Hi Stephane,�

On 15 May 2013 18:35, stephane ducasse <stephane.ducasse@free.fr> wrote:

Hi eric
Why do you need to poll for event?�

I'd rather not poll as it seems inefficient, but the logic and ordering of the Scratch commands seems to dictate that it is necessary.

Here's my example pseudo code from that picture of the Scratch script in my original email...

� � When flag clicked [

� � � �Loop forever [

� � � � � move 5 steps

� � � � � turn 5 degrees

� � � � � if key <space> pressed? [

� � � � � � �Stamp the sprite on the screen

� � � � � ]

� � � �]

� � �]

So "When flag clicked" is clearly event driven, and that's fine, that's how it works already.

But as far as I can see, that "if key <space> pressed?" cannot be event driven, because we don't want to start execution at that block if the space key is pressed, rather we want that to evaluate to true if the space key has been pressed recently ("recently" seems a problematic term to use here but that's another issue!).

Here's the code I started throwing together to make this work -- see the bit following this line:

� � type = EventTypeKeyboard

InputEventSensor>>processEvent: evt�

"Process a single event. This method is run at high priority.

The event record is:

<type><timestamp><character code><updown><modifier keys>...

where updown is:

�0 - keystroke

�1 - key down

�2 - key up

NOTE: You must ensure that there is an instance variable keyPressed."

| type updown |

type := evt at: 1.

"Treat menu events first"

type = EventTypeMenu

ifTrue: [

self processMenuEvent: evt.

^nil].

"Tackle mouse events first"

type = EventTypeMouse

ifTrue: [

"Transmogrify the button state according to the platform's button map definition"

evt at: 5 put: (ButtonDecodeTable at: (evt at: 5) + 1).

"Map the mouse buttons depending on modifiers"

evt at: 5 put: (self mapButtons: (evt at: 5) modifiers: (evt at: 6)).

"Update state for polling calls"

mousePosition := (evt at: 3) @ (evt at: 4).

modifiers := evt at: 6.

mouseButtons := evt at: 5.

^evt].

"Finally keyboard"

type = EventTypeKeyboard

ifTrue: [

"Update state for polling calls"

modifiers := evt at: 5.

updown := evt at: 4.

(updown = 2) ifTrue: [�

keyPressed := nil

] ifFalse: [ �

keyPressed := evt at: 3 ].

^evt].

"Handle all events other than Keyborad or Mouse."

^evt.

Then I use this:

InputEventSensor>>keyPressed: asciiValue

"Is this key being pressed?"

self nextEvent.

^keyPressed = asciiValue

So should I be doing this? Should I test out these changes and suggest a patch to Pharo? I'm happy that the answer might be "no", but what can I try instead?

Thanks for your help.

-Eric.

--
Eric Clack
ericclack@googlemail.com
East Sussex, England.