d3.js - Force layout zoom resets on first tick of dragging or zomming

Question

I'm trying to implement a force layout graph using d3 v4, and I'm having a problem with the default zooming and panning behaviours of the graph on the first tick of these functions. Since it's a somewhat large graph (~700 nodes) I'm using the transform(translate()) function of d3 to set the initial position and zooming after declaring the svg element as so:

var svg = d3.select("svg")
        .call(d3.zoom()
        .scaleExtent([0.05,2])
        .on("zoom", zoomed))
        .append("g"), width = +svg.attr("width"), height = +svg.attr("height");
var initialScale = 0.1,
        zoomWidth = (svg.attr("width")-initialScale*svg.attr("width"))/2,
        zoomHeight = (svg.attr("height")-initialScale*svg.attr("height")/2);

After that, I declare the initial position and scale of the element:

svg.attr("transform", "translate(" + (zoomWidth+400) + "," + (zoomHeight+325) + ")scale(" + initialScale + ")");

For the zooming, panning and tick functions, I'm using the code from this Mike Bostock example.

function dragstarted(d) {
    if (!d3.event.active) simulation.alphaTarget(0.3).restart();
    d.fx = d.x ;
    d.fy = d.y;
}
function dragged(d) {
    d.fx = d3.event.x;
    d.fy = d3.event.y;
}
function dragended(d) {
    if (!d3.event.active) simulation.alphaTarget(0);
    d.fx = null;
    d.fy = null;
}
function zoomed() {
    svg.attr("transform", d3.event.transform);
    // Manually offsets the zoom to compensate for the initial position. Should get fixed asap or the position variables made global.
    //svg.attr("transform", "translate(" + (d3.event.transform.x + 400) + "," + (d3.event.transform.y + 325) + ")scale(" +  d3.event.transform.k + ")");
}
function ticked() {
    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; });
    gnodes
        .attr("transform", function(d) {
            return "translate(" + [d.x, d.y] + ")";
        });
}

(As you can see from the comment, I even tried manually setting those initial points as modifiers to the zoomed() function, but that didn't solve anything).

The problem is that the initial 0.1 zoom that is set after declaring the svg is being reset whenever you try to drag or pan over the visualization for the first time (after that, it works correctly until the page is reloaded). It seems to default to some zooming scale that I don't seem to be able to control properly so that it starts zooming from the initialScale value that is set globally.

You can watch a gif of the behaviour on this gfycat I made.

I've also read the answer to this question in Stack Overflow, which seems to be related to my problem, but I can't implement a proper solution (my very little experience with d3 yet might be the cause for this, I'm sure). Since I'm declaring the zoom object directly on the svg declaration, I don't know if I should be declaring the zoom object elsewhere and then manually attaching it to the svg, or how I should do so (again, very little experience).

I've been fighting this for a couple of days and haven't been able to solve this even though the answer might be very simple, so any kind of help would be greatly appreciated. Thanks in advance.

Answer 1

You shouldn't be manually setting the scale like you are doing with:

svg.attr("transform", "translate(" + (zoomWidth+400) + "," + (zoomHeight+325) + ")scale(" + initialScale + ")");

Instead, create a transform and operate on that using .call zoom.transform:

  // initial setup
  var zoom = d3.zoom()
    .scaleExtent([0.05, 2])
    .on("zoom", zoomed);

  var svg = d3.select("svg").call(zoom), //<-- apply zoom to svg
    g = svg.append("g"), //<-- g for append elements, this is what you are zooming
    width = 960,
    height = 600;

  var transform = d3.zoomIdentity //<-- create your transform with your initialScale
    .translate(width / 6, height / 6)
    .scale(0.5);

  svg.call(zoom.transform, transform); //<-- apply your initial transform, this will fire you zoomed event

EDITS FOR COMMENTS

The reason for separating out the svg and the g is that the svg element here is the event receiver. It is the element to which the zoom event handlers are bound (in most d3 examples, you'll see a rect element being used for this). The g on the other hand, is the container element that's being zoomed.

Here's a full example:

<!DOCTYPE html>
<meta charset="utf-8">
<style>
  .links line {
    stroke: #999;
    stroke-opacity: 0.6;
  }
  
  .nodes circle {
    stroke: #fff;
    stroke-width: 1.5px;
  }
</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

  var zoom = d3.zoom()
    .scaleExtent([0.05, 2])
    .on("zoom", zoomed);

  var svg = d3.select("svg").call(zoom),
    g = svg.append("g"),
    width = 960,
    height = 600;
    
  var transform = d3.zoomIdentity
    .translate(width / 6, height / 6)
    .scale(0.5);

  var color = d3.scaleOrdinal(d3.schemeCategory20);

  var simulation = d3.forceSimulation()
    .force("link", d3.forceLink().id(function(d) {
      return d.id;
    }))
    .force("charge", d3.forceManyBody())
    .force("center", d3.forceCenter(width / 2, height / 2));

  svg.call(zoom.transform, transform);

  var graph = {"nodes":[{"id":"Myriel","group":1},{"id":"Napoleon","group":1},{"id":"Mlle.Baptistine","group":1},{"id":"Mme.Magloire","group":1},{"id":"CountessdeLo","group":1},{"id":"Geborand","group":1},{"id":"Champtercier","group":1},{"id":"Cravatte","group":1},{"id":"Count","group":1},{"id":"OldMan","group":1},{"id":"Labarre","group":2},{"id":"Valjean","group":2},{"id":"Marguerite","group":3},{"id":"Mme.deR","group":2},{"id":"Isabeau","group":2},{"id":"Gervais","group":2},{"id":"Tholomyes","group":3},{"id":"Listolier","group":3},{"id":"Fameuil","group":3},{"id":"Blacheville","group":3},{"id":"Favourite","group":3},{"id":"Dahlia","group":3},{"id":"Zephine","group":3},{"id":"Fantine","group":3},{"id":"Mme.Thenardier","group":4},{"id":"Thenardier","group":4},{"id":"Cosette","group":5},{"id":"Javert","group":4},{"id":"Fauchelevent","group":0},{"id":"Bamatabois","group":2},{"id":"Perpetue","group":3},{"id":"Simplice","group":2},{"id":"Scaufflaire","group":2},{"id":"Woman1","group":2},{"id":"Judge","group":2},{"id":"Champmathieu","group":2},{"id":"Brevet","group":2},{"id":"Chenildieu","group":2},{"id":"Cochepaille","group":2},{"id":"Pontmercy","group":4},{"id":"Boulatruelle","group":6},{"id":"Eponine","group":4},{"id":"Anzelma","group":4},{"id":"Woman2","group":5},{"id":"MotherInnocent","group":0},{"id":"Gribier","group":0},{"id":"Jondrette","group":7},{"id":"Mme.Burgon","group":7},{"id":"Gavroche","group":8},{"id":"Gillenormand","group":5},{"id":"Magnon","group":5},{"id":"Mlle.Gillenormand","group":5},{"id":"Mme.Pontmercy","group":5},{"id":"Mlle.Vaubois","group":5},{"id":"Lt.Gillenormand","group":5},{"id":"Marius","group":8},{"id":"BaronessT","group":5},{"id":"Mabeuf","group":8},{"id":"Enjolras","group":8},{"id":"Combeferre","group":8},{"id":"Prouvaire","group":8},{"id":"Feuilly","group":8},{"id":"Courfeyrac","group":8},{"id":"Bahorel","group":8},{"id":"Bossuet","group":8},{"id":"Joly","group":8},{"id":"Grantaire","group":8},{"id":"MotherPlutarch","group":9},{"id":"Gueulemer","group":4},{"id":"Babet","group":4},{"id":"Claquesous","group":4},{"id":"Montparnasse","group":4},{"id":"Toussaint","group":5},{"id":"Child1","group":10},{"id":"Child2","group":10},{"id":"Brujon","group":4},{"id":"Mme.Hucheloup","group":8}],"links":[{"source":"Napoleon","target":"Myriel","value":1},{"source":"Mlle.Baptistine","target":"Myriel","value":8},{"source":"Mme.Magloire","target":"Myriel","value":10},{"source":"Mme.Magloire","target":"Mlle.Baptistine","value":6},{"source":"CountessdeLo","target":"Myriel","value":1},{"source":"Geborand","target":"Myriel","value":1},{"source":"Champtercier","target":"Myriel","value":1},{"source":"Cravatte","target":"Myriel","value":1},{"source":"Count","target":"Myriel","value":2},{"source":"OldMan","target":"Myriel","value":1},{"source":"Valjean","target":"Labarre","value":1},{"source":"Valjean","target":"Mme.Magloire","value":3},{"source":"Valjean","target":"Mlle.Baptistine","value":3},{"source":"Valjean","target":"Myriel","value":5},{"source":"Marguerite","target":"Valjean","value":1},{"source":"Mme.deR","target":"Valjean","value":1},{"source":"Isabeau","target":"Valjean","value":1},{"source":"Gervais","target":"Valjean","value":1},{"source":"Listolier","target":"Tholomyes","value":4},{"source":"Fameuil","target":"Tholomyes","value":4},{"source":"Fameuil","target":"Listolier","value":4},{"source":"Blacheville","target":"Tholomyes","value":4},{"source":"Blacheville","target":"Listolier","value":4},{"source":"Blacheville","target":"Fameuil","value":4},{"source":"Favourite","target":"Tholomyes","value":3},{"source":"Favourite","target":"Listolier","value":3},{"source":"Favourite","target":"Fameuil","value":3},{"source":"Favourite","target":"Blacheville","value":4},{"source":"Dahlia","target":"Tholomyes","value":3},{"source":"Dahlia","target":"Listolier","value":3},{"source":"Dahlia","target":"Fameuil","value":3},{"source":"Dahlia","target":"Blacheville","value":3},{"source":"Dahlia","target":"Favourite","value":5},{"source":"Zephine","target":"Tholomyes","value":3},{"source":"Zephine","target":"Listolier","value":3},{"source":"Zephine","target":"Fameuil","value":3},{"source":"Zephine","target":"Blacheville","value":3},{"source":"Zephine","target":"Favourite","value":4},{"source":"Zephine","target":"Dahlia","value":4},{"source":"Fantine","target":"Tholomyes","value":3},{"source":"Fantine","target":"Listolier","value":3},{"source":"Fantine","target":"Fameuil","value":3},{"source":"Fantine","target":"Blacheville","value":3},{"source":"Fantine","target":"Favourite","value":4},{"source":"Fantine","target":"Dahlia","value":4},{"source":"Fantine","target":"Zephine","value":4},{"source":"Fantine","target":"Marguerite","value":2},{"source":"Fantine","target":"Valjean","value":9},{"source":"Mme.Thenardier","target":"Fantine","value":2},{"source":"Mme.Thenardier","target":"Valjean","value":7},{"source":"Thenardier","target":"Mme.Thenardier","value":13},{"source":"Thenardier","target":"Fantine","value":1},{"source":"Thenardier","target":"Valjean","value":12},{"source":"Cosette","target":"Mme.Thenardier","value":4},{"source":"Cosette","target":"Valjean","value":31},{"source":"Cosette","target":"Tholomyes","value":1},{"source":"Cosette","target":"Thenardier","value":1},{"source":"Javert","target":"Valjean","value":17},{"source":"Javert","target":"Fantine","value":5},{"source":"Javert","target":"Thenardier","value":5},{"source":"Javert","target":"Mme.Thenardier","value":1},{"source":"Javert","target":"Cosette","value":1},{"source":"Fauchelevent","target":"Valjean","value":8},{"source":"Fauchelevent","target":"Javert","value":1},{"source":"Bamatabois","target":"Fantine","value":1},{"source":"Bamatabois","target":"Javert","value":1},{"source":"Bamatabois","target":"Valjean","value":2},{"source":"Perpetue","target":"Fantine","value":1},{"source":"Simplice","target":"Perpetue","value":2},{"source":"Simplice","target":"Valjean","value":3},{"source":"Simplice","target":"Fantine","value":2},{"source":"Simplice","target":"Javert","value":1},{"source":"Scaufflaire","target":"Valjean","value":1},{"source":"Woman1","target":"Valjean","value":2},{"source":"Woman1","target":"Javert","value":1},{"source":"Judge","target":"Valjean","value":3},{"source":"Judge","target":"Bamatabois","value":2},{"source":"Champmathieu","target":"Valjean","value":3},{"source":"Champmathieu","target":"Judge","value":3},{"source":"Champmathieu","target":"Bamatabois","value":2},{"source":"Brevet","target":"Judge","value":2},{"source":"Brevet","target":"Champmathieu","value":2},{"source":"Brevet","target":"Valjean","value":2},{"source":"Brevet","target":"Bamatabois","value":1},{"source":"Chenildieu","target":"Judge","value":2},{"source":"Chenildieu","target":"Champmathieu","value":2},{"source":"Chenildieu","target":"Brevet","value":2},{"source":"Chenildieu","target":"Valjean","value":2},{"source":"Chenildieu","target":"Bamatabois","value":1},{"source":"Cochepaille","target":"Judge","value":2},{"source":"Cochepaille","target":"Champmathieu","value":2},{"source":"Cochepaille","target":"Brevet","value":2},{"source":"Cochepaille","target":"Chenildieu","value":2},{"source":"Cochepaille","target":"Valjean","value":2},{"source":"Cochepaille","target":"Bamatabois","value":1},{"source":"Pontmercy","target":"Thenardier","value":1},{"source":"Boulatruelle","target":"Thenardier","value":1},{"source":"Eponine","target":"Mme.Thenardier","value":2},{"source":"Eponine","target":"Thenardier","value":3},{"source":"Anzelma","target":"Eponine","value":2},{"source":"Anzelma","target":"Thenardier","value":2},{"source":"Anzelma","target":"Mme.Thenardier","value":1},{"source":"Woman2","target":"Valjean","value":3},{"source":"Woman2","target":"Cosette","value":1},{"source":"Woman2","target":"Javert","value":1},{"source":"MotherInnocent","target":"Fauchelevent","value":3},{"source":"MotherInnocent","target":"Valjean","value":1},{"source":"Gribier","target":"Fauchelevent","value":2},{"source":"Mme.Burgon","target":"Jondrette","value":1},{"source":"Gavroche","target":"Mme.Burgon","value":2},{"source":"Gavroche","target":"Thenardier","value":1},{"source":"Gavroche","target":"Javert","value":1},{"source":"Gavroche","target":"Valjean","value":1},{"source":"Gillenormand","target":"Cosette","value":3},{"source":"Gillenormand","target":"Valjean","value":2},{"source":"Magnon","target":"Gillenormand","value":1},{"source":"Magnon","target":"Mme.Thenardier","value":1},{"source":"Mlle.Gillenormand","target":"Gillenormand","value":9},{"source":"Mlle.Gillenormand","target":"Cosette","value":2},{"source":"Mlle.Gillenormand","target":"Valjean","value":2},{"source":"Mme.Pontmercy","target":"Mlle.Gillenormand","value":1},{"source":"Mme.Pontmercy","target":"Pontmercy","value":1},{"source":"Mlle.Vaubois","target":"Mlle.Gillenormand","value":1},{"source":"Lt.Gillenormand","target":"Mlle.Gillenormand","value":2},{"source":"Lt.Gillenormand","target":"Gillenormand","value":1},{"source":"Lt.Gillenormand","target":"Cosette","value":1},{"source":"Marius","target":"Mlle.Gillenormand","value":6},{"source":"Marius","target":"Gillenormand","value":12},{"source":"Marius","target":"Pontmercy","value":1},{"source":"Marius","target":"Lt.Gillenormand","value":1},{"source":"Marius","target":"Cose