Describes features that are shared by some of the layouts only; these layouts are subclasses of the class that supports the Basic Link Style Layout.

The following algorithms are subclasses of Basic Link Style Layout:

Each of these algorithms supports the features documented in this section in the same way. For the purposes of examples, Uniform Length Edges Layout is used to show how these algorithms provide this support.

If the link style is STRAIGHT_LINE_STYLE, the layout can connect the links so that they point to the node center.

Connecting the links so that they point to the node center is particularly useful when the nodes use an instance of IlvFreeLinkConnector or IlvClippingLinkConnector and no link clip interface is set.

To specify that links connect to node centers, add to the GraphLayout section:

To specify that links connect to node centers use the method:

Describes multilink and self-link features, which are supported by subclasses of Basic Link Style Layout only.

Multiple links between the same pair of nodes

Sometimes a graph has multiple links between the same pair of nodes. When these links are routed straight and use the same connection point at the nodes, they overlap and cannot be distinguished. To avoid such overlaps, the specified layouts have a multilink mode that is applied only when the link style is set to STRAIGHT_LINE_STYLE. This mode has no effect when the link style is NO_RESHAPE_STYLE.

To specify the multilink mode, add to the GraphLayout section:

To specify the multilink mode, use the method:

The valid values for mode are given with the example of Uniform Length Edges layout:

The FREE_ONE_BEND_BUNDLE mode is particularly useful when:

If the multilink mode is not NO_BUNDLE, the offset between the shifted links or between the bends of the links respectively can be specified:

Add to the GraphLayout section:

Use the methods:

The multilink offset is the offset between two neighboring links (or their bends). The value of maxSpread limits this offset to avoid having too much space used when you have too many multiple links. If the multilink offset is 10 and the value of maxSpread is 60, the effective offset is 10 if you have less than six multilinks. If you have more multilinks, the effective offset is reduced. For example, if you have 15 multilinks, the effective offset will be 4 instead of 10 to ensure that the links are shifted at most 60 units apart from each other. If the multilink mode is NARROW_STRAIGHT_LINE_BUNDLE, the effective offset is further limited by the size of the bounding box of both end nodes of a link bundle.

Self-links that start and end at the same node

Self-links are links that start and end at the same node. They can even occur as multiple links, when they are called multiself-link bundle. When links are routed straight, self-links are not visible, because they start and end at the same point in the center of the node. To avoid this effect, the layouts listed in Layout algorithms that are subclasses of Basic Link Style Layout have a self-link mode that is applied only when the link style is set to STRAIGHT_LINE_STYLE. In spite of the name of the link style, the combination of mode and style causes bends to be added to the self-links to make them visible. When the link style is NO_RESHAPE_STYLE, self-link mode has no effect.

To specify self-link mode, add to the GraphLayout section:

To specify self-link mode, use the method:

The valid values for mode are given with the example of Uniform Length Edges layout:

All these modes, except the no-bends mode, create three bends placed orthogonally, so that the segments approximately resemble three-quarters of a rectangle or of a square, the fourth quarter being the node where the self-link is attached. Depending on the node dimension, the rectangular modes create four-cornered shapes that are not squares; the square modes create squares. The square modes are useful for spline self-links in particular, because the spline can then approximately resemble three-quarters of a circle.

The connected modes place the connection points at the border of the node. The free modes place the bends at the same position as the corresponding connected modes, but the link connection point is not enforced; that is, the node and link are free to select where to place the connection point. The link segments in the free modes might not be orthogonal, because the connection point is not enforced.

The free modes are particularly useful when an IlvCenterLinkConnector or IlvPinLinkConnector is used that cannot change the connection point.

The narrow modes and the other modes behave the same for single self-links. If you have multiple self-links at the same node, the self-links are shifted by an offset to avoid overlaps. In this case, the narrow modes differ from the other modes; the multiself-link bundle may appear narrower, because the shift offset of the multiple self-links is limited by the size of the end node.

Self-links can occur at all four corners of the node. The algorithm determines automatically which corner is most appropriate, depending on the direction of all other links. You can restrict which corner should be used.

Add to the GraphLayout section:

The allowed corners must be a space-separated list from TopLeft, BottomLeft, TopRight, and BottomRight. If one of these options is not specified, all corners are allowed.

Use the method:

The allowed corners are a bitwise OR combination chosen from the following constants; for example, in Uniform Length Edges layout, IlvUnifiedLengthEdgesLayout.TOP_LEFT, IlvUnifiedLengthEdgesLayout.BOTTOM_LEFT, IlvUnifiedLengthEdgesLayout.TOP_RIGHT, and IlvUnifiedLengthEdgesLayout.BOTTOM_RIGHT.

By default, self-links are oriented clockwise. You can specify other orientations.

Add to the GraphLayoutsection:

Use the method:

Using IlvUniformLengthEdgesLayout as an example, the valid values for orientation are:

Self-links: spacing parameters

The spacing between the node bounds and the self-link bends can be specified. If a positive value is specified, this value is used to define the spacing. If a negative value is specified, the spacing is calculated automatically. The behavior with negative values is particularly useful for the square self-link modes in combination with spline links to form approximate circle shapes for self-links.

Add to the GraphLayout section:

Use the method:

You can specify the position where the self-link attaches at the bounding box of the node. If the self-link mode is a rectangular mode, the attach position can be specified at both border sides where the self-link attaches. For example, a self-link at the lower right corner attaches at the lower border side of the node, which can be specified as x-component, and at the right border side of the node, which can be specified as y-component. If the self-link mode is a square mode, it takes into account only the attach position at one of the two sides, because the shape must be a square, so the other attach position is automatically calculated.

For experts: If you specify both an x-attach position and a y-attach position when the self-link mode is a square mode, the algorithm always chooses the value that results in a smaller square size.

The attach position is always specified relative to the corner where the self-link occurs. The coordinate 0 is exactly at the corner and increasing values move the attach position farther from the corner. Therefore, the rectangular or square shape of the self-link grows ever larger with increasing values. For example, when the self-link is at the lower right corner, increasing x-components moves the attach position toward the left, and increasing y-components moves it toward the upper corner. When the self-link is at the upper left corner, increasing x-components moves the attach position toward the right, and increasing y-components moves it toward the lower corner. The attach position can be specified relative to the current size of the node; 0 specifies the corner where the self-link occurs and 0.5 specifies the middle of the side where the self-link attaches. The attach position can be specified as an absolute position. If both relative and absolute attach positions are specified, the real attach position is the sum of the two of them.

Add to the GraphLayout section:

Use the methods:

Multiple self-links

If you have multiple self-links at a node, they are bundled like multilinks. The bends of the self-links are shifted to avoid self-links overlapping each other. The multiself-links can be distributed in relation to the attachment position in various ways. The specified attachment position refers to the middle of the bundle, or it refers to the outermost link of the bundle, or it refers to the innermost link of the bundle. This is illustrated by the following figures. The attachment position is the same in all three cases and is indicated by the two small crosses (X), but the multiself-link distribution is variously centered, toward the inside of the bundle, or toward the outside of the bundle.

Add to the GraphLayout section:

Use the method:

The valid values for distribution are given with the example of Uniform Length Edges layout:

The offset between the bends of the self-links can be specified. These parameters have the same meaning as the corresponding parameters on general multilinks, but apply only to self-links that are multilink bundles.

Add to the GraphLayout section:

Use the methods:

The multiself-link offset is the offset between two neighboring self-links (or their bends). The value of maxSpread limits this offset to avoid having too much space used when you have too many multiple self-links. If the multiself-link offset is 10 and the value of maxSpread is 60, the effective offset is 10 if you have less than six multiself-links. If you have more multiself-links, the effective offset is reduced. For example, if you have 15 multiself-links, the effective offset will be 4 instead of 10 to ensure that the self-links are shifted at most 60 units apart from each other. If the self-link mode is one of the narrow modes, for example, NARROW_CONNECTED_RECTANGULAR, the effective offset is further limited by the size of the bounding box of the node where the self-links occur.