Concurrent task inside GUI

steve64

What's the preferred way to run a task concurrent to the GUI main loop with LuaRT ?
So far I tried with something like:

while win.visible do 
  ui.update() 
  --> do something else here
end

but I'm wondering if there is a better way, e.g. coroutines...

Samir

You are right, inside the ui.update() loop is the simplest method to do other things.

You can use some coroutine magic to prevent the program from becoming paralyzed. Look at the binary.wlua example that uses this method to prevent the Window to hang while reading big files.

steve64

Now I have a specific need: run a periodic task every N seconds while the main GUI event loop is processing its stuff as usual. I create a coroutine but If I put a delay inside it, the entire window is affected by delayed events.
Is there any suggestion to manage such periodic subtasks?
The subtask just does few operations that can yield, but how to apply a delay?

Samir

The best way to achieve this is to put your work in the ui.update(delay) loop and provide a delay parameter for the ui.update function, this will process events until the time provided in milliseconds has elapsed.

steve64

I need to build an app that works at the same time as a GUI and as a TCP socket server (handling multiple clients).
Can I do this with LuaRT 1.7.1 ? If so, what's the suggested way to structure the GUI event loop and the server initialization + message loop? I tried something with Task objects but so far no good results.

Samir

Yes you can do it concurrently without blocking the GUI by using a non blocking net.Socket object. Non blocking Socket returns a Task object for recv/send operations.

See examples\net\chatclient.wlua for an implementation example

steve64

Thanks! Looking at the examples, especially net\server.wlua, was great and I'm now able to run my GUI with background multi-client server...

Samir

Yes LuaRT Tasks make it very easy to do concurrency with Lua 😉

steve64

First of all, I'm now able again to install Lua 2.2.0 from standard installer!
Probably some hidden change to the firewall helped.

So I'm back to the tasking issue.
Task support changed a bit recently in LuaRT.
What I need to to is still to run a TCP server task concurrently with the GUI and some other tasks.
My current app does:

...
win:show()
local task = sysutils.watch(sys.currentdir, on_folder_change)

await ui.task
...

and I would like to add a server task. How to declare it? Should be a function with an endless loop?

Samir

Glad to see you finally installed LuaRT successfully !

I see you are using the new preprocessor syntax. What you can do for the TCP server is to use an async function like this :

-- Declare an async factory (makes the function async)
async function HttpTask(port)
    -- Init listening socket
    while true do
         -- wait for incoming connection
         -- process http request and send response
         -- call sleep() to permit other Tasks to run
         sleep()
    end
end

-- Start the Http server
HttpTask(8080)
win:show()
local task = sysutils.watch(sys.currentdir, on_folder_change)

await ui.task

steve64

I tried something like that, but I got this error (it seems 'async' is not liked):

	searcher error: error loading module 'server' from file '.\server.lua':
	.\server.lua:57: syntax error near 'function'

The code in server.lua is:

async function server_action()
  
  while true do
    ...
    sleep(1)
  end
end

Samir

Dont forget to use the line --! luart-extensions at the very first line of each script that use syntax extensions

steve64

I have the first line like that.., but the 'async' error is raised anyway

Samir

How did you load the server.lua file ? using require() ?

steve64

server = require('server')

consider that server.lua is defined as a "module" with a table of functions that is returned at the end

Samir

Requiring lua files with the new syntax works for me... show me the code of both files (or some files that reproduces this)

steve64

test.wlua:

--! luart-extensions

server = require('test_server')

server_action()

test_server.lua:

--! luart-extensions

local net = require 'net'

async function server_action()
  
  while true do
    sleep(1)    
 end

end

Error:

test_main.wlua :3: module 'test_server' not found:
	no field package.preload['test_server']
	
	searcher error: error loading module 'test_server' from file '.\test_server.lua':
	.\test_server.lua:5: syntax error near 'function'

Samir

It works perfectly on my side from the command line.
Maybe you have an old LuaRT version that conflicts with LuaRT 2.2.0 ?
Or maybe this error comes from LuaRT Studio ?

Xaon420

Samir this is what i was fighting, i have not been able to re-produce fully since switching to portable.

im guessing the installer just never overwrote them. the dates say the files are newer but it seems to just not link itself correctly

Im not sure this will help but somthing to note if using the installer on the pre-release Versions of win 11:

in my case windows defender was blocking the files Without notifying at all, but defender was changing the dates itself without an update to the file (metadata was updated).
so the metadata got updated but the contents of the file did not, and lua sees that as a new file either way apparently... and the installer is in the dark but still sees a changed file, resulting in no errors to the user.

from what i could see when i tried updating numerus times; that may be where defender is being an issue after its been fixed in Defender once it never happens again either, i cannot re-produce this issue anymore on win 11; 25h2 (26200.8457).

Oh i will also note i did re-install studio FIRST and after as well, it seemed to have no effect with my issue; even the command line could not run scripts with modules / extensions