In Cytoscape.js, how do I select the set of visible nodes that have no visible edges?

Question

After hiding a set of nodes by shape

cy.elements('[shape="ellipse"]').addClass('hidden');

I am left with a few nodes that have no remaining visible edges (incoming or outgoing), which I would also like to hide. But after a considerable time trying to find invisible roots and leaves and union'ing and differenc'ing them, I simply can't see what must be a simple solution.

Any help greatly appreciated!

question from:https://stackoverflow.com/questions/65917054/in-cytoscape-js-how-do-i-select-the-set-of-visible-nodes-that-have-no-visible-e

Answer 1

Your approach is good, it just needs some adjustments for your desired result. I'd add a filter for every non ellipse node and remove the nodes with no visible connected edges. I use the function .hidden() for that, it returns true if every edge is hidden and false if there is at least one visible edge:

cy.nodes('[shape="ellipse"]').addClass("hidden"); 
cy.nodes('[shape!="ellipse"]').each(function(node) { 
    if (node.connectedEdges().hidden()) {
        node.addClass("hidden"); 
    }
 });

This works because of the style I added. Nodes with a display value of none hide their edges automatically, so there is no need to hide edges manually:

{
    selector: '.hidden',
    css: {
        'display': 'none'
    }
}

I tried this out in this dagre graph within a click event listener. I also changed the addClass to toggleClass, you can remove and add the classes with repeated clicks that way:

var cy = window.cy = cytoscape({
  container: document.getElementById('cy'),

  boxSelectionEnabled: false,
  autounselectify: true,

  style: [{
      selector: 'node',
      css: {
        'content': 'data(id)',
        'text-valign': 'center',
        'text-halign': 'center',
        'height': '60px',
        'width': '60px',
        'border-color': 'black',
        'border-opacity': '1',
        'border-width': '10px',
        'shape': 'data(shape)'
      }
    },
    {
      selector: '$node > node',
      css: {
        'padding-top': '10px',
        'padding-left': '10px',
        'padding-bottom': '10px',
        'padding-right': '10px',
        'text-valign': 'top',
        'text-halign': 'center',
        'background-color': '#bbb'
      }
    },
    {
      selector: 'edge',
      css: {
        'target-arrow-shape': 'triangle'
      }
    },
    {
      selector: ':selected',
      css: {
        'background-color': 'black',
        'line-color': 'black',
        'target-arrow-color': 'black',
        'source-arrow-color': 'black'
      }
    },
    {
      selector: '.hidden',
      css: {
        'display': 'none'
      }
    }
  ],

  elements: {
    nodes: [{
        data: {
          id: 'n0',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n1',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n2',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n3',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n4',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n5',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n6',
          shape: 'rectangle'
        }
      },
      {
        data: {
          id: 'n7',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n8',
          shape: 'rectangle'
        }
      },
      {
        data: {
          id: 'n9',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n10',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n11',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n12',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n13',
          shape: 'rectangle'
        }
      },
      {
        data: {
          id: 'n14',
          shape: 'ellipse'
        }
      },
      {
        data: {
          id: 'n15',
          shape: 'rectangle'
        }
      },
      {
        data: {
          id: 'n16',
          shape: 'ellipse'
        }
      }
    ],
    edges: [{
        data: {
          source: 'n0',
          target: 'n1'
        }
      },
      {
        data: {
          source: 'n1',
          target: 'n2'
        }
      },
      {
        data: {
          source: 'n1',
          target: 'n3'
        }
      },
      {
        data: {
          source: 'n2',
          target: 'n7'
        }
      },
      {
        data: {
          source: 'n2',
          target: 'n11'
        }
      },
      {
        data: {
          source: 'n2',
          target: 'n16'
        }
      },
      {
        data: {
          source: 'n3',
          target: 'n4'
        }
      },
      {
        data: {
          source: 'n3',
          target: 'n16'
        }
      },
      {
        data: {
          source: 'n4',
          target: 'n5'
        }
      },
      {
        data: {
          source: 'n4',
          target: 'n6'
        }
      },
      {
        data: {
          source: 'n6',
          target: 'n8'
        }
      },
      {
        data: {
          source: 'n8',
          target: 'n9'
        }
      },
      {
        data: {
          source: 'n8',
          target: 'n10'
        }
      },
      {
        data: {
          source: 'n11',
          target: 'n12'
        }
      },
      {
        data: {
          source: 'n12',
          target: 'n13'
        }
      },
      {
        data: {
          source: 'n13',
          target: 'n14'
        }
      },
      {
        data: {
          source: 'n13',
          target: 'n15'
        }
      },
    ]
  },

  layout: {
    name: 'dagre',
    padding: 5
  }
});

cy.unbind("click");
cy.bind("click", function(event) {
  cy.nodes('[shape!="ellipse"]').toggleClass("hidden");
  cy.nodes('[shape="ellipse"]').each(function(node) {
    if (node.connectedEdges().hidden()) {
      node.toggleClass("hidden");
    }
  });
});

body {
  font: 14px helvetica neue, helvetica, arial, sans-serif;
}

#cy {
  height: 100%;
  width: 75%;
  position: absolute;
  left: 0;
  top: 0;
  float: left;
}

<html>

<head>
  <meta charset=utf-8 />
  <meta name="viewport" content="user-scalable=no, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, minimal-ui">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/cytoscape/3.2.17/cytoscape.min.js"></script>
  <script src="https://unpkg.com/jquery@3.3.1/dist/jquery.js"></script>
  <script src="https://unpkg.com/dagre@0.7.4/dist/dagre.js"></script>
  <script src="https://cdn.rawgit.com/cytoscape/cytoscape.js-dagre/1.5.0/cytoscape-dagre.js"></script>
</head>

<body>
  <div id="cy"></div>
</body>

</html>