CGAL::Arr_observer<Arrangement>

Definition

Arr_observer<Arrangement> serves as an abstract base class for all observer classes that are attached to an arrangement instance of type Arrangement and recieve notifications from the arrangement. This base class handles the attachment of the observer to a given arrangement instance or to the detachment of the observer from this arrangement instance. It also gives a default empty implementation to all notification functions that are invoked by the arrangement to notify the observer on local or global changes it undergoes. The notification functions are all virtual functions, so they can be overridden by the concrete observer classes that inherit from Arr_observer<Arrangement>.

In order to implement a concrete arrangement observer-class, one simply needs to derive from Arr_observer<Arrangement> and override the relevant notification functions. For example, if only face-split events are of interest, it is sufficient to override just before_split_face() (or just after_split_face()).

#include <CGAL/Arr_observer.h>

Types

Arr_observer<Arrangement>::Arrangement_2
	the type of the associated arrangement.

typedef typename Arrangement_2::Point_2
	Point_2;	the point type.
typedef typename Arrangement_2::X_monotone_curve_2
	X_monotone_curve_2;	the $$x-monotone curve type.
typedef typename Arrangement_2::Vertex_handle
	Vertex_handle;
typedef typename Arrangement_2::Halfedge_handle
	Halfedge_handle;
typedef typename Arrangement_2::Face_handle
	Face_handle;
typedef typename Arrangement_2::Ccb_halfedge_circulator
	Ccb_halfedge_circulator;
		represents the boundary of a connected component (CCB). In particular, holes are represented by a circulator for their outer CCB.

Creation

Arr_observer<Arrangement> obs;
	constructs an observer that is unattached to any arrangement instance.
Arr_observer<Arrangement> obs ( Arrangement_2& arr);
	constructs an observer and attaches it to the given arrangement arr.

Modifiers

void	obs.attach ( Arrangement_2& arr)
		attaches the observer to the given arrangement arr.
void	obs.detach ()	detaches the observer from its arrangement.

Notifications on Global Arrangement Operations

virtual void	obs.before_assign ( Arrangement_2 arr)
		issued just before the attached arrangement is assigned with the contents of another arrangement arr.
virtual void	obs.after_assign ()
		issued immediately after the attached arrangement has been assigned with the contents of another arrangement.
virtual void	obs.before_clear ()
		issued just before the attached arrangement is cleared.
virtual void	obs.after_clear ( Face_handle uf)
		issued immediately after the attached arrangement has been cleared, so it now consists only of a the unbounded face uf.
virtual void	obs.before_global_change ()
		issued just before a global function starts to modify the attached arrangement. It is guaranteed that no queries (especially no point-location queries) are issued until the termination of the global function is indicated by after_global_change().
virtual void	obs.after_global_change ()
		issued immediately after a global function has stopped modifying the attached arrangement.

Notifications on Attachment or Detachment

virtual void	obs.before_attach ( Arrangement_2 arr)
		issued just before the observer is attached to the arrangement instance arr.
virtual void	obs.after_attach ()
		issued immediately after the observer has been attached to an arrangement instance.
virtual void	obs.before_detach ()
		issued just before the observer is detached from its arrangement instance.
virtual void	obs.after_attach ()
		issued immediately after the observer has been detached from its arrangement instance.

Notifications on Local Changes in the Arrangement

virtual void	obs.before_create_vertex ( Point_2 p)
		issued just before a new vertex that corresponds to the point p is created.
virtual void	obs.after_create_vertex ( Vertex_handle v)
		issued immediately after a new vertex v has been created. Note that the vertex still has no incident edges and is not connected to any other vertex.
virtual void	obs.before_create_edge ( X_monotone_curve_2 c, Vertex_handle v1, Vertex_handle v2)
		issued just before a new edge that corresponds to the $$x-monotone curve c and connects the vertices v1 and v2 is created.
virtual void	obs.after_create_edge ( Halfedge_handle e)
		issued immediately after a new edge e has been created. The halfedge that is sent to this function is always directed from v1 to v2 (see above).
virtual void	obs.before_modify_vertex ( Vertex_handle v, Point_2 p)
		issued just before a vertex v is modified to be associated with the point p.
virtual void	obs.after_modify_vertex ( Vertex_handle v)
		issued immediately after an existing vertex v has been modified.
virtual void	obs.before_modify_edge ( Halfedge_handle e, X_monotone_curve_2 c)
		issued just before an edge e is modified to be associated with the $$x-monotone curve c.
virtual void	obs.after_modify_edge ( Halfedge_handle e)
		issued immediately after an existing edge e has been modified.
virtual void	obs.before_split_edge ( Halfedge_handle e, Vertex_handle v, X_monotone_curve_2 c1, X_monotone_curve_2 c2)
		issued just before an edge e is split into two edges that should be associated with the $$x-monotone curves c1 and c2. The vertex v corresponds to the split point, and will be used to separate the two resulting edges.
virtual void	obs.after_split_edge ( Halfedge_handle e1, Halfedge_handle e2)
		issued immediately after an existing edge has been split into the two given edges e1 and e2.
virtual void	obs.before_split_face ( Face_handle f, Halfedge_handle e)
		issued just before a face f is split into two, as a result of the insertion of the edge e into the arrangement.
virtual void	obs.after_split_face ( Face_handle f1, Face_handle f2, bool is_hole)
		issued immediately after the existing face f1 has been split, such that a portion of it now forms a new face f2. The flag is_hole designates whether f2 forms a hole inside f1.
virtual void	obs.before_split_hole ( Face_handle f, Ccb_halfedge_circulator h, Halfedge_handle e)
		issued just before a hole h inside a face f is split into two, as a result of the removal of the edge e from the arrangement.
virtual void	obs.after_split_hole ( Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2)
		issued immediately after a hole inside the face f has been split, resulting in the two holes h1 and h2.
virtual void	obs.before_add_hole ( Face_handle f, Halfedge_handle e)
		issued just before the edge e is inserted as a new hole inside the face f.
virtual void	obs.after_add_hole ( Ccb_halfedge_circulator h)
		issued immediately after a new hole h has been created. The hole always consists of a single pair of twin halfedges.
virtual void	obs.before_add_isolated_vertex ( Face_handle f, Vertex_handle v)
		issued just before the vertex v is inserted as an isolated vertex inside the face f.
virtual void	obs.after_add_isolated_vertex ( Vertex_handle v)
		issued immediately after the vertex v has been set as an isolated vertex.
virtual void	obs.before_merge_edge ( Halfedge_handle e1, Halfedge_handle e2, X_monotone_curve_2 c)
		issued just before the two edges e1 and e2 are merged to form a single edge that will be associated with the $$x-monotone curve c.
virtual void	obs.after_merge_edge ( Halfedge_handle e)
		issued immediately after two edges have been merged to form the edge e.
virtual void	obs.before_merge_face ( Face_handle f1, Face_handle f2, Halfedge_handle e)
		issued just before the two edges f1 and f2 are merged to form a single face, following the removal of the edge e from the arrangement.
virtual void	obs.after_merge_face ( Face_handle f)
		issued immediately after two faces have been merged to form the face f.
virtual void	obs.before_merge_hole ( Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2, Halfedge_handle e)
		issued just before two holes h1 and h2 inside the face f are merged to form a single connected component, following the insertion of the edge e into the arrangement.
virtual void	obs.after_merge_hole ( Face_handle f, Ccb_halfedge_circulator h)
		issued immediately after two holes have been merged to form a single hole h inside the face f.
virtual void	obs.before_move_hole ( Face_handle from_f, Face_handle to_f, Ccb_halfedge_circulator h)
		issued just before the hole h is moved from one face to another. This can happen if the face to_f containing the hole has just been split from from_f.
virtual void	obs.after_move_hole ( Ccb_halfedge_circulator h)
		issued immediately after the hole h has been moved to a new face.
virtual void	obs.before_move_isolated_vertex ( Face_handle from_f, Face_handle to_f, Vertex_handle v)
		issued just before the isolated vertex v is moved from one face to another. This can happen if the face to_f containing the isolated vertex has just been split from from_f.
virtual void	obs.after_move_isolated_vertex ( Vertex_handle v)
		issued immediately after the isolated vertex v has been moved to a new face.
virtual void	obs.before_remove_vertex ( Vertex_handle v)
		issued just before the vertex v is removed from arrangement.
virtual void	obs.after_remove_vertex ()
		issued immediately after a vertex has been removed (and deleted) from the arrangement.
virtual void	obs.before_remove_edge ( Halfedge_handle e)
		issued just before the edge e is removed from arrangement.
virtual void	obs.after_remove_edge ()
		issued immediately after an edge has been removed (and deleted) from the arrangement.
virtual void	obs.before_remove_hole ( Face_handle f, Ccb_halfedge_circulator h)
		issued just before the hole f is removed from inside the face f.
virtual void	obs.after_remove_hole ( Face_handle f)
		issued immediately after a hole has been removed (and deleted) from inside the face f.