Class LayeredDigraphLayout

Namespace

Northwoods.Go.Layouts

Assembly

Northwoods.GoDiagram.WinForms.LayeredDigraphLayout.dll

This arranges nodes of directed graphs into layers (rows or columns).

public class LayeredDigraphLayout : NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>

Inheritance

object

Layout

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>

LayeredDigraphLayout

Derived

SwimLaneLayout

Inherited Members

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>.Network

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>.CreateNetwork()

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>.MakeNetwork(IEnumerable<Part>)

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>.UpdateParts()

NetworkLayout<LayeredDigraphNetwork, LayeredDigraphVertex, LayeredDigraphEdge, LayeredDigraphLayout>.CommitLayout()

Layout.CloneProtected(Layout)

Layout.Copy()

Layout.Diagram

Layout.Group

Layout.IsOngoing

Layout.IsInitial

Layout.IsViewportSized

Layout.IsRouting

Layout.IsRealtime

Layout.IsValidLayout

Layout.InvalidateLayout()

Layout.GetLayoutBounds(Part)

Layout.BoundsComputation

Layout.CollectParts(Diagram)

Layout.CollectParts(Group)

Layout.CollectParts(IEnumerable<Part>)

Layout.ArrangementOrigin

Layout.InitialOrigin(Point)

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

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 FromSpot to Spot.Bottom and 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 FromSpot to Spot.BottomSide and 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 FromSpot and 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 Network<V, E, Y> 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 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 AggressiveOption to None.

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

If performance remains a problem, contact us.

Constructors

LayeredDigraphLayout()

Constructs a LayeredDigraphLayout with no Network and with no owning Diagram.

public LayeredDigraphLayout()

Properties

AggressiveOption

Gets or sets which aggressive option is being used to look for link crossings.

public LayeredDigraphAggressive AggressiveOption { get; set; }

Property Value

LayeredDigraphAggressive

Remarks

The default value is Less.

AlignOption

Gets or sets the options used by the straighten and pack function.

public LayeredDigraphAlign AlignOption { get; set; }

Property Value

LayeredDigraphAlign

Remarks

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

This tends to be faster than PackOption, 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.

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

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

See Also

PackOption

ColumnSpacing

Gets or sets the size of each column.

public double ColumnSpacing { get; set; }

Property Value

double

Remarks

This value must be positive and it defaults to 25.

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

CycleRemoveOption

Gets or set which cycle removal option is used.

public LayeredDigraphCycleRemove CycleRemoveOption { get; set; }

Property Value

LayeredDigraphCycleRemove

Remarks

The default value is DepthFirst.

Direction

Gets or sets the direction the graph grows towards.

public double Direction { get; set; }

Property Value

double

Remarks

0 is towards the right, 90 is downwards, 180 is towards the left, and 270 is upwards. The default value is 0.

InitializeOption

Gets or sets which indices initialization option is being used.

public LayeredDigraphInit InitializeOption { get; set; }

Property Value

LayeredDigraphInit

Remarks

The default value is DepthFirstOut.

Iterations

Gets or sets the number of iterations to be done.

public int Iterations { get; set; }

Property Value

int

Remarks

The value must be non-negative. The default value is 4.

LayerSpacing

Gets or sets the space between each layer.

public double LayerSpacing { get; set; }

Property Value

double

Remarks

This value must be positive and it defaults to 25.

LayeringOption

Gets or sets which layering option is being used.

public LayeredDigraphLayering LayeringOption { get; set; }

Property Value

LayeredDigraphLayering

Remarks

The default value is OptimalLinkLength.

MaxColumn

This read-only property returns the largest column value.

public int MaxColumn { get; }

Property Value

int

MaxIndex

This read-only property returns the largest index value.

public int MaxIndex { get; }

Property Value

int

MaxIndexLayer

This read-only property returns the larges index layer.

public int MaxIndexLayer { get; }

Property Value

int

MaxLayer

This read-only property returns the largest layer value.

public int MaxLayer { get; }

Property Value

int

MinIndexLayer

This read-only property returns the smallest index layer.

public int MinIndexLayer { get; }

Property Value

int

PackOption

Gets or sets the options used by the straighten and pack function.

public LayeredDigraphPack PackOption { get; set; }

Property Value

LayeredDigraphPack

Remarks

AlignOption usually produces a better alignment, faster. We recommend trying that first.

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 None to avoid most of the work.

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

The default value is All.

See Also

AlignOption

SetsPortSpots

Gets or sets whether the FromSpot and ToSpot of each link should be set to values appropriate for the given value of Direction.

public bool SetsPortSpots { get; set; }

Property Value

bool

Remarks

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

AssignLayers()

Assigns every vertex in the input network to a layer.

protected virtual void AssignLayers()

Remarks

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.

CommitLayers(List<Rect>, Point)

This overridable method is called by CommitLayout() to support custom arrangement of bands or labels across each layout layer.

protected virtual void CommitLayers(List<Rect> layerRects, Point offset)

Parameters

layerRects List<Rect>

a List 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

Remarks

By default this method does nothing.

The coordinates used in the resulting Rects may need to be offset by the ArrangementOrigin.

CommitLayout()

Set the FromSpot and ToSpot on each Link, position each Node according to the vertex position, and then position/route the Links.

protected override void CommitLayout()

Remarks

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.

CommitLinks()

Routes the links.

protected virtual void CommitLinks()

Remarks

This is called by CommitLayout(). This is only called if IsRouting is true. Please read the Introduction page on Extensions for how to override methods and how to call this base method.

See Also

CommitNodes()

CommitNodes()

Commit the position of all nodes.

protected virtual void CommitNodes()

Remarks

This is called by CommitLayout(). Please read the Introduction page on Extensions for how to override methods and how to call this base method.

See Also

CommitLinks()

DoLayout(IEnumerable<Part>)

Perform the layered digraph layout.

public override void DoLayout(IEnumerable<Part> coll = null)

Parameters

coll IEnumerable<Part>

Remarks

This removes any reflexive edges in the network, since they should be ignored.

In order to influence a vertex's layer, you can override AssignLayers().

Finally this calls UpdateParts() to commit the Node positions from the vertex positions. UpdateParts() calls CommitLayout() within a transaction.