Every Control Panel application must export the standard entry-point function,
CPlApplet (WIN32.HLP). This function receives requests,
in the form of Control Panel (CPL) messages, and carries out the requested
work, such as initializing the application, displaying and managing the dialog
box(es), and closing the application.
When the controlling application first loads the Control Panel application,
it retrieves the address of the CPlApplet function and subsequently
uses the address to call the function and pass it messages. The controlling
application may send the following messages:
CPL_DBLCLK (WIN32.HLP)
Sent to notify CPlApplet that the user has chosen the icon associated
with a given dialog box. CPlApplet should display the corresponding
dialog box and carry out any user-specified tasks.
CPL_EXIT (WIN32.HLP)
Sent after the last CPL_STOP message and immediately before the
controlling application uses the FreeLibrary function
(WIN32.HLP) to free the DLL containing the Control Panel
application. CPlApplet should free any remaining memory and prepare
to close.
CPL_GETCOUNT (WIN32.HLP)
Sent after the CPL_GETCOUNT message (WIN32.HLP) to prompt
CPlApplet to return a number indicating how many dialog boxes it
supports.
CPL_INIT (WIN32.HLP)
Sent immediately after the DLL containing the Control Panel application is
loaded, to prompt CPlApplet to perform initialization procedures,
including memory allocation.
CPL_INQUIRE (WIN32.HLP)
Sent after the CPL_GETCOUNT message, to prompt CPlApplet to
provide information about a specified dialog box. The lParam2 parameter of
CPlApplet points to a TCPLInfo structure (WIN32.HLP).
CPL_NEWINQUIRE (WIN32.HLP)
Sent after the CPL_GETCOUNT message, to prompt CPlApplet to
provide information about a specified dialog box. The lParam2 parameter is
a pointer to a TNewCPLInfo structure (WIN32.HLP).
For better performance on Windows 95 and Windows NT version 4.0, your
application should process CPL_INQUIRE and not CPL_NEWINQUIRE.
CPL_SELECT (WIN32.HLP)
This message is obsolete. Current versions of Windows do not send this message.
CPL_STOP (WIN32.HLP)
Sent once for each dialog box before the controlling application closes.
CPlApplet should free any memory associated with the given dialog box.
You will find an example of Control Panel Application in
\TMTPL\SAMPLES\WIN32\CPL subdirectory.
Win32 Programming