From da05dfa72e2c7014fbffca2b44364a0a5284d9e3 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Sun, 19 Jun 2016 12:32:45 +0200
Subject: [PATCH] fixed: Polyobject-based line portals may not cache their
 angle as it may change at any time.

---
 src/portal.cpp | 34 +++++++++++++++++++++++++++-------
 src/portal.h   |  1 +
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/portal.cpp b/src/portal.cpp
index 41f2e755e..ec3d5d90f 100644
--- a/src/portal.cpp
+++ b/src/portal.cpp
@@ -272,14 +272,31 @@ static line_t *FindDestination(line_t *src, int tag)
 
 static void SetRotation(FLinePortal *port)
 {
-	if (port != NULL && port->mDestination != NULL)
+	if (port != nullptr && port->mDestination != nullptr)
 	{
-	line_t *dst = port->mDestination;
-	line_t *line = port->mOrigin;
-	DAngle angle = dst->Delta().Angle() - line->Delta().Angle() + 180.;
-	port->mSinRot = sindeg(angle.Degrees);	// Here precision matters so use the slower but more precise versions.
-	port->mCosRot = cosdeg(angle.Degrees);
-	port->mAngleDiff = angle;
+		if (port->mType != PORTT_LINKED)
+		{
+			line_t *dst = port->mDestination;
+			line_t *line = port->mOrigin;
+			DAngle angle = dst->Delta().Angle() - line->Delta().Angle() + 180.;
+			port->mSinRot = sindeg(angle.Degrees);	// Here precision matters so use the slower but more precise versions.
+			port->mCosRot = cosdeg(angle.Degrees);
+			port->mAngleDiff = angle;
+			if ((line->sidedef[0]->Flags & WALLF_POLYOBJ) || (dst->sidedef[0]->Flags & WALLF_POLYOBJ))
+			{
+				port->mFlags |= PORTF_POLYOBJ;
+			}
+			else
+			{
+				port->mFlags &= PORTF_POLYOBJ;
+			}
+		}
+		else
+		{
+			// Linked portals have no angular difference.
+			port->mSinRot = port->mCosRot = 0.;
+			port->mAngleDiff = 0.;
+		}
 	}
 }
 
@@ -593,6 +610,7 @@ void P_TranslatePortalXY(line_t* src, double& x, double& y)
 	if (!src) return;
 	FLinePortal *port = src->getPortal();
 	if (!port) return;
+	if (port->mFlags & PORTF_POLYOBJ) SetRotation(port);	// update the angle for polyportals.
 
 	// offsets from line
 	double nposx = x - src->v1->fX();
@@ -620,6 +638,7 @@ void P_TranslatePortalVXVY(line_t* src, double &velx, double &vely)
 	if (!src) return;
 	FLinePortal *port = src->getPortal();
 	if (!port) return;
+	if (port->mFlags & PORTF_POLYOBJ) SetRotation(port);	// update the angle for polyportals.
 
 	double orig_velx = velx;
 	double orig_vely = vely;
@@ -638,6 +657,7 @@ void P_TranslatePortalAngle(line_t* src, DAngle& angle)
 	if (!src) return;
 	FLinePortal *port = src->getPortal();
 	if (!port) return;
+	if (port->mFlags & PORTF_POLYOBJ) SetRotation(port);	// update the angle for polyportals.
 	angle = (angle + port->mAngleDiff).Normalized360();
 }
 
diff --git a/src/portal.h b/src/portal.h
index a87ae207f..44d636e4b 100644
--- a/src/portal.h
+++ b/src/portal.h
@@ -145,6 +145,7 @@ enum
 	PORTF_PASSABLE = 2,
 	PORTF_SOUNDTRAVERSE = 4,
 	PORTF_INTERACTIVE = 8,
+	PORTF_POLYOBJ = 16,
 
 	PORTF_TYPETELEPORT = PORTF_VISIBLE | PORTF_PASSABLE | PORTF_SOUNDTRAVERSE,
 	PORTF_TYPEINTERACTIVE = PORTF_VISIBLE | PORTF_PASSABLE | PORTF_SOUNDTRAVERSE | PORTF_INTERACTIVE,