Archive for smalltalk

SqueakJS changes its world with ThisWebpage

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , , , , , , , , on 28 October 2016 by Craig Latta

a new platform

Since becoming a virtual-machine-based app, Smalltalk has integrated well with other operating systems, providing the illusion of a consistent unified platform. With the ascendancy of JavaScript, the common execution environment provided by web browsers is effectively another host operating system. Smalltalk runs there too now, thanks to Bert Freudenberg’s SqueakJS. So in addition to macOS, Windows, and Linux, we now have the Web host platform.

While all platforms expose some of their functionality to apps through system calls, the Web exposes much more, through its Document Object Model API (DOM). This gives Smalltalk a special opportunity to enable livecoded apps on this platform. It also means that Smalltalk can interoperate more extensively with other Web platform apps, and participate in the ecosystem of JavaScript frameworks, both as a consumer and a producer.

to JavaScript and back

The part of SqueakJS which enables this is its bidirectional JavaScript bridge. This is implemented by class JSObjectProxy, and some special support in the SqueakJS virtual machine. One may set Smalltalk variables to JavaScript objects, send messages to JavaScript objects, and provide Smalltalk block closures as callback functions to JavaScript. One may interact with any JavaScript object in the Web environment. This means we can manipulate DOM objects as any other JavaScript framework would, to create new HTML5 user interfaces and modify existing ones.

In particular, we can embed SqueakJS in a web page, and modify that web page from SqueakJS processes. It would be very useful to have a Smalltalk object model of the host web page. I have created such a thing with the new class ThisWebpage.

reaching out with ThisWebpage

I chose the name of ThisWebpage to be reminiscent of “thisContext”, the traditional Smalltalk pseudo-variable used by an expression to access its method execution context. In a similar way, expressions can use ThisWebpage to access the DOM of the hosting Web environment. One simple example is adding a button:

ThisWebpage
  createButtonLabeled: 'fullscreen'
  evaluating: [Project current fullscreen: true]

Behind the scenes, ThisWebpage is doing this:

(JS document createElement: 'input')
  at: #type
  put: 'button';
  at: #onclick:
  put: [Project current fullscreen: true]

Class JSObjectProxy creates JS, an instance of itself, during installation of the JavaScript bridge. It corresponds to the JavaScript DOM object for the current web browser window, the top of the DOM object graph. By sending createElement:, the expression is invoking one of the DOM methods. The entire set of DOM methods is well-documented online (for example, here’s the documentation for Document.createElement).

So far, ThisWebpage has some basic behavior for adding buttons and frames, and for referring to the document elements in which SqueakJS is embedded. It can also create links and synthesize clicks on them. This is an important ability, which I use in making a Squeak object memory jump from SqueakJS in a web browser to a native Cog virtual machine on the desktop (the subject of tomorrow’s post).

The possibilities here are immense. ThisWebpage is waiting for you to make it do amazing front-end things! Check it out as part of the Context 7 alpha 1 release.

 

Caffeine: live web debugging with SqueakJS

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , , , , , , , , , , , , , , , , on 26 October 2016 by Craig Latta

In February 2015 I spoke about Bert Freudenberg’s SqueakJS at FOSDEM. We were all intrigued with the potential of this system to change both Smalltalk and web programming. This year I’ve had some time to pursue that potential, and the results so far are pretty exciting.

SqueakJS is a Squeak virtual machine implemented with pure JavaScript. It runs in all the web browsers, and features a bi-directional JavaScript bridge. You can invoke JavaScript functions from Smalltalk code, and pass Smalltalk blocks for JavaScript code to invoke as callbacks. This lets Smalltalk programmers take advantage of the myriad JavaScript frameworks available, as well as the extensive APIs exposed by the browsers themselves.

The most familiar built-in browser behavior is for manipulating the structure of rendered webpages (the Document Object Model, or “DOM”). Equally important is behavior for manipulating the operation of the browser itself. The Chrome Debugging Protocol is a set of JavaScript APIs for controlling every aspect of a web browser, over a WebSocket. The developer tools built into the Chrome browser are implemented using these APIs, and it’s likely that other browsers will follow.

Using the JavaScript bridge and the Chrome Debugging Protocol, I have SqueakJS controlling the web browser running it. SqueakJS can get a list of all the browser’s tabs, and control the execution of each tab, just like the built-in devtools can. Now we can use Squeak’s user interface for debugging and building webpages. We can have persistent inspectors on particular DOM elements, rather than having only the REPL console of the built-in tools. We can build DOM structures as Smalltalk object graphs, complete with scripted behavior.

I am also integrating my previous WebDAV work, so that webpages are manifested as virtual filesystems, and can be manipulated with traditional text editors and other file-oriented tools. I call this a metaphorical filesystem. It extends the livecoding ability of Smalltalk and JavaScript to the proverbial “favorite text editor”.

This all comes together in a project I call Caffeine. had fun demoing it at ESUG 2016 in Prague. Video to come…

new website for Black Page Digital

Posted in Appsterdam, consulting, Context, GLASS, music, Naiad, Seaside, Smalltalk, Spoon with tags , , , , , , , , , , , , , , , , on 21 January 2016 by Craig Latta

I wrote a new website for Black Page Digital, my consultancy in Amsterdam and San Francisco. It features a running Squeak Smalltalk that you can use for livecoding. Please check it out, pass it on, and let me know what you think!pano

Context status 2015-01-16

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , , , on 16 January 2015 by Craig Latta

Hoi all–

Context is the umbrella project for Naiad (a distributed module system for all Smalltalks), Spoon (a minimal object memory that provides the starting point for Naiad), and Lightning (a remote-messaging framework which performs live serialization, used by Naiad for moving methods and other objects between systems). I intend for it to be a future release of Squeak, and a launcher and module system for all the other Smalltalks. I’m writing Context apps for cloud computing, web services, and distributed computation.

Commits b7676ba2cc and later of the Context git repo have:

  • Support for installable object memories as git submodule repos.
  • Submodule repos for memories for each of the known Smalltalk dialects, with Naiad support pre-loaded. I’m currently working on the submodules for Squeak and Pharo.
  • A web-browser-based console for launching and managing object memories.
  • A WebDAV-based virtual filesystem that enables Smalltalk to appear as a network-attached storage device, and mappings of the system to that filesystem that make Smalltalk accessible from external text editors (e.g., for editing code, managing processes and object memories).
  • Remote code and process browsers.

There’s a live discussion site and a mailing list. The newsgroup is gmane.comp.lang.smalltalk.squeak.context.

Thanks for checking it out!

Craig

Smalltalk Reflections episode 7: minimalism

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , on 14 January 2015 by Craig Latta

Episode 7 of Smalltalk Reflections is out. The topic is “minimalism”.

new Context active filesystem layout

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , , , , , , , , , on 22 December 2014 by Craig Latta

When you start the Context app, you start a webserver that provides a “console”. Viewed through a host web browser, the console describes what Context is, and enables control of the memories it knows about. The webserver also provides an active filesystem via WebDAV. This lets you interact with the console from a host terminal or text editor, in a manner reminiscent of a Unix procfs (content is generated live-on-read). Here’s a typical filesystem layout, and what you can do with it:

/
   README.html

   memories
      3EAD9A45-F65F-445F-89C1-4CA0A9D5C2F8
         session
            state
            performance
         classes
            Object
               metaclass
                  (etc.)
               methods
                  at:
                  (etc.)
               slots
                  all
                     (etc.)
                  inherited
                     (etc.)
                  local
                     (etc.)
               subclasses
                  (etc.)
         processes
            the idle process
               ProcessorScheduler class>>idleProcess
                  source
                  variables
                     thisContext
                     self
                     (etc.)
               [] in ProcessorScheduler class>>resume
               (etc.)
            (etc.)
         workspaces
            hello world
               source
               result
                  7

The README.html file is what the console displays initially. It has a directory sibling memories, containing a subdirectory for each memory the console knows about. Each memory is named by its UUID. In the session directory, there are files which give information about a memory. The state file looks like this:

# This memory is running. You can send it one of the following
# commands: snapshot, suspend, or stop. To do so, write this file with
# the desired command as the first word after this comment. Subsequent
# comments give other information about this memory, like host
# resource usage and virtual machine plugins loaded.

(type command here)

# host resource usage
#
# bytes used:        437,598
# bytes available: 1,328,467

# virtual machine plugins loaded
#
# FlowPlugin

In this way, a file in the active filesystem provides access to a read-eval-print loop (REPL). The user gives input to the console by writing the file; the console gives feedback to the user (including documentation) by generating appropriate content when the file is read.

The performance file looks like this:

# instructions per second: 382,184,269
# messages per second:      12,355,810

This gives general profiling information about the virtual machine.

The subdirectories of the classes directory correspond to the memory’s classes. Each one has subdirectories for its methods, subclasses, and metaclass. The methods directory has a file for each method of the class. This provides the ability to browse and change source code in the memory from a host text editor.

The processes directory has a subdirectory for each running process in the memory. Each process directory has a subdirectory for each context of that process. Each context directory has a REPL file for the source code of the context’s method, and a subdirectory for the context’s variables (including the context itself), each of which is an inspector in the form of a REPL file. In this way, much of the functionality of the traditional Smalltalk debugger is accessible from a host text editor.

Finally, the workspaces directory has subdirectories for multiple “workspaces”, where one may evaluate expressions and interact with their result objects. Each workspace has a source file, another REPL file which contains instructions, the expression to evaluate, and, on the next read after write, the textual form of the result. In addition, in a result directory, is a file named for the textual form of the result, containing a REPL inspector for that result object.

These tools are useful both for newcomers to live object systems who are more comfortable with a text editor than the Smalltalk GUI, and for those accessing systems running in the cloud, for which traditional GUI access might be awkward or prohibitive.

Smalltalk Reflections episode three is up

Posted in Appsterdam, consulting, Context, music, Smalltalk, Spoon with tags , , , , , , , , , , , , , , on 16 December 2014 by Craig Latta

Check it out!

Context release 4 alpha 1

Posted in Appsterdam, consulting, Context, Naiad, Smalltalk, Spoon with tags , , , , , , on 9 December 2014 by Craig Latta

Context 4 alpha 1 is released. This one fixes loading errors in the welcome page, supports remote debugging and process browsing, and makes Naiad and remote messaging support available as Monticello packages. Thanks in advance for reporting bugs!

a most useful virtual machine debugging aid: simulated objects

Posted in Appsterdam, consulting, Context, Smalltalk, Spoon with tags , , , , , , on 2 December 2014 by Craig Latta

Squeak’s virtual machine simulator is extremely useful for debugging. You can use it to inspect and change objects “while time is stopped”, between the execution of individual virtual machine instructions. Traditionally, though, it takes an address-based view of objects. There are several useful utility methods which, given an object address, will print useful information to the Transcript. Wouldn’t it be nicer, though, if you could use normal inspectors to look through the fields of the objects in a simulated virtual machine’s object memory?

I created simulated objects for this purpose. They are instances of a SimulatedObject class; each one has an interpreter and an address. They can print useful information about themselves, like the interpreter can, but they can also modify themselves and interact with each other, changing the interpreter’s object memory appropriately. Are you wondering about the instructions of a compiled method? Would you like to make a few choice modifications to those instructions? A simulated object for that method’s address will help you.

Simulated objects play nicely with Squeak’s object inspectors, and, more importantly, with its object explorers. You feel like you’re inspecting normal objects, except that you can’t send normal messages to them. Or can you? I’m pondering this. It might be useful, for example, to terminate a process in a simulated interpreter’s object memory, without having to do it in another process. Time is stopped, but perhaps you could queue up messages to send when it starts again, through a collaboration between simulated objects and a coordinating object in the memory they describe.

I’ve been using simulated objects recently to chase references with the absolute assurance that I won’t be creating new ones. They’re very useful for debugging virtual machine primitives. Sometimes, when I’m debugging a headless system with a broken remote messaging system, it’s the only user interface I have for inspecting things. And it’s sure a lot nicer than inspecting things in a C debugger.

What will you do with them?

the Smalltalk Reflections podcast, episode one: a tribute to James Robertson

Posted in Appsterdam, consulting, Smalltalk, Spoon with tags , , on 2 December 2014 by Craig Latta

We did it! On James Robertson’s birthday, David Buck and I released episode one of “Smalltalk Reflections”, a podcast about Smalltalk. Our first episode is a tribute to James, who started the previous incarnation of the show. It’s hosted by David and myself, and features remembrances from several friends and co-workers, as well as a few choice words from the man himself. I edited it, and wrote the theme music. Enjoy!

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