Fixes to documentation.

doc/modules/ROOT/nav.adoc

@@ -11,13 +11,14 @@
 ** xref:property_maps/pitfalls.adoc[Common Mistakes]
 * xref:visitors/overview.adoc[Visitors]
 ** Pre-built Event Visitors
-*** xref:visitors/predecessor_recorder.adoc[Predecessor Recorder]
+*** xref:visitors/predecessor_recorder.adoc[Vertex Predecessor Recorder]
+*** xref:visitors/edge_predecessor_recorder.adoc[Edge Predecessor Recorder]
 *** xref:visitors/distance_recorder.adoc[Distance Recorder]
-*** xref:visitors/time_stamper.adoc[Time Stamper]
 *** xref:visitors/property_put.adoc[Property Put]
 *** xref:visitors/property_writer.adoc[Property Writer]
-*** xref:visitors/edge_predecessor_recorder.adoc[Edge Predecessor Recorder]
+*** xref:visitors/time_stamper.adoc[Time Stamper]
 *** xref:visitors/null_visitor.adoc[Null Visitor]
+** Algorithm-specific visitors
 *** xref:visitors/tsp_tour_visitor.adoc[TSP Tour Visitor]
 *** xref:visitors/tsp_tour_len_visitor.adoc[TSP Tour Len Visitor]
 *** xref:visitors/astar_heuristic.adoc[A* Heuristic (Zero)]

doc/modules/ROOT/pages/visitors/distance_recorder.adoc

@@ -1,49 +1,92 @@
 = distance_recorder
 
-Records the hop distance of each vertex from the source during a graph search.
+Records the distance of each vertex from the source vertex into a property map.
+When applied to edge `e = (u, v)`, the distance of `v` is recorded as one more
+than the distance of `u`.
 
 *Defined in:* `<boost/graph/visitors.hpp>` +
-*Models:* EventVisitor +
-*Typical event:* `on_tree_edge` (edge events only)
+*Models:* xref:visitors/EventVisitor.adoc[EventVisitor] +
+*Typical event:* `on_tree_edge` or `on_relax_edge` (edge events only; cannot be
+used with vertex events)
 
-== Example
-
-[source,cpp]
-----
-include::example$visitors/distance_recorder.cpp[]
-----
-
-[,text]
-----
-include::example$visitors/distance_recorder.txt[]
-----
+To use it, wrap it in an algorithm adaptor and optionally combine it with other
+event visitors; see the xref:visitors/overview.adoc[visitors overview].
 
 == Synopsis
 
 [source,cpp]
 ----
 template <typename DistanceMap, typename EventTag>
-struct distance_recorder;
+struct distance_recorder {
+  typedef EventTag event_filter;
+  distance_recorder(DistanceMap pa);
+
+  template <class Edge, class Graph>
+  void operator()(Edge e, const Graph& g);
+};
 
 template <typename DistanceMap, typename EventTag>
 distance_recorder<DistanceMap, EventTag>
 record_distances(DistanceMap pa, EventTag);
 ----
 
-== Parameters
+== Template Parameters
 
 [cols="1,3",options="header"]
 |===
 | Parameter | Description
 
 | `DistanceMap`
-| WritablePropertyMap. Key type is vertex descriptor.
+| A WritablePropertyMap whose key type is the graph's vertex descriptor and whose
+  value type is the distance (a numeric type that supports adding one).
 
 | `EventTag`
-| Must be an edge event tag (e.g. `on_tree_edge`).
+| The event at which to record. Must be an edge event (e.g. `on_tree_edge`,
+  `on_relax_edge`).
+|===
+
+== Associated Types
+
+[cols="1,3",options="header"]
 |===
+| Type | Description
 
-== Behavior
+| `event_filter`
+| The event tag the visitor responds to. Same type as `EventTag`.
+|===
+
+== Member Functions
+
+[cols="1,3",options="header"]
+|===
+| Member | Description
 
-Given edge `e = (u, v)`, sets the distance of `v` to one plus the distance
-of `u`: `put(dist_map, v, get(dist_map, u) + 1)`.
+| `distance_recorder(DistanceMap pa)`
+| Constructs a recorder writing distances into the property map `pa`.
+
+| `void operator()(Edge e, const Graph& g)`
+| Given edge `e = (u, v)`, records the distance of `v` as one more than the
+  distance of `u`: `put(pa, v, get(pa, u) + 1)`.
+|===
+
+== Non-Member Functions
+
+[cols="1,3",options="header"]
+|===
+| Function | Description
+
+| `record_distances(DistanceMap pa, EventTag)`
+| Convenience factory that creates a `distance_recorder`.
+|===
+
+== Example
+
+[source,cpp]
+----
+include::example$visitors/distance_recorder.cpp[]
+----
+
+[,text]
+----
+include::example$visitors/distance_recorder.txt[]
+----

doc/modules/ROOT/pages/visitors/edge_predecessor_recorder.adoc

@@ -1,57 +1,99 @@
 = edge_predecessor_recorder
 
-Records the predecessor _edge_ (not vertex) for each vertex. Useful when a
-graph has parallel edges and you need to know which specific edge the search
-used to reach a vertex.
+Records the predecessor _edge_ of each vertex in a property map, an efficient way
+to encode the search tree traversed during a graph search. Use this instead of
+xref:visitors/predecessor_recorder.adoc[`predecessor_recorder`] (which records the
+predecessor vertex) when a graph has parallel edges and you need to know which
+specific edge the search used to reach a vertex.
 
 *Defined in:* `<boost/graph/visitors.hpp>` +
-*Models:* EventVisitor +
-*Typical event:* `on_tree_edge` or `on_relax_edge` (edge events only)
+*Models:* xref:visitors/EventVisitor.adoc[EventVisitor] +
+*Typical event:* `on_tree_edge` or `on_relax_edge` (edge events only; cannot be
+used with vertex events)
 
-== Example
-
-[source,cpp]
-----
-include::example$visitors/edge_predecessor_recorder.cpp[]
-----
-
-[,text]
-----
-include::example$visitors/edge_predecessor_recorder.txt[]
-----
+To use it, wrap it in an algorithm adaptor and optionally combine it with other
+event visitors; see the xref:visitors/overview.adoc[visitors overview].
 
 == Synopsis
 
 [source,cpp]
 ----
 template <typename PredEdgeMap, typename EventTag>
-struct edge_predecessor_recorder;
+struct edge_predecessor_recorder {
+  typedef EventTag event_filter;
+  edge_predecessor_recorder(PredEdgeMap pa);
+
+  template <class Edge, class Graph>
+  void operator()(Edge e, const Graph& g);
+};
 
 template <typename PredEdgeMap, typename EventTag>
 edge_predecessor_recorder<PredEdgeMap, EventTag>
 record_edge_predecessors(PredEdgeMap pa, EventTag);
 ----
 
-== Parameters
+== Template Parameters
 
 [cols="1,3",options="header"]
 |===
 | Parameter | Description
 
 | `PredEdgeMap`
-| WritablePropertyMap. Key type is vertex descriptor, value type is edge
-  descriptor.
+| A WritablePropertyMap whose key type is the graph's vertex descriptor and whose
+  value type is the graph's edge descriptor.
 
 | `EventTag`
-| Must be an edge event tag (e.g. `on_tree_edge`, `on_relax_edge`).
+| The event at which to record. Must be an edge event (e.g. `on_tree_edge`,
+  `on_relax_edge`).
+|===
+
+== Associated Types
+
+[cols="1,3",options="header"]
 |===
+| Type | Description
 
-== Behavior
+| `event_filter`
+| The event tag the visitor responds to. Same type as `EventTag`.
+|===
+
+== Member Functions
+
+[cols="1,3",options="header"]
+|===
+| Member | Description
 
-Given edge `e = (u, v)`, records `e` as the predecessor edge of `v`:
-`put(pred_edge_map, v, e)`.
+| `edge_predecessor_recorder(PredEdgeMap pa)`
+| Constructs a recorder writing predecessor edges into the property map `pa`.
 
-TIP: The source vertex (root of the search tree) will not have a predecessor
-edge assigned. Initialize it to a sentinel value before running the algorithm.
-For DFS (which creates a forest), do the same for every vertex so that all
-roots can be identified.
+| `void operator()(Edge e, const Graph& g)`
+| Given edge `e = (u, v)`, records `e` as the predecessor edge of `v`:
+  `put(pa, v, e)`.
+|===
+
+== Non-Member Functions
+
+[cols="1,3",options="header"]
+|===
+| Function | Description
+
+| `record_edge_predecessors(PredEdgeMap pa, EventTag)`
+| Convenience factory that creates an `edge_predecessor_recorder`.
+|===
+
+TIP: The source vertex (the root of the search tree) is not assigned a predecessor
+edge. Initialize it to a sentinel value before running the algorithm to identify
+the root. For DFS (which builds a forest), do the same for every vertex so all
+roots can be distinguished.
+
+== Example
+
+[source,cpp]
+----
+include::example$visitors/edge_predecessor_recorder.cpp[]
+----
+
+[,text]
+----
+include::example$visitors/edge_predecessor_recorder.txt[]
+----

doc/modules/ROOT/pages/visitors/null_visitor.adoc

@@ -1,19 +1,40 @@
 = null_visitor
 
-A no-op event visitor that does nothing. Used as a placeholder or default when
-combining event visitors and one slot is not needed.
+A no-op event visitor that does nothing. Useful as a placeholder or default when
+an algorithm requires a visitor but no action is needed, or to fill an unused slot
+when combining event visitors.
 
 *Defined in:* `<boost/graph/visitors.hpp>` +
-*Models:* EventVisitor
+*Models:* xref:visitors/EventVisitor.adoc[EventVisitor]
 
 == Synopsis
 
 [source,cpp]
 ----
 struct null_visitor {
-    using event_filter = void;
+  typedef on_no_event event_filter;
 
-    template <typename X, typename Graph>
-    void operator()(X, const Graph&) {}
+  template <class T, class Graph>
+  void operator()(T x, Graph& g);
 };
 ----
+
+== Associated Types
+
+[cols="1,3",options="header"]
+|===
+| Type | Description
+
+| `event_filter`
+| `on_no_event`. The visitor is not associated with any algorithm event.
+|===
+
+== Member Functions
+
+[cols="1,3",options="header"]
+|===
+| Member | Description
+
+| `void operator()(T x, Graph& g)`
+| Does nothing.
+|===