Adding a custom screensaver parameter dialog.

Most screensavers however are customizable, like how many objects are on screen or which colorschemes etc etc, or better: should be customizable. DemoGL allows you to create as customizable screensavers as you can imagine, by just using the standard DemoGL library. Examine the codesnippet below, taken from the Creating a simple screensaver example:

	// ... other code
	
	// Parse commandline for screensaver exectype.
	// lpCmdLine is a parameter of WinMain()
	pSSCLParams=DEMOGL_ParseScreenSaverCL(lpCmdLine);

	// Determine the runtype, using the parsed commandline
	// parameters.	
	switch(pSSCLParams->iSaverExecType)
	{
		case DGL_SSAVERET_CONFIG:
		{
			/////////////////////////
			// Insert your own configwindow initialisation and 
			// start up code HERE. 
			/////////////////////////
			iRunType=RUNTYPE_SAVER_CONFIG;
		}; break;
		
		// ... other code
	}

	// we've now gathered enough information to run this application
	// as a screensaver. Start the application as we did in the 
	// application, now passing the iRunType variable
	DEMOGL_AppRun(hInstance, &sdStartupDatValues, "DemoGL Example",
		false,0,0,iRunType);

	// ... other code
}

The custom dialog should pop up when the user clicks 'settings' or 'configure', thus when the screensaver (i.e. the screensaver application using DemoGL) is executed in 'configuration' mode. That dialog then, can have a button which will call DEMOGL_AppRun passing RUNTYPE_SAVER_CONFIG as the runtype to let the user configure the runtime display and soundsystem parameters. When the user clicks 'Save' in the DemoGL startup dialog, DEMOGL_AppRun() will return to the callerfunction, for example the custom dialog message handler.

Because screensavers are started by the operating system, the settings configured by the user should be stored where the screensaver application can retrieve them from when it is executed in 'normal' mode. The best place for this is the windows registry, but any other solution would do, as long as the screensaver application is able to read the settings, like how many objects an effectobject should display. The settings configurable by the startup dialog of DemoGL are already saved in the registry automatically so a developer should just focus on where and how to store the screensaver specific settings. A good place in the registry is the hive (registry key) where DemoGL saves screensaver specific data: HKCU/Software/DemoGL/Screensaver/Application title/AppData. Application title is the title specified in the m_sDemoName member of the SStartupDat structure, which is passed to DEMOGL_AppRun.