of available applets in the user interface. Control.exe only needs to enumerate all .cpl files in the Windows folder and to call the CPlApplet function in each file.
According to the DLL nature and CPlApplet API requirements, .cpl files must implement the following two public entry points:
¦ BOOL APIENTRY DllMain(HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved) Used to initialize the DLL. The system calls DllMain to load the DLL. The DLL returns true if initialization succeeded or false if initialization failed.
¦ LONG CALLBACK CPlApplet(HWND hwndCPL, UINT message, LPARAM lParam1, LPARAM lParam2) A callback function that serves as the entry point for the Control Panel to perform actions on the applet.
You must export the DllMain and CPlApplet entry points so that the Control Panel application can access these functions. Non-exported functions are private to the DLL. Make sure the function definitions are in export 'C' { } blocks to export the C interface.
The Control Panel calls the CPlApplet function to initialize the applet, obtain information, provide information about user actions, and to unload the applet. The applet must support several Control Panel messages, listed in Table 3-6, to implement a fully functional CPlApplet interface:
Table 3-6 Control Panel messages
| Control Panel Message | Description |
|---|---|
| CPL_INIT | The Control Panel sends this message to perform global initialization of the applet. Memory initialization is a typical task performed at this step. |
| CPL_GETCOUNT | The Control Panel sends this message to determine the number of Control Panel applications implemented in the .cpl file. |
| CPL_NEWINQUIRE | The Control Panel sends this message for all the Control Panel applications specified by CPL_GETCOUNT. At this step each Control Panel application must return a NEWCPLINFO structure to specify the icon and title to display in the Control Panel user interface. |
| CPL_DBLCLK | The Control Panel sends this message when the user double-clicks on an icon of the applet in the Control Panel user interface. |
| CPL_STOP | The Control Panel sends this message once for each instance specified by CPL_GETCOUNT. |
| CPL_EXIT | The Control Panel sends this message once for the applet before the system releases the DLL. |
Store the NEWCPLINFO information for each Control Panel application that you implement in a Control Panel applet in a resource embedded in the .cpl file. This facilitates the localization of icons, names, and applet descriptions returned in response to CPL_NEWINQUIRE messages.
Building Control Panel Applets
To build a Control Panel applet and generate the corresponding .cpl file, find the source code folder of the applet subproject and add the following CPL build directive on a new line at the end of the Sources file:
CPL=1
You also must add the path to the Control Panel header file to the Include Directories entry on the C/C++ tab in the applet subproject settings in Visual Studio, as illustrated in Figure 3-3:
$(_PROJECTROOT)CESysgenOakInc
Figure 3-3 Include Directories entry for a Control Panel applet
Enabling Kiosk Mode
Many Windows Embedded CE devices, such as medical monitoring devices, automated teller machines (ATM), or industrial control systems are dedicated to a single task. The standard graphical shell is not useful for these devices. Removing the standard shell restricts access to the Control Panel configuration settings and also protects users from starting additional applications. The result is a device in kiosk mode that opens an application according to the special purpose of the target device directly with no shell access.
Kiosk applications for Windows Embedded CE are developed in native code or managed code. The only requirement is to start this application in place of the standard shell (Explorer.exe). The system then starts a black shell, meaning no shell application is running on the device. You only need to configure the registry entries under the HKEY_LOCAL_MACHINEInit key to implement this configuration. As mentioned earlier in this chapter, the LaunchXX entry for Explorer.exe is Launch50. Replace Explorer.exe with your custom kiosk application and consider the job completed, as shown in Table 3-7. Keep in mind that your custom kiosk application must implement the SignalStarted API for the kernel to manage the application dependencies correctly.
Table 3-7 Startup registry parameter examples
