/* 

We call displacement to the offset we can produce to the object which the displcement object is is a child from. 
The displacement is a vector that displaces everything static drawn on on the context of the parent object. 
    
*/

function newDisplacement() {

    var displacement = {
        containerName: "",                      // This is for debugging purposes only.
        parentDisplacement: undefined,          // Here we store the displacement object of the parent cointainer, if exists. 
        container: undefined,
        x: 0,                                   // This is the actual x displacement.
        y: 0,                                   // This is the actual y displacement.
        displace: displace,
        undisplaceThisPoint: undisplaceThisPoint,
        displaceThisPoint: displaceThisPoint
    };

    return displacement;


    function displace(amountX, amountY) {

        /* First we check if by allowing this displacement we would produce the current frame to be beyond its limit. */

        tempDisplacement = newDisplacement();
        tempDisplacement.x = amountX;
        tempDisplacement.y = amountY;

        if (this.container.frame.canYouMoveHere(tempDisplacement)) {

            /* Now we displace */

            displacement.x = displacement.x + amountX;
            displacement.y = displacement.y + amountY;

            return true;
        }

        return false;
    }

    function displaceThisPoint(point) {

        if (this.parentDisplacement !== undefined) {

            point = this.parentDisplacement.displaceThisPoint(point);

        } 

        point.x = point.x + displacement.x;
        point.y = point.y + displacement.y;

        return point;
    }

    function undisplaceThisPoint(point) {

        if (this.parentDisplacement !== undefined) {

            point = this.parentDisplacement.undisplaceThisPoint(point);

        }

        point.x = point.x - displacement.x;
        point.y = point.y - displacement.y;

        return point;
    }

}