Add callback script to periodically save a backup snapshot

scripts/periodic_backup.lua

@@ -0,0 +1,38 @@
+ardour {
+	["type"]    = "EditorHook",
+	name        = "Periodically Save Snapshot",
+	author      = "Ardour Lua Task Force",
+	description = "Save a session-snapshot peridocally (every 15mins) named after the current date-time",
+}
+
+-- subscribe to signals
+-- http://manual.ardour.org/lua-scripting/class_reference/#LuaSignal.LuaSignal
+function signals ()
+	return LuaSignal.Set():add ({[LuaSignal.LuaTimerDS] = true})
+end
+
+-- create callback function
+function factory ()
+	local _last_snapshot_time = 0 -- persistent variable
+
+	-- callback function which invoked when signal is emitted, every 100ms
+	return function (signal, ref, ...)
+
+		local now = os.time (); -- unix-time, seconds since 1970
+
+		-- skip initial save when script is loaded
+		if (_last_snapshot_time == 0) then
+			_last_snapshot_time = now;
+		end
+
+		-- every 15 mins
+		if (now > _last_snapshot_time + 60 * 15) then
+			_last_snapshot_time = now
+			-- format date-time (avoid colon)
+			local snapshot_name = os.date ("%Y-%m-%d %H.%M.%S", now)
+			-- save session -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Session
+			Session:save_state ("backup " .. snapshot_name, false, false, false)
+		end
+
+	end
+end