CGAL::Arr_accessor< Arrangement > Class Template Reference

#include <CGAL/Arr_accessor.h>

Definition

template<typename Arrangement>
class CGAL::Arr_accessor< Arrangement >

Arr_accessor provides an access to some of the private Arrangement functions. Users may use these functions to achieve more efficient programs when they have the exact topological information required by the specialized functions.

It is however highly recommended to be very careful when using the accessor functions that modify the arrangement. As we have just mentioned, these functions have very specific requirement on their input on one hand, and perform no preconditions on the other hand, so providing incorrect topological input may invalidate the arrangement.

Types
typedef unspecified_type	Arrangement_2
	the type of the associated arrangement.
typedef Arrangement_2::Point_2	Point_2
	the point type.
typedef Arrangement_2::X_monotone_curve_2	X_monotone_curve_2
	the \( x\)-monotone curve type.
typedef Arrangement_2::Vertex_handle	Vertex_handle
typedef Arrangement_2::Halfedge_handle	Halfedge_handle
typedef Arrangement_2::Face_handle	Face_handle
typedef Arrangement_2::Ccb_halfedge_circulator	Ccb_halfedge_circulator
	represents the boundary of a connected component (CCB).

Creation
	Arr_accessor (Arrangement_2 &arr)
	constructs an accessor attached to the given arrangement arr.

Accessing the Notification Functions
void	notify_before_global_change ()
	notifies the arrangement observer that a global change is going to take place (for the usage of the global functions that operate on arrangements).
void	notify_after_global_change ()
	notifies the arrangement observer that a global change has taken place (for the usage of the global functions that operate on arrangements).

Arrangement Predicates
Halfedge_handle	locate_around_vertex (Vertex_handle v, const X_monotone_curve_2 &c) const
	locates a place for the curve c around the vertex v and returns a halfedge whose target is v, where c should be inserted between this halfedge and the next halfedge around v in a clockwise order.
int	halfedge_distance (Halfedge_const_handle e1, Halfedge_const_handle e2) const
	counts the number of edges along the path from e1 to e2.
bool	is_inside_new_face (Halfedge_handle pred1, Halfedge_handle pred2, const X_monotone_curve_2 &c) const
	determines whether a new halfedge we are about to create, which is to be associated with the curve c and directed from pred1->target() to pred2->target(), lies on the inner CCB of the new face that will be created, introducing this new edge.
bool	point_is_in (const Point_2 &p, Halfedge_const_handle he) const
	determines whether a given point lies within the region bounded by a boundary of the connected component that he belongs to.
bool	is_on_outer_boundary (Halfedge_const_handle he) const
	determines whether he lies on the outer boundary of its incident face.
bool	is_on_inner_boundary (Halfedge_const_handle he) const
	determines whether he lies on the inner boundary of its incident face (that is, whether it lies on the boundary of one of the inner CCBs of this face).

Arrangement Modifiers
Vertex_handle	create_vertex (const Point_2 &p)
	creates a new vertex an associates it with the point p.
Halfedge_handle	insert_in_face_interior_ex (const X_monotone_curve_2 &c, Face_handle f, Vertex_handle v1, Vertex_handle v2, Comparison_result res)
	inserts the curve c as a new inner CCBs (hole) of the face f, connecting the two isolated vertices v1 and v2.
Halfedge_handle	insert_from_vertex_ex (const X_monotone_curve_2 &c, Halfedge_handle pred, Vertex_handle v, Comparison_result res)
	inserts the curve c into the arrangement, such that one of its endpoints corresponds to an arrangement, which is the target vertex of the halfedge pred, such that c is inserted to the circular list of halfedges around pred->target() right between pred and its successor.
Halfedge_handle	insert_at_vertices_ex (const X_monotone_curve_2 &c, Halfedge_handle pred1, Halfedge_handle pred2, Comparison_result res, bool &new_face)
	inserts the curve c into the arrangement, such that both c's endpoints correspond to existing arrangement vertices, given by pred1->target() and pred2->target().
void	insert_isolated_vertex (Face_handle f, Vertex_handle v)
	inserts v as an isolated vertex inside f.
void	move_hole (Face_handle f1, Face_handle f2, Ccb_halfedge_circulator hole)
	moves the given hole (inner CCB) from the interior of the face f1 to the face f2.
bool	move_isolated_vertex (Face_handle f1, Face_handle f2, Vertex_handle v)
	moves the given isolated vertex from the interior of the face f1 inside the face f2.
void	relocate_in_new_face (Halfedge_handle he)
	relocates all inner ccbs and isolated vertices to their proper position immediately after a face has split due to the insertion of a new halfedge, namely after insert_at_vertices_ex() was invoked and indicated that a new face has been created.
void	relocate_holes_in_new_face (Halfedge_handle he)
	relocates all inner ccbs in a new face, as detailed above.
void	relocate_isolated_vertices_in_new_face (Halfedge_handle he)
	relocates all isolated vertices in a new face, as detailed above.
Vertex_handle	modify_vertex_ex (Vertex_handle v, const Point_2 &p)
	modifies the point associated with the vertex v (the point may be geometrically different than the one currently associated with v).
Halfedge_handle	modify_edge_ex (Halfedge_handle e, const X_monotone_curve_2 &c)
	modifies the \( x\)-monotone curve associated with the edge e (the curve c may be geometrically different than the one currently associated with e).
Halfedge_handle	split_edge_ex (Halfedge_handle he, const Point_2 &p, const X_monotone_curve_2 &c1, const X_monotone_curve_2 &c2)
	splits a given edge into two at the split point p, and associate the x-monotone curves c1 and c2 with the resulting edges, such that c1 connects he->source() with p and c2 connects p with he->target().
Halfedge_handle	split_edge_ex (Halfedge_handle he, Vertex_handle v, const X_monotone_curve_2 &c1, const X_monotone_curve_2 &c2)
	splits a given edge into two at by the vertex v, and associate the x-monotone curves c1 and c2 with the resulting edges, such that c1 connects he->source() with v and c2 connects v with he->target().
Face_handle	remove_edge_ex (Halfedge_handle he, bool remove_source=true, bool remove_target=true)
	removes the edge he from the arrangement, such that if the edge removal causes the creation of a new hole (inner CCB), he->target() lies on the boundary of this hole.

Member Function Documentation

create_vertex()

template<typename Arrangement >

Vertex_handle CGAL::Arr_accessor< Arrangement >::create_vertex

(

const Point_2 &

p

)

creates a new vertex an associates it with the point p.

Precondition

There is no existing vertex already associated with p.

halfedge_distance()

template<typename Arrangement >

int CGAL::Arr_accessor< Arrangement >::halfedge_distance	(	Halfedge_const_handle	e1,
		Halfedge_const_handle	e2
	)		const

counts the number of edges along the path from e1 to e2.

In case the two halfedges do not belong to the same connected component, the function returns (-1).

insert_at_vertices_ex()

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::insert_at_vertices_ex	(	const X_monotone_curve_2 &	c,
		Halfedge_handle	pred1,
		Halfedge_handle	pred2,
		Comparison_result	res,
		bool &	new_face
	)

inserts the curve c into the arrangement, such that both c's endpoints correspond to existing arrangement vertices, given by pred1->target() and pred2->target().

res is the comparison result between these two end-vertices. The function creates a new halfedge pair that connects the two vertices (with pred1 and pred2 indicate the exact place for these halfedges around the two target vertices) and returns a handle for the halfedge directed from pred1->target() to pred2->target(). The output flag new_face indicates whether a new face has been created following the insertion of the new curve.

Precondition

pred1->target() and pred2->target() are associated with c's endpoints and that if a new face is created, then is_inside_new_face (pred1, pred2, c) is true.

insert_from_vertex_ex()

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::insert_from_vertex_ex	(	const X_monotone_curve_2 &	c,
		Halfedge_handle	pred,
		Vertex_handle	v,
		Comparison_result	res
	)

inserts the curve c into the arrangement, such that one of its endpoints corresponds to an arrangement, which is the target vertex of the halfedge pred, such that c is inserted to the circular list of halfedges around pred->target() right between pred and its successor.

The other end-vertex is given by an isolated vertex v, where res is the comparison result between pred->target() and v. The function returns a handle for one of the new halfedges directed from pred->target() to v.

Precondition

pred->target() and v are associated with c's endpoints and that and that v has no incident edges.

insert_in_face_interior_ex()

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::insert_in_face_interior_ex	(	const X_monotone_curve_2 &	c,
		Face_handle	f,
		Vertex_handle	v1,
		Vertex_handle	v2,
		Comparison_result	res
	)

inserts the curve c as a new inner CCBs (hole) of the face f, connecting the two isolated vertices v1 and v2.

res is the comparison result between these two end-vertices. The function returns a handle for one of the new halfedges corresponding to the inserted curve, directed from v1 to v2.

Precondition

v1 and v2 are associated with c's endpoints, that they lie of f's interior and that and that they have no incident edges.

insert_isolated_vertex()

template<typename Arrangement >

void CGAL::Arr_accessor< Arrangement >::insert_isolated_vertex	(	Face_handle	f,
		Vertex_handle	v
	)

inserts v as an isolated vertex inside f.

Precondition

v->point() is contained in the interior of the given face.

is_inside_new_face()

template<typename Arrangement >

bool CGAL::Arr_accessor< Arrangement >::is_inside_new_face	(	Halfedge_handle	pred1,
		Halfedge_handle	pred2,
		const X_monotone_curve_2 &	c
	)		const

determines whether a new halfedge we are about to create, which is to be associated with the curve c and directed from pred1->target() to pred2->target(), lies on the inner CCB of the new face that will be created, introducing this new edge.

Precondition

pred1->target() and pred2->target() are associated with c's endpoints.

pred1 and pred2 belong to the same connected component, such that a new face is created by connecting pred1->target() and pred2->target().

modify_edge_ex()

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::modify_edge_ex	(	Halfedge_handle	e,
		const X_monotone_curve_2 &	c
	)

modifies the \( x\)-monotone curve associated with the edge e (the curve c may be geometrically different than the one currently associated with e).

The function returns a handle to the modified edge (same as e).

Precondition

The interior of c is disjoint from all existing arrangement vertices and edges.

modify_vertex_ex()

template<typename Arrangement >

Vertex_handle CGAL::Arr_accessor< Arrangement >::modify_vertex_ex	(	Vertex_handle	v,
		const Point_2 &	p
	)

modifies the point associated with the vertex v (the point may be geometrically different than the one currently associated with v).

The function returns a handle to the modified vertex (same as v).

Precondition

No other arrangement vertex is already associated with p.

The topology of the arrangement does not change after the vertex point is modified.

move_hole()

template<typename Arrangement >

void CGAL::Arr_accessor< Arrangement >::move_hole	(	Face_handle	f1,
		Face_handle	f2,
		Ccb_halfedge_circulator	hole
	)

moves the given hole (inner CCB) from the interior of the face f1 to the face f2.

Precondition

hole is currently contained in f1 and should be moved to f2.

move_isolated_vertex()

template<typename Arrangement >

bool CGAL::Arr_accessor< Arrangement >::move_isolated_vertex	(	Face_handle	f1,
		Face_handle	f2,
		Vertex_handle	v
	)

moves the given isolated vertex from the interior of the face f1 inside the face f2.

Precondition

v is indeed an isolated vertex currently contained in f1 and should be moved to f2.

point_is_in()

template<typename Arrangement >

bool CGAL::Arr_accessor< Arrangement >::point_is_in	(	const Point_2 &	p,
		Halfedge_const_handle	he
	)		const

determines whether a given point lies within the region bounded by a boundary of the connected component that he belongs to.

Note that if the function returns true, then p is contained within he->face() (but not on its boundary), or inside one of the inner CCBs of this face, or it may coincide with an isolated vertex in this face.

relocate_in_new_face()

template<typename Arrangement >

void CGAL::Arr_accessor< Arrangement >::relocate_in_new_face

(

Halfedge_handle

he

)

relocates all inner ccbs and isolated vertices to their proper position immediately after a face has split due to the insertion of a new halfedge, namely after insert_at_vertices_ex() was invoked and indicated that a new face has been created.

he is the halfedge returned by insert_at_vertices_ex(), such that he->twin()->face is the face that has just been split and he->face() is the newly created face.

remove_edge_ex()

template<typename Arrangement >

Face_handle CGAL::Arr_accessor< Arrangement >::remove_edge_ex	(	Halfedge_handle	he,
		bool	remove_source = true,
		bool	remove_target = true
	)

removes the edge he from the arrangement, such that if the edge removal causes the creation of a new hole (inner CCB), he->target() lies on the boundary of this hole.

The flags remove_source and remove_target indicate whether the end-vertices of he should be removed as well, in case they have no other incident edges. If the operation causes two faces to merge, the merged face is returned. Otherwise, the face to which the edge was incident is returned.

split_edge_ex() [1/2]

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::split_edge_ex	(	Halfedge_handle	he,
		const Point_2 &	p,
		const X_monotone_curve_2 &	c1,
		const X_monotone_curve_2 &	c2
	)

splits a given edge into two at the split point p, and associate the x-monotone curves c1 and c2 with the resulting edges, such that c1 connects he->source() with p and c2 connects p with he->target().

The function return a handle to the split halfedge directed from he->source() to the split point p.

Precondition

The endpoints of c1 and c2 correspond to p and to he's end-vertices, as indicated above.

split_edge_ex() [2/2]

template<typename Arrangement >

Halfedge_handle CGAL::Arr_accessor< Arrangement >::split_edge_ex	(	Halfedge_handle	he,
		Vertex_handle	v,
		const X_monotone_curve_2 &	c1,
		const X_monotone_curve_2 &	c2
	)

splits a given edge into two at by the vertex v, and associate the x-monotone curves c1 and c2 with the resulting edges, such that c1 connects he->source() with v and c2 connects v with he->target().

The function return a handle to the split halfedge directed from he->source() to v.

Precondition

The endpoints of c1 and c2 correspond to v and to he's end-vertices, as indicated above. It is also assumed that v has no incident edges.