song format: add support for limiting maximal length of a tag

doc/config

@@ -115,6 +115,10 @@
 ## only if all requested values are available and/or define alternate
 ## value with { }|{ } eg. {%a - %t}|{%f}
 ##
+## Note: If you want to set limit on maximal length of a tag, just
+## put the appropriate number between % and character that defines
+## tag type, e.g. to make album take max. 20 terminal cells, use '%20b'.
+##
 ## Note: Format that is similar to "%a - %t" (i.e. without any additional
 ## braces) is equal to "{%a - %t}", so if one of the tags is missing,
 ## you'll get nothing.

doc/ncmpcpp.1

@@ -369,6 +369,8 @@ For song format you can use:
 
 You can also put them in { } and then they will be displayed only if all requested values are available and/or define alternate value with { }|{ } e.g. {%a - %t}|{%f} will check if artist and title tags are available and if they are, display them. Otherwise it'll display filename.
 
+\fBNote\fR: If you want to set limit on maximal length of a tag, just put the appropriate number between % and character that defines tag type, e.g. to make album take max. 20 terminal cells, use '%20b'.
+
 \fBNote\fR: Format that is similar to "%a - %t" (i.e. without any additional braces) is equal to "{%a - %t}", so if one of the tags is missing, you'll get nothing.
 
 Text can have different color than the main window, e.g. if you want length to be green, write $3%l$9.

src/song.cpp

@@ -22,6 +22,7 @@
 #include <config.h>
 #endif
 
+#include <cstdlib>
 #include <cstring>
 #include <iomanip>
 #include <sstream>
@@ -370,13 +371,21 @@ std::string MPD::Song::ParseFormat(std::string::const_iterator &it, const char *
 		
 		if (*it == '%')
 		{
-			switch (*++it)
+			size_t delimiter = 0;
+			if (isdigit(*++it))
 			{
-				case '%':
-					result += *it; // no break here
-				default:
-					get = toGetFunction(*it);
+				delimiter = atol(&*it);
+				while (isdigit(*++it)) { }
 			}
+			
+			if (*it == '%')
+			{
+				result += *it;
+				get = 0;
+			}
+			else
+				get = toGetFunction(*it);
+			
 			if (get)
 			{
 				std::string tag = GetTags(get);
@@ -386,6 +395,12 @@ std::string MPD::Song::ParseFormat(std::string::const_iterator &it, const char *
 							tag.replace(i, 1, std::string(1, FormatEscapeCharacter) + *ch);
 				if (!tag.empty() && (get != &MPD::Song::GetLength || GetTotalLength()))
 				{
+					if (delimiter)
+					{
+						const std::basic_string<my_char_t> &s = TO_WSTRING(tag);
+						if (NCurses::Window::Length(s) > delimiter)
+							tag = Shorten(s, delimiter);
+					}
 					has_some_tags = 1;
 					result += tag;
 				}