gui_thru2 example without a separate client thread, gui is running in…

… main

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examples/gui_thru2.lua

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+-- LuaJack example: gui_thru.lua
+-- 
+-- This example implements an audio 'thru' with a simple GUI that displays
+-- the number of processed frames in its title, and has a button to 
+-- mute/unmute the output.
+--
+-- The MoonFLTK based GUI is running in the main thread where also the jack client
+-- is created. ( https://github.com/stetre/moonfltk/ ).
+--
+-- The main thread and the process thread are connected with a couple of 
+-- ringbuffers. This bidirectional channel carries a trivial 'control protocol'
+-- between the GUI and the audio processing thread. The protocol is summarized
+-- in the table below.
+--
+-- tag   data     direction      message meaning
+-- ---------------------------------------------------
+-- 1     nil      gui->process   mute
+-- 2     nil      gui->process   unmute
+-- 3     nil      gui->process   frames count request
+-- 4     nframes  process->gui   frames count response
+--
+--
+-- To run the example, launch qjackctl, start the JACK server and execute:
+-- $ lua gui_thread.lua
+--
+-- Then execute the metronome example:
+-- $ lua metro.lua
+--
+-- and via the qjackctl GUI connect the metro.lua 'out' to the gui_thru 'in'
+-- and the gui_thru 'out' to a system 'in'. 
+--
+
+
+-----------------------------------------------------------------------
+-- This is the inline script implementing the audio processing. 
+-- It runs in the client's process thread.
+
+PROCESS = [[
+client, port_in, port_out, to_proc_rbuf, from_proc_rbuf = table.unpack(arg)
+
+local fl = require("moonfltk.background")
+
+tot_frames = 0
+mute = false
+
+function process(nframes)
+
+   tot_frames = tot_frames + nframes
+
+   -- GUI <-> process protocol
+   local tag, data = jack.ringbuffer_read(to_proc_rbuf)
+   if tag then 
+      if tag==1 then mute=true        -- mute
+      elseif tag==2 then mute=false   -- unmute
+      elseif tag==3 then              -- frames count request
+         jack.ringbuffer_write(from_proc_rbuf, 4, tostring(tot_frames))
+         fl.awake()
+      else -- ignore
+      end
+   end
+      
+   -- Audio processing 
+   jack.get_buffer(port_in)
+   jack.get_buffer(port_out)
+
+   if mute then -- write 0's 
+      jack.clear(port_out)
+   else
+      jack.copy(port_out, port_in)
+   end
+
+end
+
+jack.process_callback(client, process)
+]]
+
+-----------------------------------------------------------------------
+-- This is the main script.
+
+jack = require("luajack")
+getopt = require("luajack.getopt")
+fmt = string.format
+
+my_name = arg[0]
+
+USAGE =  
+"Usage: lua " .. my_name .. " [options]" ..
+"\nRedirects input to output'"..
+"\nOptions:" ..
+"\n        -h, --help         display this help message" ..
+"\n        -v, --version      display version information and exit" ..
+"\n\n"
+
+function ShowVersion()
+   print(fmt("%s: %s, %s", my_name, jack._VERSION, jack._JACK_VERSION))
+end
+
+function ShowUsage(errmsg) 
+   if errmsg then print(errmsg, "\n") end
+   print(USAGE) 
+   if errmsg then os.exit() end
+end
+
+short_opts = "hv"
+long_opts = {
+   help = 'h',
+   version = 'v',
+}
+
+optarg, optind, opterr = getopt(arg, short_opts, long_opts)
+if opterr then ShowUsage(opterr) end
+if optarg.h then ShowUsage() os.exit(true) end
+if optarg.v then ShowVersion() os.exit(true) end
+
+
+c = jack.client_open(my_name, { no_start_server=true })
+
+jack.verbose("on")
+
+port_in = jack.input_audio_port(c, "in")
+port_out = jack.output_audio_port(c, "out")
+
+from_proc_rbuf = jack.ringbuffer(c, 1000, true) -- process -> GUI
+to_proc_rbuf   = jack.ringbuffer(c, 1000, true) -- GUI -> process
+
+jack.process_load(c, PROCESS, c, port_in, port_out, to_proc_rbuf, 
+                                                    from_proc_rbuf)
+
+jack.shutdown_callback(c, function(_, code, reason)
+   error(reason .." (".. code..")")
+end)
+
+jack.activate(c)
+
+-----------------------------------------------------------------------
+-- GUI
+
+fl = require("moonfltk")
+
+timer = require("moonfltk.timer")
+timer.init()
+
+-- The T1 timer is used to send frame count requests at regular intervals
+REQ_INTERVAL = 1.0 -- seconds
+T1 = timer.create(REQ_INTERVAL, function()
+   jack.ringbuffer_write(to_proc_rbuf, 3)
+   timer.start(T1)
+end)
+
+function mute_cb(b) -- callback for the 'mute' button
+   local tag = b:value() and 1 or 2 -- mute/unmute
+   jack.ringbuffer_write(to_proc_rbuf, tag)
+end
+
+win = fl.window(340, 180, "thru")
+b = fl.toggle_button(20, 40, 300, 100, "MUTE")
+b:callback(mute_cb)
+b:labelfont(fl.BOLD + fl.ITALIC)
+b:labelsize(36)
+b:labeltype('shadow')
+win:done()
+win:show()
+
+timer.start(T1)
+
+-- GUI thread main loop:
+while fl.wait() do
+
+   repeat
+      local tag, data = jack.ringbuffer_read(from_proc_rbuf)
+      if tag == 4 then -- frames count response
+         win:label("frames: " .. data)
+      end
+   until not tag
+
+   jack.sleep(0) -- just check for errors
+
+end
+
+