create-gojs-kit
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A CLI for downloading GoJS samples, extensions, and docs
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<meta name="description" content="Incrementally grow a tree as each node is expanded for the first time." />
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<title>
Expanding SubTree First Time Incrementally Adds Nodes | GoJS Diagramming Library
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<body>
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<script>
window.addEventListener("DOMContentLoaded", function () {
// topnav
var topButton = document.getElementById("topnavButton");
var topnavList = document.getElementById("topnavList");
if (topButton && topnavList) {
topButton.addEventListener("click", function (e) {
topnavList
.classList
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e.stopPropagation();
});
document.addEventListener("click", function (e) {
// if the clicked element isn't the list, close the list
if (!topnavList.classList.contains("hidden") && !e.target.closest("#topnavList")) {
topButton.click();
}
});
// set active <a> element
var url = window
.location
.href
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var aTags = topnavList.getElementsByTagName('a');
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var lowerhref = aTags[i]
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if (lowerhref.endsWith('.html'))
lowerhref = lowerhref.slice(0, -5);
if (url.startsWith(lowerhref)) {
aTags[i]
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}
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</script>
<div class="flex flex-col prose">
<div class="w-full max-w-screen-xl mx-auto">
<!-- * * * * * * * * * * * * * -->
<!-- Start of GoJS sample code -->
<script src="https://cdn.jsdelivr.net/npm/gojs@3.1.0"></script>
<div id="allSampleContent" class="p-4 w-full">
<script id="code">
function init() {
const blues = ['#E1F5FE', '#B3E5FC', '#81D4FA', '#4FC3F7', '#29B6F6', '#03A9F4', '#039BE5', '#0288D1', '#0277BD', '#01579B'];
myDiagram = new go.Diagram('myDiagramDiv', { // must name or refer to the DIV HTML element
initialContentAlignment: go.Spot.Center,
layout: new go.ForceDirectedLayout(),
// moving and copying nodes also moves and copies their subtrees
'commandHandler.copiesTree': true, // for the copy command
'commandHandler.deletesTree': true, // for the delete command
'draggingTool.dragsTree': true, // dragging for both move and copy
'undoManager.isEnabled': true
});
// Define the Node template.
// This uses a Spot Panel to position a button relative
// to the ellipse surrounding the text.
myDiagram.nodeTemplate =
new go.Node('Spot', {
selectionObjectName: 'PANEL',
isTreeExpanded: false,
isTreeLeaf: false
})
// the node's outer shape, which will surround the text
.add(
new go.Panel('Auto', { name: 'PANEL' })
.add(
new go.Shape('Circle', {
fill: 'whitesmoke',
stroke: 'black'
})
.bind('fill', 'rootdistance', dist => {
dist = Math.min(blues.length - 1, dist);
return blues[dist];
}),
new go.TextBlock({
font: '12pt sans-serif',
margin: 5
})
.bind('text', 'key')
),
// the expand/collapse button, at the top-right corner
go.GraphObject.build('TreeExpanderButton', {
name: 'TREEBUTTON',
width: 20,
height: 20,
alignment: go.Spot.TopRight,
alignmentFocus: go.Spot.Center,
// customize the expander behavior to
// create children if the node has never been expanded
click: (e, obj) => {
// OBJ is the Button
var node = obj.part; // get the Node containing this Button
if (node === null) return;
e.handled = true;
expandNode(node);
}
}) // end TreeExpanderButton
); // end Node
// create the model with a root node data
myDiagram.model = new go.TreeModel([{ key: 0, color: blues[0], everExpanded: false }]);
document.getElementById('zoomToFit').addEventListener('click', () => myDiagram.zoomToFit());
document.getElementById('expandAtRandom').addEventListener('click', () => expandAtRandom());
}
function expandNode(node) {
var diagram = node.diagram;
diagram.startTransaction('CollapseExpandTree');
// this behavior is specific to this incrementalTree sample:
var data = node.data;
if (!data.everExpanded) {
// only create children once per node
diagram.model.setDataProperty(data, 'everExpanded', true);
var numchildren = createSubTree(data);
if (numchildren === 0) {
// now known no children: don't need Button!
node.findObject('TREEBUTTON').visible = false;
}
}
// this behavior is generic for most expand/collapse tree buttons:
if (node.isTreeExpanded) {
diagram.commandHandler.collapseTree(node);
} else {
diagram.commandHandler.expandTree(node);
}
diagram.commitTransaction('CollapseExpandTree');
myDiagram.zoomToFit();
}
// This dynamically creates the immediate children for a node.
// The sample assumes that we have no idea of whether there are any children
// for a node until we look for them the first time, which happens
// upon the first tree-expand of a node.
function createSubTree(parentdata) {
var numchildren = Math.floor(Math.random() * 10);
if (myDiagram.nodes.count <= 1) {
numchildren += 1; // make sure the root node has at least one child
}
// create several node data objects and add them to the model
var model = myDiagram.model;
var parent = myDiagram.findNodeForData(parentdata);
var degrees = 1;
var grandparent = parent.findTreeParentNode();
while (grandparent) {
degrees++;
grandparent = grandparent.findTreeParentNode();
}
for (var i = 0; i < numchildren; i++) {
var childdata = {
key: model.nodeDataArray.length,
parent: parentdata.key,
rootdistance: degrees
};
// add to model.nodeDataArray and create a Node
model.addNodeData(childdata);
// position the new child node close to the parent
var child = myDiagram.findNodeForData(childdata);
child.location = parent.location;
}
return numchildren;
}
function expandAtRandom() {
var eligibleNodes = [];
myDiagram.nodes.each(n => {
if (!n.isTreeExpanded) eligibleNodes.push(n);
});
var node = eligibleNodes[Math.floor(Math.random() * eligibleNodes.length)];
expandNode(node);
}
window.addEventListener('DOMContentLoaded', init);
</script>
<div id="sample">
<div id="myDiagramDiv" style="background-color: white; border: solid 1px black; width: 100%; height: 700px"></div>
<p><button id="zoomToFit">Zoom to Fit</button><button id="expandAtRandom">Expand random Node</button></p>
<p>
This diagram demonstrates the expansion of a tree where nodes are only created "on-demand", when the user clicks on the "expand" Button. As you expand the
tree, it automatically performs a force-directed layout, which will make some room for the additional nodes.
</p>
<p>
The data for each node is implemented by a JavaScript object held by the Diagram's model. Each node data has an <b>everExpanded</b> property that indicates
whether we have already created all of its "child" data and added them to the model. The <b>everExpanded</b> property defaults to false, to match the
initial value of <a>Node.isTreeExpanded</a> in the node template, which specifies that the nodes start collapsed.
</p>
<p>
When the user clicks on the "expand" Button, the button click event handler finds the corresponding data object by going up the visual tree to find the Node
via the <a>GraphObject.part</a> property and then getting the node data that the Node is bound to via <a>Part.data</a>. If <b>everExpanded</b> is false, the
code creates a random number of child data for that node, each with a random <b>color</b> property. Then the button click event handler changes the value of
<b>Node.isExpandedTree</b>, thereby expanding or collapsing the node.
</p>
<p>Some initial node expansions result in there being no children at all. In this case the Button is made invisible.</p>
<p>
All changes are performed within a transaction. You should always surround your code with calls to <a>Model.startTransaction</a> and
<a>Model.commitTransaction</a>, or the same methods on <a>Diagram</a>.
</p>
<p>
The diagram's <a>Diagram.layout</a> is an instance of <a>ForceDirectedLayout</a>. The standard conditions under which the layout will be performed include
when nodes or links or group-memberships are added or removed from the model, or when they change visibility. In this case that means that when the user
expands or collapses a node, another force-directed layout occurs again, even upon repeated expansions or collapses.
</p>
</div>
</div>
<!-- * * * * * * * * * * * * * -->
<!-- End of GoJS sample code -->
</div>
<div id="allTagDescriptions" class="p-4 w-full max-w-screen-xl mx-auto">
<hr/>
<h3 class="text-xl">GoJS Features in this sample</h3>
<!-- blacklist tags that do not correspond to a specific GoJS feature -->
<h4>Force Directed Layout</h4>
<p>
This predefined layout treats the graph as if it were a system of physical bodies with forces acting on and between them.
The layout iteratively moves nodes and links to minimize the total sum of forces on each node. The resulting layout will normally not contain
overlapping Nodes, excluding cases where the graph is densely interconnected.
More information can be found in the <a href="../intro/layouts.html#ForceDirectedLayout">GoJS Intro</a>.
</p>
<p>
<a href="../samples/index.html#force-directed">Related samples</a>
</p>
<hr>
<!-- blacklist tags that do not correspond to a specific GoJS feature -->
<h4>Buttons</h4>
<p>
GoJS defines several <a href="../api/symbols/Panel.html" target="api">Panel</a>s for common uses.
These include "Button", "TreeExpanderButton", "SubGraphExpanderButton", "PanelExpanderButton", "ContextMenuButton", and "CheckBoxButton".
"ContextMenuButton"s are typically used inside of "ContextMenu" Panels;
"CheckBoxButton"s are used in the implementation of "CheckBox" Panels.
</p>
<p>
These predefined panels can be used as if they were <a href="../api/symbols/Panel.html" target="api">Panel</a>-derived classes in calls to <a href="../api/symbols/GraphObject.html#build" target="api">GraphObject.build</a>.
They are implemented as simple visual trees of <a href="../api/symbols/GraphObject.html" target="api">GraphObject</a>s in <a href="../api/symbols/Panel.html" target="api">Panel</a>s,
with pre-set properties and event handlers.
</p>
<p>
More information can be found in the <a href="../intro/buttons.html">GoJS Intro</a>.
</p>
<p>
<a href="../samples/index.html#buttons">Related samples</a>
</p>
<hr>
<!-- blacklist tags that do not correspond to a specific GoJS feature -->
<h4>Commands</h4>
<p>
A <a href="../api/symbols/CommandHandler.html" target="api">CommandHandler</a> handles all default keyboard input events in a Diagram.
There are many predefined methods on <a>CommandHandler</a> that implement common commands to operate on the Diagram or the current <a>Diagram.selection></a>.
</p>
<p>
You can override <a>CommandHandler.doKeyDown</a> to handle additional keyboard shortcuts or to change which commands are invoked via the keyboard.
<p>
Your code can invoke a command by calling the appropriate method on the <a>Diagram.commandHandler</a>.
Each command method has a corresponding <b>can...</b> predicate that your code can use to enable or disable any buttons that invoke the command.
Your code can customize the behavior of a command by overriding the method on <a>CommandHandler</a>,
or by setting properties on the <a>CommandHandler</a> or <a>Diagram</a> or <a>Part</a>s --
see <a href="../intro/permissions.html">GoJS Permissions</a>.
</p>
<p>
There are several CommandHandler extensions that provide additional functionality.
<p>
More information can be found in the <a href="../intro/commands.html">GoJS Intro</a>.
</p>
<p>
<a href="../samples/index.html#commands">Related samples</a>
</p>
<hr>
</div>
</div>
</body>
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</html>