Context-Sensitive Help in a CDialog Object

The DLGHLP sample illustrates implementing context-sensitive help in a CDialog object.

The following files are available for download from the Microsoft Download Center:


Dlghlp32.exe (http://download.microsoft.com/download/vc50pro/sample6/1/win98/en-us/dlghlp32.exe)

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The DLGHLP32 sample implements context-sensitive help in a dialog box by overriding CWnd::OnHelpInfo and CWnd::OnContextMenu in the dialog class to handle the WM_HELP and WM_CONTEXTMENU messages. WM_HELP and WM_CONTEXTMENU are new Win32 messages that are received by the active window when Help is requested. DLGHLP32 uses the information provided to these handlers to call ::WinHelp with the appropriate parameters.

DLGHLP32 includes two dialog boxes, each with a number of controls in them. The user is able to set the focus to a particular control and, by pressing F1, right-clicking, or using the ? (question mark) icon to bring up help that is specific for that control. Several of the control IDs are used in both dialog boxes. For example, each dialog box contains a radio button with the ID of IDC_RADIO1. To allow a unique help context value to be generated for each control, the ID of each dialog box is used as a base and is added to the ID of the control.

::WinHelp provides two new help commands for handling WM_HELP and WM_CONTEXTMENU. They are HELP_WM_HELP and HELP_CONTEXTMENU, respectively. In both cases, an array mapping control IDs to help contexts is passed in the dwData parameter. DLGHLP32 defines two of these arrays, one for each dialog box class. This facilitates generating unique help context for controls in both dialogs, even if the control IDs are the same.

DLGHLP32 is based on an AppWizard-generated application. Files included with the sample which are directly related to implementing context- sensitive help in a dialog box are:

• DLGBOX1.CPP: Implements context-sensitive help for Dialog Box 1 by overriding CWnd::OnHelpInfo and CWnd::OnContextMenu.
• DLGBOX2.CPP: Implements context-sensitive help for Dialog Box 2 by overriding CWnd::OnHelpInfo and CWnd::OnContextMenu.
• DLGRES.H: Defines the help context IDs based on the ID of the dialog box and the specific control.
• DLGCTRLS.HM: Help map file that defines the help context IDs for the dialog box controls.