make number of lines scrolled with mouse wheel configurable

src/screen.h

@@ -25,6 +25,7 @@
 #include "menu.h"
 #include "mpdpp.h"
 #include "helpers.h"
+#include "settings.h"
 #include "status.h"
 
 class BasicScreen
@@ -149,12 +150,12 @@ template <> inline void Screen<Scrollpad>::MouseButtonPressed(MEVENT me)
 {
 	if (me.bstate & BUTTON2_PRESSED)
 	{
-		for (size_t i = 0; i < 2; ++i)
+		for (size_t i = 0; i < Config.lines_scrolled; ++i)
 			Scroll(wDown);
 	}
 	else if (me.bstate & BUTTON4_PRESSED)
 	{
-		for (size_t i = 0; i < 2; ++i)
+		for (size_t i = 0; i < Config.lines_scrolled; ++i)
 			Scroll(wUp);
 	}
 }

src/settings.cpp

@@ -293,6 +293,7 @@ void DefaultConfiguration(ncmpcpp_config &conf)
 	conf.message_delay_time = 4;
 	conf.lyrics_db = 0;
 	conf.regex_type = 0;
+	conf.lines_scrolled = 2;
 }
 
 void ReadKeys(ncmpcpp_keys &keys)
@@ -708,6 +709,11 @@ void ReadConfiguration(ncmpcpp_config &conf)
 					conf.lyrics_db = n < Lyrics::DBs ? n : 0;
 				}
 			}
+			else if (cl.find("lines_scrolled") != std::string::npos)
+			{
+				if (!v.empty())
+					conf.lines_scrolled = StrToInt(v);
+			}
 			else if (cl.find("song_window_title_format") != std::string::npos)
 			{
 				if (!v.empty())

src/settings.h

@@ -196,6 +196,8 @@ struct ncmpcpp_config
 	int message_delay_time;
 	int lyrics_db;
 	int regex_type;
+	
+	unsigned lines_scrolled;
 };
 
 extern ncmpcpp_config Config;