Add an example script to start recording on a MIDI event

scripts/_midi_rec_start.lua

@@ -0,0 +1,37 @@
+ardour {
+	["type"]    = "session",
+	name        = "MIDI Record Enable",
+	category    = "Example", -- "Utility"
+	license     = "MIT",
+	author      = "Ardour Lua Task Force",
+	description = [[An example script to start recording on note-on.]]
+}
+
+function factory ()
+	return function (n_samples)
+		if Session:actively_recording() then return end -- when recording already, do nothing
+		-- iterate over all MIDI ports
+		_, t = Session:engine ():get_ports (ARDOUR.DataType.midi (), ARDOUR.PortList ())
+		for p in t[2]:iter () do
+			-- skip output ports
+			if not p:receives_input () then goto next end
+			local midiport = p:to_midiport ()
+			-- and skip async event ports
+			if midiport:isnil () then goto next end
+			local mb = midiport:get_midi_buffer (n_samples) -- get the midi-data buffers
+			local events = mb:table () -- copy event list into lua table
+			for _,e in pairs (events) do -- iterate over all events in the midi-buffer
+				if bit32.band (e:buffer():array()[1], 0xf0) == 0x90 then -- note on
+					Session:maybe_enable_record (true) -- global record-enable from rt-context
+					-- maybe-enable may fail if there are no tracks or step-entry is active
+					-- roll transport if record-enable suceeded:
+					if ARDOUR.Session.RecordState.Enabled == Session:record_status() then
+						Session:request_transport_speed (1.0, true) -- ...and go.
+					end
+					return
+				end
+			end
+			::next::
+		end
+	end
+end