The Queue of Events

Introduction

The queue of events is the queue where the system send events such as: input change, user action, encoder or transducer match, and from where the user's program get events to process and react to.

Structure of an Event

An event is defined in the library as an array of values:

[.opcode, .p0, .p1, .p2, .p3]

where:

• .opcode is used to uniquely identify the event
• .p0, .p1, .p2, .p3 contains informations specific to that event

Events' Library Functions

The library functions for events management are:

• #define BASE_EVENT(%1) Event:%1[.opcode, .p0, .p1, .p2, .p3] is a macro to help in creating an event container
• SysEvEnable() enable the system to post events into the queue
• SysEvDisable() disable the system to post events into the queue
• EventGet( BASE_EVENT(ev) ) get an event from the queue, if an event is not available will wait for
• EventSend( BASE_EVENT(ev) ) send an event to the queue, can be used to inject custom and/or simulated events

Processing Events

In Event-driven programming the readmain loop of a program takes care of fetch, process and/or dispatch incoming events, the following code is an example of a minimal one.

/***************************************************************
*
*		Minimal Event Processing Loop
*
*       program.p
*
***************************************************************/

// include the library for H6105-D
//
#include <hydlib_cp>

// main function
//
main()
{
	// clear display
	//
	dClear();
	
	// select system font
	//
	dFont( system5x7 );

	// place cursor
	//
	dCursor( 0, 0 );
	
	// print on display
	//
	dPrintf("Processing Events");

	// declare an event container
	//
	new BASE_EVENT(ev);

	// enable system events
	//
	SysEvEnable();
	
	// main loop
	//
	for( ;; )
	{
		// get new event from queue
		//
		EventGet( ev );
		
		// process some events
		//
		switch( ev.opcode )
		{
			// script stop command
			//
			case SevEmergExit:
			{
				break;
			}

			// push button 
			//
			case SevDinActive:
			{
				
			}
		}
	}

	
	// program end
}