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Sean Rice

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Original author: 
Lars Kappert

  

We are talking and reading a lot about responsive Web design (RWD) these days, but very little attention is given to Web applications. Admittedly, RWD still has to be ironed out. But many of us believe it to be a strong concept, and it is here to stay. So, why don’t we extend this topic to HTML5-powered applications? Because responsive Web applications (RWAs) are both a huge opportunity and a big challenge, I wanted to dive in.

Building a RWA is more feasible than you might think. In this article, we will explore ideas and solutions. In the first part, we will set up some important concepts. We will build on these in the second part to actually develop a RWA, and then explore how scalable and portable this approach is.

Part 1: Becoming Responsible

Some Lessons Learned

It’s not easy to admit, but recently it has become more and more apparent that we don’t know many things about users of our websites. Varying screen sizes, device features and input mechanisms are pretty much RWD’s reasons for existence.

From the lessons we’ve learned so far, we mustn’t assume too much. For instance, a small screen is not necessarily a touch device. A mobile device could be over 1280 pixels wide. And a desktop could have a slow connection. We just don’t know. And that’s fine. This means we can focus on these things separately without making assumptions: that’s what responsiveness is all about.

Progressive Enhancement

The “JavaScript-enabled” debate is so ’90s. We need to optimize for accessibility and indexability (i.e. SEO) anyway. Claiming that JavaScript is required for Web apps and, thus, that there is no real need to pre-render HTML is fair (because SEO is usually not or less important for apps). But because we are going responsive, we will inherently pay a lot attention to mobile and, thus, to performance as well. This is why we are betting heavily on progressive enhancement.

Responsive Web Design

RWD has mostly to do with not knowing the screen’s width. We have multiple tools to work with, such as media queries, relative units and responsive images. No matter how wonderful RWD is conceptually, some technical issues still need to be solved.

start-image_mini
Not many big websites have gone truly responsive since The Boston Globe. (Image credits: Antoine Lefeuvre)

Client-Side Solutions

In the end, RWD is mostly about client-side solutions. Assuming that the server basically sends the same initial document and resources (images, CSS and JavaScript) to every device, any responsive measures will be taken on the client, such as:

  • applying specific styles through media queries;
  • using (i.e. polyfilling) <picture> or @srcset to get responsive images;
  • loading additional content.

Some of the issues surrounding RWD today are the following:

  • Responsive images haven’t been standardized.
  • Devices still load the CSS behind media queries that they never use.
  • We lack (browser-supported) responsive layout systems (think flexbox, grid, regions, template).
  • We lack element queries.

Server-Side Solutions: Responsive Content

Imagine that these challenges (such as images not being responsive and CSS loading unnecessarily) were solved on all devices and in all browsers, and that we didn’t have to resort to hacks or polyfills in the client. This would transfer some of the load from the client to the server (for instance, the CMS would have more control over responsive images).

But we would still face the issue of responsive content. Although many believe that the constraints of mobile help us to focus, to write better content and to build better designs, sometimes it’s simply not enough. This is where server-side solutions such as RESS and HTTP Client Hints come in. Basically, by knowing the device’s constraints and features up front, we can serve a different and optimized template to it.

Assuming we want to COPE, DRY and KISS and stuff, I think it comes down to where you want to draw the line here: the more important that performance and content tailored to each device is, the more necessary server-side assistance becomes. But we also have to bet on user-agent detection and on content negation. I’d say that this is a big threshold, but your mileage may vary. In any case, I can see content-focused websites getting there sooner than Web apps.

Having said that, I am focusing on RWAs in this article without resorting to server-side solutions.

Responsive Behavior

RWD is clearly about layout and design, but we will also have to focus on responsive behavior. It is what makes applications different from websites. Fluid grids and responsive images are great, but once we start talking about Web applications, we also have to be responsive in loading modules according to screen size or device capability (i.e. pretty much media queries for JavaScript).

For instance, an application might require GPS to be usable. Or it might contain a large interactive table that just doesn’t cut it on a small screen. And we simply can’t set display: none on all of these things, nor can we build everything twice.

We clearly need more.

Part 2: Building RWAs

To quickly recap, our fundamental concepts are:

  • progressive enhancement,
  • responsive design,
  • responsive behavior.

Fully armed, we will now look into a way to build responsive, context-aware applications. We’ll do this by declaratively specifying modules, conditions for loading modules, and extended modules or variants, based on feature detection and media queries. Then, we’ll dig deeper into the mechanics of dependency injection to see how all of this can be implemented.

Declarative Module Injection

We’ll start off by applying the concepts of progressive enhancement and mobile first, and create a common set of HTML, CSS and JavaScript for all devices. Later, we’ll progressively enhance the application based on content, screen size, device features, etc. The foundation is always plain HTML. Consider this fragment:


<div data-module="myModule">
    <p>Pre-rendered content</p>
</div>

Let’s assume we have some logic to query the data-module attribute in our document, to load up the referenced application module (myModule) and then to attach it to that element. Basically, we would be adding behavior that targets a particular fragment in the document.

This is our first step in making a Web application responsive: progressive module injection. Also, note that we could easily attach multiple modules to a single page in this way.

Conditional Module Injection

Sometimes we want to load a module only if a certain condition is met — for instance, when the device has a particular feature, such as touch or GPS:


<div data-module="find/my/dog" data-condition="gps">
    <p>Pre-rendered fallback content if GPS is unavailable.</p>
</div>

This will load the find/my/dog module only if the geolocation API is available.

Note: For the smallest footprint possible, we’ll simply use our own feature detection for now. (Really, we’re just checking for 'geolocation' in navigator.) Later, we might need more robust detection and so delegate this task to a tool such as Modernizr or Has.js (and possibly PhoneGap in hybrid mode).

Extended Module Injection

What if we want to load variants of a module based on media queries? Take this syntax:


<div data-module="myModule" data-variant="large">
    <p>Pre-rendered content</p>
</div>

This will load myModule on small screens and myModule/large on large screens.

For brevity, this single attribute contains the condition and the location of the variant (by convention). Programmatically, you could go mobile first and have the latter extend from the former (or separated modules, or even the other way around). This can be decided case by case.

Media Queries

Of course, we couldn’t call this responsive if it wasn’t actually driven by media queries. Consider this CSS:


@media all and (min-width: 45em) {
	body:after {
		content: 'large';
		display: none;
	}
}

Then, from JavaScript this value can be read:


var size = window.getComputedStyle(document.body,':after').getPropertyValue('content');

And this is why we can decide to load the myModule/large module from the last example if size === "large", and load myModule otherwise. Being able to conditionally not load a module at all is useful, too:


<div data-module="myModule" data-condition="!small">
    <p>Pre-rendered content</p>
</div>

There might be cases for media queries inside module declarations:


<div data-module="myModule" data-matchMedia="min-width: 800px">
    <p>Pre-rendered content</p>
</div>

Here we can use the window.matchMedia() API (a polyfill is available). I normally wouldn’t recommend doing this because it’s not very maintainable. Following breakpoints as set in CSS seems logical (because page layout probably dictates which modules to show or hide anyway). But obviously it depends on the situation. Targeted element queries may also prove useful:


<div data-module="myModule" data-matchMediaElement="(min-width: 600px)"></div>

Please note that the names of the attributes used here represent only an example, a basic implementation. They’re supposed to clarify the idea. In a real-world scenario, it might be wise to, for example, namespace the attributes, to allow for multiple modules and/or conditions, and so on.

Device Orientation

Take special care with device orientation. We don’t want to load a different module when the device is rotated. So, the module itself should be responsive, and the page’s layout might need to accommodate for this.

Connecting The Dots

The concept of responsive behavior allows for a great deal of flexibility in how applications are designed and built. We will now look into where those “modules” come in, how they relate to application structure, and how this module injection might actually work.

Applications and Modules

We can think of a client-side application as a group of application modules that are built with low-level modules. As an example, we might have User and Message models and a MessageDetail view to compose an Inbox application module, which is part of an entire email client application. The details of implementation, such as the module format to be used (for example, AMD, CommonJS or the “revealing module” pattern), are not important here. Also, defining things this way doesn’t mean we can’t have a bunch of mini-apps on a single page. On the other hand, I have found this approach to scale well to applications of any size.

A Common Scenario

An approach I see a lot is to put something like <div id="container"> in the HTML, and then load a bunch of JavaScript that uses that element as a hook to append layouts or views. For a single application on a single page, this works fine, but in my experience it doesn’t scale well:

  • Application modules are not very reusable because they rely on a particular element to be present.
  • When multiple applications or application modules are to be instantiated on a single page, they all need their own particular element, further increasing complexity.

To solve these issues, instead of letting application modules control themselves, what about making them more reusable by providing the element they should attach to? Additionally, we don’t need to know which modules must be loaded up front; we will do that dynamically. Let’s see how things come together using powerful patterns such as Dependency Injection (DI) and Inversion of Control (IOC).

Dependency Injection

You might have wondered how myModule actually gets loaded and instantiated.

Loading the dependency is pretty easy. For instance, take the string from the data-module attribute (myModule), and have a module loader fetch the myModule.js script.

Let’s assume we are using AMD or CommonJS (either of which I highly recommended) and that the module exports something (say, its public API). Let’s also assume that this is some kind of constructor that can be instantiated. We don’t know how to instantiate it because we don’t know exactly what it is up front. Should we instantiate it using new? What arguments should be passed? Is it a native JavaScript constructor function or a Backbone view or something completely different? Can we make sure the module attaches itself to the DOM element that we provide it with?

We have a couple of possible approaches here. A simple one is to always expect the same exported value — such as a Backbone view. It’s simple but might be enough. It would come down to this (using AMD and a Backbone view):


var moduleNode = document.querySelector('[data-module]'),
    moduleName = node.getAttribute('data-module');

require([moduleName], function(MyBackBoneView) {
    new MyBackBoneView({
        el: moduleNode
    });
})

That’s the gist of it. It works fine, but there are even better ways to apply this pattern of dependency injection.

IOC Containers

Let’s take a library such as the excellent wire.js library by cujoJS. An important concept in wire.js is “wire specs,” which essentially are IOC containers. It performs the actual instantiation of the application modules based on a declarative specification. Going this route, the data-module should reference a wire spec (instead of a module) that describes what module to load and how to instantiate it, allowing for practically any type of module. Now, all we need to do is pass the reference to the spec and the viewNode to wire.js. We can simply define this:


wire([specName, { viewNode: moduleNode }]);

Much better. We let wire.js do all of the hard work. Besides, wire has a ton of other features.

In summary, we can say that our declarative composition in HTML (<div data-module="">) is parsed by the composer, and consults the advisor about whether the module should be loaded (data-condition) and which module to load (data-module or data-variant), so that the dependency injector (DI, wire.js) can load and apply the correct spec and application module:

Declarative Composition

Detections for screen size and device features that are used to build responsive applications are sometimes implemented deep inside application logic. This responsibility should be laid elsewhere, decoupled more from the particular applications. We are already doing our (responsive) layout composition with HTML and CSS, so responsive applications fit in naturally. You could think of the HTML as an IOC container to compose applications.

You might not like to put (even) more information in the HTML. And honestly, I don’t like it at all. But it’s the price to pay for optimized performance when scaling up. Otherwise, we would have to make another request to find out whether and which module to load, which defeats the purpose.

Wrapping Up

I think the combination of declarative application composition, responsive module loading and module extension opens up a boatload of options. It gives you a lot of freedom to implement application modules the way you want, while supporting a high level of performance, maintainability and software design.

Performance and Build

Sometimes RWD actually decreases the performance of a website when implemented superficially (such as by simply adding some media queries or extra JavaScript). But for RWA, performance is actually what drives the responsive injection of modules or variants of modules. In the spirit of mobile first, load only what is required (and enhance from there).

Looking at the build process to minify and optimize applications, we can see that the challenge lies in finding the right approach to optimize either for a single application or for reusable application modules across multiple pages or contexts. In the former case, concatenating all resources into a single JavaScript file is probably best. In the latter case, concatenating resources into a separate shared core file and then packaging application modules into separate files is a sound approach.

A Scalable Approach

Responsive behavior and complete RWAs are powerful in a lot of scenarios, and they can be implemented using various patterns. We have only scratched the surface. But technically and conceptually, the approach is highly scalable. Let’s look at some example scenarios and patterns:

  • Sprinkle bits of behavior onto static content websites.
  • Serve widgets in a portal-like environment (think a dashboard, iGoogle or Netvibes). Load a single widget on a small screen, and enable more as screen resolution allows.
  • Compose context-aware applications in HTML using reusable and responsive application modules.

In general, the point is to maximize portability and reach by building on proven concepts to run applications on multiple platforms and environments.

Future-Proof and Portable

Some of the major advantages of building applications in HTML5 is that they’re future-proof and portable. Write HTML5 today and your efforts won’t be obsolete tomorrow. The list of platforms and environments where HTML5-powered applications run keeps growing rapidly:

  • As regular Web applications in browsers;
  • As hybrid applications on mobile platforms, powered by Apache Cordova (see note below):
    • iOS,
    • Android,
    • Windows Phone,
    • BlackBerry;
  • As Open Web Apps (OWA), currently only in Firefox OS;
  • As desktop applications (such as those packaged by the Sencha Desktop Packager):
    • Windows,
    • OS X,
    • Linux.

Note: Tools such as Adobe PhoneGap Build, IBM Worklight and Telerik’s Icenium all use Apache Cordova APIs to access native device functionality.

Demo

You might want to dive into some code or see things in action. That’s why I created a responsive Web apps repository on GitHub, which also serves as a working demo.

Conclusion

Honestly, not many big websites (let alone true Web applications) have gone truly responsive since The Boston Globe. However, looking at deciding factors such as cost, distribution, reach, portability and auto-updating, RWAs are both a huge opportunity and a big challenge. It’s only a matter of time before they become much more mainstream.

We are still looking for ways to get there, and we’ve covered just one approach to building RWAs here. In any case, declarative composition for responsive applications is quite powerful and could serve as a solid starting point.

(al) (ea)

© Lars Kappert for Smashing Magazine, 2013.

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Before drawing anything in a browser, ask yourself three questions:

  1. Do you need to support older browsers?If the answer is yes, then your only choice is Raphaël. It handles browsers all the way back to IE 7 and Firefox 3. Raphaël even has some support for IE 6, although some of its underlying technology cannot be implemented there.
  2. Do you need to support Android?Android doesn’t support SVG, so you’ll have to use Paper.js or Processing.js. Some rumors say that Android 4 will handle SVG, but the majority of Android devices won’t support it for years.
  3. Is your drawing interactive?Raphaël and Paper.js focus on interaction with drawn elements through clicking, dragging and touch. Processing.js doesn’t support any object-level events, so responding to user gestures is very difficult. Processing.js can draw a cool animation on your home page, but the other tools are better for interactive applications.

Paper.js, Processing.js and Raphaël are the leading libraries for drawing on the Web right now. A couple of others are up and coming, and you can always use Flash, but these three work well with HTML5 and have the widest support among browser vendors.

Choosing the right framework will determine the success of your project. This article covers the advantages and disadvantages of each, and the information you need to make the best choice.

All of the code in this article is open source and can be run on the demo page that accompanies this article.

Overview

Paper.js
Processing.js
Raphaël

Technology
canvas tag
canvas tag
SVG

Language
PaperScript
Processing script
JavaScript

Browsers
IE 9
IE 9
IE 7

Mobile
Yes
Yes
iOS only

Model
Vector and raster
Raster
Vector

Size
56 KB
64 KB
20 KB

 

It’s all JavaScript once the page runs, but the frameworks take different paths to get there. Raphaël is written directly in JavaScript, but Paper.js uses PaperScript, and Processing.js uses its own script. They all support Firefox, Chrome and Safari, but Internet Explorer is an issue — Paper.js and Processing.js use the canvas tag and thus require IE 9.

PaperScript is a JavaScript extension that makes it possible to write scripts that don’t pollute the global namespace. This cuts down on JavaScript conflicts. PaperScript also supports direct math on objects such as Point and Size: you can add two points together as if they were numbers.

Processing.js is based on a framework named Processing, which runs in the Java Virtual Machine. You define int and float instead of var, and you can use classes with Java-style inheritance. While the Processing.js script looks a little like Java, it’s more like JavaScript and doesn’t require many of the more complex features of Java.

Using all three libraries is easy if you have some familiarity with JavaScript.

Getting Started

Start by importing each library. The process for setting each up is a little different.

Setting Up Paper.js

<head>
<script src="paper.js" type="text/javascript" charset="utf-8"></script>
<script type="text/paperscript" canvas="paperCircle" src="paper_circle.pjs" id="script"></script>
</head>
<body>
<canvas id="paperCircle" class="canvas" width="200" height="200" style="background-color: white;"></canvas>

Paper.js specifies a script type of text/paperscript and the ID of the canvas tag that you’ll draw on. It uses that ID to know where to draw.

Setting Up Processing.js

<head>
<script src="processing.js" type="text/javascript" charset="utf-8"></script>
</head>
<body>
<canvas width="200" height="200" class="canvas" data-processing-sources="processing_circle.java"></canvas>

Processing.js uses the data-processing-sources attribute of the canvas tag to import your drawing. I use a .java extension for Processing’s source file so that my editor color-codes it properly. Some authors use a .pde or .pjs extension. It’s up to you.

Setting Up Raphaël

<head>
<script src="raphael-min.js" type="text/javascript" charset="utf-8"></script>
<script src="raphael_circle.js" type="text/javascript" charset="utf-8"></script>
</head>

Raphaël is imported like any other JavaScript file. It works well with jQuery’s ready function or any other JavaScript framework.

Now we can start drawing.

Object-Oriented Drawing

Both Paper.js and Raphaël use object-oriented drawing: you draw a circle and get back a circle object. Processing.js draws the circle and doesn’t give you anything back. The following simple example makes it clear. Let’s start with a circle in the middle of the screen at point 100,100.

Paper.js:

var circle = new Path.Circle(new Point(100, 100), 10);
circle.fillColor = '#ee2a33';

Raphaël:

var paper = Raphael('raphaelCircle', 200, 200);
var c = paper.ellipse(100, 100, 10, 10);
c.attr({'fill': '#00aeef', 'stroke': '#00aeef'});

Processing.js:

void setup() {
   size(200, 200);
}

void draw() {
   background(#ffffff);
   translate(100, 100);
   fill(#52b755);
   noStroke();
   ellipse(0, 0, 20, 20);
}

Each code snippet draws the same circle. The difference is in what you can do with it.

Paper.js creates the circle as a path object. We can hold onto the object and change it later. In Paper.js, circle.fillColor = 'red'; fills our circle with red, and circle.scale(2) makes it twice as big.

Raphaël follows Paper.js’ object-oriented model. In Raphaël, we can change the color of our circle with circle.attr('fill', 'red');, and scale it up with circle.scale(2, 2);. The point is that the circle is an object that we can work with later.

Processing.js doesn’t use objects; the ellipse function doesn’t return anything. Once we’ve drawn our circle in Processing.js, it’s part of the rendered image, like ink on a page; it’s not a separate object that can be changed by modifying a property. To change the color, we have to draw a new circle directly on top of the old one.

When we call fill, it changes the fill color for every object we draw thereafter. After we call translate and fill, every shape will be filled with green.

Because functions change everything, we can easily end up with unwanted side effects. Call a harmless function, and suddenly everything is green! Processing.js provides the pushMatrix and popMatrix functions to isolate changes, but you have to remember to call them.

Processing.js’ no-objects philosophy means that complex drawings run faster. Paper.js and Raphaël contain references to everything you draw, and so the memory overhead created by complex animations will slow down your application. Processing.js contains no references to drawn elements, so each shape takes up a tiny amount of memory. Memory overhead pays off if you need to access an object later, but it’s overkill if you don’t. Paper.js gives you a way out of this with the Symbol object and by rasterizing objects, but you have to plan ahead to keep the app running fast.

The object-oriented versus no-objects philosophy has implications for everything you do with these libraries. It shapes the way each library handles animations.

Let’s Make It Move

Rotating circles aren’t very interesting, so we’ll make a square rotate around a circle.

Animation in Processing.js

Processing.js supports animation with the predefined setup and draw functions, like this:

float angle = 0.0;
void setup() {
   size(200, 200);
   frameRate(30);
}

void draw() {
   background(#ffffff);
   translate(100, 100);
   fill(#52b755);
   noStroke();
   ellipse(0, 0, 20, 20);

   rotate(angle);
   angle += 0.1;
   noFill();
   stroke(#52b755);
   strokeWeight(2);
   rect(-40, -40, 80, 80);
}

The setup function is called once when the application starts. We tell Processing.js to animate with a frame rate of 30 frames per second, so our draw function will be called 30 times every second. That rate might sound high, but it’s normal for making an animation look smooth.

The draw function starts by filling in the background of the canvas; it paints over anything left over from previous invocations of the draw function. This is a major difference with Processing.js: we are not manipulating objects, so we always have to clean up previously drawn shapes.

Next, we translate the coordinate system to the 100,100 point. This positions the drawing at 100 pixels from the left and 100 pixels from the top of the canvas for every drawing until we reset the coordinates. Then, we rotate by the specified angle. The angle increases with every draw, which makes the square spin around. The last step is to draw a square using the fill and rect functions.

The rotate function in Processing.js normally takes radians instead of degrees. That’s why we increase the angle of each frame by 0.2, rather than a higher number such as 3. This is one of many times when trigonometry shows up in this method of drawing.

Animation in Paper.js

Paper.js makes this simple animation easier than in Processing.js, with a persistent rectangle object:

var r;

function init() {
   var c = new Path.Circle(new Point(100, 100), 10);
   c.fillColor = '#ee2a33';

   var point = new Point(60, 60);
   var size = new Size(80, 80);
   var rectangle = new Rectangle(point, size);
   r = new Path.Rectangle(rectangle);
   r.strokeColor = '#ee2a33';
   r.strokeWidth = 2;
}

function onFrame(event) {
   r.rotate(3);
}

init();

We maintain the state of our square as an object, and Paper.js handles drawing it on the screen. We rotate it a little for each frame. Paper.js manages the path, so we don’t have to redraw everything for each frame or keep track of the angle of rotation or worry about affecting other objects.

Animation in Raphaël

Animations in Raphaël are written in standard JavaScript, so Raphaël doesn’t have specific functions for handling animation frames. Instead, we rely on JavaScript’s setInterval function.

var paper = Raphael('raphaelAnimation', 200, 200);
var c = paper.ellipse(100, 100, 10, 10);
c.attr({
   'fill': '#00aeef',
   'stroke': '#00aeef'
});

var r = paper.rect(60, 60, 80, 80);
r.attr({
   'stroke-width': 2,
   'stroke': '#00aeef'
});

setInterval(function() {
   r.rotate(6);
}, 33);

Raphaël is similar to Paper.js in its object-oriented approach. We have a square, and we call a rotate function on it. Thus, we can easily spin the square with a small amount of code.

Interaction

Raphaël shines when you need to enable interactivity in a drawing. It provides an event model similar to JavaScript’s, making it easy to detect clicks, drags and touches. Let’s make our square clickable.

Interactions With Raphaël

var paper = Raphael('raphaelInteraction', 200, 200);
var r = paper.rect(60, 60, 80, 80);
r.attr({'fill': '#00aeef', 'stroke': '#00aeef'});

var clicked = false;

r.click(function() {
   if (clicked) {
      r.attr({'fill': '#00aeef', 'stroke': '#00aeef'});
   } else {
      r.attr({'fill': '#f00ff0', 'stroke': '#f00ff0'});
   }
   clicked = !clicked;
});

The click function in Raphaël works like jQuery, and you can add it to any object. Once we get the click event, changing the color of the square is easy. Raphaël has more functions to support dragging, hovering and all of the other user interactions you expect from JavaScript.

Interactions With Paper.js

Paper.js has a different way of managing interactions, but it’s still pretty easy:

var hitOptions = {
   fill: true,
   tolerance: 5
};

function init() {
   var point = new Point(60, 60);
   var size = new Size(80, 80);
   var rectangle = new Rectangle(point, size);
   r = new Path.Rectangle(rectangle);
   r.fillColor = '#ee2a33';
}

function onMouseUp(event) {
   var hitResult = project.hitTest(event.point, hitOptions);

   if (hitResult && hitResult.item) {
      if (hitResult.item.clicked) {
         hitResult.item.fillColor = '#ee2a33';
      } else {
         hitResult.item.fillColor = '#f00ff0';
      }

      hitResult.item.clicked = !hitResult.item.clicked;
   }
}

init();

Paper.js deals with mouse gestures through a concept called “hit testing.” A hit finds the point under the mouse cursor and figures out which object it lies above. Hit options enable you to define how the hit works: you can set options for such things as how close the mouse has to be, and whether the middle of the object counts or only the edge. We can extend this hit test to any object or group of objects in Paper.js.

The Paper.js team added object-level events similar to Raphaël’s a few weeks ago. The events should show up in the next release.

Interactions With Processing.js

Processing.js makes detecting mouse clicks tricky. It doesn’t support object-level events or hit testing, so we’re pretty much on our own.

float bx;
float by;
int bs = 20;
boolean bover = false;
boolean clicked = false;

void setup() {
   size(200, 200);
   bx = width/2.0;
   by = height/2.0;
   noStroke();
   fill(#52b755);
   frameRate(10);
}

void draw() {
   background(#ffffff);

   // Test if the cursor is over the box
   if (mouseX > bx-bs && mouseX < bx+bs &&        mouseY > by-bs && mouseY < by+bs) {
      bover = true;
   } else {
      bover = false;
   }

   translate(100, 100);
   rect(-40, -40, 80, 80);
}

void mousePressed() {
   if (bover) {
      if (clicked) {
         fill(#52b755);
      } else {
         fill(#f00ff0);
      }
      clicked = !clicked;
   }
}

Once Processing.js draws the square, it forgets about it. We want the color of the square to change when we click on it, but the script doesn’t know that, so we have to do all of the calculations ourselves. The draw function detects the mouse cursor’s position and does the math to determine whether it lies within the square.

The code is not too bad for the square, but our circle would need πr2. And more complex shapes such as ovals, curves and compound shapes would require even more math.

No Clear Winner

Each framework has its advantages. Between them, the features make for cool demos and even cooler applications.

Showing Off Paper.js

Paper.js excels at manipulating complex shapes. It can turn, twist and transform any object in hundreds of ways. These transforms make it easy to convert objects based on interactive gestures. The new Google Music Tour, which makes colored lines beat in time to music, shows how one can make complex changes on simple shapes.

The other wow factor in Paper.js is its support of raster graphics. Paper.js can completely change the way images are drawn — including by turning them into spirals and Q*bert boards.

Showing Off Processing.js

Processing.js’ biggest feature is speed, making it possible to draw complex animations on slower machines. Many examples are out there, but the fluidity of Processing.js animations shows up best in Ricardo Sánchez’s koi pond.

The swishing of the tails and waving of the bodies make the koi look very natural. Processing.js makes this easy, with support for curves and customized animations.

Processing.js also supports complex drawing elements such as shading, lighting and 3-D transforms. If you want to create complex animations in canvas very quickly, then Processing.js is the clear winner.

Showing Off Raphaël

The best feature of Raphaël is its support for Internet Explorer 7 and 8. If your application has to run on older browsers, then Raphaël is the only option.

The other big feature of Raphaël is its community. Raphaël is older than Paper.js and Processing.js and thus has had more time to build examples, tutorials and user support. It has built-in support for easing, animation transforms and the event handlers that we saw in the interaction example; it also has a comprehensive charting library.

Raphaël also has the best tooling support.

The Tools

If you’ve worked with Flash, the lack of tools for these frameworks will disappoint you. Many of the frameworks will edit SVG images, but none of them offer a drag-and-drop method for creating applications.

A few simple tools are out there, but they are more like proofs of concept than actual products. Adobe is working on a tool named Edge, but it has a long way to go.

If you want to drag and drop, then Web animations aren’t for you yet. Right now, this method of drawing is more like video-game programming. Writing code to draw a circle is tougher than clicking and dragging, but it scales to more complex applications and some fun stuff.

Let’s Build Something Real

So far, we’ve looked at some simple examples, seen the best features of each platform and looked at how to choose the right one. Each framework has pluses and minuses, but judging them is difficult until you create an actual application.

To compare each framework, I’ve drawn some gears. Each gear is made up of two circles, with a set of teeth around the outer circle.

When the shapes are all given the same color, they look just like a gear.

Every gear will rotate a little with each frame of the animation. The first gear will be given a speed, and the rest will move relative to it. The gears will arrange, mesh and rotate together with a crazy amount of trigonometry. Put them together and you’ve got a complex gear system.

Paper.js:

Processing.js:

Raphaël:

Well, that wasn’t quite Raphaël. The rotate function work different in Raphaël than it does in Paper.js and Processing.js. Raphaël doesn’t support rotation around a fixed point. Instead, the teeth of the gears are drawn and redrawn independently, and they fly through the air instead of rotating around the center. The only way to really turn the gear would be to draw the entire gear as a single path, and that takes more math than I’m willing to write. If anyone wants to give it a try, everything is open source.

The Future Of Web Drawing

We gamble on every new technology that we learn: we hope that it catches on and that our investment pays off. Technologies rise and fall on their respective merits, but other factors comes into play, such as vendor support and business uses. The future of our industry is almost a guessing game.

Right now, Flash looks like a bad investment. Flash has great tools, years of development and a large community, but even Adobe is moving away from it.

SVG is in a similar situation. Browsers support it now, but it isn’t getting a lot of attention.

Every browser vendor is working hard to render canvas faster, to use hardware acceleration and to better support libraries such as Paper.js and Processing.js. All mobile devices support canvas, and their developers are working to improve it.

(al)

© Zack Grossbart for Smashing Magazine, 2012.

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