From b6f184491b44117136c2daac0224d4c2fc2febd3 Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Wed, 4 Apr 2018 16:46:01 +0300
Subject: [PATCH] Restored vanilla behavior of lightning for original Hexen

https://forum.zdoom.org/viewtopic.php?t=60103
---
 src/g_shared/a_lightning.cpp | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/src/g_shared/a_lightning.cpp b/src/g_shared/a_lightning.cpp
index aedcd7e6d..625059993 100644
--- a/src/g_shared/a_lightning.cpp
+++ b/src/g_shared/a_lightning.cpp
@@ -36,6 +36,7 @@
 #include "serializer.h"
 #include "g_levellocals.h"
 #include "events.h"
+#include "gi.h"
 
 static FRandom pr_lightning ("Lightning");
 
@@ -205,6 +206,32 @@ static DLightningThinker *LocateLightning ()
 
 void P_StartLightning ()
 {
+	const bool isOriginalHexen = (gameinfo.gametype == GAME_Hexen)
+		&& (level.flags2 & LEVEL2_HEXENHACK);
+
+	if (isOriginalHexen)
+	{
+		bool hasLightning = false;
+
+		for (const sector_t &sector : level.sectors)
+		{
+			hasLightning = sector.GetTexture(sector_t::ceiling) == skyflatnum
+				|| sector.special == Light_IndoorLightning1
+				|| sector.special == Light_IndoorLightning2;
+
+			if (hasLightning)
+			{
+				break;
+			}
+		}
+
+		if (!hasLightning)
+		{
+			level.flags &= ~LEVEL_STARTLIGHTNING;
+			return;
+		}
+	}
+
 	DLightningThinker *lightning = LocateLightning ();
 	if (lightning == NULL)
 	{