Class TreeLayout

GoJS® Diagramming Components
version 3.0.5
by Northwoods Software®

Hierarchy

This layout positions nodes of a tree-structured graph in layers (rows or columns).

For a discussion and examples of the most commonly used properties, see Trees page in the Introduction. If you want to experiment interactively with most of the properties, try the Tree Layout sample. See samples that make use of TreeLayout in the samples index.

This layout makes use of a LayoutNetwork of TreeVertexes and TreeEdges that normally correspond to the Nodes and Links of the Diagram.

The most commonly set properties for controlling the results of a TreeLayout are:

  • angle: the direction in which the tree grows, from parent to child; the default value of zero means that the tree grows towards the right, with the children of a node arranged in a layer that is a column. An angle of 0 or 180 means that children form vertical layers -- breadth is height and depth is width; an angle of 90 or 270 means that children form horizontal layers -- breadth is width and depth is height.
  • layerSpacing: the distance between layers -- between a parent node and its child nodes.
  • nodeSpacing: the distance between nodes within a layer -- between siblings.
  • alignment: the relative position of a parent node with its children.
  • sorting and comparer: specify the order of the immediate children of a parent node.
  • compaction: whether subtrees should be packed closer together if there is room.
  • layerStyle: whether the children of one node are aligned with the children of a sibling node.
  • setsPortSpot, portSpot, setsChildPortSpot, and childPortSpot: this controls whether to set the Link.fromSpot and Link.toSpot to be sensible for the angle.
  • nodeIndent and nodeIndentPastParent: if the alignment is TreeAlignment.Start or TreeAlignment.End, control how much extra space the first child is given when positioned.
  • breadthLimit, rowSpacing: try to limit the total breadth of a subtree to a certain distance; when there are too many children or when they are too broad, this puts children into additional rows (or columns, depending on the angle) thereby limiting the breadth while increasing the depth of the tree.

When you set one of the TreeLayout properties listed above, that property normally applies to all of the nodes in the tree. What if you want alignment to be TreeAlignment.CenterChildren for the root node but TreeAlignment.Bus for the other nodes in the tree? Or what if you want want layerSpacing to be 50 for all layers except for the layer separating "leaf" nodes from their parent?

One common solution is to set treeStyle. For the former scenario, you could set treeStyle to TreeStyle.RootOnly; the value of alignment would only apply to the root node. For the latter scenario, you could set it to TreeStyle.LastParents; the value of layerSpacing would apply to all nodes except those that have children but that do not have grandchildren. How do you then set the alignment or layerSpacing for the other nodes? By setting the TreeLayout properties whose names start with "alternate...". In these cases that would mean setting alternateAlignment or alternateLayerSpacing.

These TreeLayout properties actually apply to the TreeVertex that the TreeLayout uses to represent a Node within the LayoutNetwork. All of those TreeLayout properties are actually stored in rootDefaults; all of the "alternate..." properties are stored in alternateDefaults. Depending on the value of treeStyle, the actual TreeVertex properties for each Node are copied appropriately from either rootDefaults or alternateDefaults. In the default case where treeStyle is TreeStyle.Layered, the alternateDefaults are ignored. (Note that treeStyle, and a few other properties such as path and arrangement, apply to the whole layout, not to an individual node/vertex.)

The use of treeStyle and "alternate..." TreeLayout properties will cover a lot of common needs for tree layout customization. However, there may be times when that is not enough. Imagine a situation where you want a special TreeVertex property value for a particular Node. The solution is to override assignTreeVertexValues, where you can examine the given TreeVertex, including its corresponding LayoutVertex.node, to decide what TreeVertex property values should apply.

Index

Constructors

Accessors

  • Gets or sets the alternate direction for tree growth.

    The default value is 0; the value must be one of: 0, 90, 180, 270.

    These values are in degrees, where 0 is along the positive X axis, and where 90 is along the positive Y axis. This sets the alternateDefaults' property of the same name.

  • Gets or sets an alternate limit on how broad a tree should be.

    A value of zero (the default) means there is no limit; a positive value specifies a limit. The default value is zero.

    This property is just a suggested constraint on how broadly the tree will be laid out. When there isn't enough breadth for all of the children of a node, the children are placed in as many rows as needed to try to stay within the given breadth limit. If the value is too small, since this layout algorithm does not modify the size or shape of any node, the nodes will just be laid out in a line, one per row, and the breadth is determined by the broadest node. The distance between rows is specified by alternateRowSpacing. To make room for the links that go around earlier rows to get to later rows, when the alignment is not a "center" alignment, the alternateRowIndent property specifies that space at the start of each row. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate spot that children nodes' ports get as their ToSpot The default value is Spot.Default.

    A value of Spot.Default will cause the TreeLayout to assign a ToSpot based on the parent node's TreeVertex.angle.

    If the value is other than NoSpot, it is just assigned. When path is Source, the port's FromSpot is set instead of the ToSpot. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate comparison function used for sorting the immediate children of a vertex.

    The default comparer compares the LayoutVertex.node Text values.

    This sets the alternateDefaults' property of the same name. Whether this comparison function is used is determined by the value of alternateSorting.

  • Gets or sets the alternate distance between a parent node and its children.

    The default value is 50.

    This is the distance between a parent node and its first row of children, in case there are multiple rows of its children. The alternateNodeSpacing property determines the distance between siblings. The alternateRowSpacing property determines the distance between rows of children. Negative values may cause children to overlap with the parent. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate fraction of the node's depth for which the children's layer starts overlapped with the parent's layer.

    The default value is 0.0 -- there is overlap between layers only if alternateLayerSpacing is negative. A value of 1.0 and a zero alternateLayerSpacing will cause child nodes to completely overlap the parent.

    A value greater than zero may still cause overlap between layers, unless the value of alternateLayerSpacing is large enough. A value of zero might still allow overlap between layers, if alternateLayerSpacing is negative. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate indentation of the first child.

    The default value is zero. The value should be non-negative.

    This property is only sensible when the alignment is Start or End. Having a positive value is useful if you want to reserve space at the start of the row of children for some reason. For example, if you want to pretend the parent node is infinitely deep, you can set this to be the breadth of the parent node. This sets the alternateDefaults' property of the same name.

  • Gets or sets the fraction of this node's breadth is added to alternateNodeIndent to determine any spacing at the start of the children.

    The default value is 0.0 -- the only indentation is specified by alternateNodeIndent. When the value is 1.0, the children will be indented past the breadth of the parent node.

    This property is only sensible when the alignment is Start or End.

  • Gets or sets the alternate distance between child nodes.

    The default value is 20.

    A negative value causes sibling nodes to overlap. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate spot that this node's port gets as its FromSpot.

    The default value is Spot.Default.

    A value of Spot.Default will cause the TreeLayout to assign a FromSpot based on the parent node's TreeVertex.angle. If the value is other than NoSpot, it is just assigned. When path is Source, the port's ToSpot is set instead of the FromSpot. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate indentation of the first child of each row, if the alignment is not a "Center" alignment.

    The default value is 10. The value should be non-negative.

    This is used to leave room for the links that connect a parent node with the child nodes that are in additional rows. This sets the alternateDefaults' property of the same name.

  • Gets or sets the alternate distance between rows of children.

    The default value is 25.

    This property is only used when there is more than one row of children for a given parent node. The alternateLayerSpacing property determines the distance between the parent node and its first row of child nodes. This sets the alternateDefaults' property of the same name.

  • Gets or sets whether the TreeLayout should set the ToSpot for each child node port.

    The default value is true -- this may modify the spot of the ports of the children nodes, if the node has only a single port.

    The spot used depends on the value of alternateChildPortSpot. This sets the alternateDefaults' property of the same name.

  • Gets or sets whether the TreeLayout should set the FromSpot for this parent node port.

    The default value is true -- this may modify the spot of the port of this node, the parent, if the node has only a single port.

    The spot used depends on the value of alternatePortSpot. This sets the alternateDefaults' property of the same name.

  • Gets or sets the default direction for tree growth.

    The default value is 0; the value must be one of: 0, 90, 180, 270.

    These values are in degrees, where 0 is along the positive X axis, and where 90 is along the positive Y axis.

    This sets the rootDefaults' property of the same name.

  • Gets or sets a limit on how broad a tree should be.

    A value of zero (the default) means there is no limit; a positive value specifies a limit. The default value is zero.

    This property is just a suggested constraint on how broadly the tree will be laid out. When there isn't enough breadth for all of the children of a node, the children are placed in as many rows as needed to try to stay within the given breadth limit. If the value is too small, since this layout algorithm does not modify the size or shape of any node, the nodes will just be laid out in a line, one per row, and the breadth is determined by the broadest node. The distance between rows is specified by rowSpacing. To make room for the links that go around earlier rows to get to later rows, when the alignment is not a "center" alignment, the rowIndent property specifies that space at the start of each row.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the spot that children nodes' ports get as their ToSpot.

    The default value is Spot.Default.

    A value of Spot.Default will cause the TreeLayout to assign a ToSpot based on the parent node's TreeVertex.angle. If the value is other than NoSpot, it is just assigned. When path is Source, the port's FromSpot is set instead of the ToSpot.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the distance between a node and its comments.

    The default value is 20.

    This is used by addComments and layoutComments.

    This sets the rootDefaults' property of the same name.

  • Gets or sets whether this layout should find all Nodes whose category is "Comment" and whose anchors are nodes represented in the network, and increase the size of the corresponding TreeVertex to make room for the comment nodes. The default value is true.

  • Gets or sets how closely to pack the child nodes of a subtree. Must be a TreeCompaction value.

    The default value is Block.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the default comparison function used for sorting the immediate children of a vertex.

    The default comparer compares the LayoutVertex.node Text values.

    This sets the rootDefaults' property of the same name. Whether this comparison function is used is determined by the value of sorting.

      $(go.TreeLayout,
    {
    sorting: go.TreeSorting.Ascending,
    comparer: (va, vb) => {
    const da = va.node.data;
    const db = vb.node.data;
    if (da.someProperty < db.someProperty) return -1;
    if (da.someProperty > db.someProperty) return 1;
    return 0;
    }
    }
    )
  • Gets or sets the distance between a parent node and its children.

    This is the distance between a parent node and the layer of its children. Negative values may cause children to overlap with the parent. The default value is 50.

    The nodeSpacing property determines the distance between siblings. The rowSpacing property determines the distance between multiple rows or columns of children.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the fraction of the node's depth for which the children's layer starts overlapped with the parent's layer.

    The default value is 0.0 -- there is overlap between layers only if layerSpacing is negative. A value of 1.0 and a zero layerSpacing will cause child nodes to completely overlap the parent.

    A value greater than zero may still cause overlap between layers, unless the value of layerSpacing is large enough. A value of zero might still allow overlap between layers, if layerSpacing is negative.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the default indentation of the first child.

    The default value is zero. The value should be non-negative.

    This property is only sensible when the alignment is Start or End. Having a positive value is useful if you want to reserve space at the start of the row of children for some reason. For example, if you want to pretend the parent node is infinitely deep, you can set this to be the breadth of the parent node.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the fraction of this node's breadth is added to nodeIndent to determine any spacing at the start of the children.

    The default value is 0.0 -- the only indentation is specified by nodeIndent. When the value is 1.0, the children will be indented past the breadth of the parent node.

    This property is only sensible when the alignment is Start or End.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the distance between child nodes.

    This is the distance between sibling nodes. A negative value causes sibling nodes to overlap. The default value is 20.

    The layerSpacing property determines the distance between a parent node and the layer of its children.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the spot that this node's port gets as its FromSpot.

    The default value is Spot.Default.

    A value of Spot.Default will cause the TreeLayout to assign a FromSpot based on the parent node's TreeVertex.angle. If the value is other than NoSpot, it is just assigned. When path is Source, the port's ToSpot is set instead of the FromSpot.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the collection of root vertexes.

    Initially this will be an empty GSet.

    If the path is either Destination or Source, this layout can easily determine all of the tree roots by searching the whole network. Otherwise, you should explicitly initialize this collection with one or more TreeVertexes.

  • Gets or sets the default indentation of the first child of each row, if the alignment is not a "Center" alignment.

    The default value is 10. The value should be non-negative.

    This is used to leave room for the links that connect a parent node with the child nodes that are in additional rows.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the distance between rows or columns of a parent node's immediate children.

    The default value is 25.

    This property is only used when there is more than one row of children for a given parent node. The nodeSpacing property determines the distance between siblings. The layerSpacing property determines the distance between the parent node and its first row or column of child nodes.

    This sets the rootDefaults' property of the same name.

  • Gets or sets whether the TreeLayout should set the ToSpot for each child node port.

    The default value is true -- this may modify the spot of the ports of the children nodes, if the node has only a single port.

    The spot used depends on the value of childPortSpot.

    This sets the rootDefaults' property of the same name.

  • Gets or sets whether the TreeLayout should set the FromSpot for this parent node port.

    The default value is true -- this may modify the spot of the port of this node, the parent, if the node has only a single port.

    The spot used depends on the value of portSpot.

    This sets the rootDefaults' property of the same name.

  • Gets or sets the default sorting policy for ordering the immediate children of a vertex. Must be a TreeSorting value.

    The default value is TreeSorting.Forwards.

    This sets the rootDefaults' property of the same name. The sort order is determined by comparer.

Methods

  • Find any associated objects to be positioned along with the LayoutVertex.node.

    This looks for visible Node's whose category is "Comment" and that refer to the tree vertex's Node. This method is only called when comments is true.

    You may want to override this method in order to customize how any associated objects are found and how the node's LayoutVertex.bounds are set to reserve space for those associated objects. This method should not walk the tree, since it is called for each TreeVertex in an indeterminate order. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Parameters

    Returns void

  • Position each separate tree.

    This is called after each tree has been laid out and thus each subtree bounds are known. The arrangement and arrangementSpacing and Layout.arrangementOrigin properties affect this method's behavior. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Returns void

  • Assign final property values for a TreeVertex.

    This method is commonly overridden in order to provide tree layout properties for particular nodes. This method is called after values have been inherited from other TreeVertexes, so you can examine and modify the values of related tree nodes. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    However, when TreeVertex.alignment is TreeAlignment.BusBranching, changing the TreeVertex.sorting or TreeVertex.comparer properties in this method will have no effect.

    This method should not walk the tree, since it is called for each TreeVertex in a depth-first manner starting at a root.

    Here is an example where the children are squeezed together if there are many of them, but only on nodes that have no grandchildren. This makes use of two TreeVertex properties that are automatically computed for you, TreeVertex.childrenCount and TreeVertex.descendantCount.

    class SqueezingTreeLayout extends go.TreeLayout {
    assignTreeVertexValues(v) {
    if (v.childrenCount > 6 && v.childrenCount === v.descendantCount) {
    v.alignment = go.TreeAlignment.BottomRightBus;
    v.layerSpacing = 10;
    v.rowSpacing = 0;
    }
    }
    }

    If you need to assign TreeVertex values and also have them be "inherited" by the child vertexes, you should override initializeTreeVertexValues instead. However at the time that method is called, the computed properties of TreeVertex will not be available.

    Parameters

    Returns void

  • This overridable method is called by commitLayout if layerStyle is LayerUniform to support custom arrangement of bands or labels across each layout layer. By default this method does nothing.

    The coordinates used in the resulting Rects may need to be offset by the Layout.arrangementOrigin and/or by the arrangement of subtrees done by arrangeTrees.

    Parameters

    • layerRects: Rect[]

      an Array of Rects with the bounds of each of the "layers"

    • offset: Point

      the position of the top-left corner of the banded area relative to the coordinates given by the layerRects

    Returns void

  • Set the fromSpot and toSpot on each Link, position each Node according to the vertex position, and then position/route the Links.

    This calls the commitNodes and commitLinks methods, the latter only if isRouting is true. You should not call this method -- it is a "protected virtual" method. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Returns void

  • Routes the links.

    This is called by commitLayout. This is only called if Layout.isRouting is true. See also commitNodes. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Returns void

  • Commit the position of all nodes.

    This is called by commitLayout. See also commitLinks. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Returns void

  • Position and TreeVertex.comments around the vertex.

    This method should not walk the tree, since it is called for each TreeVertex in an indeterminate order. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

    Parameters

    Returns void

Properties

deprecated

See TreeAlignment.Bus.

deprecated

See TreeAlignment.End.

deprecated

See TreeAlignment.Start.

deprecated

See TreeAlignment.TopLeftBus.

deprecated

See TreeArrangement.Vertical.

deprecated

See TreeCompaction.Block.

deprecated

See TreeCompaction.None.

deprecated

See TreeLayerStyle.Siblings.

deprecated

See TreeLayerStyle.Uniform.

deprecated

See TreePath.Default.

deprecated

See TreePath.Destination.

deprecated

See TreePath.Source.

deprecated

See TreeSorting.Ascending.

deprecated

See TreeSorting.Descending.

deprecated

See TreeSorting.Forwards.

deprecated

See TreeSorting.Reverse.

deprecated

See TreeStyle.Alternating.

deprecated

See TreeStyle.LastParents.

deprecated

See TreeStyle.Layered.

deprecated

See TreeStyle.RootOnly.