ActionScript: How come i cant draw diagonally? - actionscript-3

Question

So, I'm learning ActionScript on my own with a book ('Foundation AS3.0 with Flash...').
And I'm stuck on an excercise.
I have to make a drawing app with using the arrowkeys and spacebar.
It doesn't work 100%. I can draw up, down, right, left. Even diagonal, only right-up, and left-down.
Do you guys know where my mistake is? I also want to draw left-up and right-down....
Here's my code so far:
package classes{
import flash.display.Shape;
import flash.display.Sprite;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
import flash.events.Event;
public class KeyboardDrawing extends Sprite{
private const PIXEL_DISTANCE_TO_DRAW:uint = 2;
private var _canvas:Sprite;
private var _crosshair:Shape;
private var _xDirection:int = 0;
private var _yDirection:int = 0;
private var _isDrawing:Boolean = false;
public function KeyboardDrawing(){
_canvas=new Sprite();
addChild(_canvas);
_crosshair=new Shape();
drawCrosshair();
addChild(_crosshair);
_canvas.graphics.lineStyle(2, 0x000000);
stage.focus=_canvas;
_canvas.addEventListener(KeyboardEvent.KEY_DOWN, onCanvasKeyDown);
_canvas.addEventListener(KeyboardEvent.KEY_UP, onCanvasKeyUp);
_canvas.addEventListener(Event.ENTER_FRAME, onCanvasEnterFrame);
}
private function drawCrosshair():void{
_crosshair.graphics.lineStyle(1, 0x000000);
_crosshair.graphics.moveTo(-5, 0);
_crosshair.graphics.lineTo(6, 0);
_crosshair.graphics.moveTo(0, -5);
_crosshair.graphics.lineTo(0, 6);
}
private function onCanvasKeyDown(event:KeyboardEvent):void{
switch(event.keyCode){
case Keyboard.UP:
_yDirection = -PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.DOWN:
_yDirection = PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.LEFT:
_xDirection = -PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.RIGHT:
_xDirection = PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.SPACE:
_isDrawing = true;
break;
}
}
private function onCanvasKeyUp(event:KeyboardEvent):void{
switch(event.keyCode){
case Keyboard.UP:
case Keyboard.DOWN:
_yDirection = 0;
break;
case Keyboard.LEFT:
case Keyboard.RIGHT:
_xDirection = 0;
break;
case Keyboard.SPACE:
_isDrawing = false;
break;
}
}
private function onCanvasEnterFrame(event:Event):void{
_crosshair.x += _xDirection;
_crosshair.y += _yDirection;
if (_isDrawing){
_canvas.graphics.lineTo(_crosshair.x, _crosshair.y);
}else{
_canvas.graphics.moveTo(_crosshair.x, _crosshair.y);
}
}
}
}

Answer 1

It's an issue with the keyboard and certain combinations of keys.
If you change the keys to WASD like so it works fine:
private function onCanvasKeyDown(event:KeyboardEvent):void{
switch(event.keyCode){
case Keyboard.W:
_yDirection = -PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.S:
_yDirection = PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.A:
_xDirection = -PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.D:
_xDirection = PIXEL_DISTANCE_TO_DRAW;
break;
case Keyboard.SPACE:
_isDrawing = true;
break;
}
}
private function onCanvasKeyUp(event:KeyboardEvent):void{
switch(event.keyCode){
case Keyboard.W:
case Keyboard.S:
_yDirection = 0;
break;
case Keyboard.A:
case Keyboard.D:
_xDirection = 0;
break;
case Keyboard.SPACE:
_isDrawing = false;
break;
}
}
Basically it's due to flawed keyboard design that simplifies the wiring at the expense of some key combinations.
I found this article that explains it in full: http://www.microsoft.com/appliedsciences/antighostingexplained.mspx