2009/3/21 Igor Stasenko <siguctua at gmail.com>:
> 2009/3/21 John M McIntosh <johnmci at smalltalkconsulting.com>:
>>
>> On 21-Mar-09, at 3:09 AM, Igor Stasenko wrote:
>>
>>> Right, but here we're talking about doing such conversion much more
>>> earlier (at event source object),
>>> so then event sensor already deals with first class event objects.
>>> I want to know, if such scheme (which i described in first post) is
>>> plausible.
>>
>> For the iPhone VM I return a complex event type, which then points to
>> Smalltalk objects which are the
>> representation of the touch events. For location and acceleration data I
>> return the actual objective-C objects.
>> This data is then processed by EventSensor.
>>
>> If you choose to push the responsibility to the VM for creating event
>> objects then you need to be cognizant
>> of the fact that whatever is proposed has to change very little over time,
>> otherwise you end up with the issue
>> of image versus VM compatibility and the fact that VM version changes
>> proceed at a slow rate.
>>
> Nope. I don't want VM to deal with real event objects.
> VM will still use the old event buffers to deliver events to image.
> But once image receiving it, it should convert it to an instance of
> event as soon as source.
> This is the role of EventSource class - represent VM as event source,
> which producing an instances of KernelXXXEvent classes, and hiding the
> details of converting raw event buffers from the eyes of higher
> layers, which then going to handle the event (EventSensor/Morphic etc)
>

To give an example what i talking about, here the bits of prototype
implementation:

KernelEvent class>>initialize
	"Initialize the array of event types.
	Note, the order of array elements is important and should
	be same as event type returned by VM in event buffer"
	EventTypes := {
		KernelMouseEvent.
		KernelKeyboardEvent.
		KernelDragDropEvent.
		KernelMenuEvent.
		KernelWindowEvent.
		}
-----

KernelEvent class>>fromBuffer: eventBuffer
	"Decode a raw VM event into an instance of KernelEvent subclass"
	
	| type |
	type := EventTypes at: (eventBuffer at: 1) ifAbsent: [ ^
KernelUnknownEvent from: eventBuffer ].
	^ type new from: eventBuffer

-----

KernelEvent>>from: buffer
	"Initialize an event instance from raw event buffer.
	Note, all subclasses should call super to initialize fields correctly"

	eventType := buffer at: 1.
	timeStamp := buffer at: 2.
	timeStamp = 0 ifTrue: [timeStamp := Time millisecondClockValue].
	windowIndex := buffer at: 8.	
----

KernelMouseEvent>>from: buffer

	super from: buffer.

	position := Point x: (buffer at: 3) y: (buffer at: 4).
	buttons := buffer at: 5.
	modifiers := buffer at: 6.

as you can see, there is nothing complicated. It simply frees
underlaying event handling layers from deciphering event buffers by
themselves, instead, they deal with first class even objects, with
harmonized protocol.

>
> --
> Best regards,
> Igor Stasenko AKA sig.
>



-- 
Best regards,
Igor Stasenko AKA sig.