D3v6 zoom causing wrong pointer position

The general issue is dealt with in this question with accepted answer by @Andrew Reid

For your specific issue, try the following to illustrate what is happening:

include console.log(point) in your mousemoveSVG function
run the snippet
right click node 2 and add a link
move the pointer to the centre of the 'zero' node and observe [x, y] in the console
do some pan and zoom
move the dragline about - you will see the [x, y] has changed and the dragline is off
stop the snippet and in mousemoveSVG update this line to const point = d3.pointer(event, svg.node());
now repeat the test above - the pointer in the centre of the 'zero' node should have the same [x,y] for any different pan/ zoom actions

This 2nd argument to d3.pointer called target:

If the target is an SVG element, the event’s coordinates are transformed using the inverse of the screen coordinate transformation matrix.

Transforming the [x,y] of the pointer with this screen coordinate transformation matrix is basically saying keep my mouse in step with the zoom.

Here is your full code with the update - I commented out the log as it stuffs up the snippet, but you can uncomment to try the steps above.

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <title>D3v6 Refactor</title>
    <!-- call external d3.js framework -->
    <script src="https://d3js.org/d3.v6.js"></script>
</head>

<style>
    body {
        overflow: hidden;
        background-color: rgb(220, 220, 220);
        margin: 0px;
    }

    .node {
        stroke: white;
        stroke-width: 2px;
        cursor: pointer;
    }

    .node:hover {
        stroke: red
    }

    .link {
        fill: none;
        cursor: default;
        stroke: rgb(0, 0, 0);
        stroke-width: 3px;
    }

    .dragline {
        stroke-width: 2;
        pointer-events: none;
    }

    .dragline.hidden {
        stroke-width: 0;
    }

    #context-menu-node {
        font-family: "Open Sans", sans-serif;
        position: fixed;
        z-index: 10000;
        width: 190px;
        background: whitesmoke;
        border: 2px;
        border-radius: 6px;
        border-color: white;
        border-style: solid;
        transform: scale(0);
        transform-origin: top left;
    }

    #context-menu-node.active {
        transform: scale(1);
        transition: transform 200ms ease-in-out;
    }

    #context-menu-node .item {
        padding: 8px 10px;
        font-size: 15px;
        color: black;
    }

    #context-menu-node .item i {
        display: inline-block;
        margin-right: 5px;
    }

    #context-menu-node hr {
        margin: 5px 0px;
        border-color: whitesmoke;
    }

    #context-menu-node .item:hover {
        background: lightblue;
    }
</style>

<body>
    <!-- right click context menu node -->
    <div id="context-menu-node">
        <div id="addLink" class="item">
            <i class="fas fa-link"></i></i> Add Link
        </div>
        <hr>
        <div id="addNode" class="item">
            <i class="fas fa-link"></i></i> Add Node
        </div>
    </div>

    <svg id="svg"> </svg>

    <script>
        var graph = {
            "nodes": [
                {
                    "id": 0,
                },
                {
                    "id": 1,
                },
                {
                    "id": 2,
                }
            ],
            "links": [
                {
                    "source": 0,
                    "target": 1,
                },
                {
                    "source": 1,
                    "target": 2,
                }
            ]
        }

        var width = window.innerWidth
        var height = window.innerHeight

        var svg = d3.select("svg")
            .attr("class", "canvas")
            .attr("width", width)
            .attr("height", height)
            .call(d3.zoom().on("zoom", function (event) {
                svg.attr("transform", event.transform)
            }))
            //.on("mousedown", mousedownSVG)
            .on("mousemove", mousemoveSVG)
            .on("mouseup", mouseupSVG)
            .append("g")

        // remove zoom on dblclick listener
        d3.select("svg").on("dblclick.zoom", null)

        var linkContainer = svg.append("g").attr("class", "linkContainer")
        var nodeContainer = svg.append("g").attr("class", "nodeContainer")

        var mousedownNode = "";
        var targetLink = "";
        var addLinkClicked = false;

        var simulation = d3.forceSimulation()
            .force("link", d3.forceLink().id(function (d) {
                return d.id;
            }).distance(100))
            .force("charge", d3.forceManyBody().strength(-500))
            .force("center", d3.forceCenter(width / 2, height / 2))
            .force("collision", d3.forceCollide().radius(50))

        var dragLine = svg.append("path")
            .attr("class", "link dragline")
            .attr("d", "M0,0 L0,0");

        initialize()

        function initialize() {

            link = linkContainer.selectAll(".link")
                .data(graph.links)
                .join("line")
                .attr("class", "link")

            node = nodeContainer.selectAll(".node")
                .data(graph.nodes, d => d.id)
                .join("g")
                .attr("class", "node")

                .call(d3.drag()
                    .on("start", dragStarted)
                    .on("drag", dragged)
                    .on("end", dragEnded)
                )

            node
                .data(graph.nodes, d => d.id)
                .append("circle")
                .attr("r", 30)
                .style("fill", "whitesmoke")
                .on("contextmenu", contextMenuNode)
                .on("mouseenter", (event, d) => {
                    targetLink = d
                })
                .on("mousedown", (event, d) => {
                    mousedownNode = d;
                })
                .on("click", function (event, d) {
                    if (!addLinkClicked) return

                    // needed by FF
                    dragLine
                        .classed('hidden', true)

                    console.log(targetLink.id)

                    graph.links.push({ source: thisElement.id, target: targetLink.id });

                    addLinkClicked = false;

                    initialize();

                    simulation.alpha(0.3).restart()
                });

            node
                .append("text")
                .style("class", "icon")
                .attr("font-family", "FontAwesome")
                .attr("dominant-baseline", "central")
                .attr("text-anchor", "middle")
                .attr("font-size", 30)
                .attr("fill", "black")
                .attr("stroke-width", "0px")
                .attr("pointer-events", "none")
                .text((d) => {
                    return d.id
                })

            simulation
                .nodes(graph.nodes)
                .on("tick", ticked);

            simulation
                .force("link")
                .links(graph.links)

        }


        function contextMenuNode(event, d) {
            thisElement = d

            event.preventDefault()

            document.getElementById("context-menu-node").classList.remove("active")

            var contextMenu = document.getElementById("context-menu-node")
            contextMenu.style.top = event.clientY + "px"
            contextMenu.style.left = event.clientX + "px"
            contextMenu.classList.add("active")

            window.addEventListener("click", function () {
                contextMenu.classList.remove("active")
            })

            document.getElementById("addNode").addEventListener("click", addNode)
            document.getElementById("addLink").addEventListener("click", addLink)
        }

        function addLink() {
            addLinkClicked = true

            const point = d3.pointer(event)

            dragLine
                .classed("hidden", false)
                .attr('d', `M${thisElement.x},${thisElement.y}L${thisElement.x},${thisElement.y}`);
        }

        function addNode() {
            var newID = Math.floor(Math.random() * 1000)
            
            graph.nodes.push({
                "id": newID
            })

            graph.links.push({ source: newID, target: thisElement.id })

            initialize()

            simulation.alpha(0.3).restart()
        }


        /*
        function mousedownSVG(event) {
            var point = d3.pointer(event)
            
            var newNode = { id: graph.nodes.length, x: point[0], y: point[1] }
            
            graph.nodes.push(newNode)
            
            initialize()
            
            simulation.alpha(0.3).restart()
        }
        */

        function mousemoveSVG(event) {
            if (!addLinkClicked) return

            const point = d3.pointer(event, svg.node()); // <--- add svg.node() as 'target'
            //console.log(point);

            // update drag line
            dragLine.attr('d', `M${mousedownNode.x},${mousedownNode.y}L${point[0]},${point[1]}`);
        }

        function mouseupSVG(event) {
            if (mousedownNode) {
                //hide drag line
                dragLine
                    .classed("hidden", true)
            }
        }

        function ticked() {
            // update link positions
            link
                .attr("x1", function (d) {
                    return d.source.x;
                })
                .attr("y1", function (d) {
                    return d.source.y;
                })
                .attr("x2", function (d) {
                    return d.target.x;
                })
                .attr("y2", function (d) {
                    return d.target.y;
                });


            // update node positions
            node
                .attr("transform", function (d) {
                    return "translate(" + d.x + ", " + d.y + ")";
                });
        }


        function dragStarted(event, d) {
            if (!event.active) simulation.alphaTarget(0.3).restart();
            d.fx = d.x;
            d.fy = d.y;
        }

        function dragged(event, d) {
            d.fx = event.x;
            d.fy = event.y;
        }

        function dragEnded(event, d) {
            if (!event.active) simulation.alphaTarget(0);
            d.fx = undefined;
            d.fy = undefined;
        }
    </script>
</body>

</html>

D3v6 zoom causing wrong pointer position

1 Answers