Disabling the Mnemonic on a Disabled Static Text Control

• Microsoft Windows Software Development Kit (SDK) versions 3.0 and 3.1
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

SUMMARY

Disabling a static text control that contains a mnemonic does not prevent the control from responding to that key. For more information on static text controls with mnemonics, query in this Knowledge Base on the word "mnemonic".

To keep a static text control from processing mnemonics, it must be subclassed. When the control is disabled, WM_GETTEXT messages must be intercepted and the subclass procedure should return an empty string in response to the message.

MORE INFORMATION

When a static text control with a mnemonic is disabled using EnableWindow(), it turns gray but it does not stop responding to the mnemonic. This can cause problems because Windows processes the mnemonic by setting the focus to the next nonstatic, enabled control.

It is necessary to resort to subclassing to prevent the static control from processing the mnemonic. The subclass procedure should process the WM_GETTEXT message as follows:

    ...
    // Windows asks the control, hChild, for its text.
    case WM_GETTEXT:
        if (!IsWindowEnabled(hChild))
            {
            *(LPSTR)(lParam) = 0;    // A null terminated empty string
            return 0L;
            }
        break;
    ....

Because the mnemonic must work when the control is enabled, the IsWindowEnabled() function is used to determine the state of the control. If it is enabled, default processing occurs. Otherwise, the control is disabled and no text is returned, effectively disabling the mnemonic.