Emit click events from one canvas to another

Question

I'm using a Threejs canvas to render a 3d model and another (this one hidden) Fabricjs canvas to apply as a texture.

I achieved to transform the 3d coords from the threejs canvas to the 2d canvas. Now what i need is to "replicate" or "emit" the click and drag events from the 3d canvas to the hidden 2d one as suggested in a comment from this question.

I made a codepen with my progres. If you click the left canvas a dot will spawn in the same coords but in 2d canvas. I need to be able to click and drag the canvas objects directly from the left threejs canvas.

See the codepen i made Codepen

    <div id="c-left">
        <h3>Renderer</h3>
        <div id="renderer"></div>
    </div>

    <div id="c-right">
        <h3>Canvas</h3>
        <canvas id="canvas" width="512" height="512"></canvas>
    </div>

    <script>
        console.clear();
        console.log("starting scripts...");

        /**
         * Fabricjs
         * @type {fabric}
         */

        var canvas = new fabric.Canvas( "canvas" );
        canvas.backgroundColor = "#FFBE9F";

        var rectangle = new fabric.Rect( {
            top: 100,
            left: 100,
            fill: '#FF6E27',
            width: 100,
            height: 100,
            transparentCorners: false,
            centeredScaling: true,
            borderColor: 'black',
            cornerColor: 'black',
            corcerStrokeColor: 'black'
        } );

        canvas.add( rectangle );


        /**
         * Threejs
         */

        var containerHeight = "512";
        var containerWidth = "512";
        var camera, renderer, container, scene, texture, material, geometry,
            cube;

        var raycaster = new THREE.Raycaster();
        var mouse = new THREE.Vector2();
        var onClickPosition = new THREE.Vector2();

        init();
        animate();


        /**
         * Configurator init function
         */

        function init() {

            /**
             * Camera
             */

            camera = new THREE.PerspectiveCamera( 30, window.innerWidth / window.innerHeight, 0.01, 100 );
            camera.position.set( 0, 0, 3.5 );


            /**
             * Renderer
             */

            container = document.getElementById( "renderer" );
            renderer = new THREE.WebGLRenderer( { antialias: true } );
            renderer.setPixelRatio( window.devicePixelRatio );
            renderer.setSize( containerWidth, containerHeight );
            camera.aspect = container.clientWidth / container.clientHeight;
            camera.updateProjectionMatrix();
            container.appendChild( renderer.domElement );


            /**
             * Scene
             */

            scene = new THREE.Scene();
            scene.background = new THREE.Color( 0x000000 );


            /**
             * Texture and material
             */

            texture = new THREE.Texture( document.getElementById( "canvas" ) );
            texture.anisotropy = renderer.capabilities.getMaxAnisotropy();

            material = new THREE.MeshBasicMaterial( { map: texture } );


            /**
             * Model
             */

             geometry = new THREE.BoxGeometry( 1, 1, 1 );
             cube = new THREE.Mesh( geometry, material );
             scene.add( cube );
        }


        /**
         * Configurator frame render function
         */

        function animate() {
            requestAnimationFrame( animate );

            cube.rotation.x += 0.004;
            cube.rotation.y += 0.001;
            texture.needsUpdate = true;

            renderer.render( scene, camera );
        }


        /**
         * Listeners
         */

        container.addEventListener( "mousedown", onMouseClick, false );


        /**
         * Other methods
         */

        function onMouseClick( evt ) {
            evt.preventDefault();

            var array = getMousePosition( container, evt.clientX, evt.clientY );
            onClickPosition.fromArray( array );

            var intersects = getIntersects( onClickPosition, scene.children );

            if ( intersects.length > 0 && intersects[ 0 ].uv ) {
                var uv = intersects[ 0 ].uv;
                intersects[ 0 ].object.material.map.transformUv( uv );

                var circle = new fabric.Circle({
                    radius: 3,
                    left: getRealPosition( "x", uv.x ),
                    top: getRealPosition( "y", uv.y ),
                    fill: 'red'
                });
                canvas.add( circle );
            }
        }

        function getRealPosition( axis, value ) {
            let CORRECTION_VALUE = axis === "x"
                                    ? 4.5
                                    : 5.5;

            return Math.round( value * 512 ) - CORRECTION_VALUE;
        }

        var getMousePosition = function ( dom, x, y ) {
            var rect = dom.getBoundingClientRect();
            return [ ( x - rect.left ) / rect.width, ( y - rect.top ) / rect.height ];
        };

        var getIntersects = function ( point, objects ) {
            mouse.set( ( point.x * 2 ) - 1, - ( point.y * 2 ) + 1 );
            raycaster.setFromCamera( mouse, camera );
            return raycaster.intersectObjects( objects );
        };
     </script>

Answer 1

You need to use element.dispatchEvent.

You create a new event:

var evt2 = new Event('mousedown', { clientX: value, clientY: value2 });

You find value and value2 starting from the circle top and left and adding the values for x and y you find in canvas._offset

At that point you have an evt2 with the right values, and you can use

canvas.upperCanvasEl.dispatchEvent(evt2);