# OpenGraph DrawingFramework

v. 2022.02 (Dogwood)

ogdf::PlanarStraightLayout Class Reference

Implementation of the Planar-Straight layout algorithm. More...

#include <ogdf/planarlayout/PlanarStraightLayout.h>

Inheritance diagram for ogdf::PlanarStraightLayout:

## Public Member Functions

PlanarStraightLayout ()
Constructs an instance of the Planar-Straight layout algorithm. More...

~PlanarStraightLayout ()

Optional parameters
bool sizeOptimization () const
Returns the current setting of option sizeOptimization. More...

void sizeOptimization (bool opt)
Sets the option sizeOptimization to opt. More...

double baseRatio () const
Returns the current setting of option baseRatio. More...

void baseRatio (double ratio)
Sets the option baseRatio to ratio. More...

Module options
void setAugmenter (AugmentationModule *pAugmenter)
Sets the augmentation module. More...

void setShellingOrder (ShellingOrderModule *pOrder)
Sets the shelling order module. More...

void setEmbedder (EmbedderModule *pEmbedder)
Sets the module option for the graph embedding algorithm. More...

Public Member Functions inherited from ogdf::PlanarGridLayoutModule
PlanarGridLayoutModule ()
Initializes a planar grid layout module. More...

virtual ~PlanarGridLayoutModule ()

Calls the grid layout algorithm with a fixed planar embedding (general call). More...

Calls the grid layout algorithm with a fixed planar embedding (call for GridLayout). More...

Public Member Functions inherited from ogdf::GridLayoutModule
GridLayoutModule ()
Initializes a grid layout module. More...

virtual ~GridLayoutModule ()

virtual void call (GraphAttributes &GA) override final
Calls the grid layout algorithm (general call). More...

void callGrid (const Graph &G, GridLayout &gridLayout)
Calls the grid layout algorithm (call for GridLayout). More...

const IPointgridBoundingBox () const

double separation () const
Returns the current setting of the minimum distance between nodes. More...

void separation (double sep)
Sets the minimum distance between nodes. More...

Public Member Functions inherited from ogdf::LayoutModule
LayoutModule ()
Initializes a layout module. More...

virtual ~LayoutModule ()

void operator() (GraphAttributes &GA)
Computes a layout of graph GA. More...

## Private Member Functions

void computeCoordinates (const Graph &G, ShellingOrder &lmc, NodeArray< int > &x, NodeArray< int > &y)

virtual void doCall (const Graph &G, adjEntry adjExternal, GridLayout &gridLayout, IPoint &boundingBox, bool fixEmbedding) override
Implements the algorithm call. More...

## Private Attributes

std::unique_ptr< AugmentationModulem_augmenter
The augmentation module. More...

double m_baseRatio
The option for specifying the base ratio. More...

std::unique_ptr< ShellingOrderModulem_computeOrder
The shelling order module. More...

std::unique_ptr< EmbedderModulem_embedder
The planar embedder module. More...

bool m_sizeOptimization
The option for size optimization. More...

Protected Member Functions inherited from ogdf::PlanarGridLayoutModule
virtual void doCall (const Graph &G, GridLayout &gridLayout, IPoint &boundingBox) override
Implements the GridLayoutModule::doCall(). More...

bool handleTrivial (const Graph &G, GridLayout &gridLayout, IPoint &boundingBox)
Handles the special cases of graphs with less than 3 nodes. More...

Protected Attributes inherited from ogdf::GridLayoutModule
IPoint m_gridBoundingBox
The computed bounding box of the grid layout. More...

## Detailed Description

Implementation of the Planar-Straight layout algorithm.

The class PlanarStraightLayout implements a straight-line drawing algorithm for planar graphs. It draws a planar graph on a grid of size at most (2n-4) * (n-2) without edge crossings.

The algorithm runs in several phases. In the first phase, the graph is augmented by adding edges to achieve a certain connectivity (e.g., biconnected or triconnected). Then, a shelling order of the the resulting graph is computed. Both phases are implemented by using module options, so you can replace them with different implementations. However, you have to make sure, that the connectivity achieved by the augmentation module is sufficient for the shelling order module (or the input graph already has the required connectivity).

The implementation used in PlanarStraightLayout is an improved version of an algorithm presented in:

Goos Kant: Drawing Planar Graphs Using the Canonical Ordering. Algorithmica 16(1), pp. 4-32, 1996.

### Precondition

The input graph needs to be planar and simple (i.e., no self-loops and no multiple edges).

### Optional parameters

OptionTypeDefaultDescription
sizeOptimizationbooltrue If this option is set to true, the algorithm tries to reduce the size of the resulting grid layout.
baseRatiodouble0.33 This option specifies the maximal number of nodes placed on the base line. The algorithm tries to place as many nodes as possible on the base line, but takes at most max(2, baseRatio * size of external face) many.

### Module options

Instances of type PlanarDrawLayout provide the following module options:

OptionTypeDefaultDescription
augmenterAugmentationModulePlanarAugmentation Augments the graph by adding edges to obtain a planar graph with a certain connectivity (e.g., biconnected or triconnected).
embedderEmbedderModuleSimpleEmbedder Planar embedding algorithm applied after planar augmentation.
shellingOrderShellingOrderModuleBiconnectedShellingOrder The algorithm to compute a shelling order. The connectivity assured by the planar augmentation module has to be sufficient for the shelling order module!

### Running Time

The computation of the layout takes time O(n), where n is the number of nodes of the input graph.

Definition at line 112 of file PlanarStraightLayout.h.

## ◆ PlanarStraightLayout()

 ogdf::PlanarStraightLayout::PlanarStraightLayout ( )

Constructs an instance of the Planar-Straight layout algorithm.

## ◆ ~PlanarStraightLayout()

 ogdf::PlanarStraightLayout::~PlanarStraightLayout ( )
inline

Definition at line 118 of file PlanarStraightLayout.h.

## ◆ baseRatio() [1/2]

 double ogdf::PlanarStraightLayout::baseRatio ( ) const
inline

Returns the current setting of option baseRatio.

This option specifies the maximal number of nodes placed on the base line. The algorithm tries to place as many nodes as possible on the base line, but takes at most max(2, m_baseRatio * size of external face) many.

Definition at line 144 of file PlanarStraightLayout.h.

## ◆ baseRatio() [2/2]

 void ogdf::PlanarStraightLayout::baseRatio ( double ratio )
inline

Sets the option baseRatio to ratio.

Definition at line 147 of file PlanarStraightLayout.h.

## ◆ computeCoordinates()

 void ogdf::PlanarStraightLayout::computeCoordinates ( const Graph & G, ShellingOrder & lmc, NodeArray< int > & x, NodeArray< int > & y )
private

## ◆ doCall()

 virtual void ogdf::PlanarStraightLayout::doCall ( const Graph & G, adjEntry adjExternal, GridLayout & gridLayout, IPoint & boundingBox, bool fixEmbedding )
overrideprivatevirtual

Implements the algorithm call.

A derived algorithm must implement this method and return the computed grid layout in gridLayout.

Parameters
 G is the input graph. adjExternal is an adjacency entry on the external face, or 0 if no external face is specified. gridLayout is assigned the computed grid layout. boundingBox returns the bounding box of the grid layout. The lower left corner of the bounding box is always (0,0), thus this IPoint defines the upper right corner as well as the width and height of the grid layout. fixEmbedding determines if the input graph is embedded and that embedding has to be preserved (true), or if an embedding needs to be computed (false).

Implements ogdf::PlanarGridLayoutModule.

## ◆ setAugmenter()

 void ogdf::PlanarStraightLayout::setAugmenter ( AugmentationModule * pAugmenter )
inline

Sets the augmentation module.

The augmentation module needs to make sure that the graph gets the connectivity required for calling the shelling order module.

Definition at line 161 of file PlanarStraightLayout.h.

## ◆ setEmbedder()

 void ogdf::PlanarStraightLayout::setEmbedder ( EmbedderModule * pEmbedder )
inline

Sets the module option for the graph embedding algorithm.

Definition at line 171 of file PlanarStraightLayout.h.

## ◆ setShellingOrder()

 void ogdf::PlanarStraightLayout::setShellingOrder ( ShellingOrderModule * pOrder )
inline

Sets the shelling order module.

Definition at line 166 of file PlanarStraightLayout.h.

## ◆ sizeOptimization() [1/2]

 bool ogdf::PlanarStraightLayout::sizeOptimization ( ) const
inline

Returns the current setting of option sizeOptimization.

If this option is set to true, the algorithm tries to reduce the size of the resulting grid layout.

Definition at line 132 of file PlanarStraightLayout.h.

## ◆ sizeOptimization() [2/2]

 void ogdf::PlanarStraightLayout::sizeOptimization ( bool opt )
inline

Sets the option sizeOptimization to opt.

Definition at line 135 of file PlanarStraightLayout.h.

## ◆ m_augmenter

 std::unique_ptr ogdf::PlanarStraightLayout::m_augmenter
private

The augmentation module.

Definition at line 182 of file PlanarStraightLayout.h.

## ◆ m_baseRatio

 double ogdf::PlanarStraightLayout::m_baseRatio
private

The option for specifying the base ratio.

Definition at line 179 of file PlanarStraightLayout.h.

## ◆ m_computeOrder

 std::unique_ptr ogdf::PlanarStraightLayout::m_computeOrder
private

The shelling order module.

Definition at line 183 of file PlanarStraightLayout.h.

## ◆ m_embedder

 std::unique_ptr ogdf::PlanarStraightLayout::m_embedder
private

The planar embedder module.

Definition at line 181 of file PlanarStraightLayout.h.

## ◆ m_sizeOptimization

 bool ogdf::PlanarStraightLayout::m_sizeOptimization
private

The option for size optimization.

Definition at line 178 of file PlanarStraightLayout.h.

The documentation for this class was generated from the following file: