From ce872ed4e62cc2178a7c7bcb5ca552079d2e72c2 Mon Sep 17 00:00:00 2001
From: Arthur <spaddlewit@gmail.com>
Date: Sun, 1 Jan 2023 12:57:15 -0500
Subject: [PATCH] Fixes issue #299 by ensuring Knuckles's angle normal
 intersects the linedef before latching

---
 src/p_map.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/src/p_map.c b/src/p_map.c
index 5c8ccbb19..a0620627c 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -3477,6 +3477,53 @@ static void PTR_GlideClimbTraverse(line_t *li)
 
 		canclimb = (li->backsector ? P_IsClimbingValid(slidemo->player, climbangle) : true);
 
+		if (!slidemo->player->climbing && canclimb)
+		{
+			// When latching on from a glide, ensure that the line segment of Knuckles's movement intersects with the line segment of the linedef.
+
+			// Position in front of the player. Think of it like the facing normal.
+			// Uses 20*FRACUNIT as an arbitrary distance
+			fixed_t posPlusNormalX = slidemo->x + FixedMul(slidemo->radius + 20*FRACUNIT, FINECOSINE(slidemo->angle >> ANGLETOFINESHIFT));
+			fixed_t posPlusNormalY = slidemo->y + FixedMul(slidemo->radius + 20*FRACUNIT, FINESINE(slidemo->angle >> ANGLETOFINESHIFT));
+
+			INT32 pointOnSides[4];
+			vector3_t pointVec, lineVec[2];
+			pointVec.z = 0;
+			lineVec[0].z = 0;
+			lineVec[1].z = 0;
+
+			// Player's position
+			pointVec.x = slidemo->x;
+			pointVec.y = slidemo->y;
+			lineVec[0].x = li->v1->x;
+			lineVec[0].y = li->v1->y;
+			lineVec[1].x = li->v2->x;
+			lineVec[1].y = li->v2->y;
+			pointOnSides[0] = FV3_PointOnLineSide(&pointVec, lineVec);
+
+			// Player's position + radius + 20*FRACUNIT
+			pointVec.x = posPlusNormalX;
+			pointVec.y = posPlusNormalY;
+			pointOnSides[1] = FV3_PointOnLineSide(&pointVec, lineVec);
+
+			// Linedef vertex 1
+			lineVec[0].x = slidemo->x;
+			lineVec[0].y = slidemo->y;
+			lineVec[1].x = posPlusNormalX;
+			lineVec[1].y = posPlusNormalY;
+			pointVec.x = li->v1->x;
+			pointVec.y = li->v1->y;
+			pointOnSides[2] = FV3_PointOnLineSide(&pointVec, lineVec);
+
+			// Linedef vertex 2
+			pointVec.x = li->v2->x;
+			pointVec.y = li->v2->y;
+			pointOnSides[3] = FV3_PointOnLineSide(&pointVec, lineVec);
+
+			if (pointOnSides[0] == pointOnSides[1] || pointOnSides[2] == pointOnSides[3])
+				canclimb = false;
+		}
+
 		if (((!slidemo->player->climbing && abs((signed)(slidemo->angle - ANGLE_90 - climbline)) < ANGLE_45)
 			|| (slidemo->player->climbing == 1 && abs((signed)(slidemo->angle - climbline)) < ANGLE_135))
 			&& canclimb)