Everything tagged sencha (9 posts)

Sencha Con 2013 Wrapup

So another great Sencha Con is over, and I'm left to reflect on everything that went on over the last few days. This time was easily the biggest and best Sencha Con that I've been to, with 800 people in attendance and a very high bar set by the speakers. The organization was excellent, the location fun (even if the bars don't open until 5pm...), and the enthusiasm palpable.

I've made a few posts over the last few days so won't repeat the content here - if you want to see what else happened check these out too:

What I will do though is repeat my invitation to take a look at what we're doing with JavaScript at C3 Energy. I wrote up a quick post about it yesterday and would love to hear from you - whether you're at Sencha Con or not.

Now on to some general thoughts.

Content

There was a large range in the technical difficulty of the content, with perhaps a slightly stronger skew up the difficulty chain compared to previous events. This is a good thing, though there's probably still room for more advanced content. Having been there before though, I know how hard it is to pitch that right so that everyone enjoys and gets value of out it.

The biggest challenge for me was the sheer number of tracks - at any one time there would be seven talks happening simultaneously, two or three of which I'd really want to watch. Personally I'd really love it if the hackathon was dropped in favor of a third day of sessions, with a shift down to 4-5 tracks. I'm sure there's a cost implication to that, but it's worth thinking about.

Videos

There were cameras set up in at least the main hall on the first day, but I didn't see any on day 2. I did overhear that the video streams were being recorded directly from what was being shown on the projectors, with the audio recorded separately. If that's true I'd guess it would make editing a bit easier so maybe that'll means a quick release.

Naturally, take this with a pinch of salt until the official announcement comes out. In the meantime, there's at least one video available so far:

Fun Things

The community pavilion was a great idea, and served as the perfect space for attendees with hang out away from the other rascals running around the hotel. Coffee and snacks were available whenever I needed them, and there was plenty of seating to chill out in.

I missed out on the visit to the theme park, which I hear was by far the most fun part of the event. Having a theme park kick out everyone but Sencha Con attendees while serving copious amounts of alcohol seemed to go down very well with the attendees!

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Sencha Con 2013: Ext JS Performance tips

Just as with Jacky's session, I didn't plan on making a separate post about this, but again the content was so good and I ended up taking so many notes that it also warrants its own space. To save myself from early carpal tunnel syndrome I'm going to leave this one in more of a bullet point format.

Ext JS has been getting more flexible with each release. You can do many more things with it these days than you used to be able to, but there has been a performance cost associated with that. In many cases this performance degradation is down to the way the framework is being used, as opposed to a fundamental problem with the framework itself.

There's a whole bunch of things that you can do to dramatically speed up the performance of an app you're not happy with, and Nige "Animal" White took us through them this morning. Here's what I was able to write down in time:

Slow things

Nige identified three of the top causes of sluggish apps, which we'll go through one by one:

  • Network latency
  • JS execution
  • Layout activity

Network latency:

  • Bad ux - got to stare at blank screen for a while
  • Use Sencha Command to build the app - single file, minimized
  • 4810ms vs 352ms = dynamic loading vs built

JavaScript execution:

  • Avoid slow JS engines (he says with a wry smile)
  • Optimize repeated code - for loops should be tight, cache variables outside
  • Ideally, don't do any processing at render time
  • Minimize function calls
  • Lazily instantiate items
  • Use the PageAnalyzer (in the Ext JS SDK examples folder) to benchmark your applications
  • Start Chrome with --enable-benchmarking to get much more accurate timing information out of the browser

Layouts

Suspend store events when adding/removing many records. Otherwise we're going to get a full Ext JS layout pass for each modification

grid.store.suspendEvents();
//do lots of updating
grid.store.resumeEvents();
grid.view.refresh()

grid.store.suspendEvents();
//do lots of updating
grid.store.resumeEvents();
grid.view.refresh()

Ditto on trees (they're the same as grids) Coalesce multiple layouts. If you're adding/removing a bunch of Components in a single go, do it like this:

Ext.suspendLayouts();
//do a bunch of UI updates
Ext.resumeLayouts(true);

Ext.suspendLayouts();
//do a bunch of UI updates
Ext.resumeLayouts(true);

Container#add accepts an array of items, which is faster than iterating over that array yourself and calling .add for each one. Avoid layout constraints where possible - in box layouts, align: 'stretchmax' is slow because it has to do multiple layout runs. Avoid minHeight, maxHeight, minWidth, maxWidth if possible

At startup:

  • Embed initialization data inside the HTML if possible - avoids AJAX requests
  • Configure the entire layout in one shot using that data
  • Do not make multiple Ajax requests, and build the layout in response

Use the 'idle' event

  • Similar to the AnimationQueue
  • Ext.globalEvents.on('idle', myFunction) - called once a big layout/repaint run has finished
  • Using the idle listener sometimes preferable to setTimeout(myFunction, 1), because it's synchronous in the same repaint cycle. The setTimeout approach means the repaint happens, then your code is called. If your code itself requires a repaint, that means you'll have 2 repaints in setTimeout vs 1 in on.('idle')

Reduce layout depth

Big problem - overnesting. People very often do this with grids:

{
xtype: 'tabpanel',
items: [
{
title: 'Results',
items: {
xtype: 'grid'
}
}
]
}
{
xtype: 'tabpanel',
items: [
{
title: 'Results',
items: {
xtype: 'grid'
}
}
]
}

Better:

{
xtype: 'tabpanel',
items: {
title: 'Results',
xtype: 'grid'
}
}
{
xtype: 'tabpanel',
items: {
title: 'Results',
xtype: 'grid'
}
}

This is important because redundant components still cost CPU and memory. Everything is a Component now - panel headers, icons, etc etc. Can be constructing more Components than you realize. Much more flexible, but easy to abuse

Lazy Instantiation

New plugin at https://gist.github.com/ExtAnimal/c93148f5194f2a232464

{
xtype: 'tabpanel',
ptype: 'lazyitems',
items: {
title: 'Results',
xtype: 'grid'
}
}
{
xtype: 'tabpanel',
ptype: 'lazyitems',
items: {
title: 'Results',
xtype: 'grid'
}
}

Overall impact

On a real life large example contributed by a Sencha customer:

Bad practices: 5187ms (IE8) Good practices: 1813ms (IE8) 1300ms vs 550ms on Chrome (same example)

Colossal impact on the Ext.suspendLayout example - 4700ms vs 100ms on Chrome

Summary

This is definitely a talk you'll want to watch when they go online. It was absolutely brimming with content and the advice comes straight from the horse's mouth. Nige did a great job presenting, and reminded us that performance is a shared responsibility - the framework is getting faster as time goes by, but we the developers need to do our share too to make sure it stays fast.

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Sencha Con 2013: Fastbook

I didn't plan on writing a post purely on Fastbook, but Jacky's presentation just now was so good I felt it needed one. If you haven't seen Fastbook yet, it is Sencha's answer to the (over reported) comments by Zuckerburg that using HTML5 for Facebook's mobile app was a mistake.

After those comments there was a lot of debate around whether HTML5 is ready for the big time. Plenty of opinions were thrown around, but not all based on evidence. Jacky was curious about why Facebook's old app was so slow, and wondered if he could use the same technologies to achieve a much better result. To say he was successful would be a spectacular understatement - Fastbook absolutely flies.

Performance can be hard to describe in words, so Sencha released this video that demonstrates the HTML5 Fastbook app against the new native Facebook apps. As you can see, not only is the HTML5 version at least as fast and fluid as the native versions, in several cases it's actually significantly better (especially on Android).

Fastbook

Challenges

The biggest challenge here is dynamically loading and scrolling large quantities of data while presenting a 60fps experience to the user. 60fps means you have just 16.7ms per frame to do everything, which is a hugely tall order on a CPU and memory constrained mobile device.

The way to achieve this is to treat the page as an app rather than a traditional web page. This means we need to be a lot more proactive in managing how and when things are rendered - something that traditionally has been in the domain of the browser's own rendering and layout engines. Thankfully, the framework will do all of this for you.

As an example, Jacky loaded up Gmail's web app and showed what happens when you scroll a long way down your inbox. The more you scroll, the more divs are added to the document (one new div per message). Each div contains a bunch of child elements too, so we're adding maybe a dozen or so nodes to our DOM tree per message.

The problem with this is that as the DOM tree gets larger and larger, everything slows down. You could see the inspector showing slower and slower layout recalculations, making the app sluggish.

The solution is to recycle DOM nodes once they're no longer visible. In this way, a list that seems to have infinite content could contain only say 10 elements - just enough to fill the screen. Once you scroll down the list, DOM nodes that scrolled off the top are detached, updated with new data and placed at the bottom of the list. Simple. Ingenius. Beautiful.

Prioritization

There's usually a lot more going on in an app than just animating a scrolling view though. There's data to load via AJAX, images to load, compositing, processing, and whatever else your app needs to do. And then there are touch events, which need to feel perfectly responsive at all times, even while all of this is going on.

To make this sane and manageable, we have a new class called AnimationQueue. All of the jobs I just mentioned above - handling touch events, animation, network requests and so on - are dispatched through the AnimationQueue with a given priority. Touch event handling has the top priority, followed by animation, followed by everything else.

AnimationQueue does as much as it can in that 16.7ms window, then breaks execution again to allow the browser to reflow/repaint/whatever else it needs to do. What this means is that while scrolling down a large list, it's likely that our CPU/GPU is being taxed so much that we don't have any time to load images or other low priority jobs.

This is a Good Thing, because if we're scrolling through a large list there's a good chance we are going to skip right over those images anyway. In the end they're loaded as soon as the AnimationQueue has some spare time, which is normally when your scrolling of the list has slowed down or stopped.

Sandboxing

The final, and most complex technique Jacky discussed was Sandboxing. The larger your application gets, the larger the DOM tree. Even if you are using best practices, there's an expense to simply having so many components on the same page. The bottleneck here is in the browser itself - looks like we need another hack.

To get around this, we can dynamically create iframes that contain parts of our DOM tree. This way our main page DOM tree can remain small but we can still have a huge application. This not only speeds up browser repaint and reflow, it also improves compositing performance, DOM querying and more.

This all happens under the covers and Jacky's aiming on including Ext.Sandbox in Sencha Touch 2.3 so that all apps can take advantage of this huge improvement. He cautioned (rightly) that it'll only make 2.3 if it's up to his high standards though, so watch this space.

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Anatomy of a Sencha Touch 2 App

At its simplest, a Sencha Touch 2 application is just a small collection of text files - html, css and javascript. But applications often grow over time so to keep things organized and maintainable we have a set of simple conventions around how to structure and manage your application's code.

A little while back we introduced a technology called Sencha Command. Command got a big overhaul for 2.0 and today it can generate all of the files your application needs for you. To get Sencha Command you'll need to install the SDK Tools and then open up your terminal. To run the app generator you'll need to make sure you've got a copy of the Sencha Touch 2 SDK, cd into it in your terminal and run the app generate command:

sencha generate app MyApp ../MyApp
sencha generate app MyApp ../MyApp

This creates an application called MyApp with all of the files and folders you'll need to get started generated for you. You end up with a folder structure that looks like this:

Sencha Touch 2 Directory Overview

This looks like a fair number of files and folders because I've expanded the app folder in the image above but really there are only 4 files and 3 folders at the top level. Let's look at the files first:

  • index.html: simplest HTML file ever, just includes the app JS and CSS, plus a loading spinner
  • app.js: this is the heart of your app, sets up app name, dependencies and a launch function
  • app.json: used by the microloader to cache your app files in localStorage so it boots up faster
  • packager.json: configuration file used to package your app for native app stores

To begin with you'll only really need to edit app.js - the others come in useful later on. Now let's take a look at the folders:

  • app: contains all of your application's source files - models, views, controllers etc
  • resources: contains the images and CSS used by your app, including the source SASS files
  • sdk: contains the important parts of the Touch SDK, including Sencha Command

The app folder

You'll spend 90%+ of your time inside the app folder, so let's drill down and take a look at what's inside that. We've got 5 subfolders, all of which are empty except one - the view folder. This just contains a template view file that renders a tab panel when you first boot the app up. Let's look at each:

The resources folder

Moving on, let's take a look at the resources folder:

Sencha Touch 2 resources folder

Five folders this time - in turn:

  • icons: the set of icons used when your app is added to the home screen. We create some nice default ones for you
  • loading: the loading/startup screen images to use when your app's on a home screen or natively packaged
  • images: this is where you should put any app images that are not icons or loading images
  • sass: the source SASS files for your app. This is the place to alter the theming for your app, remove any CSS you're not using and add your own styles
  • css: the compiled SASS files - these are the CSS files your app will use in production and are automatically minified for you

There are quite a few icon and loading images needed to cover all of the different sizes and resolutions of the devices that Sencha Touch 2 supports. We've included all of the different formats with the conventional file names as a guide - you can just replace the contents of resources/icons and resources/loading with your own images.

The sdk folder

Finally there's the SDK directory, which contains the SDK's source code and all of the dependencies used by Sencha Command. This includes Node.js, Phantom JS and others so it can start to add up. Of course, none of this goes into your production builds, which we keep as tiny and fast-loading as possible, but if you're not going to use the SDK Tools (bad move, but your call!) you can remove the sdk/command directory to keep things leaner.

By vendoring all third-party dependencies like Node.js into your application directory we can be confident that there are no system-specific dependencies required, so you can zip up your app, send it to a friend and so long as she has the SDK Tools installed, everything should just work.

Hopefully that lays out the large-scale structure of what goes where and why - feel free to ask questions!

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Sencha Touch 2 Hits Beta

Earlier today we released Sencha Touch 2 Beta 1 - check out the official sencha.com blog post and release notes to find out all of the awesome stuff packed into this release.

This is a really important release for us - Sencha Touch 2 is another huge leap forward for the mobile web and hitting beta is a massive milestone for everyone involved with the project. From a personal standpoint, working on this release with the amazing Touch team has been immensely gratifying and I hope the end result more than meets your expectations of what the mobile web can do.

While you should check out the official blog post and release notes to find out the large scale changes, there are a number of things I'd really like to highlight today.

A Note on Builds

Before we get into the meat of B1 itself, first a quick note that we've updated the set of builds that we generate with the release. Previously there had been some confusion around which build you should be using in which circumstances so we've tried to simplify that.

Most people, most of the time should be using the new sencha-touch-debug.js while developing their app as it is unminified code that contains all of the debug warnings and comments. If you're migrating from 1.x, use the new builds/sencha-touch-all-compat.js build as it provides an easier migration path by logging additional warnings when you use 1.x-style class configurations.

Because we provide 5 builds in total we created a guide on the shipped builds and JSBuilder (the tool that creates a custom build specifically for your app). The guide contains a table showing all of the options enabled for each build - hopefully that makes it easy to choose which build is best for your needs.

Performance

In case you haven't seen Sencha Touch 2 yet the first thing you need to know is that it's fast. Crazy fast. Check out this side by side comparison between 1.x and 2.x:

Sencha Touch 2 Performance

Layout performance is enormously faster in 2.x due to a brand new layout engine that operates much closer to the browser's optimized CSS layout engine. The difference is pretty startling, especially on Android devices, which had sometimes struggled with Sencha Touch 1. Performance remains a top priority for us and we're really pleased with the improvements that we've secured with 2.0.

Navigation View

The new Navigation View is one of the slickest, sexiest things we've created for 2.0. I could play with this thing all day. If you've got a phone in your pocket or a tablet near by open up the Navigation View example and see it for yourself. If you're not, check out this beautiful video of it in action:

Getting Started with Sencha Touch 2

Navigation Views are really easy to put together and make your application immediately come to life. Check out the Navigation View docs to see how easy it is to add this to your own applications.

Awesome new examples

As of beta 1 we have 24 examples shipped with the SDK, including no fewer than 6 MVC examples - Kitchen Sink, Jogs with Friends, Twitter, Kiva, Navigation View and GeoCongress.

The Kitchen Sink and Twitter examples also take advantage of Device Profiles, which are a powerful way to customize your app to render customized UI for tablets and phones. Take a look at the Kitchen Sink on your phone and on an iPad to see how it rearranges itself depending on the screen size.

Finally, if you're seeing Sencha Touch 2 for the first time you may not have seen the new inline examples in the documentation center. This is a brand new thing for Sencha Touch and allows you to edit code live on the documentation page and immediately see the results - give it a go on the Carousel docs.

Ludicrous Amounts of Documentation

Speaking of docs, we have a stunning amount of learning material for Sencha Touch 2. We've been through all of the major classes, making sure that the functions are clearly documented and that each one has some great intro text that describes what the class does and how it fits in with the rest of the framework.

We've also created over 20 brand new guides for Sencha Touch 2, covering everything from getting started through to developing using MVC, using Components and creating custom builds for your applications. We've put a huge amount of effort into our docs for Sencha Touch 2 and I really hope it pays off for you guys and makes it easier than ever to create great mobile web apps.

Go Build Something

It's only beta 1 but we're very happy with the performance, stability, API and documentation of Sencha Touch 2. I think it's the best thing we've ever created, and really highlights what the mobile web is capable of. 2012 looks set to be a very exciting year for Sencha Touch so I hope you'll join us on the adventure and build something amazing with it.

Download Sencha Touch 2 Beta 1 Now

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The Class System in Sencha Touch 2 - What you need to know

Sencha Touch 1 used the class system from Ext JS 3, which provides a simple but powerful inheritance system that makes it easier to write big complex things like applications and frameworks.

With Sencha Touch 2 we've taken Ext JS 4's much more advanced class system and used it to create a leaner, cleaner and more beautiful framework. This post takes you through what has changed and how to use it to improve your apps.

Syntax

The first thing you'll notice when comparing code from 1.x and 2.x is that the class syntax is different. Back in 1.x we would define a class like this:

MyApp.CustomPanel = Ext.extend(Ext.Panel, {
html: 'Some html'
});
MyApp.CustomPanel = Ext.extend(Ext.Panel, {
html: 'Some html'
});

This would create a subclass of Ext.Panel called MyApp.CustomPanel, setting the html configuration to 'Some html'. Any time we create a new instance of our subclass (by calling new MyApp.CustomPanel()), we'll now get a slightly customized Ext.Panel instance.

Now let's see how the same class is defined in Sencha Touch 2:

Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html'
}
});
Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html'
}
});

There are a few changes here, let's go through them one by one. Firstly and most obviously we've swapped out Ext.extend for Ext.define. Ext.define operates using strings - notice that both 'MyApp.CustomPanel' and 'Ext.Panel' are now wrapped in quotes. This enables one of the most powerful parts of the new class system - dynamic loading.

I actually talked about this in a post about Ext JS 4 last year so if you're not familiar you should check out the post, but in a nutshell Sencha Touch 2 will automatically ensure that the class you're extending (Ext.Panel) is loaded on the page, fetching it from your server if necessary. This makes development easier and enables you to create custom builds that only contain the class your app actually uses.

The second notable change is that we're using a 'config' block now. Configs are a special thing in Sencha Touch 2 - they are properties of a class that can be retrieved and updated at any time, and provide extremely useful hook functions that enable you to run any custom logic you like whenever one of them is changed.

Whenever you want to customize any of the configurations of a subclass in Sencha Touch 2, just place them in the config block and the framework takes care of the rest, as we'll see in a moment.

Consistency

The biggest improvement that comes from the config system is consistency. Let's take our MyApp.CustomPanel class above and create an instance of it:

var myPanel = Ext.create('MyApp.CustomPanel');
var myPanel = Ext.create('MyApp.CustomPanel');

Every configuration has an automatically generated getter and setter function, which we can use like this:

myPanel.setHtml('New HTML');
myPanel.getHtml(); //returns 'New HTML'
myPanel.setHtml('New HTML');
myPanel.getHtml(); //returns 'New HTML'

This might not seem much, but the convention applies to every single configuration in the entire framework. This eliminates the guesswork from the API - if you know the config name, you know how to get it and update it. Contrast this with Sencha Touch 1 where retrieving the html config meant finding some property on the instance, and updating it meant calling myPanel.update('New HTML'), which is nowhere near as predictable.

Instantiating

You probably noticed that we used a new function above - Ext.create. This is very similar to just calling 'new MyApp.CustomPanel()', with the exception that Ext.create uses the dynamic loading system to automatically load the class you are trying to instantiate if it is not already on the page. This can make life much easier when developing your app as you don't have to immediately manage dependencies - it just works.

In the example above we just instantiated a default MyApp.CustomPanel but of course we can customize it at instantiation time by passing configs into Ext.create:

var myPanel = Ext.create('MyApp.CustomPanel', {
html: 'Some Custom HTML'
});
var myPanel = Ext.create('MyApp.CustomPanel', {
html: 'Some Custom HTML'
});

We can still call getHtml() and setHtml() to retrieve and update our html config at any time.

Subclassing and Custom Configs

We created a simple subclass above that provided a new default value for Ext.Panel's html config. However, we can also add our own configs to our subclasses:

Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html',
anotherConfig: 'default value'
}
});
Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html',
anotherConfig: 'default value'
}
});

The 'anotherConfig' configuration doesn't exist on Ext.Panel so it's defined for the first time on MyApp.CustomPanel. This automatically creates our getter and setter functions for us:

var myPanel = Ext.create('MyApp.CustomPanel');
myPanel.setAnotherConfig('Something else');
myPanel.getAnotherConfig(); //now returns 'Something else'
var myPanel = Ext.create('MyApp.CustomPanel');
myPanel.setAnotherConfig('Something else');
myPanel.getAnotherConfig(); //now returns 'Something else'

Notice how the getter and setter names were automatically capitalized to use camelCase like all of the other functions in the framework. This was done automatically, but Sencha Touch 2 does another couple of very nice things for you - it creates hook functions:

Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html',
anotherConfig: 'default value'
},

applyAnotherConfig: function(value) {
return "[TEST] " + value;
},

updateAnotherConfig: function(value, oldValue) {
this.setHtml("HTML is now " + value);
}
});
Ext.define('MyApp.CustomPanel', {
extend: 'Ext.Panel',

config: {
html: 'Some html',
anotherConfig: 'default value'
},

applyAnotherConfig: function(value) {
return "[TEST] " + value;
},

updateAnotherConfig: function(value, oldValue) {
this.setHtml("HTML is now " + value);
}
});

We've added two new functions to our class - applyAnotherConfig and updateAnotherConfig - these are both called when we call setAnotherConfig. The first one that is called is applyAnotherConfig. This is passed the value of the configuration ('default value' by default in this case) and is given the opportunity to modify it. In this case we're prepending "[TEST] " to whatever anotherConfig is set to:

var myPanel = Ext.create('MyApp.CustomPanel');
myPanel.setAnotherConfig('Something else');
myPanel.getAnotherConfig(); //now returns '[TEST] Something else'
var myPanel = Ext.create('MyApp.CustomPanel');
myPanel.setAnotherConfig('Something else');
myPanel.getAnotherConfig(); //now returns '[TEST] Something else'

The second function, updateAnotherConfig, is called after applyAnotherConfig has had a chance to modify the value and is usually used to effect some other change - whether it's updating the DOM, sending an AJAX request, or setting another config as we do here.

When we run the code above, as well as '[TEST] ' being prepended to our anotherConfig configuration, we're calling this.setHtml to update the html configuration too. There's no limit to what you can do inside these hook functions, just remember the rule - the apply functions are used to transform new values before they are saved, the update functions are used to perform the actual side-effects of changing the value (e.g. updating the DOM or configuring other classes).

How we use it

The example above is a little contrived to show the point - let's look at a real example from Sencha Touch 2's Ext.Panel class:

applyBodyPadding: function(bodyPadding) {
if (bodyPadding === true) {
bodyPadding = 5;
}

bodyPadding = Ext.dom.Element.unitizeBox(bodyPadding);

return bodyPadding;
},

updateBodyPadding: function(newBodyPadding) {
this.element.setStyle('padding', newBodyPadding);
}
applyBodyPadding: function(bodyPadding) {
if (bodyPadding === true) {
bodyPadding = 5;
}

bodyPadding = Ext.dom.Element.unitizeBox(bodyPadding);

return bodyPadding;
},

updateBodyPadding: function(newBodyPadding) {
this.element.setStyle('padding', newBodyPadding);
}

Here we see the apply and update functions for the bodyPadding config. Notice that in the applyBodyPadding function we set a default and use the framework's unitizeBox function to parse CSS padding strings (like '5px 5px 10px 15px') into top, left, bottom and right paddings, which we then return as the transformed value.

The updateBodyPadding then takes this modified value and performs the actual updates - in this case setting the padding style on the Panel's element based on the new configuration. You can see similar usage in almost any component class in the framework.

Find out more

This is just a look through the most important aspects of the new class system and how they impact you when writing apps in Sencha Touch 2. To find out more about the class system we recommend taking a look at the Class System guide and if you have any questions the forums are a great place to start.

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Sencha Touch 2 - Thoughts from the Trenches

As you may have seen, we put out the first public preview release of Sencha Touch 2 today. It only went live a few hours ago but the feedback has been inspiring so far. For the full scoop see the post on the sencha.com blog. A few thoughts on where we are with the product:

Performance

Performance on Android devices in particular is breathtaking. I never thought I'd see the day where I could pick up an Android 2.3 device and have it feel faster than an iPhone 4, and yet that's exactly what Sencha Touch 2 brings to the table. I recorded this short video on an actual device to show real world performance:

Video

Now try the same on Sencha Touch 1.x (or any other competing framework) and (if you're anything like me) cringe at what we were accustomed to using before. That video's cool, but the one that's really driving people wild is the side by side comparison of the layout engines in 1.x and 2.x.

Getting our hands on a high speed camera and recording these devices at 120fps was a lot of fun. Slowing time down to 1/4 of normal speed shows just how much faster the new layout engine is than what we used to have:

Video

The most amazing part here is that we actually finish laying out before the phone's rotation animation has completed. Skipping through the video frame by frame there are at least 5 frames where the app is fully laid out and interactive while the phone's rotation animation is still running. Beating the phone's own rotation speed is the holy grail - it's not possible to make it any faster.

Documentation

I'll admit it, I'm fanatical about great documentation. I'm sure I drive everyone else on the team crazy but I think it's worth it. This is only a preview release but it already contains by far the best, most complete documentation we've ever shipped in an initial release.

In fact, the team's worked so hard on documenting classes that it's probably better than the (already good) Ext JS 4 docs. Naturally, this makes it time to further improve the Ext JS documentation.

We've added some awesome features here - lots of videos, 11 brand new guides and illustrations. My favourite new feature is definitely the inline examples with live previews though - seeing Sencha Touch running live in a phone/tablet right there in the docs is just amazing. Little gems like the live twitter feed in the bottom-most example in the DataView docs really sell just how easy it is to configure these components.

We set a high bar for this though. We've gone from woeful documentation in 1.x to good documentation in 2.x, but what we're shooting for is excellence. We'll continue to round out our content over coming weeks, and have a few new features rolling out soon that will raise the bar once again.

Onwards

We have a few features left to implement, which is why we're calling this preview and not beta. Probably the biggest thing now is getting routing/deep linking back into the framework, along with a nice new syntax that I think you'll find really easy to use. We're also missing carousel animations and a handful of other things that will be going back in over the coming weeks. We have Sencha Con 2011 in just 12 days now though so we'll share more details there.

Finally though, I want to thank everyone who participated in the closed preview phase, and for everyone sending their support and kind words on the blog, the forums and on twitter. We really appreciate all the great feedback and I hope we can exceed your expectations with a fast, polished, gorgeous 2.0 final!

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Proxies in Ext JS 4

One of the classes that has a lot more prominence in Ext JS 4 is the data Proxy. Proxies are responsible for all of the loading and saving of data in an Ext JS 4 or Sencha Touch application. Whenever you're creating, updating, deleting or loading any type of data in your app, you're almost certainly doing it via an Ext.data.Proxy.

If you've seen January's Sencha newsletter you may have read an article called Anatomy of a Model, which introduces the most commonly-used Proxies. All a Proxy really needs is four functions - create, read, update and destroy. For an AjaxProxy, each of these will result in an Ajax request being made. For a LocalStorageProxy, the functions will create, read, update or delete records from HTML5 localStorage.

Because Proxies all implement the same interface they're completely interchangeable, so you can swap out your data source - at design time or run time - without changing any other code. Although the local Proxies like LocalStorageProxy and MemoryProxy are self-contained, the remote Proxies like AjaxProxy and ScriptTagProxy make use of Readers and Writers to encode and decode their data when communicating with the server.

Ext.data.Proxy Reader and Writer

Whether we are reading data from a server or preparing data to be sent back, usually we format it as either JSON or XML. Both of our frameworks come with JSON and XML Readers and Writers which handle all of this for you with a very simple API.

Using a Proxy with a Model

Proxies are usually used along with either a Model or a Store. The simplest setup is just with a model:

var User = Ext.regModel('User', {
fields: ['id', 'name', 'email'],

proxy: {
type: 'rest',
url : '/users',
reader: {
type: 'json',
root: 'users'
}
}
});
var User = Ext.regModel('User', {
fields: ['id', 'name', 'email'],

proxy: {
type: 'rest',
url : '/users',
reader: {
type: 'json',
root: 'users'
}
}
});

Here we've created a User model with a RestProxy. RestProxy is a special form of AjaxProxy that can automatically figure out Restful urls for our models. The Proxy that we set up features a JsonReader to decode any server responses - check out the recent data package post on the Sencha blog to see Readers in action.

When we use the following functions on the new User model, the Proxy is called behind the scenes:

var user = new User({name: 'Ed Spencer'});

//CREATE: calls the RestProxy's create function because the user has never been saved
user.save();

//UPDATE: calls the RestProxy's update function because it has been saved before
user.set('email', 'ed@sencha.com');

//DESTROY: calls the RestProxy's destroy function
user.destroy();

//READ: calls the RestProxy's read function
User.load(123, {
success: function(user) {
console.log(user);
}
});
var user = new User({name: 'Ed Spencer'});

//CREATE: calls the RestProxy's create function because the user has never been saved
user.save();

//UPDATE: calls the RestProxy's update function because it has been saved before
user.set('email', 'ed@sencha.com');

//DESTROY: calls the RestProxy's destroy function
user.destroy();

//READ: calls the RestProxy's read function
User.load(123, {
success: function(user) {
console.log(user);
}
});

We were able to perform all four CRUD operations just by specifying a Proxy for our Model. Notice that the first 3 calls are instance methods whereas the fourth (User.load) is static on the User model. Note also that you can create a Model without a Proxy, you just won't be able to persist it.

Usage with Stores

In Ext JS 3.x, most of the data manipulation was done via Stores. A chief purpose of a Store is to be a local subset of some data plus delta. For example, you might have 1000 products in your database and have 25 of them loaded into a Store on the client side (the local subset). While operating on that subset, your user may have added, updated or deleted some of the Products. Until these changes are synchronized with the server they are known as a delta.

In order to read data from and sync to the server, Stores also need to be able to call those CRUD operations. We can give a Store a Proxy in the same way:

var store = new Ext.data.Store({
model: 'User',
proxy: {
type: 'rest',
url : '/users',
reader: {
type: 'json',
root: 'users'
}
}
});
var store = new Ext.data.Store({
model: 'User',
proxy: {
type: 'rest',
url : '/users',
reader: {
type: 'json',
root: 'users'
}
}
});

We created the exact same Proxy for the Store because that's how our server side is set up to deliver data. Because we'll usually want to use the same Proxy mechanism for all User manipulations, it's usually best to just define the Proxy once on the Model and then simply tell the Store which Model to use. This automatically picks up the User model's Proxy:

//no need to define proxy - this will reuse the User's Proxy
var store = new Ext.data.Store({
model: 'User'
});
//no need to define proxy - this will reuse the User's Proxy
var store = new Ext.data.Store({
model: 'User'
});

Store invokes the CRUD operations via its load and sync functions. Calling load uses the Proxy's read operation, which sync utilizes one or more of create, update and destroy depending on the current Store delta.

//CREATE: calls the RestProxy's create function to create the Tommy record on the server
store.add({name: 'Tommy Maintz'});
store.sync();

//UPDATE: calls the RestProxy's update function to update the Tommy record on the server
store.getAt(1).set('email', 'tommy@sencha.com');
store.sync();

//DESTROY: calls the RestProxy's destroy function
store.remove(store.getAt(1));
store.sync();

//READ: calls the RestProxy's read function
store.load();
//CREATE: calls the RestProxy's create function to create the Tommy record on the server
store.add({name: 'Tommy Maintz'});
store.sync();

//UPDATE: calls the RestProxy's update function to update the Tommy record on the server
store.getAt(1).set('email', 'tommy@sencha.com');
store.sync();

//DESTROY: calls the RestProxy's destroy function
store.remove(store.getAt(1));
store.sync();

//READ: calls the RestProxy's read function
store.load();

Store has used the exact same CRUD operations on the shared Proxy. In all of the examples above we have used the exact same RestProxy instance from three different places: statically on our Model (User.load), as a Model instance method (user.save, user.destroy) and via a Store instance (store.load, store.sync):

Data Proxy Reuse

Of course, most Proxies have their own private methods to do the actual work, but all a Proxy needs to do is implement those four functions to be usable with Ext JS 4 and Sencha Touch. This means it's easy to create new Proxies, as James Pearce did in a recent Sencha Touch example where he needed to read address book data from a mobile phone. Everything he does to set up his Proxy in the article (about 1/3rd of the way down) works the same way for Ext JS 4 too.

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Offline Apps with HTML5: A case study in Solitaire

One of my contributions to the newly-launched Sencha Touch mobile framework is the Touch Solitaire game. This is not the first time I have ventured into the dizzying excitement of Solitaire game development; you may remember the wonderful Ext JS Solitaire from 18 months ago. I'm sure you'll agree that the new version is a small improvement.

Solitaire

Solitaire is a nice example of a fun application that can be written with Sencha Touch. It makes use of the provided Draggables and Droppables, CSS-based animations, the layout manager and the brand new data package. The great thing about a game like this though is that it can be run entirely offline. Obviously this is simple with a native application, but what about a web app? Our goal is not just having the game able to run offline, but to save your game state locally too.

The answer comes in two parts:

Web Storage and the Sencha data package

HTML5 provides a brand new API called Web Storage for storing data locally. You can read all about it on my Web Storage post on Sencha's blog but the summary is that you can store string data locally in the browser and retrieve it later, even if the browser or the user's computer had been restarted in the meantime.

The crucial part of the sentence above is that we can only store string data. In the case of a game of Solitaire we need to store data on the elapsed time and number of moves as well as the location and status of each card. This doesn't sound like the kind of data we want to manually encode into a string, so thankfully the data package comes to the rescue.

The Sencha Touch data package is a complete rewrite of the package that has been so successful in powering Ext JS 3.x. It shares many of the same philosophies and adds the learning we have gained from developing Ext JS 3.x over the past year. One of the new capabilities it offers us is a Local Storage proxy, which automatically marshalls your model data into local storage and transparently restores it when you need it.

Using the new proxy is simple - all we need to do is set up a new Store, specifying the Proxy and the Model that will be saved to it. Models are the spiritual successor to Ext JS 3.x's Records. Now whenever we add, remove or update model instances in the store they are automatically saved to localStorage for us. Loading the store again is equally easy:

//set the store up
var gameStore = new Ext.data.Store({
proxy: new Ext.data.LocalStorageProxy({
id: 'solitaire-games'
}),
model: 'Game'
});

//saves all outstanding modifications, deletions or creations to localStorage
gameStore.sync();

//load our saved games
gameStore.read({
scope: this,
callback: function(records) {
//code to load the first record
}
});
//set the store up
var gameStore = new Ext.data.Store({
proxy: new Ext.data.LocalStorageProxy({
id: 'solitaire-games'
}),
model: 'Game'
});

//saves all outstanding modifications, deletions or creations to localStorage
gameStore.sync();

//load our saved games
gameStore.read({
scope: this,
callback: function(records) {
//code to load the first record
}
});

And just like that we can save and restore games with Web Storage. We can visit our app's webpage and start a game then come back later and find it automatically restored. But we still can't play offline, for that we need the application cache.

The HTML5 Application Cache Manifest

The application cache is one of the best features of HTML5. It provides a simple (though sometimes frustrating) way of telling the browser about all of the files your application relies on so that it can download them all ready for offline use. All you have to do is create what's known as a manifest file which lists all of the files the application needs - the Solitaire manifest looks like this:

CACHE MANIFEST
#rev49

resources/icon.png
resources/loading.png

resources/themes/wood/board.jpg
resources/themes/wood/cards.png

resources/css/ext-touch.css
resources/solitaire-notheme.css
resources/themes/wood/wood.css
resources/themes/metal/metal.css

ext-touch-debug.js
solitaire-all-debug.js
CACHE MANIFEST
#rev49

resources/icon.png
resources/loading.png

resources/themes/wood/board.jpg
resources/themes/wood/cards.png

resources/css/ext-touch.css
resources/solitaire-notheme.css
resources/themes/wood/wood.css
resources/themes/metal/metal.css

ext-touch-debug.js
solitaire-all-debug.js

We tell the browser about the manifest file by pointing to it in the tag's manifest atttibute. When the browser finds this file it downloads each of the listed assets so that they are ready for offline consumption. Note that it does not automatically include them on the page, you still need to do that yourself via the usual link and script tags. Here's a snippet of the Solitaire index.html file:

<!doctype html>
<html manifest="solitaire.manifest">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Solitaire</title>

<link rel="stylesheet" href="resources/css/ext-touch.css" type="text/css">
<link rel="stylesheet" href="resources/solitaire-notheme.css" type="text/css">
<link rel="stylesheet" href="resources/themes/wood/wood.css" type="text/css">

<script type="text/javascript" src="ext-touch-debug.js"></script>
<script type="text/javascript" src="solitaire-all-debug.js"></script>
<!doctype html>
<html manifest="solitaire.manifest">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Solitaire</title>

<link rel="stylesheet" href="resources/css/ext-touch.css" type="text/css">
<link rel="stylesheet" href="resources/solitaire-notheme.css" type="text/css">
<link rel="stylesheet" href="resources/themes/wood/wood.css" type="text/css">

<script type="text/javascript" src="ext-touch-debug.js"></script>
<script type="text/javascript" src="solitaire-all-debug.js"></script>

Note the manifest file definition in the html element at the top, and the fact that we still include our page resources the normal way. It sounds easy, but without a little setup first it can be a very frustrating experience. Usually your browser will try to cache as many files as possible, including the manifest file itself - we don't want this. As soon as your browser has a long-term cache of the manifest file it is extremely difficult to update your application - all of the files are already offline and won't be updated, and the browser won't even ask the server for an updated manifest file.

Preventing this behaviour turns out to be fairly easy, and the solution in its simplest form comes in the shape of a .htaccess file with contents like the following:

<Files solitaire.manifest>
ExpiresActive On
ExpiresDefault "access"
</Files>
<Files solitaire.manifest>
ExpiresActive On
ExpiresDefault "access"
</Files>

This directs Apache to tell the browser not to cache the manifest file at all, instead requesting the file from the server on every page load. Note that if the device is currently offline it will use the last manifest file it received.

This is half the battle won, but let's say you change one of your application files and reload - you'll find nothing happened. This is because when your browser asked the server for the manifest file it actually asked if the file had changed or not. As the manifest itself wasn't updated, the server responds with a 304 (Not Modified) and your browser keeps the old file.

To make the browser pick up on the change to the application file you need to update the manifest file itself. This is where the mysterious "#rev49" comes in on the manifest example file above. This is a suggestion from the excellent diveintohtml5 article on the subject - whenever you change any application files just bump up the revision number in the manifest file and your browser will know to download the updated files.

One final detail is that your Apache server probably isn't set up to server manifest files with the correct mime type, so be sure to add the following line to your Apache config and restart the server:

AddType text/cache-manifest .manifest
AddType text/cache-manifest .manifest

Wrapping it up

Offline access is a big deal for mobile apps and Sencha Touch makes them much easier to write. The benefit is not so much that the apps can run without an internet connection (many modern touch devices have a near-permanent connection to the internet already), but that web apps can now be treated as first-class citizens alongside native apps.

The fact that many devices allow your users to save your app to their home screen and load it as though it were native is an important step - you keep all of the advantages of web app deployment while gaining some of the benefits of native apps. As more and more native hardware APIs become available to web apps their importance will only grow.

If you want to check out Solitaire's offline support for yourself visit the application's site and save it to your iPad's home page. Try turning on airplane mode and loading the app and see how it behaves as though it were native. If you don't have an iPad, you can load the app in up-to-date versions of Chrome or Safari and get a similar experience.

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