* 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

5 files changed, 29 insertions, 38 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: