This arranges nodes of directed graphs into layers (rows or columns). There are many samples that use LayeredDigraphLayout.
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
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
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
(Of course if the direction is zero or 180, you'll want to use
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).
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 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 LayeredDigraphLayout.AggressiveNone.
The Straightening and Packing step is usually slow, but you can set packOption at the expense of less nicely placed nodes. Moreover, if you do not set this property, the layout will automatically remove the LayeredDigraphLayout.PackExpand flag if the graph is large enough, in order to improve performance. It is also worth experimenting whether using alignOption to straighten and pack provides good results for your graphs, as it is faster than packOption.
If performance remains a problem, contact us.
Gets or sets the options used by the straighten and pack function, as a potentially 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 following bit flags: LayeredDigraphLayout.AlignUpperLeft, LayeredDigraphLayout.AlignUpperRight, LayeredDigraphLayout.AlignLowerLeft, and LayeredDigraphLayout.AlignLowerRight.
Using LayeredDigraphLayout.AlignAll will tend to provide the most balanced results and is what we recommend starting with.
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.
Gets or sets which layering option is being used. The value must be one of the following values: LayeredDigraphLayout.LayerLongestPathSink, LayeredDigraphLayout.LayerLongestPathSource, or LayeredDigraphLayout.LayerOptimalLinkLength. The default value is LayeredDigraphLayout.LayerOptimalLinkLength, which is also the slowest option.
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 -- we recommend using alignOption instead for better alignment and speed.
The value must be a combination of the following bit flags: LayeredDigraphLayout.PackMedian, LayeredDigraphLayout.PackStraighten, and LayeredDigraphLayout.PackExpand. The default value is LayeredDigraphLayout.PackAll, which is a combination of all three flags.
Each of the flags has a cost; PackExpand is particularly slow. However if you do not set this property, this layout will automatically turn off the PackExpand 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 LayeredDigraphLayout.AlignNone. This tends to be slower than alignOption, particularly for larger graphs. Larger graphs, however, will usually be more compact than when using alignOption.
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.
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.
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.
an Array of Rects with the bounds of each of the "layers"
the position of the top-left corner of the banded area relative to the coordinates given by the layerRects
Set the fromSpot and toSpot on each Link, position each Node according to the vertex position, and then position/route the Links.
Routes the links.
Commit the position of all nodes.
Perform the layered digraph layout.
In order to influence a vertex's layer, you can override assignLayers.
The faster, less aggressive, crossing reduction algorithm; a valid value for LayeredDigraphLayout.aggressiveOption.
The slower, more aggressive, crossing reduction algorithm, a valid value for LayeredDigraphLayout.aggressiveOption.
The fastest, but poorest, crossing reduction algorithm; a valid value for LayeredDigraphLayout.aggressiveOption.
Enable all options for the LayeredDigraphLayout.alignOption property; See also LayeredDigraphLayout.AlignUpperLeft, LayeredDigraphLayout.AlignUpperRight, LayeredDigraphLayout.AlignLowerLeft, and LayeredDigraphLayout.AlignLowerRight.
This option will tend to balance nodes compared to their neighbors.
This option aligns and compacts nodes based on lower neighbors, favoring leftmost neighbors, a valid value for LayeredDigraphLayout.alignOption.
This option aligns and compacts nodes based on lower neighbors, favoring rightmost neighbors, a valid value for LayeredDigraphLayout.alignOption.
This option aligns and compacts nodes based on upper neighbors, favoring leftmost neighbors, a valid value for LayeredDigraphLayout.alignOption.
This option aligns and compacts nodes based on upper neighbors, favoring rightmost neighbors, a valid value for LayeredDigraphLayout.alignOption.
Remove cycles using depth first cycle removal; a valid value of LayeredDigraphLayout.cycleRemoveOption.
Remove cycles using greedy cycle removal; a valid value of LayeredDigraphLayout.cycleRemoveOption.
Initialize using depth first in initialization; a valid value for LayeredDigraphLayout.initializeOption.
Initialize using depth first out initialization; a valid value for LayeredDigraphLayout.initializeOption.
Initialize using naive initialization; a valid value for LayeredDigraphLayout.initializeOption.
Assign layers using longest path sink layering, so that nodes are placed in the latest layer possible possibly resulting in longer links to nodes at the last/deepest layers; a valid value for LayeredDigraphLayout.layeringOption.
Assign layers using longest path source layering, so that nodes without any predecessors are placed in the first layer possibly resulting in longer links from nodes at the first/shallowest layers; a valid value for LayeredDigraphLayout.layeringOption.
Assign layers using optimal link length layering, so that links tend to cross the fewest number of layers; A valid value for LayeredDigraphLayout.layeringOption.