From 64c7043123f3bf3d638f2a83d7e92bea915eddac Mon Sep 17 00:00:00 2001
From: Thomas Goyne <plorkyeran@aegisub.org>
Date: Fri, 20 Jan 2012 21:33:20 +0000
Subject: [PATCH] Add aegisub.cancel(), which immediates ends macro execution
 without applying any of the changes that have been made

Originally committed to SVN as r6325.
---
 aegisub/src/auto4_lua.cpp | 15 ++++++++++++---
 aegisub/src/auto4_lua.h   |  1 +
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/aegisub/src/auto4_lua.cpp b/aegisub/src/auto4_lua.cpp
index 8d1c6bd18..c3c941901 100644
--- a/aegisub/src/auto4_lua.cpp
+++ b/aegisub/src/auto4_lua.cpp
@@ -263,6 +263,7 @@ namespace Automation4 {
 			set_field(L, "video_size", LuaVideoSize);
 			set_field(L, "keyframes", LuaGetKeyframes);
 			set_field(L, "decode_path", LuaDecodePath);
+			set_field(L, "cancel", LuaCancel);
 			set_field(L, "lua_automation_version", 4);
 
 			// store aegisub table to globals
@@ -525,14 +526,22 @@ namespace Automation4 {
 		return 1;
 	}
 
+	int LuaScript::LuaCancel(lua_State *L)
+	{
+		lua_pushnil(L);
+		return lua_error(L);
+	}
+
 	static void lua_threaded_call(ProgressSink *ps, lua_State *L, int nargs, int nresults, bool can_open_config, bool *failed)
 	{
 		LuaProgressSink lps(L, ps, can_open_config);
 
 		if (lua_pcall(L, nargs, nresults, 0)) {
-			// if the call failed, log the error here
-			ps->Log("\n\nLua reported a runtime error:\n");
-			ps->Log(lua_tostring(L, -1));
+			if (!lua_isnil(L, -1)) {
+				// if the call failed, log the error here
+				ps->Log("\n\nLua reported a runtime error:\n");
+				ps->Log(lua_tostring(L, -1));
+			}
 			lua_pop(L, 1);
 			*failed = true;
 		}
diff --git a/aegisub/src/auto4_lua.h b/aegisub/src/auto4_lua.h
index fd419fced..95caab948 100644
--- a/aegisub/src/auto4_lua.h
+++ b/aegisub/src/auto4_lua.h
@@ -310,6 +310,7 @@ namespace Automation4 {
 		static int LuaVideoSize(lua_State *L);
 		static int LuaGetKeyframes(lua_State *L);
 		static int LuaDecodePath(lua_State *L);
+		static int LuaCancel(lua_State *L);
 
 	public:
 		LuaScript(const wxString &filename);