* Changed the createEngine() factory function of our plugins to return an error code (the engine is now passed indirectly via a double pointer)

* Removed Engine_Empty (obsolete now that engines can return actual error codes)

svn-id: r22199

16 files changed, 92 insertions, 80 deletions

diff --git a/base/engine.cpp b/base/engine.cpp
index 55cbf2f65b..ecc0f6dbf2 100644
--- a/base/engine.cpp
+++ b/base/engine.cpp
@@ -259,7 +259,3 @@ void Engine::GUIErrorMessage(const Common::String msg) {
 	GUI::MessageDialog dialog(msg);
 	dialog.runModal();
 }
-
-Engine_Empty::Engine_Empty(OSystem *syst, const Common::String msg) : Engine(syst), _message(msg) {
-}
-
diff --git a/base/engine.h b/base/engine.h
index 49515bd40a..b9cc17a29c 100644
--- a/base/engine.h
+++ b/base/engine.h
@@ -75,34 +75,13 @@ public:
 	/** On some systems, check if the game appears to be run from CD. */
 	void checkCD();
 
-	/* Indicate if an autosave should be performed */
+	/* Indicate if an autosave should be performed. */
 	bool shouldPerformAutoSave(int lastSaveTime);
 
-	/** Initialized graphics and shows error message */
+	/** Initialized graphics and shows error message. */
 	void GUIErrorMessage(const Common::String msg);
 };
 
-// Used when no valid game was found in the directory
-// Just pops up an error message and returns to launcher
-class Engine_Empty : public Engine {
-public:
-	Engine_Empty(OSystem *syst, const Common::String msg = "No valid games were found in specified directory.");
-	virtual ~Engine_Empty() {}
-
-	// Displays error message and do not run go() method
-	int init() { GUIErrorMessage(_message); return 1; }
-
-	// Just indicate that we want return to launcher
-	int go() { return 1; }
-
-	void errorString(char *buf_input, char *buf_output) {}
-
-private:
-	Common::String _message;
-};
-
-
-
 extern Engine *g_engine;
 
 #endif
diff --git a/base/main.cpp b/base/main.cpp
index 409a42ad9d..2a46357af4 100644
--- a/base/main.cpp
+++ b/base/main.cpp
@@ -180,9 +180,11 @@ static int runGame(const Plugin *plugin, OSystem &system, const Common::String &
 	}
 
 	// Create the game engine
-	Engine *engine = plugin->createInstance(&system);
-	if (!engine) {
+	Engine *engine = 0;
+	PluginError err = plugin->createInstance(&system, &engine);
+	if (!engine || err != kNoError) {
 		// TODO: Show an error dialog or so?
+		// TODO: Also take 'err' into consideration...
 		//GUI::MessageDialog alert("ScummVM could not find any game in the specified directory!");
 		//alert.runModal();
 		warning("Failed to instantiate engine for target %s", ConfMan.getActiveDomainName().c_str());
diff --git a/base/plugins.cpp b/base/plugins.cpp
index 8cb1e1e6ae..13b18c3eab 100644
--- a/base/plugins.cpp
+++ b/base/plugins.cpp
@@ -28,7 +28,7 @@
 #include "common/util.h"
 
 /** Type of factory functions which make new Engine objects. */
-typedef Engine *(*EngineFactory)(OSystem *syst);
+typedef PluginError (*EngineFactory)(OSystem *syst, Engine **engine);
 
 typedef const char *(*NameFunc)();
 typedef GameDescriptor (*GameIDQueryFunc)(const char *gameid);
@@ -116,9 +116,9 @@ public:
 
 	const char *getName() const { return _plugin->_name; }
 
-	Engine *createInstance(OSystem *syst) const {
+	PluginError createInstance(OSystem *syst, Engine **engine) const {
 		assert(_plugin->_ef);
-		return (*_plugin->_ef)(syst);
+		return (*_plugin->_ef)(syst, engine);
 	}
 
 	GameList getSupportedGames() const { return _plugin->_games; }
@@ -157,9 +157,9 @@ public:
 
 	const char *getName() const					{ return _name.c_str(); }
 
-	Engine *createInstance(OSystem *syst) const {
+	PluginError createInstance(OSystem *syst, Engine **engine) const {
 		assert(_ef);
-		return (*_ef)(syst);
+		return (*_ef)(syst, engine);
 	}
 
 	GameList getSupportedGames() const { return _games; }
diff --git a/base/plugins.h b/base/plugins.h
index f0318a8008..b0178f3e89 100644
--- a/base/plugins.h
+++ b/base/plugins.h
@@ -66,6 +66,20 @@ typedef Common::Array<DetectedGame> DetectedGameList;
 
 
 /**
+ * Error codes which mayb be reported by plugins under various circumstances.
+ * @todo Turn this into a global 'ErrorCode' enum used by all of ScummVM ?
+ */
+enum PluginError {
+	kNoError = 0,	// No error occured
+	kInvalidPathError,
+	kNoGameDataFoundError,
+	kUnsupportedGameidError,
+	
+	kUnknownError		// Catch-all error, used if no other error code matches
+};
+
+
+/**
  * Abstract base class for the plugin system.
  * Subclasses for this can be used to wrap both static and dynamic
  * plugins.
@@ -84,7 +98,7 @@ public:
 	virtual GameDescriptor findGame(const char *gameid) const = 0;
 	virtual DetectedGameList detectGames(const FSList &fslist) const = 0;
 
-	virtual Engine *createInstance(OSystem *syst) const = 0;
+	virtual PluginError createInstance(OSystem *syst, Engine **engine) const = 0;
 };
 
 
@@ -106,7 +120,7 @@ public:
  * - DetectedGameList Engine_##ID##_detectGames(const FSList &fslist)
  *   -> scans through the given file list (usually the contents of a directory),
  *      and attempts to detects games present in that location.
- * - Engine *Engine_##ID##_create(OSystem *syst)
+ * - PluginError Engine_##ID##_create(OSystem *syst, Engine **engine)
  *   -> factory function, create an instance of the Engine class.
  *
  * @todo	add some means to query the plugin API version etc.
@@ -130,7 +144,7 @@ public:
 		PLUGIN_EXPORT const char *PLUGIN_name() { return name; } \
 		PLUGIN_EXPORT GameList PLUGIN_gameIDList() { return Engine_##ID##_gameIDList(); } \
 		PLUGIN_EXPORT GameDescriptor PLUGIN_findGameID(const char *gameid) { return Engine_##ID##_findGameID(gameid); } \
-		PLUGIN_EXPORT Engine *PLUGIN_createEngine(OSystem *syst) { return Engine_##ID##_create(syst); } \
+		PLUGIN_EXPORT PluginError PLUGIN_createEngine(OSystem *syst, Engine **engine) { return Engine_##ID##_create(syst, engine); } \
 		PLUGIN_EXPORT DetectedGameList PLUGIN_detectGames(const FSList &fslist) { return Engine_##ID##_detectGames(fslist); } \
 	} \
 	void dummyFuncToAllowTrailingSemicolon()
@@ -145,7 +159,7 @@ class PluginRegistrator {
 	friend class StaticPlugin;
 public:
 	typedef GameDescriptor (*GameIDQueryFunc)(const char *gameid);
-	typedef Engine *(*EngineFactory)(OSystem *syst);
+	typedef PluginError (*EngineFactory)(OSystem *syst, Engine **engine);
 	typedef DetectedGameList (*DetectFunc)(const FSList &fslist);
 
 protected:
diff --git a/engines/cine/cine.cpp b/engines/cine/cine.cpp
index 9f504b76f0..cb61fbf1cd 100644
--- a/engines/cine/cine.cpp
+++ b/engines/cine/cine.cpp
@@ -110,8 +110,10 @@ DetectedGameList Engine_CINE_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_CINE_create(OSystem *syst) {
-	return new Cine::CineEngine(syst);
+PluginError Engine_CINE_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new Cine::CineEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(CINE, "CINE Engine");
diff --git a/engines/gob/gob.cpp b/engines/gob/gob.cpp
index 108368006e..6fd6255a9a 100644
--- a/engines/gob/gob.cpp
+++ b/engines/gob/gob.cpp
@@ -361,7 +361,7 @@ DetectedGameList Engine_GOB_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_GOB_create(OSystem *syst) {
+PluginError Engine_GOB_create(OSystem *syst, Engine **engine) {
 	// Detect game features based on MD5
 	uint8 md5sum[16];
 	char md5str[32 + 1];
@@ -403,7 +403,9 @@ Engine *Engine_GOB_create(OSystem *syst) {
 		printf("Unknown MD5 (%s)! Please report the details (language, platform, etc.) of this game to the ScummVM team\n", md5str);
 	}
 
-	return new GobEngine(syst, features, g->lang);
+	assert(engine);
+	*engine = new GobEngine(syst, features, g->lang);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(GOB, "Gob Engine");
diff --git a/engines/kyra/kyra.cpp b/engines/kyra/kyra.cpp
index 920f5c02a2..81a73db6f7 100644
--- a/engines/kyra/kyra.cpp
+++ b/engines/kyra/kyra.cpp
@@ -204,8 +204,10 @@ DetectedGameList Engine_KYRA_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_KYRA_create(OSystem *system) {
-	return new KyraEngine(system);
+PluginError Engine_KYRA_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new KyraEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(KYRA, "Legend of Kyrandia Engine");
diff --git a/engines/lure/lure.cpp b/engines/lure/lure.cpp
index 5ec33994a3..dab02a5ca3 100644
--- a/engines/lure/lure.cpp
+++ b/engines/lure/lure.cpp
@@ -154,8 +154,10 @@ DetectedGameList Engine_LURE_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_LURE_create(OSystem *system) {
-	return new LureEngine(system);
+PluginError Engine_LURE_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new LureEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(LURE, "Lure of the Temptress Engine");
diff --git a/engines/queen/queen.cpp b/engines/queen/queen.cpp
index 611832c439..129d8358c2 100644
--- a/engines/queen/queen.cpp
+++ b/engines/queen/queen.cpp
@@ -128,8 +128,10 @@ DetectedGameList Engine_QUEEN_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_QUEEN_create(OSystem *syst) {
-	return new Queen::QueenEngine(syst);
+PluginError Engine_QUEEN_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new Queen::QueenEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(QUEEN, "Flight of the Amazon Queen");
diff --git a/engines/saga/game.cpp b/engines/saga/game.cpp
index e9b215e99d..cad25c7aff 100644
--- a/engines/saga/game.cpp
+++ b/engines/saga/game.cpp
@@ -83,8 +83,10 @@ DetectedGameList Engine_SAGA_detectGames(const FSList &fslist) {
 	return Saga::GAME_detectGames(fslist);
 }
 
-Engine *Engine_SAGA_create(OSystem *syst) {
-	return new Saga::SagaEngine(syst);
+PluginError Engine_SAGA_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new Saga::SagaEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SAGA, "SAGA Engine");
diff --git a/engines/scumm/plugin.cpp b/engines/scumm/plugin.cpp
index abeaae20e0..12d048d308 100644
--- a/engines/scumm/plugin.cpp
+++ b/engines/scumm/plugin.cpp
@@ -1278,8 +1278,9 @@ DetectedGameList Engine_SCUMM_detectGames(const FSList &fslist) {
  *
  * This is heavily based on our MD5 detection scheme.
  */
-Engine *Engine_SCUMM_create(OSystem *syst) {
-	Engine *engine;
+PluginError Engine_SCUMM_create(OSystem *syst, Engine **engine) {
+	assert(syst);
+	assert(engine);
 	const char *gameid = ConfMan.get("gameid").c_str();
 
 	// We start by checking whether the specified game ID is obsolete.
@@ -1313,8 +1314,8 @@ Engine *Engine_SCUMM_create(OSystem *syst) {
 
 	// Unable to locate game data
 	if (results.empty()) {
-		warning("ScummEngine: unable to locate game data");
-		return new Engine_Empty(syst);
+		warning("ScummEngine: unable to locate game data at path '%s'", dir.path().c_str());
+		return kNoGameDataFoundError;
 	}
 	
 	DetectorResult res(*(results.begin()));
@@ -1374,74 +1375,74 @@ Engine *Engine_SCUMM_create(OSystem *syst) {
 	// instantiate the appropriate game engine. Hooray!
 	switch (res.game.version) {
 	case 0:
-		engine = new ScummEngine_c64(syst, res);
+		*engine = new ScummEngine_c64(syst, res);
 		break;
 	case 1:
 	case 2:
-		engine = new ScummEngine_v2(syst, res);
+		*engine = new ScummEngine_v2(syst, res);
 		break;
 	case 3:
 		if (res.game.features & GF_OLD_BUNDLE)
-			engine = new ScummEngine_v3old(syst, res);
+			*engine = new ScummEngine_v3old(syst, res);
 		else
-			engine = new ScummEngine_v3(syst, res);
+			*engine = new ScummEngine_v3(syst, res);
 		break;
 	case 4:
-		engine = new ScummEngine_v4(syst, res);
+		*engine = new ScummEngine_v4(syst, res);
 		break;
 	case 5:
-		engine = new ScummEngine_v5(syst, res);
+		*engine = new ScummEngine_v5(syst, res);
 		break;
 	case 6:
 		switch (res.game.heversion) {
 #ifndef DISABLE_HE
 		case 100:
-			engine = new ScummEngine_v100he(syst, res);
+			*engine = new ScummEngine_v100he(syst, res);
 			break;
 		case 99:
-			engine = new ScummEngine_v99he(syst, res);
+			*engine = new ScummEngine_v99he(syst, res);
 			break;
 		case 98:
 		case 95:
 		case 90:
-			engine = new ScummEngine_v90he(syst, res);
+			*engine = new ScummEngine_v90he(syst, res);
 			break;
 		case 80:
-			engine = new ScummEngine_v80he(syst, res);
+			*engine = new ScummEngine_v80he(syst, res);
 			break;
 		case 73:
 		case 72:
-			engine = new ScummEngine_v72he(syst, res);
+			*engine = new ScummEngine_v72he(syst, res);
 			break;
 		case 71:
-			engine = new ScummEngine_v71he(syst, res);
+			*engine = new ScummEngine_v71he(syst, res);
 			break;
 		case 70:
-			engine = new ScummEngine_v70he(syst, res);
+			*engine = new ScummEngine_v70he(syst, res);
 			break;
 #endif
 #ifndef PALMOS_68K
 		case 61:
-			engine = new ScummEngine_v60he(syst, res);
+			*engine = new ScummEngine_v60he(syst, res);
 			break;
 #endif
 		default:
-			engine = new ScummEngine_v6(syst, res);
+			*engine = new ScummEngine_v6(syst, res);
 		}
 		break;
 #ifndef DISABLE_SCUMM_7_8
 	case 7:
-		engine = new ScummEngine_v7(syst, res);
+		*engine = new ScummEngine_v7(syst, res);
 		break;
 	case 8:
-		engine = new ScummEngine_v8(syst, res);
+		*engine = new ScummEngine_v8(syst, res);
 		break;
 #endif
 	default:
 		error("Engine_SCUMM_create(): Unknown version of game engine");
 	}
 
-	return engine;
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SCUMM, "Scumm Engine");
diff --git a/engines/simon/game.cpp b/engines/simon/game.cpp
index 34a135ef90..1685fd35b2 100644
--- a/engines/simon/game.cpp
+++ b/engines/simon/game.cpp
@@ -111,7 +111,7 @@ DetectedGameList Engine_SIMON_detectGames(const FSList &fslist) {
 	return Simon::GAME_detectGames(fslist);
 }
 
-Engine *Engine_SIMON_create(OSystem *syst) {
+PluginError Engine_SIMON_create(OSystem *syst, Engine **engine) {
 	const char *gameid = ConfMan.get("gameid").c_str();
 
 	for (const ObsoleteGameID *o = obsoleteGameIDsTable; o->from; ++o) {
@@ -129,7 +129,9 @@ Engine *Engine_SIMON_create(OSystem *syst) {
 		}
 	}
 
-	return new Simon::SimonEngine(syst);
+	assert(engine);
+	*engine = new Simon::SimonEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SIMON, "Simon the Sorcerer");
diff --git a/engines/sky/sky.cpp b/engines/sky/sky.cpp
index f3b286a5ea..941f9df017 100644
--- a/engines/sky/sky.cpp
+++ b/engines/sky/sky.cpp
@@ -110,8 +110,10 @@ DetectedGameList Engine_SKY_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_SKY_create(OSystem *syst) {
-	return new Sky::SkyEngine(syst);
+PluginError Engine_SKY_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new Sky::SkyEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SKY, "Beneath a Steel Sky");
diff --git a/engines/sword1/sword1.cpp b/engines/sword1/sword1.cpp
index cba1e97bb8..fd49b0de06 100644
--- a/engines/sword1/sword1.cpp
+++ b/engines/sword1/sword1.cpp
@@ -117,8 +117,10 @@ DetectedGameList Engine_SWORD1_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_SWORD1_create(OSystem *syst) {
-	return new SwordEngine(syst);
+PluginError Engine_SWORD1_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new SwordEngine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SWORD1, "Broken Sword");
diff --git a/engines/sword2/sword2.cpp b/engines/sword2/sword2.cpp
index 13e97dc0d8..fdbcbb5c07 100644
--- a/engines/sword2/sword2.cpp
+++ b/engines/sword2/sword2.cpp
@@ -111,8 +111,10 @@ DetectedGameList Engine_SWORD2_detectGames(const FSList &fslist) {
 	return detectedGames;
 }
 
-Engine *Engine_SWORD2_create(OSystem *syst) {
-	return new Sword2::Sword2Engine(syst);
+PluginError Engine_SWORD2_create(OSystem *syst, Engine **engine) {
+	assert(engine);
+	*engine = new Sword2::Sword2Engine(syst);
+	return kNoError;
 }
 
 REGISTER_PLUGIN(SWORD2, "Broken Sword 2");