Class LayeredDigraphLayout

GoJS® Diagramming Components
version 3.0.5
by Northwoods Software®

Hierarchy

This arranges nodes of directed graphs into layers (rows or columns). There are many samples that use LayeredDigraphLayout.

If you want to experiment interactively with most of the properties, try the Layered Digraph Layout sample. See samples that make use of LayeredDigraphLayout in the samples index.

The layerSpacing property controls the distance between layers. The columnSpacing property controls the breadth of each "column" -- this affects the distance between nodes within a layer, although the exact distance also depends on the breadth of each node. The layeringOption property determines whether nodes without links coming in or without links going out are lined up at the edge of the graph, or whether they are positioned close to their connected nodes.

By default the layout will route the links in a manner that is consistent with the direction. So, for example, if the direction is 90 degrees (i.e. downward), the links are expected to go from the top towards the bottom. That means the links should come out from the bottom of the ports and should go into the top of the ports. Basically the layout will set Link.fromSpot to Spot.Bottom and Link.toSpot to Spot.Top.

If you want to the links to use the spots that are given by the ports or by the links themselves, you will need to set setsPortSpots to false to prevent this layout from setting the spots on the links. For example, if each node only has one port that is the whole node, and if you want the links to be spread out along the sides of the nodes, then you should set setsPortSpots to false and set the node's GraphObject.fromSpot to Spot.BottomSide and GraphObject.toSpot to Spot.TopSide.

This layout handles links that form cycles better than TreeLayout does. The normal routing behavior for "backwards" links is to route them "around" the source node and "around" the destination node, so that all links come in one side and go out the other side. However if you want "backwards" links to go more directly between nodes, set setsPortSpots to false and the node's GraphObject.fromSpot and GraphObject.toSpot both to Spot.TopBottomSides. (Of course if the direction is zero or 180, you'll want to use Spot.LeftRightSides.)

If the diagram is structured in a tree-like fashion, it may be better to use TreeLayout, which has more options specific to trees. TreeLayout is much faster than LayeredDigraphLayout, and can handle a limited number of links that would prevent the graph structure from being a true tree (i.e. some nodes having multiple parents).

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

The layout algorithm consists of four-major steps: Cycle Removal, Layer Assignment, Crossing Reduction, and Straightening and Packing. The layout cannot guarantee that it provides optimal positioning of nodes or routing of links.

The Layer Assignment step can be slow if layeringOption is LayeredDigraphLayering.OptimalLinkLength, which is the default value.

The CrossingReduction step is usually slow, but it can be avoided if you want to maintain a certain order within each layer by setting LayeredDigraphLayout.aggressiveOption to LayeredDigraphAggressive.None.

The Straightening and Packing step is usually much slower if you set alignOption to LayeredDigraphAlign.None, which causes the older packOption to be used.

If performance remains a problem, contact us.

Index

Constructors

Accessors

  • Gets or sets the options used by the straighten and pack function, as a faster alternative to packOption.

    When using this option, nodes are assigned coordinates within their layers to produce straighter paths of nodes and small edge lengths.

    When used as an alternative to packOption, this tends to be faster, particularly for larger graphs. Larger graphs, however, will usually be less compact than when using packOption. If this option is set, packOption is ignored.

    This option does not use columns, but rather uses columnSpacing to space nodes within a layer.

    The value must be a combination of the LayeredDigraphAlign bit flags.

    Using LayeredDigraphAlign.All will tend to provide the most balanced results and is what we recommend starting with.

    The default value is LayeredDigraphAlign.All. When the value is LayeredDigraphAlign.None, the packOption is used instead.

    since

    2.3

  • Gets or sets the size of each column. This value must be positive and it defaults to 25.

    When using alignOption, this will act as node spacing for nodes within a layer.

  • Gets or sets the direction the graph grows towards. 0 is towards the right, 90 is downwards, 180 is towards the left, and 270 is upwards. The default value is 0.

  • Gets or sets the number of iterations to be done. The value must be non-negative. The default value is 4.

  • Gets or sets the space between each layer. This value must be non-negative and it defaults to 25.

  • This read-only property returns the largest column value.

  • This read-only property returns the largest index value.

  • This read-only property returns the larges index layer.

  • This read-only property returns the largest layer value.

  • This read-only property returns the smallest index layer.

  • Gets or sets the options used by the straighten and pack function; this option is deprecated -- alignOption usually produces a better alignment, faster.

    The value must be a combination of bit flags. The default value is LayeredDigraphLayout.PackAll, which is a combination of all three flags.

    Each of the flags has a cost; Expand is particularly slow. However if you do not set this property, this layout will automatically turn off the Expand option for you if the graph is large enough. You can set this property value to LayeredDigraphLayout.PackNone to avoid most of the work.

    This option is ignored if alignOption is set to a value other than LayeredDigraphAlign.None. This tends to be slower than alignOption, particularly for larger graphs. Larger graphs, however, will usually be more compact than when using alignOption.

    deprecated
  • Gets or sets whether the FromSpot and ToSpot of each link should be set to values appropriate for the given value of LayeredDigraphLayout.direction. The default value is true.

    If you set this to false, the spot values of the links and port objects will be used. If you do not set the spot values to sensible values matching the direction, the routing results may be poor and they may cross over nodes.

Methods

  • Assigns every vertex in the input network to a layer. The layer is a non-negative integer describing which row of vertexes each vertex belongs in. (Do not confuse this concept of "layer" with Layers that control the Z-ordering of Parts.)

    The layering satisfies the following relationship: if L is a link from node U to node V, then U.layer > V.layer.

    This method can be overridden to customize how nodes are assigned layers. Please read the Introduction page on Extensions for how to override methods and how to call this base method. By default, this does the appropriate assignments given the value of layeringOption.

    Returns void

  • This overridable method is called by commitLayout 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.

    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

Properties

deprecated

See LayeredDigraphAlign.All.

deprecated

See LayeredDigraphAlign.None.

deprecated

See LayeredDigraphInit.Naive.

deprecated
deprecated
deprecated
deprecated
deprecated