Add a function to test whether the current thread is the main thread.

src/openttd.cpp

@@ -63,6 +63,7 @@
 #include "subsidy_func.h"
 #include "gfx_layout.h"
 #include "viewport_sprite_sorter.h"
+#include "thread/thread.h"
 
 #include "linkgraph/linkgraphschedule.h"
 
@@ -553,6 +554,7 @@ static const OptionData _options[] = {
  */
 int openttd_main(int argc, char *argv[])
 {
+	SetSelfAsMainThread();
 	char *musicdriver = NULL;
 	char *sounddriver = NULL;
 	char *videodriver = NULL;

src/thread/thread.h

@@ -122,4 +122,14 @@ private:
  */
 uint GetCPUCoreCount();
 
+/**
+ * Set the current thread as the "main" thread
+ */
+void SetSelfAsMainThread();
+
+/**
+ * @return true if the current thread definitely the "main" thread. If in doubt returns false.
+ */
+bool IsMainThread();
+
 #endif /* THREAD_H */

src/thread/thread_morphos.cpp

@@ -199,3 +199,7 @@ private:
 	if (thread != NULL) *thread = to;
 	return true;
 }
+
+void SetSelfAsMainThread() { }
+
+bool IsMainThread() { return false; }

src/thread/thread_none.cpp

@@ -33,3 +33,7 @@ public:
 {
 	return new ThreadMutex_None();
 }
+
+void SetSelfAsMainThread() { }
+
+bool IsMainThread() { return true; }

src/thread/thread_os2.cpp

@@ -145,3 +145,7 @@ public:
 {
 	return new ThreadMutex_OS2();
 }
+
+void SetSelfAsMainThread() { }
+
+bool IsMainThread() { return false; }

src/thread/thread_pthread.cpp

@@ -172,3 +172,15 @@ public:
 {
 	return new ThreadMutex_pthread();
 }
+
+static pthread_t main_thread;
+
+void SetSelfAsMainThread()
+{
+	main_thread = pthread_self();
+}
+
+bool IsMainThread()
+{
+	return main_thread == pthread_self();
+}

src/thread/thread_win32.cpp

@@ -158,3 +158,15 @@ public:
 {
 	return new ThreadMutex_Win32();
 }
+
+static uint main_thread_id;
+
+void SetSelfAsMainThread()
+{
+	main_thread_id = GetCurrentThreadId();
+}
+
+bool IsMainThread()
+{
+	return main_thread_id == GetCurrentThreadId();
+}