--- a/util/debug.lua	Sun Apr 29 02:09:12 2012 +0100
+++ b/util/debug.lua	Sun Apr 29 02:10:55 2012 +0100
@@ -7,8 +7,25 @@
 	pass = true;
 	pwd = true;
 };
+local optimal_line_length = 65;
 
-local function get_locals_table(level)
+local termcolours = require "util.termcolours";
+local getstring = termcolours.getstring;
+local styles;
+do
+	_ = termcolours.getstyle;
+	styles = {
+		boundary_padding = _("bright");
+		filename         = _("bright", "blue");
+		level_num        = _("green");
+		funcname         = _("yellow");
+		location         = _("yellow");
+	};
+end
+module("debugx", package.seeall);
+
+function get_locals_table(level)
+	level = level + 1; -- Skip this function itself
 	local locals = {};
 	for local_num = 1, math.huge do
 		local name, value = debug.getlocal(level, local_num);
@@ -18,7 +35,7 @@
 	return locals;
 end
 
-local function get_upvalues_table(func)
+function get_upvalues_table(func)
 	local upvalues = {};
 	if func then
 		for upvalue_num = 1, math.huge do
@@ -30,7 +47,7 @@
 	return upvalues;
 end
 
-local function string_from_var_table(var_table, max_line_len, indent_str)
+function string_from_var_table(var_table, max_line_len, indent_str)
 	local var_string = {};
 	local col_pos = 0;
 	max_line_len = max_line_len or math.huge;
@@ -71,46 +88,72 @@
 	for level = start_level, math.huge do
 		local info;
 		if thread then
-			info = debug.getinfo(thread, level);
+			info = debug.getinfo(thread, level+1);
 		else
-			info = debug.getinfo(level);
+			info = debug.getinfo(level+1);
 		end
 		if not info then break; end
 		
 		levels[(level-start_level)+1] = {
 			level = level;
 			info = info;
-			locals = get_locals_table(level);
+			locals = get_locals_table(level+1);
 			upvalues = get_upvalues_table(info.func);
 		};
 	end	
 	return levels;
 end
 
-function debug.traceback(thread, message, level)
-	if type(thread) ~= "thread" then
-		thread, message, level = coroutine.running(), thread, message;
+function traceback(...)
+	local ok, ret = pcall(_traceback, ...);
+	if not ok then
+		return "Error in error handling: "..ret;
 	end
-	if level and type(message) ~= "string" then
-		return nil, "invalid message";
-	elseif not level then
-		level = message or 2;
+	return ret;
+end
+
+local function build_source_boundary_marker(last_source_desc)
+	local padding = string.rep("-", math.floor(((optimal_line_length - 6) - #last_source_desc)/2));
+	return getstring(styles.boundary_padding, "v"..padding).." "..getstring(styles.filename, last_source_desc).." "..getstring(styles.boundary_padding, padding..(#last_source_desc%2==0 and "-v" or "v "));
+end
+
+function _traceback(thread, message, level)
+
+	-- Lua manual says: debug.traceback ([thread,] [message [, level]])
+	-- I fathom this to mean one of:
+	-- ()
+	-- (thread)
+	-- (message, level)
+	-- (thread, message, level)
+
+	if thread == nil then -- Defaults
+		thread, message, level = coroutine.running(), message, level;
+	elseif type(thread) == "string" then
+		thread, message, level = coroutine.running(), thread, message;
+	elseif type(thread) ~= "thread" then
+		return nil; -- debug.traceback() does this
 	end
-	
+
+	level = level or 1;
+
 	message = message and (message.."\n") or "";
 	
-	local levels = get_traceback_table(thread, level+2);
+	-- +3 counts for this function, and the pcall() and wrapper above us
+	local levels = get_traceback_table(thread, level+3);
+	
+	local last_source_desc;
 	
 	local lines = {};
 	for nlevel, level in ipairs(levels) do
 		local info = level.info;
 		local line = "...";
 		local func_type = info.namewhat.." ";
+		local source_desc = (info.short_src == "[C]" and "C code") or info.short_src or "Unknown";
 		if func_type == " " then func_type = ""; end;
 		if info.short_src == "[C]" then
-			line = "[ C ] "..func_type.."C function "..(info.name and ("%q"):format(info.name) or "(unknown name)")
+			line = "[ C ] "..func_type.."C function "..getstring(styles.location, (info.name and ("%q"):format(info.name) or "(unknown name)"));
 		elseif info.what == "main" then
-			line = "[Lua] "..info.short_src.." line "..info.currentline;
+			line = "[Lua] "..getstring(styles.location, info.short_src.." line "..info.currentline);
 		else
 			local name = info.name or " ";
 			if name ~= " " then
@@ -119,19 +162,32 @@
 			if func_type == "global " or func_type == "local " then
 				func_type = func_type.."function ";
 			end
-			line = "[Lua] "..info.short_src.." line "..info.currentline.." in "..func_type..name.." defined on line "..info.linedefined;
+			line = "[Lua] "..getstring(styles.location, info.short_src.." line "..info.currentline).." in "..func_type..getstring(styles.funcname, name).." (defined on line "..info.linedefined..")";
+		end
+		if source_desc ~= last_source_desc then -- Venturing into a new source, add marker for previous
+			last_source_desc = source_desc;
+			table.insert(lines, "\t "..build_source_boundary_marker(last_source_desc));
 		end
 		nlevel = nlevel-1;
-		table.insert(lines, "\t"..(nlevel==0 and ">" or " ").."("..nlevel..") "..line);
+		table.insert(lines, "\t"..(nlevel==0 and ">" or " ")..getstring(styles.level_num, "("..nlevel..") ")..line);
 		local npadding = (" "):rep(#tostring(nlevel));
-		local locals_str = string_from_var_table(level.locals, 65, "\t            "..npadding);
+		local locals_str = string_from_var_table(level.locals, optimal_line_length, "\t            "..npadding);
 		if locals_str then
 			table.insert(lines, "\t    "..npadding.."Locals: "..locals_str);
 		end
-		local upvalues_str = string_from_var_table(level.upvalues, 65, "\t            "..npadding);
+		local upvalues_str = string_from_var_table(level.upvalues, optimal_line_length, "\t            "..npadding);
 		if upvalues_str then
 			table.insert(lines, "\t    "..npadding.."Upvals: "..upvalues_str);
 		end
 	end
+
+--	table.insert(lines, "\t "..build_source_boundary_marker(last_source_desc));
+
 	return message.."stack traceback:\n"..table.concat(lines, "\n");
 end
+
+function use()
+	debug.traceback = traceback;
+end
+
+return _M;