help text for control 1

   .topic 2

   help text for control 2

After you create the .txt file, add it to the [Files] section in your .hhp file.

To support help for resources in a dialog box, you must create a two-dimensional array that maps control IDs to help IDs (topic numbers).

To create the two-dimensional array

• In the .cpp file, for every class that represents a dialog box, add a two-dimensional array to the end of the class. For example:

  static DWORD myarray[] = {
     IDC_CHECK1, 1,
     IDC_BUTTON1, 2,
     IDC_EDIT1, (DWORD)-1,
     0,0
  };
  

Each entry in the two-dimensional array pairs a resource ID for a dialog-box control with a topic number from the context-sensitive help text file. If you do not want a specific resource to have What's This? Help, use –1. The last pair in this array should be 0,0.

F1 access to context-sensitive help means that users will be able to press F1 when a control has focus to access help.

To enable F1 access to context-sensitive help

• Implement a handler for the WM_HELPINFO message (in each dialog-box class where you want F1 access to context-sensitive help) and implement the following code for the handler:

  BOOL CMyDlg::OnHelpInfo(HELPINFO* pHelpInfo)
  {
     BOOL bRet = TRUE;
  
     if (pHelpInfo->iContextType == HELPINFO_WINDOW)
     {
        HWND hwnd = ::HtmlHelp(
           (HWND)pHelpInfo->hItemHandle,
           _T("my_chm.chm::/ctrlhlp.txt"),
           HH_TP_HELP_WM_HELP,
           (DWORD)(LPVOID)myarray);
        bRet = (NULL != hwnd);
     }
  
     return bRet;
  }
  

What's This? Help displays the control's help when a user right-clicks the control.

To implement right-click What's This? Help

• Implement a handler (see Mapping Messages to Functions) for the WM_CONTEXTMENU message in each dialog-box class where you want What's This? Help (select the ID for the dialog box from the list of Object IDs). Implement the following code for the handler:

  void CMyDlg::OnContextMenu(CWnd* pWnd, CPoint point)
  {
     UNREFERENCED_PARAMETER(point);
  
     ::HtmlHelp(
        pWnd->GetSafeHwnd(),
        _T("my_chm.chm::/ctrlhlp.txt"),
        HH_TP_HELP_CONTEXTMENU,
        (DWORD)(LPVOID)myarray);
  }
  

When you specify the .chm file, the expected location is the project's working directory. See the Debug tab of the Property Pages dialog box for the location of the working directory (by default, the project directory). When you specify the text file in the .chm that contains the context-sensitive help, you must specify the same location information as is specified for the .txt file in the .chm's .hhp file.

If you already implement F1 access to context-sensitive help, you can easily enable the What's This? pointer, which causes a question mark to appear on the title bar, in the upper right-hand corner of the dialog box.

To enable the What's This? Help question-mark pointer

• Select the Context help check box in the Extended Styles tab of the dialog box properties.

See Also

Concepts

HTML Help: Context-Sensitive Help for Your Programs