Isolates: how to work with multithreading in Dart

Here we are again with another topic about Dart language, first of all I’d like to start this article with an off-topic.

I joined to FluentJS in San Francisco few weeks ago, an event organize by O’Reilly focus on Javascript development, and I saw a Dart language session, the most amazing thing I’ve seen was the passion behind this project, trust me that it’s not easy today find people that believe in that way in something, Seth Ladd, the speaker and team member of Dart, gave us a great technical introduction to Dart but gave us something more, he transmitted us all his passion on Dart, really amazing!

After this quick off-topic, let’s go ahead with Isolates tutorial.

First of all, Isolates is the Dart way to work with threads and allow to take advantage of your multicore computer, but what is multithreading and when we should use it.

Multithreading

This is a good definition for me: “Multithreading is the ability of a CPU to execute several threads of execution apparently at the same time. CPUs are very fast at executing instructions. Modern PCs can execute nearly a billion instructions every second. Instead of running the same program for one second, the CPU will run one program for perhaps a few hundred microseconds then switch to another and run it for a short while and so on.” (source: cplus.about.com)

And when should we use threads?!

Basically every time you need to speed up an intensive process, for example when you have an heavy process like unzip of a big file or a for cycle with a lots of elements, you should use the threads to don’t freeze the main one and allow your user to work the interface without any issues.

Dart adds this capability in 2 different ways because, as you know you, it can export a project for Dart VM or in Javascript, with Dartium we can use the power of CPUs of your multicore computer and create different threads in each CPU where will be executed your code, in Javascript, Dart converts Isolates in web workers.

Before starting with code I decide to show in a chart how we’ll work with isolates, so basically first of all we create 2 isolates launched from the main isolate and then we pass the final informations elaborated in different isolates to the main one.

Isolates Schema

Last note, when you work with isolate you can have a sender and a receiver, so in the main isolate (launched by the application) you have a port object where you can listen when you receive informations from other isolates and you can pass the sendport object where you can send message to other isolates.

port.receive((data, SendPort replyTo){
replyTo.send("something");
});

Another important thing to remember when you work with isolates, if you need to receive messages from other isolates, is that you always set  the receiver in the main isolate, or you will n0t receive any message from other isolates because the execution of your program is not waiting for any reply without a receiver set.

I created a small project around this topic to show the powerful of the isolates, take a look here:

As you can see when I click on MONO link my CSS animation stops until to the heavy iteration is finished instead when I click on ISOLATE  link everything works well because all the iterations are accomplished in different isolates so the main one could go ahead with own job.

When you want to launch an isolate you have to call the spawnfunction method and pass the main isolate sender:

var isolate = spawnFunction(bigForCycle);
isolate.send("data", port.toSendPort());

After that you can operate with your isolate in this way for example:

void bigForCycle(){
 
 port.receive((data, SendPort replyTo){
 var count;
 for(var i = 0; i < FINAL_AMOUNT; i++){
   count = i;
 }
 replyTo.send(count);
});

}

It’s finally important remember to close isolates after received the message so when they have finished to accomplish own function, to do that you have only to call the close method in the main isolate and it will not receive any other information from other isolates.
In my example I launched 2 isolates to accomplish the task, so I created a counter variables to store how many reply the main isolate received, after received all replies I can close the communication with other isolates:

port.receive((data, SendPort replyTo){
 
 counterIsolate++;
 end = new DateTime.now();
 
 if(counterIsolate == 2){
 var finalTime = end.difference(start).toString();
 myH1.appendHtml("isolate total time: <b>$finalTime</b><br/>");
 // if you want to close isolates you have to use the line below
 port.close();
 
 }

 });

The most interesting thing is that you can accomplish the same task in 2 different way, the first one, as I did in my example, with inline isolates and the second one is loading code dinamically from external Dart files.
To take a look to the second one I suggest to read this post made by Seth Ladd.

Isolate technique is very useful also when you are working on a serverside project with Dart because it could optimize some intensive process that you have to achieve during your project.

I’ve just opened a github repository with all Dart examples that I’m working on, so feel free to check out at this link.
Enjoy!

A long weekend with Tizen, CreateJS and JQuery Mobile

Let’s start from the end of my weekend, this is what I’ve just finished:

And now it’s time to explain what there is behind.

What you have just seen is a PoC (Proof of Concept) for an application that I’ve in mind, it allowed me to study, test and having fun with different technologies, in this post I’d like to share what I’ve learnt in less than 24 hours.
I worked with different technologies as the post title suggest, I was really curios to see how I can create good application UI on Tizen OS and understand more about its limits (if there were of course) and performances.
At the beginning, I worked on the 2.5D animation where I had to scale, skew and rotate any images chosen by the user from the Gallery application.
When I started this part I tried immediately the CSS3 transitions, I thought: “They are new, so probably they care about performances on mobile!”, so after 3 hours to play with CSS3 transitions and trying to have a smooth animation on Tizen, I decide to move on Canvas!
CSS3 transitions are very good for web and desktop, but for mobile when you start to do many heavy animations they really suck, in this Tizen device (it has an hardware similar to Galaxy S3) that is so powerful everything has to work well and with them I can’t achieve my idea.

So I moved to Canvas, but I thought to find something that could help me during my “coding time” and that it feels me more comfortable so I remembered that I’ve used long time ago CreateJS for some test and in this case it helps me a lot.
When you work with CreateJS, more or less you are working with Actionscript with some small changes, for any Actionscript developer it should be a good start to move on Javascript, but there are many other options as Dart or Typescript for example that are good enough for any developer that is looking for something more than Javascript (my 2 cents).
But in this case CreateJS  helps me a lot because is highly focused on Canvas development so definitely what I was looking for.
I haven’t any trouble with this library on Tizen, the performance are so good as you have seen on the video and I didn’t write so much code, my Javascript file for the whole app is less than 260 lines, not a lot I guess.

After that I moved on and I start to work with Tizen web APIs to get images from the Gallery application.
In this case the Tizen developer forum and the online guide help me so much, in fact I found a working example in the forum that I had only to customise for my PoC.
The big issue that I found here is if I want to select more than one image, working with Gallery instance, I couldn’t do that or maybe I couldn’t find a way to do that, so I decided to create a quick picker (at the beginning of my application) to allow me to choose more than one image to the time.
To do that I had to work with filesystem APIs instead of the Gallery one, but in a while I had done everything, this is the code to retrieve all images from Image folder of Tizen OS, but you can use to retrieve any kind of files on Tizen OS:

function onResolveError() {
    console.log("error retrieve data");
}
function onsuccess(files) {
    for (var i = 0; i < files.length; i++) {
        console.log("File name is " + files[i].name + " and URL is " + files[i].toURI()); 
    }
}
function onResolveSuccess(dir) {
    dir.listFiles(onsuccess, onResolveError);
}
function openImages() {
    tizen.filesystem.resolve('images', onResolveSuccess, onResolveError, 'w'); 
}

After that I spend few hours to skin my app and get the right look and feel I had in mind with CSS and JQuery mobile and to create this post with the video.
A quick recap of my last experience:

  • on Tizen if you need to improve performances try to work with Canvas instead of CSS transitions
  • when you have to retrieve files (images, video or whatever) remember to set the right privileges on config.xml and then add the code you can find above
  • CreateJS is a really good library if you want to work with Canvas efficiently and without wasting your time
  • CreateJS has a good community and if you have a problem you can find a lot of solutions and suggestions
  • CreateJS is familiar for any Actionscript 3 developer

That’s it!
Ah, if you are asking if I changed my “religion”? Don’t worry, soon you’ll have news about Flash Platform in this blog, but sometimes I want to experiment new things.

Dart: elements iteration and CSS manipulation

In my exploration of Dart I’m trying to work in some easy examples that could help me to understand how to accomplish some tasks with this technology.
In this example I tried to understand better how iteration of elements works in Dart, how to create a layout with custom elements (more or less the same topic of a custom item renderer in Flex for example) and finally how to create some animations with CSS3 at runtime.

To accomplish those topics I decided to create a responsive image gallery that works on smartphone, tablet and web too.

image gallery with dart

Responsive image gallery

Iteration

Dart gives few opportunities to iterate trough elements:

  • with Dart language (a classic for cycle)
  • with an HTML template
  • with elements composed by an HTML template and some dart code to cover the business logic of the final element

I jump directly to the second and third method, the first one is quite easy for any developer 😉
In my sample I decide to use a simple HTML template, so basically you can define inside your html a tag <template/> that will allow you to repeat the HTML inside this tag associating it to a list for example, I give you a quick sample:

 <div id="imageCont" class="wrap">
      <template iterate="data in results">
        <div class="image">
          <img id="img_{{data[0]}}" class="faded" src={{data[1]}} width="320" height="240" on-click="onClick($event)" on-mouse-out="onOut($event)" on-mouse-over="onOver($event)" on-load="fadeIn($event)"/>
          <img id="zoom_{{data[0]}}" src="images/zoom.png" class="zoom"/>
          <h2><span>{{data[2]}}</span></h2>
         </div>
      </template>
    </div>

First of all take a look on how I can iterate this part of code; I add a simple iterate attribute associated to a list object (called results in my example) added in my dart file as a public variable.
The list could be a plain list or a list of objects, in this last case you can create multiple iteration item inside the template cycling trough your objects in the same way you have just seen.
I can substitute my data variable with any other name and I don’t need to define in my dart file, as you can see I can also define some variables inside the template getting values from my list object with this syntax: {{data[0]}} (or {{data[“value”]}} it’s the same, depends how you have create the list object).
If you need, you can also made your source variables bindable and any time you’ll change the values of your list, also the view will change the number of elements or the values showed in the HTML page.

Finally when you need to create an iterable object with a complex business logic and you want to separate from the original HTML file you can do that creating a Web Components, but in this case I suggest you to take a look to the Dart language guide that explain very well how to achieve this topic.

Modifying CSS with Dart

Another interesting topic is how to change, add or remove css styles to my DOM objects.
In Dart is so easy like any other javascript library, so basically any DOM element in Dart has a property called “classes” with its associated method add and remove, so when you want to change your CSS class with another one, you have, if you have any classes already associated to the element, remove the old class and then add the new one:

var myDomObj = query("#idObject");
myDomObj.classes.remove("class-to-remove");
myDomObj.classes.add("class-to-add");

You can also style any single property directly with “style” property and set them directly in this easy way:

var myDomObj = query("#idObject");
myDomObj.style
             ..color = "0xFFF"
             ..fontSize = "15px";

As you can see working with CSS in Dart is relative simple, if you want to take a look to the whole project feel free to download it.

Another cool thing that is so useful when you work with mobile apps or websites is to test quickly and frequently your content on the devices, so with DartIDE (you can find it downloading Dart SDK) you can easily test your content trough a web server that starts any time you are testing your app into the browser.
It’s so interesting because you save a lot of time in this way!

I’m trying to figure out right now an hypothetical workflow to create web app, web sites or any other thing with Dart and HTML5.
I believe that use Dart in combination with Edge Reflow could be the best way to create responsive application for any kind of devices, but we have to wait until the release of Edge Reflow (17th June) to know if my supposition is true or not.
When it’ll be released and I’ve few time to invest, I’ll prepare another tutorial around this workflow.
In the meanwhile I hope you are enjoying those experiments with Dart and if you are interesting in any kind of topics on Dart feel free to suggest trough a comment in this post or sending an email

HaXe, my new toy!

After Adobe MAX 2011 everything should not be the same for me and maybe for a lot of flash platform developers around the world, Adobe brings some “directions”  that didn’t find my consent mainly for the way that communicate these news and the impact that had in the market, but we know that Flash Platform is not dead and it will go ahead for many years.
Obviously nothing was the same after that, in fact many developers started to look around for new technologies and frameworks like Backbone.js, Sencha Touch, Ext JS and so on.
Personally I started to checked in last few months many Javascript frameworks because my aim was find something that could replace Flash Platform in the future and I have to spend time in next years to consolidate it and go ahead with Flash Platform too.
Last week a big friend of mine gave me this link: http://www.haxenme.org/ and when I started to read what you can do and how you can do it, I immediately started to go in deep with HaXe in my spare time and trust me that I had a lot of fun!

First of all what is HaXe?
HaXe is an open source multiplatform programming language, it allows to write once and deploy everywhere (in the right meaning of therm “everywhere”).
In fact with HaXe we can write in a programming language similar to Actionscript 3 (strictly typed, OOP, …) but more powerful (it has enum, generics, dynamic type, …), with HaXe we can target our projects for Flash, C++, Neko, HTML5, Node.JS, PHP, iOS, Android… if we work with multiplatform APIs we can write once and deploy our project for multiple targets.
So for many developers that come from Javascript, Actionscript, Java and so on, will be so easy to start deal with HaXe.
Another interesting thing of HaXe is that we can work with the library present in the SWF files and integrate movieclip in our project, we can create also SWF file without Flash Professional with SWFMill that is used for the generation of asset libraries containing images (PNG and JPEG), fonts (TTF) or other SWF movies.
That’s so interesting because it means that designers that usually prepare assets for developers don’t need to change own daily workflow!
If you need to extend your target platform we can add new features with external libraries, it’s so important because we can really cover everything with this feature; we can find a lot of ready to use libraries directly on the lib HaXe website.
With HaXe you can communicate between different languages like JS and Flash in both direction, you can easily find many frameworks and library porting in HaXe, for example javascript like JQuery, Sencha Touch, Node.JS and so on.

What about the IDE to work with HaXe (so important for a developer!)!?
On Mac you can use TextMate or FDT on Win FDT or FlashDevelop this one seems the best one but I didn’t try it. For more specs I suggest to take a look at HaXe site section, maybe you can find your favorite IDE in the list.

Finally I made an easy sample to understand better the powerful of HaXe NME, this sample loads an external XML file and an external SWF library with a movieclip inside exported for Actionscript, so I added a drag&drop feature to the list. Then I tried to compile it for iOS, Mac OS X Lion, C++ and SWF with the same basecode and everything work so well and smooth!


You can download source files here, to compile it take a look at HaXeNME section and you can find everything you need to try this sample and start to play with HaXeNME!

If you want to deal with HaXe, I suggest two books, the first one is really a good start to work with this fantastic language:
HaXe 2 beginner’s guide
Professional HaXe and Neko

Last but not least, next April in Paris there will be World Wide HaXe conference, I’ll be there to learn more about the future of this amazing platform if you are planning to be there it will be a pleasure for me catch up for a beer!

I hope soon to publish more experiments and informations about HaXe because it is a thrilling programming language!!!
So stay tuned!

Review: HTML5 Mobile Web Development

A couple of weeks ago I became blogger reviewer for O’really, so I take this opportunity to open my mind and learn new stuff about new technologies, programmation languages, etc.

So this is my first review and I start with an HTML5 video course.
Why am I talking about HTML5 in this blog? Because I think it’s important to know and learn if it could be useful in some projects or not.

Starting with this idea I’ve decided to watch this video course about HTML5 on mobile development.
Video courses aren’t my favorite media to learn new stuff because I love to sign my books, add some notes…you know what I mean… but this time I was really impressed about how O’Reilly organized it.
Seems you are in a real classroom with teacher in front of you that show code examples, tips & tricks using HTML5, CSS3 on iPad or iPhone.
Course is focused on mobile development, Jake Carter, the author, shows also Android world, how to configure your computer to work with emulator and simulator for Android, iPhone and so on.

I really love the way that he works in the classroom because first of all he explains the powerful of a particular feature, then show how to implement it and finally a little part of Q&A from internet people (I suppose).
During this video course you can learn useful stuff, take a look at table of contents in O’reilly website.
It was my first time with HTML5 and I think is an interesting technology, in particular, during this course I learn how to work with geolocation,  with JS and Canvas, with audio and video API and again how to save data directly on the device in a database.
I appreciate a lot al meta and css dedicated to iPhone and iPad, very useful.
Finally if you are interesting to learn a new way to develop on mobile, I suggest to take a look at this reference.
It’s useful, easy and I think is a fast method to learn.

onAIR tour in Europe

Finally it’s coming!!!

OnAIR tour is coming in Europe, 12 dates from March to June in all Europe… that’s wonderful!
Registrations are open so choose your city and register yourself, I’ll go to Italian date (13 June) in Milan with a lots of Italian developers and designers.

If you come in Milan, please send me an email so we could meet to have dinner togheter!