Control Panel communicates with an application DLL through the CPlApplet function. Be sure to export this function by listing it in the EXPORTS statement of your module-definition (.DEF) file. The CPlApplet function handles the messages listed previously, performing three main tasks:
| Task | Result |
| Initializing the application (CPL_INIT, CPL_INQUIRE) | Allocates any memory needed and gives Control Panel the information needed to display the application icon. |
| Running the application (CPL_DBLCLK) | Passes control to a dialog box and its associated message processor. |
| Closing the application (CPL_STOP, CPL_EXIT) | Frees any memory allocated and prepares to exit. |
The CPlApplet function has the following format:
LONG CALLBACK* CPlApplet(hwndCPL, iMessage, lParam1, lParam2)
The hwndCPL parameter contains the handle of the Control Panel window.
The iMessage parameter contains one of the CPL messages listed previously.
The lParam1 and lParam2 parameters contain message-dependent values. For more information about the CPlApplet function, see the Microsoft Windows Programmer's Reference, Volume 2.