vis.js - fit a set of nodes on screen

Question

I have a network graph in vis.js with many nodes. When selecting a certain group, I would like to pan and zoom the graph so that all nodes of that group fit on screen.

I am traversing each node in the graph and calculating a bounding box for all the nodes I am interested in, then I use the moveTo method to move and scale the graph to the center of that bounding box. Pseudo-code:

var allNodes = data.nodes.get({
    returnType: "Object"
});
var bounds;
for (n in allNodes) {
    if (matchesCondition(allNodes[n])) {
        bounds = extendBounds(bounds, graph.getBoundingBox(allNodes[n]));                   
    }
}
var newViewport = {
    position: {
        x: (bounds.x1+bounds.x2)/2;
        y: (bounds.y1+bounds.y2)/2;
    },
    // What is the visible width, where do I get it from?
    scale: Math.min(??? / (bounds.x2-bounds.x1), ??? / (bounds.y2-bounds.y1))
}
graph.moveTo(newViewport);

The question: how do I calculate the scale, i.e. what do I replace the ??? with in the pseudo-code above?

Answer 1

Sample data from Vis.js groups example.

For fitting the viewport, you can simply use the native .fit() method. Since the documentation doesn't provide hashtaggable links, here's the API description:

Zooms out so all nodes fit on the canvas. You can supply options to customize this:

{
  nodes:[Array of nodeIds],
  animation: { //can be a boolean too
    duration: Number
    easingFunction: String
  }
}

The nodes can be used to zoom to fit only specific nodes in the view.

With this in mind, all we need to do is get all nodes in a given group. Surprisingly, the user-land API doesn't seem to offer a method for this (?), so a small filtering method is necessary.

//TODO: Is there no user-land API for this?
var getGroup = function getGroup(nodeId) {
  var nodesHandler = network.nodesHandler;
  var innerNodes = nodesHandler.body.nodes;
  //Lazily assume ids match indices
  var node = innerNodes[nodeId];
  return node.options.group;
};

var getGroupNodes = function getGroupNodes(group) {
  // http://elijahmanor.com/reducing-filter-and-map-down-to-reduce/
  var filtered = nodes.reduce(function(output, node) {
    if (node.group === group) {
      output.push(node.id);
    }
    return output;
  }, []);
  return filtered;
};

//START Vis.js group example

var color = 'gray';
var len = undefined;

var nodes = [{
  id: 0,
  label: "0",
  group: 0
}, {
  id: 1,
  label: "1",
  group: 0
}, {
  id: 2,
  label: "2",
  group: 0
}, {
  id: 3,
  label: "3",
  group: 1
}, {
  id: 4,
  label: "4",
  group: 1
}, {
  id: 5,
  label: "5",
  group: 1
}, {
  id: 6,
  label: "6",
  group: 2
}, {
  id: 7,
  label: "7",
  group: 2
}, {
  id: 8,
  label: "8",
  group: 2
}, {
  id: 9,
  label: "9",
  group: 3
}, {
  id: 10,
  label: "10",
  group: 3
}, {
  id: 11,
  label: "11",
  group: 3
}, {
  id: 12,
  label: "12",
  group: 4
}, {
  id: 13,
  label: "13",
  group: 4
}, {
  id: 14,
  label: "14",
  group: 4
}, {
  id: 15,
  label: "15",
  group: 5
}, {
  id: 16,
  label: "16",
  group: 5
}, {
  id: 17,
  label: "17",
  group: 5
}, {
  id: 18,
  label: "18",
  group: 6
}, {
  id: 19,
  label: "19",
  group: 6
}, {
  id: 20,
  label: "20",
  group: 6
}, {
  id: 21,
  label: "21",
  group: 7
}, {
  id: 22,
  label: "22",
  group: 7
}, {
  id: 23,
  label: "23",
  group: 7
}, {
  id: 24,
  label: "24",
  group: 8
}, {
  id: 25,
  label: "25",
  group: 8
}, {
  id: 26,
  label: "26",
  group: 8
}, {
  id: 27,
  label: "27",
  group: 9
}, {
  id: 28,
  label: "28",
  group: 9
}, {
  id: 29,
  label: "29",
  group: 9
}];
var edges = [{
  from: 1,
  to: 0
}, {
  from: 2,
  to: 0
}, {
  from: 4,
  to: 3
}, {
  from: 5,
  to: 4
}, {
  from: 4,
  to: 0
}, {
  from: 7,
  to: 6
}, {
  from: 8,
  to: 7
}, {
  from: 7,
  to: 0
}, {
  from: 10,
  to: 9
}, {
  from: 11,
  to: 10
}, {
  from: 10,
  to: 4
}, {
  from: 13,
  to: 12
}, {
  from: 14,
  to: 13
}, {
  from: 13,
  to: 0
}, {
  from: 16,
  to: 15
}, {
  from: 17,
  to: 15
}, {
  from: 15,
  to: 10
}, {
  from: 19,
  to: 18
}, {
  from: 20,
  to: 19
}, {
  from: 19,
  to: 4
}, {
  from: 22,
  to: 21
}, {
  from: 23,
  to: 22
}, {
  from: 22,
  to: 13
}, {
  from: 25,
  to: 24
}, {
  from: 26,
  to: 25
}, {
  from: 25,
  to: 7
}, {
  from: 28,
  to: 27
}, {
  from: 29,
  to: 28
}, {
  from: 28,
  to: 0
}];

// create a network
var container = document.getElementById('mynetwork');
var data = {
  nodes: nodes,
  edges: edges
};
var options = {
  nodes: {
    shape: 'dot',
    size: 30,
    font: {
      size: 32,
      color: '#ffffff'
    },
    borderWidth: 2
  },
  edges: {
    width: 2
  }
};
network = new vis.Network(container, data, options);

//END Vis.js group example

network.on("click", function(e) {
  //Zoom only on single node clicks, zoom out otherwise
  if (e.nodes.length !== 1) {
    network.fit();
    return;
  }
  var nodeId = e.nodes[0];
  //Find out what group the node belongs to
  var group = getGroup(nodeId);
  //TODO: How do you want to handle ungrouped nodes?
  if (group === undefined) return;
  var groupNodes = getGroupNodes(group);
  network.fit({
    nodes: groupNodes
  });
});

html,
body,
#mynetwork {
  width: 100%;
  height: 100%;
  margin: 0;
}

<script src="http://cdnjs.cloudflare.com/ajax/libs/vis/4.3.0/vis.min.js"></script>
<div id="mynetwork"></div>