Key combo example.

This is a small tutorial explaining how I implemented player key combos resulting in different actions. Like the systems used in arcade beat 'em ups. Go easy on me if something can be done better, i'm sure it can, and i'd like to know where. I like making tutorials as it helps me learn, and if another person can make use of this then all the better.

I have this as my ActionMap:

new ActionMap(moveMap);
moveMap.bind(keyboard, left, "moveLeft");
moveMap.bind(keyboard, right, "moveRight");
moveMap.bind(keyboard, up, "jump");
moveMap.bind(keyboard, down, "duck");
moveMap.push();

With the following functions for movement:

function moveLeft(%val)
{
	$moveLeft = %val;
	//Update combo when only key is pressed.
	if (%val)
        {
          setCombo("Left");
        }
}

function moveRight(%val)
{
	$moveRight = %val;
	//Update combo only when key is pressed.
        if (%val)
        {
          setCombo("Right");
        }
}

function jump(%val)
{
	$jump = %val;

	//Update combo only when key is pressed.
        if (%val)
        {
          setCombo("Jump");
        }
}

function duck(%val)
{
   $duck = %val;
   //Update combo only when key is pressed.
   if (%val)
   {
      setCombo("Duck");
   }
}

All of the above functions are basically the same. The movement of my character is based off the Platformer tutorial available on TDN here.

The %val in each of the movement functions is changed whenever the corresponding key is pressed. %val = 1 on key down, and 0 on key up.

To make sure that the current combo is updated only when a key is pressed and not also when the key is released an If statement is used. then the setCombo is called with a string of which key is pressed.

function setCombo(%key)
{
  if ($keyPressOne $= "")
  {
    $keyPressOne = %key;
  }
  else if ($keyPressTwo $= "")
  {
    $keyPressTwo = %key;
  }
  else
  {
    $keyPressThree = %key;
  }
  schedule(1000,0,resetCombo);
}

A string of the key pressed is passed into this function. If there is no current combo started the first key press is saved into $keyPressOne, the next time this function is called the value is saved in the next global variable until, in my example, the three key variables are saved. This could easily be altered to save a longer chain of keys.

The final line, schedule(), calls resetCombo function every 1 second. This means that the player has one second to complete their combination of keystrokes before the system is reset.

function resetCombo()
{
  $keyPressOne = "";
  $keyPressTwo = "";
  $keyPressThree = "";

  echo("Reset");
}

This function just resets the values to nothing so that a new chain of keystrokes can be monitored. I also placed a call to this function when I initially create my player, only to get the variables set up.

The above should let you monitor which 3 keys have been used in the last 1 second and store them in the appropriate variables...

Continued in next post.