bindings: Support a bindings file in $XDG_CONFIG_HOME/ncmpcpp

Fixes https://github.com/arybczak/ncmpcpp/issues/91

This also rewrites the intro in doc/bindings to be more like doc/config.

doc/bindings

@@ -1,7 +1,8 @@
-##########################################################
+##############################################################
-## this is example bindings configuration file, copy it ##
+## This is the example bindings file. Copy it to            ##
-## to ~/.ncmpcpp/bindings and set up your preferences   ##
+## ~/.ncmpcpp/bindings or $XDG_CONFIG_HOME/ncmpcpp/bindings ##
-##########################################################
+## and set up your preferences                              ##
+##############################################################
 ##
 ##### General rules #####
 ##

src/bindings.cpp

@@ -467,6 +467,17 @@ bool BindingsConfiguration::read(const std::string &file)
 	return result;
 }
 
+bool BindingsConfiguration::read(const std::vector<std::string> &binding_paths)
+{
+	return std::all_of(
+		binding_paths.begin(),
+		binding_paths.end(),
+		[&](const std::string &binding_path) {
+			return read(binding_path);
+		}
+	);
+}
+
 void BindingsConfiguration::generateDefaults()
 {
 	NC::Key::Type k = NC::Key::None;

src/bindings.h

@@ -92,7 +92,7 @@ public:
 	typedef BindingsMap::value_type::second_type::const_iterator ConstBindingIterator;
 	typedef std::pair<BindingIterator, BindingIterator> BindingIteratorPair;
 
-	bool read(const std::string &file);
+	bool read(const std::vector<std::string> &binding_paths);
 	void generateDefaults();
 
 	const Command *findCommand(const std::string &name);
@@ -111,6 +111,8 @@ private:
 		m_bindings[k].push_back(std::forward<ArgT>(t));
 	}
 
+	bool read(const std::string &file);
+
 	BindingsMap m_bindings;
 	CommandsSet m_commands;
 };

src/configuration.cpp

@@ -74,7 +74,12 @@ bool configure(int argc, char **argv)
 		xdg_config_home() + "ncmpcpp/config"
 	};
 
-	std::string bindings_path;
+	const std::vector<std::string> default_bindings_paths = {
+		"~/.ncmpcpp/bindings",
+		xdg_config_home() + "ncmpcpp/bindings"
+	};
+
+	std::vector<std::string> bindings_paths;
 	std::vector<std::string> config_paths;
 
 	po::options_description options("Options");
@@ -85,7 +90,7 @@ bool configure(int argc, char **argv)
 		("config,c", po::value<std::vector<std::string>>(&config_paths)->value_name("PATH")->default_value(default_config_paths, join<std::string>(default_config_paths, " AND ")), "specify configuration file(s)")
 		("ignore-config-errors", "ignore unknown and invalid options in configuration files")
 		("test-lyrics-fetchers", "check if lyrics fetchers work")
-		("bindings,b", po::value<std::string>(&bindings_path)->value_name("PATH")->default_value("~/.ncmpcpp/bindings"), "specify bindings file")
+		("bindings,b", po::value<std::vector<std::string>>(&bindings_paths)->value_name("PATH")->default_value(default_bindings_paths, join<std::string>(default_bindings_paths, " AND ")), "specify bindings file(s)")
 		("screen,s", po::value<std::string>()->value_name("SCREEN"), "specify the startup screen")
 		("slave-screen,S", po::value<std::string>()->value_name("SCREEN"), "specify the startup slave screen")
 		("help,?", "show help message")
@@ -190,14 +195,9 @@ bool configure(int argc, char **argv)
 		if (Config.read(config_paths, vm.count("ignore-config-errors")) == false)
 			exit(1);
 
-		// if bindings file was not specified, use the one from main directory.
-		if (vm["bindings"].defaulted())
-			bindings_path = Config.ncmpcpp_directory + "bindings";
-		else
-			expand_home(bindings_path);
-
 		// read bindings
-		if (Bindings.read(bindings_path) == false)
+		std::for_each(bindings_paths.begin(), bindings_paths.end(), expand_home);
+		if (Bindings.read(bindings_paths) == false)
 			exit(1);
 		Bindings.generateDefaults();