window: support 'previous' background value for better composability

src/clock.cpp

@@ -58,7 +58,7 @@ Clock::Clock()
 	Width = Config.clock_display_seconds ? 60 : 40;
 	
 	m_pane = NC::Window(0, MainStartY, COLS, MainHeight, "", Config.main_color, NC::Border::None);
-	w = NC::Window((COLS-Width)/2, (MainHeight-Height)/2+MainStartY, Width, Height-1, "", Config.main_color, NC::Border(Config.main_color.foreground()));
+	w = NC::Window((COLS-Width)/2, (MainHeight-Height)/2+MainStartY, Width, Height-1, "", Config.main_color, NC::Border::None);
 }
 
 void Clock::resize()

src/display.cpp

@@ -120,7 +120,7 @@ void showSongs(NC::Menu<T> &menu, const MPD::Song &s,
 			x_off -= Config.now_playing_suffix_length;
 		if (is_selected)
 			x_off -= Config.selected_item_suffix_length;
-		menu << NC::XY(x_off, y) << right_aligned;
+		menu << NC::TermManip::ClearToEOL << NC::XY(x_off, y) << right_aligned;
 	}
 
 	if (is_now_playing)

src/format.cpp

@@ -189,14 +189,18 @@ expressions<CharT> parseBracket(const string<CharT> &s,
 			{
 				++it;
 				rangeCheck(s, it, end);
+				auto jt = it;
 				string<CharT> scolor;
 				do
 					scolor += *it++;
 				while (it != end && *it != ')');
 				rangeCheck(s, it, end);
-				result.push_back(boost::lexical_cast<NC::Color>(
-					convertString<char, CharT>::apply(scolor)
-				));
+				auto value = convertString<char, CharT>::apply(scolor);
+				try {
+					result.push_back(boost::lexical_cast<NC::Color>(value));
+				} catch (boost::bad_lexical_cast &) {
+					throwError(s, jt, "invalid color \"" + value + "\"");
+				}
 			}
 			else
 				throwError(s, it, invalidCharacter(*it));

src/help.cpp

@@ -444,7 +444,7 @@ void write_bindings(NC::Scrollpad &w)
 
 	section(w, "", "List of available colors");
 	for (int i = 0; i < COLORS; ++i)
-		w << NC::Color(i) << i+1 << NC::Color::End << " ";
+		w << NC::Color(i, NC::Color::transparent) << i+1 << NC::Color::End << " ";
 }
 
 }

src/window.cpp

@@ -198,47 +198,45 @@ int add_base()
 
 namespace NC {
 
-Color Color::Default(0, -1, true, false);
-Color Color::Black(COLOR_BLACK, -1);
-Color Color::Red(COLOR_RED, -1);
-Color Color::Green(COLOR_GREEN, -1);
-Color Color::Yellow(COLOR_YELLOW, -1);
-Color Color::Blue(COLOR_BLUE, -1);
-Color Color::Magenta(COLOR_MAGENTA, -1);
-Color Color::Cyan(COLOR_CYAN, -1);
-Color Color::White(COLOR_WHITE, -1);
+const short Color::transparent = -1;
+const short Color::previous = -2;
+
+Color Color::Default(0, 0, true, false);
+Color Color::Black(COLOR_BLACK, Color::transparent);
+Color Color::Red(COLOR_RED, Color::transparent);
+Color Color::Green(COLOR_GREEN, Color::transparent);
+Color Color::Yellow(COLOR_YELLOW, Color::transparent);
+Color Color::Blue(COLOR_BLUE, Color::transparent);
+Color Color::Magenta(COLOR_MAGENTA, Color::transparent);
+Color Color::Cyan(COLOR_CYAN, Color::transparent);
+Color Color::White(COLOR_WHITE, Color::transparent);
 Color Color::End(0, 0, false, true);
 
-std::ostream &operator<<(std::ostream &os, const Color &c)
+int Color::pairNumber() const
 {
-	if (c.isDefault())
-		os << "default";
-	else if (c == Color::Black)
-		os << "black";
-	else if (c == Color::Red)
-		os << "red";
-	else if (c == Color::Green)
-		os << "green";
-	else if (c == Color::Yellow)
-		os << "yellow";
-	else if (c == Color::Blue)
-		os << "blue";
-	else if (c == Color::Magenta)
-		os << "magenta";
-	else if (c == Color::Cyan)
-		os << "cyan";
-	else if (c == Color::White)
-		os << "white";
-	else if (c.isEnd())
-		os << "end";
+	int result;
+	if (isDefault())
+		result = 0;
+	else if (previousBackground())
+		throw std::logic_error("color depends on the previous background value");
+	else if (isEnd())
+		throw std::logic_error("'end' doesn't have a corresponding pair number");
 	else
-		os << c.foreground() << "_" << c.background();
-	return os;
+	{
+		// colors start with 0, but pairs start with 1. additionally
+		// first pairs are for transparent background, which has a
+		// value of -1, so we need to add 1 to both foreground and
+		// background value.
+		result = background() + 1;
+		result *= COLORS;
+		result += foreground() + 1;
+	}
+	return result;
 }
 
 std::istream &operator>>(std::istream &is, Color &c)
 {
-	auto get_single_color = [](const std::string &s) {
+	auto get_single_color = [](const std::string &s, bool background) {
 		short result = -1;
 		if (s == "black")
 			result = COLOR_BLACK;
@@ -256,6 +254,8 @@ std::istream &operator>>(std::istream &is, Color &c)
 			result = COLOR_CYAN;
 		else if (s == "white")
 			result = COLOR_WHITE;
+		else if (background && s == "previous")
+			result = NC::Color::previous;
 		else if (std::all_of(s.begin(), s.end(), isdigit))
 		{
 			result = atoi(s.c_str());
@@ -274,16 +274,16 @@ std::istream &operator>>(std::istream &is, Color &c)
 		c = Color::End;
 	else
 	{
-		short value = get_single_color(sc);
+		short value = get_single_color(sc, false);
 		if (value != -1)
-			c = Color(value);
+			c = Color(value, NC::Color::transparent);
 		else
 		{
 			size_t underscore = sc.find('_');
 			if (underscore != std::string::npos)
 			{
-				short fg = get_single_color(sc.substr(0, underscore));
-				short bg = get_single_color(sc.substr(underscore+1));
+				short fg = get_single_color(sc.substr(0, underscore), false);
+				short bg = get_single_color(sc.substr(underscore+1), true);
 				if (fg != -1 && bg != -1)
 					c = Color(fg, bg);
 				else
@@ -471,22 +471,6 @@ void destroyScreen()
 	endwin();
 }
 
-int Color::pairNumber() const
-{
-	int result;
-	if (isDefault())
-		result = 0;
-	else if (isEnd())
-		throw std::logic_error("'end' doesn't have a corresponding pair number");
-	else
-	{
-		result = background();
-		result *= COLORS;
-		result += foreground();
-	}
-	return result;
-}
-
 Window::Window(size_t startx,
 		size_t starty,
 		size_t width,
@@ -622,7 +606,11 @@ void Window::setColor(Color c)
 	if (c.isDefault())
 		c = m_base_color;
 	if (c != Color::Default)
+	{
+		if (c.previousBackground())
+			c = Color(c.foreground(), m_color.background());
 		wcolor_set(m_window, c.pairNumber(), nullptr);
+	}
 	else
 		wcolor_set(m_window, m_base_color.pairNumber(), nullptr);
 	m_color = std::move(c);

src/window.h

@@ -128,10 +128,15 @@ private:
 
 struct Color
 {
-	Color() : m_rep(0, -1, true, false) { }
-	Color(short foregound_value, short background_value = -1,
+	friend struct Window;
+
+	static const short transparent;
+	static const short previous;
+
+	Color() : m_rep(0, transparent, true, false) { }
+	Color(short foreground_value, short background_value,
 			 bool is_default = false, bool is_end = false)
-	: m_rep(foregound_value + 1, background_value + 1, is_default, is_end)
+	: m_rep(foreground_value, background_value, is_default, is_end)
 	{
 		if (isDefault() && isEnd())
 			throw std::logic_error("Color flag can't be marked as both 'default' and 'end'");
@@ -150,14 +155,6 @@ struct Color
 		return m_rep < rhs.m_rep;
 	}
 
-	short foreground() const
-	{
-		return std::get<0>(m_rep);
-	}
-	short background() const
-	{
-		return std::get<1>(m_rep);
-	}
 	bool isDefault() const
 	{
 		return std::get<2>(m_rep);
@@ -181,10 +178,22 @@ struct Color
 	static Color End;
 
 private:
+	short foreground() const
+	{
+		return std::get<0>(m_rep);
+	}
+	short background() const
+	{
+		return std::get<1>(m_rep);
+	}
+	bool previousBackground() const
+	{
+		return background() == previous;
+	}
+
 	std::tuple<short, short, bool, bool> m_rep;
 };
 
-std::ostream &operator<<(std::ostream &os, const Color &c);
 std::istream &operator>>(std::istream &is, Color &f);
 
 /// Terminal manipulation functions