#124 implement new query change detection

flecs.h

@@ -2831,7 +2831,7 @@ typedef struct ecs_filter_iter_t {
 /** Query-iterator specific data */
 typedef struct ecs_query_iter_t {
     ecs_query_t *query;
-    ecs_query_table_node_t *node;
+    ecs_query_table_node_t *node, *prev;
     int32_t sparse_smallest;
     int32_t sparse_first;
     int32_t bitset_first;
@@ -6055,18 +6055,52 @@ bool ecs_query_next_instanced(
     ecs_iter_t *iter);
 
 /** Returns whether the query data changed since the last iteration.
- * This operation must be invoked before obtaining the iterator, as this will
- * reset the changed state. The operation will return true after:
+ * The operation will return true after:
  * - new entities have been matched with
+ * - new tables have been matched/unmatched with
  * - matched entities were deleted
  * - matched components were changed
  * 
- * @param query The query.
+ * The operation will not return true after a write-only (EcsOut) or filter
+ * (EcsInOutFilter) term has changed, when a term is not matched with the
+ * current table (This subject) or for tag terms.
+ * 
+ * The changed state of a table is reset after it is iterated. If a iterator was
+ * not iterated until completion, tables may still be marked as changed.
+ * 
+ * If no iterator is provided the operation will return the changed state of the
+ * all matched tables of the query. 
+ * 
+ * If an iterator is provided, the operation will return the changed state of 
+ * the currently returned iterator result. The following preconditions must be
+ * met before using an iterator with change detection:
+ * 
+ * - The iterator is a query iterator (created with ecs_query_iter)
+ * - The iterator must be valid (ecs_query_next must have returned true)
+ * - The iterator must be instanced
+ * 
+ * @param query The query (optional if 'it' is provided).
+ * @param it The iterator result to test (optional if 'query' is provided).
  * @return true if entities changed, otherwise false.
  */
 FLECS_API
 bool ecs_query_changed(
-    const ecs_query_t *query);
+    ecs_query_t *query,
+    ecs_iter_t *it);
+
+/** Skip a table while iterating.
+ * This operation lets the query iterator know that a table was skipped while
+ * iterating. A skipped table will not reset its changed state, and the query
+ * will not update the dirty flags of the table for its out columns.
+ * 
+ * Only valid iterators must be provided (next has to be called at least once &
+ * return true) and the iterator must be a query iterator.
+ * 
+ * @param it The iterator result to skip.
+ */
+FLECS_API
+void ecs_query_skip(
+    ecs_iter_t *it);
 
 /** Returns whether query is orphaned.
  * When the parent query of a subquery is deleted, it is left in an orphaned
@@ -18526,7 +18560,7 @@ struct query_base {
      * @return true if entities changed, otherwise false.
      */
     bool changed() {
-        return ecs_query_changed(m_query);
+        return ecs_query_changed(m_query, 0);
     }
 
     /** Returns whether query is orphaned.

include/flecs.h

@@ -2885,18 +2885,52 @@ bool ecs_query_next_instanced(
     ecs_iter_t *iter);
 
 /** Returns whether the query data changed since the last iteration.
- * This operation must be invoked before obtaining the iterator, as this will
- * reset the changed state. The operation will return true after:
+ * The operation will return true after:
  * - new entities have been matched with
+ * - new tables have been matched/unmatched with
  * - matched entities were deleted
  * - matched components were changed
  * 
- * @param query The query.
+ * The operation will not return true after a write-only (EcsOut) or filter
+ * (EcsInOutFilter) term has changed, when a term is not matched with the
+ * current table (This subject) or for tag terms.
+ * 
+ * The changed state of a table is reset after it is iterated. If a iterator was
+ * not iterated until completion, tables may still be marked as changed.
+ * 
+ * If no iterator is provided the operation will return the changed state of the
+ * all matched tables of the query. 
+ * 
+ * If an iterator is provided, the operation will return the changed state of 
+ * the currently returned iterator result. The following preconditions must be
+ * met before using an iterator with change detection:
+ * 
+ * - The iterator is a query iterator (created with ecs_query_iter)
+ * - The iterator must be valid (ecs_query_next must have returned true)
+ * - The iterator must be instanced
+ * 
+ * @param query The query (optional if 'it' is provided).
+ * @param it The iterator result to test (optional if 'query' is provided).
  * @return true if entities changed, otherwise false.
  */
 FLECS_API
 bool ecs_query_changed(
-    const ecs_query_t *query);
+    ecs_query_t *query,
+    ecs_iter_t *it);
+
+/** Skip a table while iterating.
+ * This operation lets the query iterator know that a table was skipped while
+ * iterating. A skipped table will not reset its changed state, and the query
+ * will not update the dirty flags of the table for its out columns.
+ * 
+ * Only valid iterators must be provided (next has to be called at least once &
+ * return true) and the iterator must be a query iterator.
+ * 
+ * @param it The iterator result to skip.
+ */
+FLECS_API
+void ecs_query_skip(
+    ecs_iter_t *it);
 
 /** Returns whether query is orphaned.
  * When the parent query of a subquery is deleted, it is left in an orphaned

include/flecs/addons/cpp/mixins/query/impl.hpp

@@ -47,7 +47,7 @@ struct query_base {
      * @return true if entities changed, otherwise false.
      */
     bool changed() {
-        return ecs_query_changed(m_query);
+        return ecs_query_changed(m_query, 0);
     }
 
     /** Returns whether query is orphaned.

include/flecs/private/api_types.h

@@ -133,7 +133,7 @@ typedef struct ecs_filter_iter_t {
 /** Query-iterator specific data */
 typedef struct ecs_query_iter_t {
     ecs_query_t *query;
-    ecs_query_table_node_t *node;
+    ecs_query_table_node_t *node, *prev;
     int32_t sparse_smallest;
     int32_t sparse_first;
     int32_t bitset_first;

src/private_types.h

@@ -295,6 +295,8 @@ struct ecs_query_table_match_t {
 
     /* Next match in cache for same table (includes empty tables) */
     ecs_query_table_match_t *next_match;
+
+    int32_t *monitor;                /* Used to monitor table for changes */
 };
 
 /** A single table can occur multiple times in the cache when a term matches
@@ -303,7 +305,6 @@ typedef struct ecs_query_table_t {
     ecs_table_cache_hdr_t hdr;       /* Header for ecs_table_cache_t */
     ecs_query_table_match_t *first;  /* List with matches for table */
     ecs_query_table_match_t *last;   /* Last discovered match for table */
-    int32_t *monitor;                /* Used to monitor table for changes */
 } ecs_query_table_t;
 
 /** Points to the beginning & ending of a query group */
@@ -322,6 +323,7 @@ typedef struct ecs_query_table_list_t {
 #define EcsQueryIsOrphaned (512)     /* Is subquery orphaned */
 #define EcsQueryHasOutColumns (1024) /* Does query have out columns */
 #define EcsQueryHasOptional (2048)   /* Does query have optional columns */
+#define EcsQueryHasMonitor (4096)    /* Does query track changes */
 
 /* Query event type for notifying queries of world events */
 typedef enum ecs_query_eventkind_t {