[Cuis-dev] Cuis headless

[Juan Vuletich]

Hi Erik!

On 4/21/2020 3:55 PM, Erik Stel via Cuis-dev wrote:
> Hi,
>
> Big kudos to the Cuis community! Up to now I have been a very passive participant (ie reader), but I really like the helpful atmosphere and good discussions.
> I’ve been I’ve been using Cuis next to some other Smalltalk dialects and I really appreciate the philosophy. I am building a learning environment for kids and want to use Cuis for this because of this philosophy.

Nice!

> I have a question regarding headless Cuis:
> Is there a working/standard approach for creating a headless image for Cuis? I would like to run images on a server and therefore do not need the whole GUI part for those images. Removing it from an image is one option, but maybe there is a sort of bootstrap process to create an initial headless image as well.

We don't have a bootstrap process yet. Although it would be something 
really nice to have, nobody has yet given this enough priority to put 
serious effort. Completely removing Morphic is an option, but there are 
others too.

If you will run many images and care about image size, just doing 
`StrikeFont saveSpace.` will save 3Mb. I'm sure it is reasonably easy to 
shave at least another Mb.

If you want to avoid running Morphic, but don't mind having it loaded in 
the image (it might be good to be able to start Morphic if necessary, 
for example for debugging),  then take a look at  
#snapshot:andQuit:embedded:clearAllClassState: . On every image save we 
stop the Morphic process, and create a new one on startup. So, to avoid 
running Morphic at all, you can disable the following lines (haven't 
tried it!)
     UISupervisor spawnNewMorphicProcessFor: (guiRootObject ifNil: [ 
guiRootObject _ guiRootObjectClass newWorld ]).
     Display triggerEvent: #screenSizeChanged.
     self restoreLostChangesIfNecessary.
     clearAllStateFlag ifTrue: [
         UISupervisor whenUIinSafeState: [
             guiRootObject recreateDefaultDesktop ]].

Additionally, take a look at AppLauncher . It is a way to to start 
application specific code at startup. To set up an Application images, 
call #appGlobalName:appSelector, and save the image. This way, your app 
will run on image startup, possibly (if you disabled it as I say above) 
without Morphic.

Alternatively, you can run the VM with command line arguments to run a 
specific doIt that will start your stuff.

> There has been a thread (back in 2016) about a REPL-mechanism using stdio which could be helpful for removing the GUI/head. It did not seem to have lead to a headless image. I have a WebSocket-based REPL and did a short experiment, but before continuing this road I want to check there isn’t a better solution already available.

What we did some time ago is essentially only useful for debugging. The 
reason is that waiting on StdIn blocks the VM, suspending all Smalltalk 
code. Check the comment at StdIOReadStream. A headless image based on 
this would only be useful for running user commands. It would only run 
Smalltalk code for each command you type.

I think your WebSocket based REPL is a good approach, and it would be 
very useful for others. Please consider contributing it to Cuis (under 
MIT license, as usual).

> Any pointers are welcome.
>
> Regards,
> Erik

Cheers,

-- 
Juan Vuletich
www.cuis-smalltalk.org
https://github.com/Cuis-Smalltalk/Cuis-Smalltalk-Dev
https://github.com/jvuletich
https://www.linkedin.com/in/juan-vuletich-75611b3
@JuanVuletich