From 71626dbc76db89871cb164128946f2b9207a781a Mon Sep 17 00:00:00 2001
From: James R <justsomejames2@gmail.com>
Date: Fri, 31 Mar 2023 01:41:31 -0700
Subject: [PATCH] K_GetBestWaypointForMobj: add a hint argument

The hint argument is a known nearby waypoint that can be
used to optimize the waypoint search.
---
 src/k_kart.c       |  2 +-
 src/k_waypoint.cpp | 32 +++++++++++++++++++-------------
 src/k_waypoint.h   |  3 ++-
 src/objects/spb.c  |  4 ++--
 4 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/src/k_kart.c b/src/k_kart.c
index d90e4e98c..cbb0e6d53 100644
--- a/src/k_kart.c
+++ b/src/k_kart.c
@@ -8358,7 +8358,7 @@ static waypoint_t *K_GetPlayerNextWaypoint(player_t *player)
 
 	if ((player != NULL) && (player->mo != NULL) && (P_MobjWasRemoved(player->mo) == false))
 	{
-		waypoint_t *waypoint     = K_GetBestWaypointForMobj(player->mo);
+		waypoint_t *waypoint     = K_GetBestWaypointForMobj(player->mo, NULL);
 		boolean    updaterespawn = false;
 
 		// Our current waypoint.
diff --git a/src/k_waypoint.cpp b/src/k_waypoint.cpp
index 70613e598..191a751ba 100644
--- a/src/k_waypoint.cpp
+++ b/src/k_waypoint.cpp
@@ -343,11 +343,11 @@ static void K_CompareOverlappingWaypoint
 }
 
 /*--------------------------------------------------
-	waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
+	waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj, waypoint_t *const hint)
 
 		See header file for description.
 --------------------------------------------------*/
-waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
+waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj, waypoint_t *const hint)
 {
 	waypoint_t *bestwaypoint = NULL;
 
@@ -357,21 +357,15 @@ waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
 	}
 	else
 	{
-		size_t     i              = 0U;
-		waypoint_t *checkwaypoint = NULL;
 		fixed_t    closestdist    = INT32_MAX;
 		fixed_t    checkdist      = INT32_MAX;
 		fixed_t    bestfindist    = INT32_MAX;
 
-		for (i = 0; i < numwaypoints; i++)
+		auto sort_waypoint = [&](waypoint_t *const checkwaypoint)
 		{
-			fixed_t rad;
-
-			checkwaypoint = &waypointheap[i];
-
 			if (!K_GetWaypointIsEnabled(checkwaypoint))
 			{
-				continue;
+				return;
 			}
 
 			checkdist = P_AproxDistance(
@@ -379,7 +373,7 @@ waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
 				(mobj->y / FRACUNIT) - (checkwaypoint->mobj->y / FRACUNIT));
 			checkdist = P_AproxDistance(checkdist, ((mobj->z / FRACUNIT) - (checkwaypoint->mobj->z / FRACUNIT)) * 4);
 
-			rad = (checkwaypoint->mobj->radius / FRACUNIT);
+			fixed_t rad = (checkwaypoint->mobj->radius / FRACUNIT);
 
 			// remember: huge radius
 			if (closestdist <= rad && checkdist <= rad && finishline != NULL)
@@ -387,7 +381,7 @@ waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
 				if (!P_TraceWaypointTraversal(mobj, checkwaypoint->mobj))
 				{
 					// Save sight checks when all of the other checks pass, so we only do it if we have to
-					continue;
+					return;
 				}
 
 				// If the mobj is touching multiple waypoints at once,
@@ -405,12 +399,24 @@ waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj)
 				if (!P_TraceWaypointTraversal(mobj, checkwaypoint->mobj))
 				{
 					// Save sight checks when all of the other checks pass, so we only do it if we have to
-					continue;
+					return;
 				}
 
 				bestwaypoint = checkwaypoint;
 				closestdist = checkdist;
 			}
+		};
+
+		if (hint != NULL)
+		{
+			// The hint is a waypoint that is already known to be close to the player. It is used to exclude
+			// most of the other waypoints by distance so fewer expensive sight checks are performed.
+			sort_waypoint(hint);
+		}
+
+		for (size_t i = 0U; i < numwaypoints; i++)
+		{
+			sort_waypoint(&waypointheap[i]);
 		}
 	}
 
diff --git a/src/k_waypoint.h b/src/k_waypoint.h
index 051798036..fce73bebc 100644
--- a/src/k_waypoint.h
+++ b/src/k_waypoint.h
@@ -196,11 +196,12 @@ waypoint_t *K_GetClosestWaypointToMobj(mobj_t *const mobj);
 
 	Input Arguments:-
 		mobj - mobj to get the waypoint for.
+		hint - a previously known nearby waypoint to optimize searching.
 
 	Return:-
 		The best waypoint for the mobj, or NULL if there were no matches
 --------------------------------------------------*/
-waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj);
+waypoint_t *K_GetBestWaypointForMobj(mobj_t *const mobj, waypoint_t *const hint);
 
 
 /*--------------------------------------------------
diff --git a/src/objects/spb.c b/src/objects/spb.c
index 6ed876522..722fc4eee 100644
--- a/src/objects/spb.c
+++ b/src/objects/spb.c
@@ -403,7 +403,7 @@ static void SPBSeek(mobj_t *spb, mobj_t *bestMobj)
 	if (spb_curwaypoint(spb) == -1)
 	{
 		// Determine first waypoint.
-		curWaypoint = K_GetBestWaypointForMobj(spb);
+		curWaypoint = K_GetBestWaypointForMobj(spb, NULL);
 		spb_curwaypoint(spb) = (INT32)K_GetWaypointHeapIndex(curWaypoint);
 	}
 	else
@@ -421,7 +421,7 @@ static void SPBSeek(mobj_t *spb, mobj_t *bestMobj)
 	}
 	else
 	{
-		destWaypoint = K_GetBestWaypointForMobj(bestMobj);
+		destWaypoint = K_GetBestWaypointForMobj(bestMobj, NULL);
 	}
 
 	if (curWaypoint != NULL)