Redesign Session+Route Template Meta Script API

Remove special-cased script types. Allow Action-Scripts to be re-used
for session-setup or route-templates.

scripts/_route_template_example.lua

@@ -1,11 +1,52 @@
 ardour {
-	["type"]    = "TrackSetup",
-	name        = "Route Test",
-	description = [[ FOR TESTING AND PROTOTYING ONLY ]]
+	["type"]    = "EditorAction",
+	name        = "Generic Audio Track",
+	description = [[Example ]]
 }
 
--- DON'T COUNT ON THIS TO REMAIN AS IS.
--- This may turn into a factory method, re-usable as ActionScript.
-function session_setup ()
-	Session:new_audio_track (1, 1, nil, 1, "Hello",  ARDOUR.PresentationInfo.max_order, ARDOUR.TrackMode.Normal)
+-- If a route_setup function is present in an Editor Action Script
+-- the script is also listed in the "add track/bus" dialog as meta-template
+--
+-- The function is expected to return a Lua table. The table may be empty.
+function route_setup ()
+	local e = Session:engine()
+	local _, t = e:get_backend_ports ("", ARDOUR.DataType("audio"), ARDOUR.PortFlags.IsOutput | ARDOUR.PortFlags.IsPhysical, C.StringVector())
+	return
+	{
+		-- keys control which AddRouteDialog controls are made sensitive.
+		-- The following keys accept a default value to pre-seed the dialog
+		['how_many'] = t[4]:size(),
+		['name'] = 'Audio',
+		['channels'] = 2,
+		-- these keys just need to be set (to something other than nil)
+		['insert_at'] = ARDOUR.PresentationInfo.max_order,
+		['group'] = false,
+		--[[
+		['track_mode'] = ARDOUR.TrackMode.Normal,
+		['strict_io'] = true,
+		--]]
+	}
 end
+
+-- The Script can be used as EditorAction in which case it can
+-- optionally provide instantiation parmaters
+function action_params ()
+	return
+	{
+		['how_many'] = { title = "How Many tracks to add", default = "1" },
+		["name"]     = { title = "Track Name Prefix", default = "Audio" },
+	}
+end
+
+
+function factory (params) return function ()
+	local p         = params or route_setup ()
+	local name      = p["name"] or 'Audio'
+	local how_many  = p["how_many"] or 1
+	local channels  = p["channels"] or 1
+	local insert_at = p["insert_at"] or ARDOUR.PresentationInfo.max_order;
+	local group     = p["group"] or nil
+
+	Session:new_audio_track (channels, channels, group, how_many, name, insert_at, ARDOUR.TrackMode.Normal)
+
+end end