From e094b7f1d629342ebbd82d321d3c9badbf8b6de4 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 5 Apr 2021 20:25:45 +0100
Subject: [PATCH] Partially fix thread safety issues around _cur_palette

Replaces: 4c59dfb6
See also: https://github.com/OpenTTD/OpenTTD/issues/8712
---
 src/gfx.cpp                |  2 ++
 src/openttd.cpp            | 11 ++++++++++-
 src/video/video_driver.cpp |  7 ++++++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/gfx.cpp b/src/gfx.cpp
index e16ec1064c..6f165ab013 100644
--- a/src/gfx.cpp
+++ b/src/gfx.cpp
@@ -53,6 +53,7 @@ GameMode _game_mode;
 SwitchMode _switch_mode;  ///< The next mainloop command.
 PauseMode _pause_mode;
 Palette _cur_palette;
+std::mutex _cur_palette_mutex;
 std::string _switch_baseset;
 
 static byte _stringwidth_table[FS_END][224]; ///< Cache containing width of often used characters. @see GetCharacterWidth()
@@ -1162,6 +1163,7 @@ void DoPaletteAnimations();
 
 void GfxInitPalettes()
 {
+	std::lock_guard<std::mutex> lock_state(_cur_palette_mutex);
 	memcpy(&_cur_palette, &_palette, sizeof(_cur_palette));
 	DoPaletteAnimations();
 }
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 45eaaf2a19..5db3b75cc9 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -82,6 +82,11 @@
 #include "linkgraph/linkgraphschedule.h"
 #include "tracerestrict.h"
 
+#include <mutex>
+#if defined(__MINGW32__)
+#include "../3rdparty/mingw-std-threads/mingw.mutex.h"
+#endif
+
 #include <stdarg.h>
 #include <system_error>
 
@@ -1971,7 +1976,11 @@ void GameLoop()
 		StateGameLoop();
 	}
 
-	if (!_pause_mode && HasBit(_display_opt, DO_FULL_ANIMATION)) DoPaletteAnimations();
+	if (!_pause_mode && HasBit(_display_opt, DO_FULL_ANIMATION)) {
+		extern std::mutex _cur_palette_mutex;
+		std::lock_guard<std::mutex> lock_state(_cur_palette_mutex);
+		DoPaletteAnimations();
+	}
 
 	SoundDriver::GetInstance()->MainLoop();
 	MusicLoop();
diff --git a/src/video/video_driver.cpp b/src/video/video_driver.cpp
index d3ac95e6ab..178a42044c 100644
--- a/src/video/video_driver.cpp
+++ b/src/video/video_driver.cpp
@@ -174,7 +174,12 @@ void VideoDriver::Tick()
 			this->PopulateSystemSprites();
 		}
 
-		this->CheckPaletteAnim();
+		{
+			extern std::mutex _cur_palette_mutex;
+			std::lock_guard<std::mutex> lock_state(_cur_palette_mutex);
+			this->CheckPaletteAnim();
+		}
+
 		this->Paint();
 
 		this->UnlockVideoBuffer();