Archive for the Spoon Category

The Big Shake-Out

Posted in Appsterdam, Caffeine, consulting, Context, livecoding, Naiad, Smalltalk, Spoon, SqueakJS with tags , , , , , , , , , , , , , , , , , on 25 March 2019 by Craig Latta
Golden Retriever shaking off water

Some of those methods were there for a very long time!

I have adapted the minimization technique from the Naiad module system to Caffeine, my integration of OpenSmalltalk with the Web and Node platforms. Now, from a client Squeak, Pharo, or Cuis system in a web browser, I can make an EditHistory connection to a history server Smalltalk system, remove via garbage collection every method not run since the client was started, and imprint needed methods from the server as the client continues to run.

This is a garbage collection technique that I had previously called “Dissolve”, but I think the details are easier to explain with a different metaphor: “shaking” loose and removing everything which isn’t attached to the system through usage. This is a form of dynamic dead code elimination. The technique has two phases: “fusing” methods that must not be removed, and “shaking” loose all the others, removing them. This has a cascading effect, as the literals of removed methods without additional references are also removed, and further objects without references are removed as well.

After unfused methods and their associated objects are removed, the subsystems that provided them are effectively unloaded. For the system to use that functionality again, the methods must be reloaded. This is possible using the Naiad module system. By connecting a client system to a history server before shaking, the client can reload missing methods from the server as they are needed. For example, if the Morphic UI subsystem is shaken away, and the user then attempts to use the UI, the parts of Morphic needed by the user’s interactions are reloaded as needed.

This technology is useful for delineating subsystems that were created without regard to modularity, and creating deployable modules for them. It’s also useful for creating minimal systems suited to a specific purpose. You can fuse all the methods run by the unit tests for an app, and shake away all the others, while retaining the ability to debug and extend the system.

how it works

Whether a method is fused or not is part of the state of the virtual machine running the system, and is reset when the virtual machine starts. On system resumption, no method is fused. Each method can be told to fuse itself manually, through a primitive interface. Otherwise, methods are fused by the virtual machine as they are run. A class called Shaker knows which methods in a typical system are essential for operation. A Shaker instance can ensure those methods are fused, then shake the system.

Shaking itself invokes a variant of the normal OpenSmalltalk garbage collector. It replaces each unfused method with a special method which, when run, knows how to install the original method from a connected history server. In effect, all unfused methods are replaced by a single method.

Reinstallation of a method uses Naiad behavior history metadata, obtained by remote messaging with a history server, to reconstruct the method and put it in the proper method dictionary. The process creates any necessary prerequisites, such as classes and shared pools. No compiler is needed, because methods are constructed from previously-generated instructions; source code is merely an optional annotation.

the benefits of livecoding all the way down

I developed the virtual machine support for this feature with Bert Freudenberg‘s SqueakJS virtual machine, making heavy use of the JavaScript debugger in a web browser. I was struck by how much faster this sort of work is with a completely livecoded environment, rather than the C-based environment in which we usually develop the virtual machine. It’s similar to the power of Squeak’s virtual machine simulator. The tools, living in JavaScript, aren’t as powerful as Smalltalk-based ones, but they operate on the final Squeak virtual machine, rather than a simulation that runs much more slowly. Rebuilding the virtual machine amounts to reloading the web page in which it runs, and takes a few seconds, rather than the ordeal of a C-based build.

Much of the work here involved trial and error. How does Shaker know which methods are essential for system operation? I found out directly, by seeing where the system broke after being shaken. One can deduce some of the answer; for example, it’s obvious that the methods used by method contexts of current processes should be fused. Most of the essential methods yet to run, however, are not obvious. It was only because I had an interactive virtual machine development environment that it was feasible to restart the system and modify the virtual machine as many times as I needed (many, many times!), in a reasonable timeframe. Being able to tweak the virtual machine in real time from Smalltalk was also indispensable for debugging and feature development.

I want to thank Bert again for his work on SqueakJS. Also, many thanks to Dan Ingalls and the rest of the Lively team for creating the environment in which SqueakJS was originally built.

release schedule

I’m preparing Shaker for the next seasonal release of Caffeine, on the first 2019 solstice, 21 June 2019. I’ll make the virtual machine changes available for all OpenSmalltalk host platforms, in addition to the Web and Node platforms that Caffeine uses via the SqueakJS virtual machine. There may be alpha and beta releases before then.

If this technology sounds interesting to you, please let me know. I’m interested in use cases for testing. Thanks!

livecoding VueJS with Caffeine

Posted in Appsterdam, Caffeine, consulting, Context, Smalltalk, Spoon, SqueakJS with tags , , , , , , , on 30 August 2018 by Craig Latta

Vue component

Livecoding Vue.js with Caffeine: using a self-contained third-party Vue component compiled live from the web, no offline build step.

a tour of Caffeine

Posted in Appsterdam, consulting, Context, Smalltalk, Spoon, SqueakJS with tags , , , , , , , , , , , , , on 27 August 2018 by Craig Latta

https://player.vimeo.com/video/286872152

Here’s a tour of the slides from a Caffeine talk I’m going to give at ESUG 2018. I hope to see you there!

retrofitting Squeak Morphic for the web

Posted in Appsterdam, consulting, Context, Smalltalk, Spoon, SqueakJS with tags , , , , , , , , on 30 June 2017 by Craig Latta

Google ChromeScreenSnapz022

Last time, we explored a way to improve SqueakJS UI responsiveness by replacing Squeak Morphic entirely, with morphic.js. Now let’s look at a technique that reuses all the Squeak Morphic code we already have.

many worlds, many canvases

Traditionally, Squeak Morphic has a single “world” where morphs draw themselves. To be a coherent GUI, Morphic must provide all the top-level effects we’ve come to expect, like dragging windows and redrawing them in their new positions, and redrawing occluded windows when they are brought to the top. Today, this comes at an acceptable but noticeable cost. Until WebAssembly changes the equation again, we want to do all we can to shift UI work from Squeak Morphic to the HTML5 environment hosting it. This will also make the experience of using SqueakJS components more consistent with that of the other elements on the page.

Just as we created an HTML5 canvas for morphic.js to use in the last post, we can do so for individual morphs. This means we’ll need a new Canvas subclass, called HTML5FormCanvas:

Object
  ...
    Canvas
       FormCanvas
         HTML5FormCanvas

An HTML5FormCanvas draws onto a Form, as instances of its parent class do, but instead of flushing damage rectangle from the Form onto the Display, it flushes them to an HTML5 canvas. This is enabled by a primitive I added to the SqueakJS virtual machine, which reuses the normal canvas drawing code path.

Accompanying HTML5FormCanvas are new subclasses of PasteUpMorph and WorldState:

Object
  Morph
    ...
      PasteUpMorph
        HTML5PasteUpMorph

Object
  WorldState
    HTML5WorldState

HTML5PasteUpMorph provides a message interface for other Smalltalk objects to create HTML5 worlds, and access the HMTL5FormCanvas of each world and the underlying HTML5 canvas DOM element. An HTML5WorldState works on behalf of an HTML5PasteUpMorph, to establish event handlers for the HTML5 canvas (such as for keyboard and mouse events).

HTML5 Morphic in action

You don’t need to know all of that just to create an HTML5 Morphic world. You only need to know about HTML5PasteUpMorph. In particular, (HTML5PasteUpMorph class)>>newWorld. All of the traditional Squeak Morphic tools can use HTML5PasteUpMorph as a drop-in replacement for the usual PasteUpMorph class.

There are two examples of single-window Morphic worlds in the current Caffeine release, for a workspace and classes browser. I consider these two tools to be the “hello world” exercise for UI framework experimentation, since you can use them to implement all the other tools.

We get an immediate benefit from the web browser handling window movement and clipping for us, with opaque window moves rendering at 60+ frames per second. We can also interleave Squeak Morphic windows with other DOM elements on the page, which enables a more natural workflow when creating hybrid webpages. We can also style our Squeak Morphic windows with CSS, as we would any other DOM element, since as far as the web browser is concerned they are just HTML5 canvases. This makes effects like the rounded corners and window buttons trays that Caffeine uses very easy.

Now, we have flexible access to the traditional Morphic tools while we progress with adapting them to new worlds like morphic.js. What shall we build next?

Pharo comes to Caffeine and SqueakJS

Posted in Appsterdam, consulting, Context, GLASS, Naiad, Seaside, Smalltalk, Spoon, SqueakJS with tags , , , , , , , , , on 29 June 2017 by Craig Latta

Google ChromeScreenSnapz025

The Caffeine web livecoding project has added Pharo to the list of Smalltalk distributions it runs with SqueakJS. Bert Freudenberg and I spent some time getting SqueakJS to run Pharo at ESUG 2016 in Prague last summer, and it mostly worked. I think Bert got a lot further since then, because now there are just a few Pharo primitives that need implementing. All I’ve had to do so far this time is a minor fix to the input event loop and add the JavaScript bridge. The bridge now works from Pharo, and it’s the first time I’ve seen that.

Next steps include getting the Tether remote messaging protocol and Snowglobe app streaming working between Pharo and Squeak, all running in SqueakJS. Of course, I’d like to see fluid code-sharing of all kinds between Squeak, Pharo, and all the other Smalltalk implementations.

So, let the bugfixing begin! :)  You can run it at https://caffeine.js.org/pharo/. Please do get in touch if you find and fix things. Thanks!

a faster Morphic with morphic.js

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon, SqueakJS with tags , , , , , , , , , , on 28 June 2017 by Craig Latta

Google ChromeScreenSnapz017

Caffeine is powered by SqueakJS. The performance of SqueakJS is amazingly good, thanks in large part to its dynamic translation of Smalltalk compiled methods to JavaScript functions (which are in turn translated to machine code by your web browser’s JS engine). In the HTML5 environment where SqueakJS finds itself, there are several other tactics we can use to further improve user interface performance.

Delegate!

In a useful twist of fate, SqueakJS emerges into a GUI ecosystem descended from Smalltalk, now brimming with JavaScript frameworks to which SqueakJS can delegate much of its work. To make Caffeine an attractive environment for live exploration, I’m addressing each distraction I see.

The most prominent one is user interface responsiveness. SqueakJS is quite usable, even with large object memories, but its Morphic UI hasn’t reached the level of snappiness that we expect from today’s web apps. Squeak is a virtual machine, cranking away to support what is essentially an entire operating system, with a process scheduler, window system, compiler, and many other facilities. Since, with SqueakJS, that OS has access to a multitude of similar behavior in the JavaScript world, we should take advantage.

Of course, the UI design goals of the web are different than those of other operating systems. Today’s web apps are still firmly rooted in the web’s original “page” metaphor. “Single Page Applications” that scroll down for meters are the norm. While there are many frameworks for building SPAs, support for open-ended GUIs is uncommon. There are a few, though; one very good one is morphic.js.

morphic.js

Morphic.js is the work of Jens Mönig, and part of the Snap! project at UC Berkeley, a Scratch-like environment which teaches advanced computer science concepts. It’s a standalone JavaScript implementation of the Morphic UI framework. By using morphic.js, Squeak can save its cycles for other things, interacting with it only when necessary.

To use morphic.js in Caffeine, we need to give morphic.js an HTML5 canvas for drawing. The Webpage class can create new DOM elements, and use jQuery UI to give them effects like dragging and rotation. With one line we create a draggable canvas with window decorations:

canvas := Webpage createWindowOfKind: 'MorphicJS'

Now, after loading morphic.js, we can create a morphic.js WorldMorph object that uses the canvas:

world := (JS top at: #WorldMorph) newWithParameters: {canvas. false}

Finally, we need to create a rendering loop that regularly gets the world to draw itself on the canvas:

(JS top)
  at: #world
  put: world;
  at: #morphicJSRenderingLoop
  put: (
    (JS Function) new: '
      requestAnimationFrame(morphicJSRenderingLoop)
      world.doOneCycle()').

JS top morphicJSRenderingLoop

Now we have an empty morphic.js world to play with. The first thing to know about morphic.js is that you can get a world menu by control-clicking:

Google ChromeScreenSnapz018

Things are a lot more interesting if you choose development mode:

Google ChromeScreenSnapz019.png

Take some time to play around with the world menu, creating some morphs and modifying them. Note that you can also control-click on morphs to get morph-specific menus, and that you can inspect any morph.

Google ChromeScreenSnapz020.png

Also notice that this user interface is noticeably snappier than the current SqueakJS Morphic. MorphicJS isn’t trying to do all of the OS-level stuff that Squeak does, it’s just animating morphs, using a rendering loop that is runs as machine code in your web browser’s JavaScript engine.

Smalltalk tools in another world, with Hex

The inspector gives us an example of a useful morphic.js tool. Since we can pass Smalltalk blocks to JavaScript as callback functions, we have two-way communication between Smalltalk and JavaScript, and we can build morphic.js tools that mimic the traditional Squeak tools.

I’ve built two such tools so far, a workspace and a classes browser. You can try them out with these expressions:

HexMorphicJSWorkspace open.
HexMorphicJSClassesBrowser open

“Hex” refers to a user interface framework I wrote called Hex, which aggregates several JavaScript UI frameworks. HexMorphicJSWorkspace and HexMorphicJSClassesBrowser are subclasses of HexMorphicJSWindow. Each instance of every subclass of HexMorphicJSWindow can be used either as a standalone morphic.js window, or as a component in a more complex window. This is the case with these first two tools; a HexMorphicJSClassesBrowser uses a HexMorphicJSWorkspace as a pane for live code evaluation, and you can also use a HexMorphicJSWorkspace by itself as a workspace.

With a small amount of work, we get much snappier versions of the traditional Smalltalk tools. When using them, SqueakJS only has to do work when the tools request information from them. For example, when a workspace wants to print the result of evaluating some Smalltalk code, it asks SqueakJS to compile and evaluate it.

coming up…

It would be a shame not to reuse all the UI construction effort that went into the original Squeak Morphic tools, though. What if we were to put each Morphic window onto its own canvas, so that SqueakJS didn’t have to support moving windows, clipping and so on? Perhaps just doing that would yield a performance improvement. I’ll write about that next time.

Backend Caffeine with Node.js and Tweetcoding

Posted in Appsterdam, consulting, Context, Smalltalk, Spoon, SqueakJS with tags , , , , , , on 27 June 2017 by Craig Latta

tweetcodingWe’ve seen a couple of examples of frontend Caffeine development, using jQuery UI and voxel.js. Let’s look at something on the backend, using Node.js and something I like to call tweetcoding.

Social Livecoding

Livecoding means having all the capabilities of your development environment while your system is live. Runtime is all the time. Smalltalk programmers have always enjoyed this way of working. It is particularly effective in domains such as music performance, where the ability to make changes while your system is running is critical, both for fixing bugs and for artistic expression. One of my artistic goals with musical livecoding (writing code that makes live music for an audience) is audience accessibility. I want the audience to have some understanding of what’s going on in my code, even if they aren’t coders (yet).

Another aspect I like to incorporate is audience participation. If the audience actually does understand what I’m doing in my code, why not let them join in? Social media has become a ubiquitous communication platform; billions of people are using it with prose and pictures. I think the time has come to use it with live code as well. Nearly everyone in the audience has a powerful computer with social media access in a pocket. We can all livecode together.

Let’s Do This

We need three things to make this happen: a way for people to submit code, something that listens for that code and evaluates it, and a shared artifact everyone can see that shows the code’s effects. I like Twitter as a coding medium, for its minimalism. It also has a culture of hashtag use, and a streaming API, which make listening for code straightforward. For the shared artifact, we can use something viewed with Caffeine in a web browser.

For our first example, let’s use something simple for our coding domain, like turtle graphics. A person can tweet instructions to a turtle which draws on a square piece of paper, 100 units on a side. There are four commands:

  • color, for the turtle to change its pen for one of the given color
  • down, for the turtle to put its pen down on the paper
  • rotate, for the turtle to change direction
  • move, for the turtle to move some distance
  • up, for the turtle to take its pen up from the paper

We’ll say that that the turtle can be identified by some ID, and is initially at the center of the paper. A tweetcoded instruction for the turtle might look like:

FranzScreenSnapz002

Tweetcoding tweets start with the #tweetcoding hashtag, so people seeing one for the first time can look at others with that hashtag, to see what it’s about. This is followed by hashtags identifying our turtle-graphics protocol, and the turtle we’re using. We end the tweet with a drawing instruction, using our instruction set above.

Livecoding NodeJS

To detect these tweets, we’ll use the Twitter streaming API from Node.js. In the spirit of livecoding, we won’t use an application-specific Node.js module for this directly, but instead inject JavaScript code live into a Node.js instance, from Caffeine in a web browser. I’ve written a node-livecode Node.js module which takes commands over a websocket. It starts with three instructions:

  • require, for loading another Node.js module into itself with npm
  • add instruction, for adding an instruction to itself
  • eval, for evaluating JavaScript code

You can see the implementation at GitHub. It can use SSL to keep injected code secure in transit, so you may want to set up a certificate for your server with Let’s Encrypt. Also note that it exposes the listening server as a global variable, so that you can use it in your injected code.

Once we have node-livecode on a server listening for commands, we can inject code into it from Caffeine. First we’ll inject code to listen to #tweetcoding tweets from Twitter:

| websocket |

websocket := JS WebSocket newWithParameters: {'wss://yourserver:port'}.
JS top at: #websocket put:websocket.

websocket
  at: #onmessage
  put: [:message |
    Transcript
      cr;
      nextPutAll: message data asString;
      endEntry];
  at: #onopen
  put: (
    (JS Function) new: '
      window.top.ws.send(JSON.stringify({
        credential: ''shared secret'',
        verb: ''require'',
        parameters: {
          package: ''node-tweet-stream'',
          then: ''
            var Twitter = require(''node-tweet-stream'')
              , twitter = new Twitter({
                  consumer_key: '''',
                  consumer_secret: '''',
                  token: '''',
                  token_secret: ''''})

            twitter.on(
              ''tweet'',
              function (tweet) {
                if (instructions[''broadcast'']) {
                  instructions[''broadcast''](tweet)}}

            twitter.on(
              ''error'',
              function (err) {
                console.log(''error in uploaded code'')})

            twitter.track(''#tweetcoding #turtlegraphics '')''}})))

The example above uses handwritten JavaScript code, but we could also use Caffeine’s JavaScript code generation to produce it from Smalltalk code (see the method MethodNode>>javaScript for the implementation). Also, since we’ll be injecting several things, it would be nice to have a more compact way of writing it. Let’s move that workspace code to a class.

Next we’ll inject a new instruction, for initializing a set of drawing-command listeners:

| client |

client := (
  NodeJSLivecodingClient
    at: 'wss://yourserver:port'
    withCredential: 'shared secret').

client
  addInstruction: 'initialize listeners'
  from: '
    function () {
      global.listeners = []
      return ''initialized listeners''}'

To round out our tweetcoding protocol, we’ll add instructions for accepting listeners, and broadcasting tweets detected from Twitter:

client
  addInstruction: 'start listening'
  from: '
    function () {
      listeners.push(this)
      return ''added listener''}'
  addInstruction: 'stop listening'
  from: '
    function () {
      listeners.splice(listeners.indexOf(this), 1);
      return ''removed listener''}'
  addInstruction: 'broadcast'
  from: '
    function (payload) {
      listeners.forEach(
        function (listener) {listener.send(payload)})
      return ''broadcasted''}'

Putting It All Together

Now we can write other Smalltalk classes which subscribe to tracked tweets from the server, and collaborate to do something interesting with them in the web browser. I’ve implemented the following classes:

Object
  NodeJSLivecodingClient
    TweetcodingClient
      TurtleGraphicsTweetcodingClient
  Turtle
  Tweet

Instances of NodeJSLivecodingClient can inject code into a node-livecoding server, and invoke code added by other clients. Instances of TweetcodingClient can also set tracking filters for tweets, and process matching tweets when they occur. Instances of TurtleGraphicsTweetcodingClient can also control Turtles, which can draw on canvases in Caffeine windows. Instances of Tweet bundle up the text and metadata of tweets. For the implementation, clear your browser’s cache for caffeine.js.org (including IndexedDB), and reload https://caffeine.js.org/.

I’m also running a node-livecoding server injected with turtle-graphics tweetcoding code, at wss://frankfurt.demo.blackpagedigital.com:8087/. Once you get connected (and tweets are flowing), you might see something like this:

Google ChromeScreenSnapz014

After developing this system, I’ve realized I don’t really need to run SqueakJS from within NodeJS; just injecting code into it is fine. There are many possibilities here. :)

Have fun, and please let me know what you think!

 

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