BASE: Remove bad casts between incompatible Plugin types

Previously, a C-style cast was used to convert a
Common::Array<Plugin *>, populated with pointers to StaticPlugin
and DynamicPlugin instances, to a
Common::Array<PluginSubclass<T> *>, but PluginSubclass<T> is a
*sibling* class to StaticPlugin/DynamicPlugin, so this cast was
invalid and the results undefined. The methods for retrieving
subclasses of plugins can't be easily changed to just generate an
array of temporary wrapper objects that expose an identical API
which dereferences to the preferred PluginObject subclass because
pointers to these objects are retained by other parts of ScummVM,
so the wrappers would needed to be persisted or they would need to
just re-expose the underlying Plugin object again. This indicated
that a way to solve this problem is to have the callers receive
Plugin objects and get the PluginObject from the Plugin by
explicitly stating their desired type, in a similar manner to
std::get(std::variant), so that the pattern used by this patch to
solve the problem.

Closes gh-1051.

1 files changed, 12 insertions, 9 deletions

diff --git a/base/commandLine.cpp b/base/commandLine.cpp
index 640daa1793..2e981fb75a 100644
--- a/base/commandLine.cpp
+++ b/base/commandLine.cpp
@@ -673,9 +673,9 @@ static void listGames() {
 	printf("Game ID              Full Title                                            \n"
 	       "-------------------- ------------------------------------------------------\n");
 
-	const EnginePlugin::List &plugins = EngineMan.getPlugins();
-	for (EnginePlugin::List::const_iterator iter = plugins.begin(); iter != plugins.end(); ++iter) {
-		GameList list = (**iter)->getSupportedGames();
+	const PluginList &plugins = EngineMan.getPlugins();
+	for (PluginList::const_iterator iter = plugins.begin(); iter != plugins.end(); ++iter) {
+		GameList list = (*iter)->get<MetaEngine>().getSupportedGames();
 		for (GameList::iterator v = list.begin(); v != list.end(); ++v) {
 			printf("%-20s %s\n", v->gameid().c_str(), v->description().c_str());
 		}
@@ -741,7 +741,7 @@ static Common::Error listSaves(const char *target) {
 	gameid.toLowercase();	// Normalize it to lower case
 
 	// Find the plugin that will handle the specified gameid
-	const EnginePlugin *plugin = 0;
+	const Plugin *plugin = nullptr;
 	GameDescriptor game = EngineMan.findGame(gameid, &plugin);
 
 	if (!plugin) {
@@ -749,13 +749,15 @@ static Common::Error listSaves(const char *target) {
 						Common::String::format("target '%s', gameid '%s", target, gameid.c_str()));
 	}
 
-	if (!(*plugin)->hasFeature(MetaEngine::kSupportsListSaves)) {
+	const MetaEngine &metaEngine = plugin->get<MetaEngine>();
+
+	if (!metaEngine.hasFeature(MetaEngine::kSupportsListSaves)) {
 		// TODO: Include more info about the target (desc, engine name, ...) ???
 		return Common::Error(Common::kEnginePluginNotSupportSaves,
 						Common::String::format("target '%s', gameid '%s", target, gameid.c_str()));
 	} else {
 		// Query the plugin for a list of saved games
-		SaveStateList saveList = (*plugin)->listSaves(target);
+		SaveStateList saveList = metaEngine.listSaves(target);
 
 		if (saveList.size() > 0) {
 			// TODO: Include more info about the target (desc, engine name, ...) ???
@@ -793,13 +795,14 @@ static void listThemes() {
 
 /** Lists all output devices */
 static void listAudioDevices() {
-	MusicPlugin::List pluginList = MusicMan.getPlugins();
+	PluginList pluginList = MusicMan.getPlugins();
 
 	printf("ID                             Description\n");
 	printf("------------------------------ ------------------------------------------------\n");
 
-	for (MusicPlugin::List::const_iterator i = pluginList.begin(), iend = pluginList.end(); i != iend; ++i) {
-		MusicDevices deviceList = (**i)->getDevices();
+	for (PluginList::const_iterator i = pluginList.begin(), iend = pluginList.end(); i != iend; ++i) {
+		const MusicPluginObject &musicObject = (*i)->get<MusicPluginObject>();
+		MusicDevices deviceList = musicObject.getDevices();
 		for (MusicDevices::iterator j = deviceList.begin(), jend = deviceList.end(); j != jend; ++j) {
 			printf("%-30s %s\n", Common::String::format("\"%s\"", j->getCompleteId().c_str()).c_str(), j->getCompleteName().c_str());
 		}