create-gojs-kit
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A CLI for downloading GoJS samples, extensions, and docs
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<h1>Trees and TreeLayout</h1>
<p>
There is no limit to the kinds of graphs that you can build in <b>GoJS</b>.
But the most common kind of graph forms a "tree".
A tree is a graph where each node may have at most one "tree parent" and at most one link connecting to that parent node,
and where there are no cycles within the graph.
</p>
<p>
Because trees occur so frequently in diagrams, there is also a predefined tree layout that offers many customizations specifically for trees.
</p>
<h2 id="ManualLayoutOfTreeStructure">Manual layout of a tree structure</h2>
<p>
You can of course position the nodes manually, either by hand or programmatically.
In this first example, the node locations are stored in the node data, and there is a Binding of <a>Part.location</a> to the node data property.
</p>
<pre class="lang-js" id="tree"><code>
diagram.nodeTemplate =
new go.Node("Auto")
.bind("location", "loc", go.Point.parse)
.add(
new go.Shape("Ellipse", { fill: "white" }),
new go.TextBlock()
.bind("text", "key")
);
diagram.linkTemplate =
new go.Link({ routing: go.Routing.Orthogonal, corner: 5 })
.add(
new go.Shape()
);
const nodeDataArray = [
{ key: "Alpha", loc: "0 60" },
{ key: "Beta", loc: "100 15" },
{ key: "Gamma", loc: "200 0" },
{ key: "Delta", loc: "200 30" },
{ key: "Epsilon", loc: "100 90" },
{ key: "Zeta", loc: "200 60" },
{ key: "Eta", loc: "200 90" },
{ key: "Theta", loc: "200 120" }
];
const linkDataArray = [
{ from: "Alpha", to: "Beta" },
{ from: "Beta", to: "Gamma" },
{ from: "Beta", to: "Delta" },
{ from: "Alpha", to: "Epsilon" },
{ from: "Epsilon", to: "Zeta" },
{ from: "Epsilon", to: "Eta" },
{ from: "Epsilon", to: "Theta" }
];
diagram.model = new go.GraphLinksModel(nodeDataArray, linkDataArray);
</code></pre>
<script>
goCode('tree', 600, 200);
</script>
<p>
You can also get the same results by using a <a>TreeModel</a>.
Note how the node template and the link template are exactly the same as when using a <a>GraphLinksModel</a>, above.
</p>
<pre class="lang-js" id="tree2"><code>
diagram.nodeTemplate =
new go.Node("Auto")
.bind("location", "loc", go.Point.parse)
.add(
new go.Shape("Ellipse", { fill: "white" }),
new go.TextBlock()
.bind("text", "key")
);
diagram.linkTemplate =
new go.Link({ routing: go.Routing.Orthogonal, corner: 5 })
.add(
new go.Shape()
);
const nodeDataArray = [
{ key: "Alpha", loc: "0 60" },
{ key: "Beta", loc: "100 15", parent: "Alpha" },
{ key: "Gamma", loc: "200 0", parent: "Beta" },
{ key: "Delta", loc: "200 30", parent: "Beta" },
{ key: "Epsilon", loc: "100 90", parent: "Alpha" },
{ key: "Zeta", loc: "200 60", parent: "Epsilon" },
{ key: "Eta", loc: "200 90", parent: "Epsilon" },
{ key: "Theta", loc: "200 120", parent: "Epsilon" }
];
diagram.model = new go.TreeModel(nodeDataArray);
</code></pre>
<script>
goCode('tree2', 600, 200);
</script>
<h2 id="AutomaticTreeLayout">Automatic TreeLayout</h2>
<p>
It is most common to use <a>TreeLayout</a> for laying out trees.
Just assign <a>Diagram.layout</a> to an instance of <a>TreeLayout</a>.
This example also defines the <code>setupTree</code> function that is used in later examples on this page.
</p>
<pre class="lang-js" id="treeLayout"><code>
function setupTree(diagram) {
diagram.nodeTemplate =
new go.Node("Auto")
.add(
new go.Shape("Ellipse", { fill: "white" }),
new go.TextBlock()
.bind("text", "key")
);
diagram.linkTemplate =
new go.Link({ routing: go.Routing.Orthogonal, corner: 5 })
.add(
new go.Shape()
);
const nodeDataArray = [
{ key: "Alpha" },
{ key: "Beta", parent: "Alpha" },
{ key: "Gamma", parent: "Beta" },
{ key: "Delta", parent: "Beta" },
{ key: "Epsilon", parent: "Alpha" },
{ key: "Zeta", parent: "Epsilon" },
{ key: "Eta", parent: "Epsilon" },
{ key: "Theta", parent: "Epsilon" }
];
diagram.model = new go.TreeModel(nodeDataArray);
}
setupTree(diagram);
// automatic tree layout
diagram.layout = new go.TreeLayout();
</code></pre>
<script>
goCode('treeLayout', 600, 200);
</script>
<script>
function setupTree(diagram) {
diagram.nodeTemplate =
new go.Node("Auto")
.bind("location", "loc", go.Point.parse)
.add(
new go.Shape("Ellipse", { fill: "white" }),
new go.TextBlock()
.bind("text", "key")
);
diagram.linkTemplate =
new go.Link({ routing: go.Routing.Orthogonal, corner: 5 })
.add(
new go.Shape()
);
const nodeDataArray = [
{ key: 'Alpha' },
{ key: 'Beta', parent: 'Alpha' },
{ key: 'Gamma', parent: 'Beta' },
{ key: 'Delta', parent: 'Beta' },
{ key: 'Epsilon', parent: 'Alpha' },
{ key: 'Zeta', parent: 'Epsilon' },
{ key: 'Eta', parent: 'Epsilon' },
{ key: 'Theta', parent: 'Epsilon' },
];
diagram.model = new go.TreeModel(nodeDataArray);
}
</script>
<h2 id="CommonTreeLayoutProperties">Common TreeLayout properties</h2>
<p>
The <a>TreeLayout.angle</a> property controls the general direction of tree growth. This must be zero (towards the right), 90 (downward), 180 (leftward), or
270 (upward).
</p>
<pre class="lang-js" id="angle"><code>
setupTree(diagram);
diagram.layout = new go.TreeLayout({ angle: 90 });
</code></pre>
<script>
goCode('angle', 600, 200);
</script>
<p>The <code>setupTree</code> function was defined above.</p>
<p>
The <a>TreeLayout.alignment</a> property controls how the parent node is positioned relative to its children. This must be one of the Alignment... constants
defined on <a>TreeLayout</a>.
</p>
<pre class="lang-js" id="alignment"><code>
setupTree(diagram);
diagram.layout = new go.TreeLayout({ angle: 90, alignment: go.TreeAlignment.Start });
</code></pre>
<script>
goCode('alignment', 600, 200);
</script>
<p>
For tree layouts, all of the nodes are placed into "layers" according to the length of the chain of links from the root node. These layers are not to be
confused with Diagram <a>Layer</a>s, which control the Z-ordering of the nodes. The <a>TreeLayout.layerSpacing</a> property controls how close the layers are
to each other. The <a>TreeLayout.nodeSpacing</a> property controls how close nodes are to each other in the same layer.
</p>
<pre class="lang-js" id="spacing"><code>
setupTree(diagram);
diagram.layout = new go.TreeLayout({ layerSpacing: 20, nodeSpacing: 0 });
</code></pre>
<script>
goCode('spacing', 600, 200);
</script>
<p>
The children of each node can be sorted. By default the <a>TreeLayout.comparer</a> function compares the <a>Part.text</a> property. So if that property is
data bound by the node template, and if you set the <a>TreeLayout.sorting</a> property to sort in either ascending or descending order, each parent node will
have all of its children sorted in that order by their text strings. (In this example that means alphabetical ordering of the English names of the letters of
the Greek alphabet.)
</p>
<pre class="lang-js" id="sort"><code>
setupTree(diagram);
diagram.nodeTemplate =
new go.Node("Auto")
.bind("text", "key") // bind Part.text to support sorting
.add(
new go.Shape("Ellipse", { fill: "white" }),
new go.TextBlock()
.bind("text", "key")
);
diagram.layout = new go.TreeLayout({ sorting: go.TreeSorting.Ascending });
</code></pre>
<script>
goCode('sort', 600, 200);
</script>
<p>But you can provide your own function for ordering the children, such as:</p>
<pre class="lang-js"><code>
new go.Diagram(. . .,
{
layout:
new go.TreeLayout({
sorting: go.TreeSorting.Ascending,
comparer: (a, b) => {
// A and B are TreeVertexes
const av = a.node.data.someProp;
const bv = b.node.data.someProp;
if (av < bv) return -1;
if (av > bv) return 1;
return 0;
},
. . .
})
. . .
})
</code></pre>
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