Add Lua bindings to modify region gain curve

share/scripts/s_region_gain_curve.lua

@@ -0,0 +1,52 @@
+ardour { ["type"] = "Snippet", name = "Set Region Gain Curve" }
+
+function factory () return function ()
+	-- get Editor GUI Selection
+	-- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:Selection
+	local sel = Editor:get_selection ()
+
+	-- prepare undo operation
+	Session:begin_reversible_command ("Lua Region Gain Curve")
+
+	-- iterate over selected regions
+	-- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:RegionSelection
+	for r in sel.regions:regionlist ():iter () do
+
+		-- test if it's an audio region
+		local ar = r:to_audioregion ();
+		if ar:isnil () then
+			goto next
+		end
+
+		-- get region-gain-curve is-a
+		-- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:AutomationList
+		local al = ar:envelope ()
+
+		-- get state for undo
+		local before = al:get_state ()
+
+		-- delete all current events
+		al:clear_list ()
+
+		-- add some new ones
+		for i=0,50 do
+			al:add (i * r:length () / 50,
+			        1 - math.sqrt (i / 50),
+			        false, true)
+		end
+
+		-- remove dense events
+		al:thin (20)
+
+		-- save undo
+		local after = al:get_state ()
+		Session:add_command (al:memento_command (before, after))
+
+		::next::
+	end
+
+	if not Session:abort_empty_reversible_command () then
+		Session:commit_reversible_command (nil)
+	end
+
+end end