Code archives/Miscellaneous/Simple Event Handling

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Simple Event Handling by deps
(Posted 21 years ago)
Found a simple event handling tutorial and wanted to try it out in BlitzMax.

The original one can be found here: http://www.gamedev.net/reference/articles/article2141.asp
Another one here: http://gpwiki.org/index.php/Programming_Techniques:Events

Usage example:
Strict

Include "events.bmx"

' Some events
Const E_NEWGAME = 0
Const E_PAUSEGAME = 1
Const E_RESUMEGAME = 2
Const E_STOPGAME = 3
Const E_APPCLOSE = 4
Const E_INCSCORE = 5
Const E_POWERUP = 6




Type A Extends EventHandler

	Method EventHandler( e:Tevent )
		Select e.t
		
			Case E_NEWGAME
				Print "A: New game started"
			Case E_PAUSEGAME
				Print "A: Tea time"
			Case E_RESUMEGAME
				Print "A: No tea for you!"
			Case E_STOPGAME
				Print "A: *Chicken noises*"
			Case E_APPCLOSE
				Print "A: Shutdown"				
							
		EndSelect	
	EndMethod

EndType


Type B Extends EventHandler

	Method EventHandler( e:Tevent )
		Select e.t
		
			Case E_PAUSEGAME
				Print "B: Tea time"
			Case E_RESUMEGAME
				Print "B: No tea for you!"
			Case E_INCSCORE							
				Print "B: Yay! Score! Got "+e.arg1+" points!"
			Case E_POWERUP
				Print "B: Powerup taken"
		EndSelect	
	EndMethod

EndType


Type C Extends EventHandler

	Method EventHandler( e:Tevent )
		Select e.t
		
			Case E_PAUSEGAME
				Print "C: Tea time"
			Case E_RESUMEGAME
				Print "C: No tea for you!"
		EndSelect	
	EndMethod

EndType



Print "- Creating A and B"
Local a1:A = New A ; a1.init()
Local b1:B = New B ; b1.init()

Print "- Sending events"
EventDispatcher.SendEvent( E_NEWGAME )
EventDispatcher.SendEvent( E_INCSCORE, 1000 )
EventDispatcher.SendEvent( E_PAUSEGAME )

Print "- Creating C"
Local c1:C = New C ; c1.init()

Print "- Sending some more events"
EventDispatcher.SendEvent( E_RESUMEGAME )
EventDispatcher.SendEvent( E_POWERUP )

Type Tevent
	Field t:Int
	Field arg1:Int, arg2:Int
EndType


Type EventHandler

	' Overload this
	Method EventHandler( e:Tevent ) 
	EndMethod


	Field _nexthandler:EventHandler

	Method init()
		EventDispatcher.RegisterHandler(Self)
	EndMethod
	

	Method GetNextHandler:EventHandler()
		Return _nexthandler
	EndMethod
	

	Method SetNextHandler( n:EventHandler )
		_nexthandler = n
	EndMethod
	
	
	Method SendEvent( event_type:Int, arg1:Int = 0, arg2:Int = 0 )
		EventDispatcher.SendEvent( event_type, arg1, arg2 )
	EndMethod

EndType




Type EventDispatcher

	Global _devicelist:EventHandler

	Function RegisterHandler( device:EventHandler )
		device.SetNextHandler( _devicelist )
		_devicelist = device
	EndFunction
	
	Function SendEvent( event_type:Int, arg1:Int = 0, arg2:Int = 0 )
		Local e:Tevent = New Tevent
		e.t = event_type
		e.arg1 = arg1
		e.arg2 = arg2
		Local curDevice:EventHandler = _deviceList
		While curDevice
			curDevice.EventHandler(e)
			curDevice = CurDevice.GetNextHandler()
		Wend
	EndFunction


EndType