scratch-vm/src/blocks/scratch3_motion.js

const Cast = require('../util/cast');
const MathUtil = require('../util/math-util');
const Timer = require('../util/timer');

const Scratch3MotionBlocks = function (runtime) {
    /**
     * The runtime instantiating this block package.
     * @type {Runtime}
     */
    this.runtime = runtime;
};

/**
 * Retrieve the block primitives implemented by this package.
 * @return {object.<string, Function>} Mapping of opcode to Function.
 */
Scratch3MotionBlocks.prototype.getPrimitives = function () {
    return {
        motion_movesteps: this.moveSteps,
        motion_gotoxy: this.goToXY,
        motion_goto: this.goTo,
        motion_turnright: this.turnRight,
        motion_turnleft: this.turnLeft,
        motion_pointindirection: this.pointInDirection,
        motion_pointtowards: this.pointTowards,
        motion_glidesecstoxy: this.glide,
        motion_ifonedgebounce: this.ifOnEdgeBounce,
        motion_setrotationstyle: this.setRotationStyle,
        motion_changexby: this.changeX,
        motion_setx: this.setX,
        motion_changeyby: this.changeY,
        motion_sety: this.setY,
        motion_xposition: this.getX,
        motion_yposition: this.getY,
        motion_direction: this.getDirection
    };
};

Scratch3MotionBlocks.prototype.moveSteps = function (args, util) {
    const steps = Cast.toNumber(args.STEPS);
    const radians = MathUtil.degToRad(90 - util.target.direction);
    const dx = steps * Math.cos(radians);
    const dy = steps * Math.sin(radians);
    util.target.setXY(util.target.x + dx, util.target.y + dy);
};

Scratch3MotionBlocks.prototype.goToXY = function (args, util) {
    const x = Cast.toNumber(args.X);
    const y = Cast.toNumber(args.Y);
    util.target.setXY(x, y);
};

Scratch3MotionBlocks.prototype.goTo = function (args, util) {
    let targetX = 0;
    let targetY = 0;
    if (args.TO === '_mouse_') {
        targetX = util.ioQuery('mouse', 'getX');
        targetY = util.ioQuery('mouse', 'getY');
    } else if (args.TO === '_random_') {
        const stageWidth = this.runtime.constructor.STAGE_WIDTH;
        const stageHeight = this.runtime.constructor.STAGE_HEIGHT;
        targetX = Math.round(stageWidth * (Math.random() - 0.5));
        targetY = Math.round(stageHeight * (Math.random() - 0.5));
    } else {
        const goToTarget = this.runtime.getSpriteTargetByName(args.TO);
        if (!goToTarget) return;
        targetX = goToTarget.x;
        targetY = goToTarget.y;
    }
    util.target.setXY(targetX, targetY);
};

Scratch3MotionBlocks.prototype.turnRight = function (args, util) {
    const degrees = Cast.toNumber(args.DEGREES);
    util.target.setDirection(util.target.direction + degrees);
};

Scratch3MotionBlocks.prototype.turnLeft = function (args, util) {
    const degrees = Cast.toNumber(args.DEGREES);
    util.target.setDirection(util.target.direction - degrees);
};

Scratch3MotionBlocks.prototype.pointInDirection = function (args, util) {
    const direction = Cast.toNumber(args.DIRECTION);
    util.target.setDirection(direction);
};

Scratch3MotionBlocks.prototype.pointTowards = function (args, util) {
    let targetX = 0;
    let targetY = 0;
    if (args.TOWARDS === '_mouse_') {
        targetX = util.ioQuery('mouse', 'getX');
        targetY = util.ioQuery('mouse', 'getY');
    } else {
        const pointTarget = this.runtime.getSpriteTargetByName(args.TOWARDS);
        if (!pointTarget) return;
        targetX = pointTarget.x;
        targetY = pointTarget.y;
    }

    const dx = targetX - util.target.x;
    const dy = targetY - util.target.y;
    const direction = 90 - MathUtil.radToDeg(Math.atan2(dy, dx));
    util.target.setDirection(direction);
};

Scratch3MotionBlocks.prototype.glide = function (args, util) {
    if (!util.stackFrame.timer) {
        // First time: save data for future use.
        util.stackFrame.timer = new Timer();
        util.stackFrame.timer.start();
        util.stackFrame.duration = Cast.toNumber(args.SECS);
        util.stackFrame.startX = util.target.x;
        util.stackFrame.startY = util.target.y;
        util.stackFrame.endX = Cast.toNumber(args.X);
        util.stackFrame.endY = Cast.toNumber(args.Y);
        if (util.stackFrame.duration <= 0) {
            // Duration too short to glide.
            util.target.setXY(util.stackFrame.endX, util.stackFrame.endY);
            return;
        }
        util.yield();
    } else {
        const timeElapsed = util.stackFrame.timer.timeElapsed();
        if (timeElapsed < util.stackFrame.duration * 1000) {
            // In progress: move to intermediate position.
            const frac = timeElapsed / (util.stackFrame.duration * 1000);
            const dx = frac * (util.stackFrame.endX - util.stackFrame.startX);
            const dy = frac * (util.stackFrame.endY - util.stackFrame.startY);
            util.target.setXY(
                util.stackFrame.startX + dx,
                util.stackFrame.startY + dy
            );
            util.yield();
        } else {
            // Finished: move to final position.
            util.target.setXY(util.stackFrame.endX, util.stackFrame.endY);
        }
    }
};

Scratch3MotionBlocks.prototype.ifOnEdgeBounce = function (args, util) {
    const bounds = util.target.getBounds();
    if (!bounds) {
        return;
    }
    // Measure distance to edges.
    // Values are positive when the sprite is far away,
    // and clamped to zero when the sprite is beyond.
    const stageWidth = this.runtime.constructor.STAGE_WIDTH;
    const stageHeight = this.runtime.constructor.STAGE_HEIGHT;
    const distLeft = Math.max(0, (stageWidth / 2) + bounds.left);
    const distTop = Math.max(0, (stageHeight / 2) - bounds.top);
    const distRight = Math.max(0, (stageWidth / 2) - bounds.right);
    const distBottom = Math.max(0, (stageHeight / 2) + bounds.bottom);
    // Find the nearest edge.
    let nearestEdge = '';
    let minDist = Infinity;
    if (distLeft < minDist) {
        minDist = distLeft;
        nearestEdge = 'left';
    }
    if (distTop < minDist) {
        minDist = distTop;
        nearestEdge = 'top';
    }
    if (distRight < minDist) {
        minDist = distRight;
        nearestEdge = 'right';
    }
    if (distBottom < minDist) {
        minDist = distBottom;
        nearestEdge = 'bottom';
    }
    if (minDist > 0) {
        return; // Not touching any edge.
    }
    // Point away from the nearest edge.
    const radians = MathUtil.degToRad(90 - util.target.direction);
    let dx = Math.cos(radians);
    let dy = -Math.sin(radians);
    if (nearestEdge === 'left') {
        dx = Math.max(0.2, Math.abs(dx));
    } else if (nearestEdge === 'top') {
        dy = Math.max(0.2, Math.abs(dy));
    } else if (nearestEdge === 'right') {
        dx = 0 - Math.max(0.2, Math.abs(dx));
    } else if (nearestEdge === 'bottom') {
        dy = 0 - Math.max(0.2, Math.abs(dy));
    }
    const newDirection = MathUtil.radToDeg(Math.atan2(dy, dx)) + 90;
    util.target.setDirection(newDirection);
    // Keep within the stage.
    const fencedPosition = util.target.keepInFence(util.target.x, util.target.y);
    util.target.setXY(fencedPosition[0], fencedPosition[1]);
};

Scratch3MotionBlocks.prototype.setRotationStyle = function (args, util) {
    util.target.setRotationStyle(args.STYLE);
};

Scratch3MotionBlocks.prototype.changeX = function (args, util) {
    const dx = Cast.toNumber(args.DX);
    util.target.setXY(util.target.x + dx, util.target.y);
};

Scratch3MotionBlocks.prototype.setX = function (args, util) {
    const x = Cast.toNumber(args.X);
    util.target.setXY(x, util.target.y);
};

Scratch3MotionBlocks.prototype.changeY = function (args, util) {
    const dy = Cast.toNumber(args.DY);
    util.target.setXY(util.target.x, util.target.y + dy);
};

Scratch3MotionBlocks.prototype.setY = function (args, util) {
    const y = Cast.toNumber(args.Y);
    util.target.setXY(util.target.x, y);
};

Scratch3MotionBlocks.prototype.getX = function (args, util) {
    return util.target.x;
};

Scratch3MotionBlocks.prototype.getY = function (args, util) {
    return util.target.y;
};

Scratch3MotionBlocks.prototype.getDirection = function (args, util) {
    return util.target.direction;
};

module.exports = Scratch3MotionBlocks;