Show error message popup on assertion error in client

Add assertion handler function to base system. Set handler in client to show a message box on assertion errors.

src/base/system.cpp

@@ -169,6 +169,7 @@ static NETSOCKET_INTERNAL invalid_socket = {NETTYPE_INVALID, -1, -1, -1};
 #define AF_WEBSOCKET_INET (0xee)
 
 std::atomic_bool dbg_assert_failing = false;
+DBG_ASSERT_HANDLER dbg_assert_handler;
 
 bool dbg_assert_has_failed()
 {
@@ -179,8 +180,17 @@ void dbg_assert_imp(const char *filename, int line, int test, const char *msg)
 {
 	if(!test)
 	{
+		const bool already_failing = dbg_assert_has_failed();
 		dbg_assert_failing.store(true, std::memory_order_release);
-		dbg_msg("assert", "%s(%d): %s", filename, line, msg);
+		char error[256];
+		str_format(error, sizeof(error), "%s(%d): %s", filename, line, msg);
+		dbg_msg("assert", "%s", error);
+		if(!already_failing)
+		{
+			DBG_ASSERT_HANDLER handler = dbg_assert_handler;
+			if(handler)
+				handler(error);
+		}
 		log_global_logger_finish();
 		dbg_break();
 	}
@@ -195,6 +205,11 @@ void dbg_break()
 #endif
 }
 
+void dbg_assert_set_handler(DBG_ASSERT_HANDLER handler)
+{
+	dbg_assert_handler = std::move(handler);
+}
+
 void dbg_msg(const char *sys, const char *fmt, ...)
 {
 	va_list args;

src/base/system.h

@@ -108,6 +108,9 @@ bool dbg_assert_has_failed();
 void
 dbg_break();
 
+typedef std::function<void(const char *message)> DBG_ASSERT_HANDLER;
+void dbg_assert_set_handler(DBG_ASSERT_HANDLER handler);
+
 /**
  * Prints a debug message.
  *

src/engine/client/client.cpp

@@ -4534,6 +4534,7 @@ int main(int argc, const char **argv)
 	CWindowsComLifecycle WindowsComLifecycle(true);
 #endif
 	CCmdlineFix CmdlineFix(&argc, &argv);
+
 	bool Silent = false;
 	bool RandInitFailed = false;
 
@@ -4582,6 +4583,12 @@ int main(int argc, const char **argv)
 	pKernel->RegisterInterface(pClient, false);
 	pClient->RegisterInterfaces();
 
+	dbg_assert_set_handler([pClient](const char *pMsg) {
+		char aMessage[256];
+		str_format(aMessage, sizeof(aMessage), "An assertion error occured. Please write down or take a screenshot of the following information and report this error.\n\n%s", pMsg);
+		pClient->ShowMessageBox("Assertion Error", aMessage);
+	});
+
 	// create the components
 	IEngine *pEngine = CreateEngine(GAME_NAME, pFutureConsoleLogger, 2);
 	IConsole *pConsole = CreateConsole(CFGFLAG_CLIENT).release();