PluginFactory: Fix LMMS_PLUGIN_DIR search path, add ~/lmms/plugins/

Fixes #3392, supersedes #3431

Author: lukas-w

src/core/PluginFactory.cpp

@@ -29,6 +29,8 @@
 #include <QtCore/QDir>
 #include <QtCore/QLibrary>
 
+#include "ConfigManager.h"
+
 #ifdef LMMS_BUILD_WIN32
 	QStringList nameFilters("*.dll");
 #else
@@ -39,7 +41,7 @@ PluginFactory* PluginFactory::s_instance = nullptr;
 
 PluginFactory::PluginFactory()
 {
-	// Adds a search path relative to the main executable to if the path exists.
+	// Adds a search path relative to the main executable if the path exists.
 	auto addRelativeIfExists = [this] (const QString& path) {
 		QDir dir(qApp->applicationDirPath());
 		if (!path.isEmpty() && dir.cd(path)) {
@@ -68,6 +70,8 @@ PluginFactory::PluginFactory()
 	if (!(env_path = qgetenv("LMMS_PLUGIN_DIR")).isEmpty())
 		QDir::addSearchPath("plugins", env_path);
 
+	QDir::addSearchPath("plugins", ConfigManager::inst()->workingDir() + "plugins");
+
 	discoverPlugins();
 }
 
@@ -127,7 +131,11 @@ void PluginFactory::discoverPlugins()
 	PluginInfoList pluginInfos;
 	m_pluginByExt.clear();
 
-	const QFileInfoList& files = QDir("plugins:").entryInfoList(nameFilters);
+	QFileInfoList files;
+	for (const QString& searchPath : QDir::searchPaths("plugins"))
+	{
+		files << QDir(searchPath).entryInfoList(nameFilters);
+	}
 
 	// Cheap dependency handling: zynaddsubfx needs ZynAddSubFxCore. By loading
 	// all libraries twice we ensure that libZynAddSubFxCore is found.
@@ -142,6 +150,7 @@ void PluginFactory::discoverPlugins()
 
 		if (! library->load()) {
 			m_errors[file.baseName()] = library->errorString();
+			qWarning(library->errorString().toLocal8Bit());
 			continue;
 		}
 		if (library->resolve("lmms_plugin_main") == nullptr) {