scratch-vm/src/blocks/scratch3_motion.js

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

class Scratch3MotionBlocks {
    constructor (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.
     */
    getPrimitives () {
        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_glideto: this.glideTo,
            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
        };
    }

    getMonitored () {
        return {
            motion_xposition: {isSpriteSpecific: true},
            motion_yposition: {isSpriteSpecific: true},
            motion_direction: {isSpriteSpecific: true}
        };
    }

    moveSteps (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);
    }

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

    getTargetXY (targetName, util) {
        let targetX = 0;
        let targetY = 0;
        if (targetName === '_mouse_') {
            targetX = util.ioQuery('mouse', 'getX');
            targetY = util.ioQuery('mouse', 'getY');
        } else if (targetName === '_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(targetName);
            if (!goToTarget) return;
            targetX = goToTarget.x;
            targetY = goToTarget.y;
        }
        return [targetX, targetY];
    }

    goTo (args, util) {
        const targetXY = this.getTargetXY(args.TO, util);
        if (targetXY) {
            util.target.setXY(targetXY[0], targetXY[1]);
        }
    }

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

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

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

    pointTowards (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);
    }

    glide (args, util) {
        if (util.stackFrame.timer) {
            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);
            }
        } else {
            // 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();
        }
    }
    
    glideTo (args, util) {
        const targetXY = this.getTargetXY(args.TO, util);
        if (targetXY) {
            this.glide({SECS: args.SECS, X: targetXY[0], Y: targetXY[1]}, util);
        }
    }

    ifOnEdgeBounce (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]);
    }

    setRotationStyle (args, util) {
        util.target.setRotationStyle(args.STYLE);
    }

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

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

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

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

    getX (args, util) {
        return util.target.x;
    }

    getY (args, util) {
        return util.target.y;
    }

    getDirection (args, util) {
        return util.target.direction;
    }
}

module.exports = Scratch3MotionBlocks;