Definition

Arr_observer serves as an abstract base class for all observer classes that are attached to an arrangement instance of type Arrangement and receive 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.

In order to implement a concrete arrangement observer-class, one simply needs to derive from Arr_observer 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()).

Examples:: Arrangement_on_surface_2/face_extension.cpp, and Arrangement_on_surface_2/observer.cpp.

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). More...

Creation
	Arr_observer ()
	constructs an observer that is unattached to any arrangement instance.

	Arr_observer (Arrangement_2 &arr)
	constructs an observer and attaches it to the given arrangement `arr`.

Modifiers
void	attach (Arrangement_2 &arr)
	attaches the observer to the given arrangement `arr`.

void	detach ()
	detaches the observer from its arrangement.

Notifications on Global Arrangement Operations
virtual void	before_assign (const Arrangement_2 &arr)
	issued just before the attached arrangement is assigned with the contents of another arrangement `arr`.

virtual void	after_assign ()
	issued immediately after the attached arrangement has been assigned with the contents of another arrangement.

virtual void	before_clear ()
	issued just before the attached arrangement is cleared.

virtual void	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	before_global_change ()
	issued just before a global function starts to modify the attached arrangement. More...

virtual void	after_global_change ()
	issued immediately after a global function has stopped modifying the attached arrangement.

Notifications on Attachment or Detachment
virtual void	before_attach (const Arrangement_2 &arr)
	issued just before the observer is attached to the arrangement instance `arr`.

virtual void	after_attach ()
	issued immediately after the observer has been attached to an arrangement instance.

virtual void	before_detach ()
	issued just before the observer is detached from its arrangement instance.

virtual void	after_attach ()
	issued immediately after the observer has been detached from its arrangement instance.

Notifications on Local Changes in the Arrangement
virtual void	before_create_vertex (const Point_2 &p)
	issued just before a new vertex that corresponds to the point `p` is created.

virtual void	after_create_vertex (Vertex_handle v)
	issued immediately after a new vertex `v` has been created. More...

virtual void	before_create_boundary_vertex (const X_monotone_curve_2 &cv, Arr_curve_end ind, Arr_parameter_space ps_x, Arr_parameter_space ps_y)
	issued just before a new vertex at infinity is created, `cv` is the curve incident to the surface boundary, `ind` is the relevant curve-end, `ps_x` is the boundary condition of the vertex in \( x\) and `ps_y` is the boundary condition of the vertex in \( y\).

virtual void	after_create_boundary_vertex (Vertex_handle v)
	issued immediately after a new vertex `v` has been created. More...

virtual void	before_create_edge (const 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	after_create_edge (Halfedge_handle e)
	issued immediately after a new edge `e` has been created. More...

virtual void	before_modify_vertex (Vertex_handle v, const Point_2 &p)
	issued just before a vertex `v` is modified to be associated with the point `p`.

virtual void	after_modify_vertex (Vertex_handle v)
	issued immediately after an existing vertex `v` has been modified.

virtual void	before_modify_edge (Halfedge_handle e, const X_monotone_curve_2 &c)
	issued just before an edge `e` is modified to be associated with the \( x\)-monotone curve `c`.

virtual void	after_modify_edge (Halfedge_handle e)
	issued immediately after an existing edge `e` has been modified.

virtual void	before_split_edge (Halfedge_handle e, Vertex_handle v, const X_monotone_curve_2 &c1, const 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`. More...

virtual void	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	before_split_fictitious_edge (Halfedge_handle e, Vertex_handle v)
	issued just before a fictitious edge `e` is split into two. More...

virtual void	after_split_fictitious_edge (Halfedge_handle e1, Halfedge_handle e2)
	issued immediately after an existing fictitious edge has been split into the two given fictitious edges `e1` and `e2`.

virtual void	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	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`. More...

virtual void	before_split_outer_ccb (Face_handle f, Ccb_halfedge_circulator h, Halfedge_handle e)
	issued just before outer ccb `h` inside a face `f` is split into two, as a result of the removal of the edge `e` from the arrangement.

virtual void	after_split_outer_ccb (Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2)
	issued immediately after outer ccb the face `f` has been split, resulting in the two holes `h1` and `h2`.

virtual void	before_split_inner_ccb (Face_handle f, Ccb_halfedge_circulator h, Halfedge_handle e)
	issued just before inner ccb `h` inside a face `f` is split into two, as a result of the removal of the edge `e` from the arrangement.

virtual void	after_split_inner_ccb (Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2)
	issued immediately after inner ccb the face `f` has been split, resulting in the two holes `h1` and `h2`.

virtual void	before_add_outer_ccb (Face_handle f, Halfedge_handle e)
	issued just before the edge `e` is inserted as a new outer ccb inside the face `f`.

virtual void	after_add_outer_ccb (Ccb_halfedge_circulator h)
	issued immediately after a new outer ccb `h` has been created. More...

virtual void	before_add_inner_ccb (Face_handle f, Halfedge_handle e)
	issued just before the edge `e` is inserted as a new inner ccb inside the face `f`.

virtual void	after_add_inner_ccb (Ccb_halfedge_circulator h)
	issued immediately after a new inner ccb `h` has been created. More...

virtual void	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	after_add_isolated_vertex (Vertex_handle v)
	issued immediately after the vertex `v` has been set as an isolated vertex.

virtual void	before_merge_edge (Halfedge_handle e1, Halfedge_handle e2, const 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	after_merge_edge (Halfedge_handle e)
	issued immediately after two edges have been merged to form the edge `e`.

virtual void	before_merge_fictitious_edge (Halfedge_handle e1, Halfedge_handle e2)
	issued just before the two fictitious edges `e1` and `e2` are merged to form a single fictitious edge.

virtual void	after_merge_fictitious_edge (Halfedge_handle e)
	issued immediately after two fictitious edges have been merged to form the fictitious edge `e`.

virtual void	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	after_merge_face (Face_handle f)
	issued immediately after two faces have been merged to form the face `f`.

virtual void	before_merge_outer_ccb (Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2, Halfedge_handle e)
	issued just before two outer ccbs `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	after_merge_outer_ccb (Face_handle f, Ccb_halfedge_circulator h)
	issued immediately after two outer ccbs have been merged to form a single outer ccb `h` inside the face `f`.

virtual void	before_merge_inner_ccb (Face_handle f, Ccb_halfedge_circulator h1, Ccb_halfedge_circulator h2, Halfedge_handle e)
	issued just before two inner ccbs `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	after_merge_inner_ccb (Face_handle f, Ccb_halfedge_circulator h)
	issued immediately after two inner ccbs have been merged to form a single inner ccb `h` inside the face `f`.

virtual void	before_move_outer_ccb (Face_handle from_f, Face_handle to_f, Ccb_halfedge_circulator h)
	issued just before the outer ccb `h` is moved from one face to another. More...

virtual void	after_move_outer_ccb (Ccb_halfedge_circulator h)
	issued immediately after the outer ccb `h` has been moved to a new face.

virtual void	before_move_inner_ccb (Face_handle from_f, Face_handle to_f, Ccb_halfedge_circulator h)
	issued just before the inner ccb `h` is moved from one face to another. More...

virtual void	after_move_inner_ccb (Ccb_halfedge_circulator h)
	issued immediately after the inner ccb `h` has been moved to a new face.

virtual void	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. More...

virtual void	after_move_isolated_vertex (Vertex_handle v)
	issued immediately after the isolated vertex `v` has been moved to a new face.

virtual void	before_remove_vertex (Vertex_handle v)
	issued just before the vertex `v` is removed from the arrangement.

virtual void	after_remove_vertex ()
	issued immediately after a vertex has been removed (and deleted) from the arrangement.

virtual void	before_remove_edge (Halfedge_handle e)
	issued just before the edge `e` is removed from the arrangement.

virtual void	after_remove_edge ()
	issued immediately after an edge has been removed (and deleted) from the arrangement.

virtual void	before_remove_outer_ccb (Face_handle f, Ccb_halfedge_circulator h)
	issued just before the outer ccb `f` is removed from inside the face `f`.

virtual void	after_remove_outer_ccb (Face_handle f)
	issued immediately after a outer ccb has been removed (and deleted) from inside the face `f`.

virtual void	before_remove_inner_ccb (Face_handle f, Ccb_halfedge_circulator h)
	issued just before the inner ccb `f` is removed from inside the face `f`.

virtual void	after_remove_inner_ccb (Face_handle f)
	issued immediately after a inner ccb has been removed (and deleted) from inside the face `f`.