window: add ScopedStringHelper and use it where appropriate

src/actions.cpp

@@ -842,10 +842,11 @@ void ExecuteCommand::run()
 	std::string cmd_name;
 	{
 		Statusbar::ScopedLock lock;
+		NC::Window::ScopedStringHelper helper(*wFooter,
+			Statusbar::Helpers::TryExecuteImmediateCommand()
+		);
 		Statusbar::put() << NC::Format::Bold << ":" << NC::Format::NoBold;
-		wFooter->setGetStringHelper(Statusbar::Helpers::TryExecuteImmediateCommand());
 		cmd_name = wFooter->getString();
-		wFooter->setGetStringHelper(Statusbar::Helpers::getString);
 	}
 
 	auto cmd = Bindings.findCommand(cmd_name);
@@ -1882,10 +1883,11 @@ void ApplyFilter::run()
 	try
 	{
 		Statusbar::ScopedLock lock;
+		NC::Window::ScopedStringHelper helper(*wFooter,
+			Statusbar::Helpers::ApplyFilterImmediately(f, filter)
+		);
 		Statusbar::put() << NC::Format::Bold << "Apply filter: " << NC::Format::NoBold;
-		wFooter->setGetStringHelper(Statusbar::Helpers::ApplyFilterImmediately(f, filter));
 		wFooter->getString(filter);
-		wFooter->setGetStringHelper(Statusbar::Helpers::getString);
 	}
 	catch (NC::PromptAborted &)
 	{

src/status.cpp

@@ -167,7 +167,7 @@ void Status::handleServerError(MPD::ServerError &e)
 	Statusbar::printf("MPD: %1%", e.what());
 	if (e.code() == MPD_SERVER_ERROR_PERMISSION)
 	{
-		wFooter->setGetStringHelper(nullptr);
+		NC::Window::ScopedStringHelper helper(*wFooter, nullptr);
 		Statusbar::put() << "Password: ";
 		Mpd.SetPassword(wFooter->getString(0, true));
 		try {
@@ -176,7 +176,6 @@ void Status::handleServerError(MPD::ServerError &e)
 		} catch (MPD::ServerError &e_prim) {
 			handleServerError(e_prim);
 		}
-		wFooter->setGetStringHelper(Statusbar::Helpers::getString);
 	}
 	else if (e.code() == MPD_SERVER_ERROR_NO_EXIST && myScreen == myBrowser)
 	{

src/window.h

@@ -188,6 +188,23 @@ struct XY
 /// Main class of NCurses namespace, used as base for other specialized windows
 struct Window
 {
+	/// Sets helper to a specific value for the current scope
+	struct ScopedStringHelper
+	{
+		template <typename HelperT>
+		ScopedStringHelper(Window &w, HelperT &&helper) noexcept
+		: m_w(w), m_helper(std::move(w.m_get_string_helper)) {
+			m_w.m_get_string_helper = std::forward<HelperT>(helper);
+		}
+		~ScopedStringHelper() noexcept {
+			m_w.m_get_string_helper = std::move(m_helper);
+		}
+
+	private:
+		Window &m_w;
+		GetStringHelper m_helper;
+	};
+
 	Window() : m_window(0), m_border_window(0) { }
 	
 	/// Constructs an empty window with given parameters
@@ -254,11 +271,11 @@ struct Window
 	/// @see setGetStringHelper()
 	/// @see SetTimeout()
 	/// @see CreateHistory()
-	std::string getString(const std::string &base, size_t width = 0, bool encrypted = 0);
+	std::string getString(const std::string &base, size_t width = 0, bool encrypted = false);
 	
 	/// Wrapper for above function that doesn't take base string (it will be empty).
 	/// Taken parameters are the same as for above.
-	std::string getString(size_t width = 0, bool encrypted = 0)
+	std::string getString(size_t width = 0, bool encrypted = false)
 	{
 		return getString("", width, encrypted);
 	}
@@ -285,7 +302,11 @@ struct Window
 	/// Sets helper function used in getString()
 	/// @param helper pointer to function that matches getStringHelper prototype
 	/// @see getString()
-	void setGetStringHelper(GetStringHelper helper) { m_get_string_helper = helper; }
+	template <typename HelperT>
+	void setGetStringHelper(HelperT &&helper)
+	{
+		m_get_string_helper = std::forward<HelperT>(helper);
+	}
 
 	/// Run current GetString helper function (if defined).
 	/// @see getString()