some love for session-scripts.

scripts/session_test.lua

@@ -1,15 +1,14 @@
 ardour {
 	["type"]    = "session",
-	name        = "Example",
+	name        = "Good Night",
 	license     = "MIT",
 	author      = "Robin Gareus",
 	email       = "robin@gareus.org",
 	site        = "http://gareus.org",
 	description = [[
-	An Example Ardour Session Process Plugin.
-	Install a 'hook' that is called on every process cycle
-	(before doing any processing).
-	This example stops the transport after rolling for a specific time.]]
+	Example Ardour Session Script.
+	Session scripts are called at the beginning of every process-callback (before doing any audio processing).
+	This example stops the transport after rolling for a configurable time which can be set when instantiating the script.]]
 }
 
 function sess_params ()

scripts/stop_at_marker.lua

@@ -0,0 +1,42 @@
+ardour {
+	["type"]    = "session",
+	name        = "Stop at Marker",
+	license     = "MIT",
+	author      = "Robin Gareus",
+	email       = "robin@gareus.org",
+	site        = "http://gareus.org",
+	description = [[An example session script which stops the transport on every location marker when rolling forward.]]
+}
+
+function factory ()
+	return function (n_samples)
+		if (not Session:transport_rolling ()) then
+			-- not rolling, nothing to do.
+			return
+		end
+
+		local pos = Session:transport_frame () -- current playhead position
+		local loc = Session:locations () -- all marker locations
+
+		-- find first marker after the current playhead position, ignore loop + punch ranges
+		-- (this only works when rolling forward, to extend this example see
+		-- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Locations )
+		local m = loc:first_mark_after (pos, false)
+
+		if (m == -1) then
+			-- no marker was found
+			return
+		end
+
+		-- since ardour may split the process cycle for events,
+		-- n_samples may be smaller.
+		local blk = Session:get_block_size ()
+
+		-- transport stop can only happen on a process-cycle boundary.
+		-- This callback happens from within the process callback,
+		-- so we need to queue it ahead of time.
+		if (pos + n_samples + blk >= m and pos + n_samples < m) then
+			Session:request_transport_speed (0.0, true)
+		end
+	end
+end