phaser/src/actions/ShiftPosition.js
2024-02-19 17:12:24 +00:00

119 lines
3.5 KiB
JavaScript

/**
* @author Richard Davey <rich@phaser.io>
* @copyright 2013-2024 Phaser Studio Inc.
* @license {@link https://opensource.org/licenses/MIT|MIT License}
*/
var Vector2 = require('../math/Vector2');
/**
* Takes an array of items, such as Game Objects, or any objects with public `x` and
* `y` properties and then iterates through them. As this function iterates, it moves
* the position of the current element to be that of the previous entry in the array.
* This repeats until all items have been moved.
*
* The direction controls the order of iteration. A value of 0 (the default) assumes
* that the final item in the array is the 'head' item.
*
* A direction value of 1 assumes that the first item in the array is the 'head' item.
*
* The position of the 'head' item is set to the x/y values given to this function.
* Every other item in the array is then updated, in sequence, to be that of the
* previous (or next) entry in the array.
*
* The final x/y coords are returned, or set in the 'output' Vector2.
*
* Think of it as being like the game Snake, where the 'head' is moved and then
* each body piece is moved into the space of the previous piece.
*
* @function Phaser.Actions.ShiftPosition
* @since 3.0.0
*
* @generic {Phaser.GameObjects.GameObject[]} G - [items]
* @generic {Phaser.Math.Vector2} O - [output,$return]
*
* @param {(Phaser.Types.Math.Vector2Like[]|Phaser.GameObjects.GameObject[])} items - An array of Game Objects, or objects with public x and y positions. The contents of this array are updated by this Action.
* @param {number} x - The x coordinate to place the head item at.
* @param {number} y - The y coordinate to place the head item at.
* @param {number} [direction=0] - The iteration direction. 0 = first to last and 1 = last to first.
* @param {Phaser.Types.Math.Vector2Like} [output] - An optional Vec2Like object to store the final position in.
*
* @return {Phaser.Types.Math.Vector2Like} The output vector.
*/
var ShiftPosition = function (items, x, y, direction, output)
{
if (direction === undefined) { direction = 0; }
if (output === undefined) { output = new Vector2(); }
var px;
var py;
var len = items.length;
if (len === 1)
{
px = items[0].x;
py = items[0].y;
items[0].x = x;
items[0].y = y;
}
else
{
var i = 1;
var pos = 0;
if (direction === 0)
{
pos = len - 1;
i = len - 2;
}
px = items[pos].x;
py = items[pos].y;
// Update the head item to the new x/y coordinates
items[pos].x = x;
items[pos].y = y;
for (var c = 0; c < len; c++)
{
if (i >= len || i === -1)
{
continue;
}
// Current item
var cur = items[i];
// Get current item x/y, to be passed to the next item in the list
var cx = cur.x;
var cy = cur.y;
// Set current item to the previous items x/y
cur.x = px;
cur.y = py;
// Set current as previous
px = cx;
py = cy;
if (direction === 0)
{
i--;
}
else
{
i++;
}
}
}
// Return the final set of coordinates as they're effectively lost from the shift and may be needed
output.x = px;
output.y = py;
return output;
};
module.exports = ShiftPosition;