some more example lua scripts

scripts/s_fader_automation.lua

@@ -0,0 +1,56 @@
+ardour { ["type"] = "Snippet", name = "fader automation" }
+
+function factory () return function ()
+	local playhead = Session:transport_frame ()
+	local samplerate = Session:nominal_frame_rate ()
+
+	-- get selected tracks
+	rl = Editor:get_selection().tracks:routelist()
+	-- prepare undo operation
+	Session:begin_reversible_command ("Fancy Fade Out")
+	local add_undo = false -- keep track if something has changed
+	-- iterate over selected tracks
+	for r in rl:iter() do
+		local ac = r:amp():gain_control() -- ARDOUR:AutomationControl
+		local acl = ac:alist() -- ARDOUR:AutomationControlList (state, high-level)
+		local cl = acl:list()  -- Evoral:ControlList (actual events)
+
+		ac:set_automation_state(ARDOUR.AutoState.Touch)
+
+		if cl:isnil() then
+			goto out
+		end
+
+		-- query the value at the playhead position
+		local g = cl:eval(playhead)
+
+		-- get state for undo
+		local before = acl:get_state()
+
+		-- delete all events after the playhead...
+		cl:truncate_end (playhead)
+		-- ...and generate some new ones.
+		for i=0,50 do
+			cl:add (playhead + i * samplerate / 50,
+				 g * (1 - math.sqrt (i / 50)),
+				 false, true)
+		end
+		-- remove dense events
+		cl:thin(20)
+
+		-- save undo
+		local after = acl:get_state()
+		Session:add_command (acl:memento_command(before, after))
+		add_undo = true
+
+		::out::
+	end
+
+	-- all done, commit the combined Undo Operation
+	if add_undo then
+		-- the 'nil' Commend here mean to use the collected diffs added above
+		Session:commit_reversible_command (nil)
+	else
+		Session:abort_reversible_command ()
+	end
+end end