| 147 |
Christmas Is In The AIR |
That’s right, Christmas is coming up fast and there’s plenty of things to do. Get the tree and lights up, get the turkey, buy presents and who know what else. And what about Santa? He’s got a list. I’m pretty sure he’s checking it twice.
Sure, we could use an existing list making web site or even a desktop widget. But we’re geeks! What’s the fun in that? Let’s build our own to-do list application and do it with Adobe AIR!
What’s Adobe AIR?
Adobe AIR, formerly codenamed Apollo, is a runtime environment that runs on both Windows and OSX (with Linux support to follow). This runtime environment lets you build desktop applications using Adobe technologies like Flash and Flex. Oh, and HTML. That’s right, you web standards lovin’ maniac. You can build desktop applications that can run cross-platform using the trio of technologies, HTML, CSS and JavaScript.
If you’ve tried developing with AIR before, you’ll need to get re-familiarized with the latest beta release as many things have changed since the last one (such as the API and restrictions within the sandbox.)
To get started
To get started in building an AIR application, you’ll need two basic things:
The AIR runtime. The runtime is needed to run any AIR-based application.
The SDK. The software development kit gives you all the pieces to test your application. Unzip the SDK into any folder you wish.
You’ll also want to get your hands on the JavaScript API documentation which you’ll no doubt find yourself getting into before too long. (You can download it, too.)
Also of interest, some development environments have support for AIR built right in. Aptana doesn’t have support for beta 3 yet but I suspect it’ll be available shortly.
Within the SDK, there are two main tools that we’ll use: one to test the application (ADL) and another to build a distributable package of our application (ADT). I’ll get into this some more when we get to that stage of development.
Building our To-do list application
The first step to building an application within AIR is to create an XML file that defines our default application settings. I call mine application.xml, mostly because Aptana does that by default when creating a new AIR project. It makes sense though and I’ve stuck with it. Included in the templates folder of the SDK is an example XML file that you can use.
The first key part to this after specifying things like the application ID, version, and filename, is to specify what the default content should be within the content tags. Enter in the name of the HTML file you wish to load. Within this HTML file will be our application.
<content>ui.html</content>
Create a new HTML document and name it ui.html and place it in the same directory as the application.xml file. The first thing you’ll want to do is copy over the AIRAliases.js file from the frameworks folder of the SDK and add a link to it within your HTML document.
<script type="text/javascript" src="AIRAliases.js"></script>
The aliases create shorthand links to all of the Flash-based APIs.
Now is probably a good time to explain how to debug your application.
Debugging our application
So, with our XML file created and HTML file started, let’s try testing our ‘application’. We’ll need the ADL application located in BIN folder of the SDK and tell it to run the application.xml file.
/path/to/adl /path/to/application.xml
You can also just drag the XML file onto ADL and it’ll accomplish the same thing. If you just did that and noticed that your blank application didn’t load, you’d be correct. It’s running but isn’t visible. Which at this point means you’ll have to shut down the ADL process. Sorry about that!
Changing the visibility
You have two ways to make your application visible. You can do it automatically by setting the placing true in the visible tag within the application.xml file.
<visible>true</visible>
The other way is to do it programmatically from within your application. You’d want to do it this way if you had other startup tasks to perform before showing the interface. To turn the UI on programmatically, simple set the visible property of nativeWindow to true.
<script type="text/javascript">
nativeWindow.visible = true;
</script>
Sandbox Security
Now that we have an application that we can see when we start it, it’s time to build the to-do list application. In doing so, you’d probably think that using a JavaScript library is a really good idea — and it can be but there are some limitations within AIR that have to be considered.
An HTML document, by default, runs within the application sandbox. You have full access to the AIR APIs but once the onload event of the window has fired, you’ll have a limited ability to make use of eval and other dynamic script injection approaches. This limits the ability of external sources from gaining access to everything the AIR API offers, such as database and local file system access. You’ll still be able to make use of eval for evaluating JSON responses, which is probably the most important if you wish to consume JSON-based services.
If you wish to create a greater wall of security between AIR and your HTML document loading in external resources, you can create a child sandbox. We won’t need to worry about it for our application so I won’t go any further into it but definitely keep this in mind.
Finally, our application
Getting tired of all this preamble? Let’s actually build our to-do list application. I’ll use jQuery because it’s small and should suit our needs nicely. Let’s begin with some structure:
<body>
<input type="text" id="text" value="">
<input type="button" id="add" value="Add">
<ul id="list"></ul>
</body>
Now we need to wire up that button to actually add a new item to our to-do list.
<script type="text/javascript">
$(document).ready(function(){
// make sure the application is visible
nativeWindow.visible = true;
$('#add').click(function(){
var t = $('#text').val();
if(t)
{
// use DOM methods to create the new list item
var li = document.createElement('li');
// the extra space at the end creates a buffer between the text
// and the delete link we're about to add
li.appendChild(document.createTextNode(t + ' '));
// create the delete link
var del = document.createElement('a');
// this makes it a true link. I feel dirty doing this.
del.setAttribute('href', '#');
del.addEventListener('click', function(evt){
this.parentNode.parentNode.removeChild(this.parentNode);
});
del.appendChild(document.createTextNode('[del]'));
li.appendChild(del);
// append everything to the list
$('#list').append(li);
//reset the text box
$('#text').val('');
}
})
});
</script>
And just like that, we’ve got a to-do list! That’s it! Just never close your application and you’ll remember everything. Okay, that’s not very practical. You need to have some way of storing your to-do items until the next time you open up the application.
Storing Data
You’ve essentially got 4 different ways that you can store data:
Using the local database. AIR comes with SQLLite built in. That means you can create tables and insert, update and select data from that database just like on a web server.
Using the file system. You can also create files on the local machine. You have access to a few folders on the local system such as the documents folder and the desktop.
Using EcryptedLocalStore. I like using the EcryptedLocalStore because it allows you to easily save key/value pairs and have that information encrypted. All this within just a couple lines of code.
Sending the data to a remote API. Our to-do list could sync up with Remember the Milk, for example.
To demonstrate some persistence, we’ll use the file system to store our files. In addition, we’ll let the user specify where the file should be saved. This way, we can create multiple to-do lists, keeping them separate and organized.
The application is now broken down into 4 basic tasks:
Load data from the file system.
Perform any interface bindings.
Manage creating and deleting items from the list.
Save any changes to the list back to the file system.
Loading in data from the file system
When the application starts up, we’ll prompt the user to select a file or specify a new to-do list. Within AIR, there are 3 main file objects: File, FileMode, and FileStream. File handles file and path names, FileMode is used as a parameter for the FileStream to specify whether the file should be read-only or for write access. The FileStream object handles all the read/write activity.
The File object has a number of shortcuts to default paths like the documents folder, the desktop, or even the application store. In this case, we’ll specify the documents folder as the default location and then use the browseForSave method to prompt the user to specify a new or existing file. If the user specifies an existing file, they’ll be asked whether they want to overwrite it.
var store = air.File.documentsDirectory;
var fileStream = new air.FileStream();
store.browseForSave("Choose To-do List");
Then we add an event listener for when the user has selected a file. When the file is selected, we check to see if the file exists and if it does, read in the contents, splitting the file on new lines and creating our list items within the interface.
store.addEventListener(air.Event.SELECT, fileSelected);
function fileSelected()
{
air.trace(store.nativePath);
// load in any stored data
var byteData = new air.ByteArray();
if(store.exists)
{
fileStream.open(store, air.FileMode.READ);
fileStream.readBytes(byteData, 0, store.size);
fileStream.close();
if(byteData.length > 0)
{
var s = byteData.readUTFBytes(byteData.length);
oldlist = s.split(“\r\n”);
// create todolist items
for(var i=0; i < oldlist.length; i++)
{
createItem(oldlist[i], (new Date()).getTime() + i );
}
}
}
}
Perform Interface Bindings
This is similar to before where we set the click event on the Add button but we’ve moved the code to save the list into a separate function.
$('#add').click(function(){
var t = $('#text').val();
if(t){
// create an ID using the time
createItem(t, (new Date()).getTime() );
}
})
Manage creating and deleting items from the list
The list management is now in its own function, similar to before but with some extra information to identify list items and with calls to save our list after each change.
function createItem(t, id)
{
if(t.length == 0) return;
// add it to the todo list
todolist[id] = t;
// use DOM methods to create the new list item
var li = document.createElement('li');
// the extra space at the end creates a buffer between the text
// and the delete link we're about to add
li.appendChild(document.createTextNode(t + ' '));
// create the delete link
var del = document.createElement('a');
// this makes it a true link. I feel dirty doing this.
del.setAttribute('href', '#');
del.addEventListener('click', function(evt){
var id = this.id.substr(1);
delete todolist[id]; // remove the item from the list
this.parentNode.parentNode.removeChild(this.parentNode);
saveList();
});
del.appendChild(document.createTextNode('[del]'));
del.id = 'd' + id;
li.appendChild(del);
// append everything to the list
$('#list').append(li);
//reset the text box
$('#text').val('');
saveList();
}
Save changes to the file system
Any time a change is made to the list, we update the file. The file will always reflect the current state of the list and we’ll never have to click a save button. It just iterates through the list, adding a new line to each one.
function saveList(){
if(store.isDirectory) return;
var packet = '';
for(var i in todolist)
{
packet += todolist[i] + '\r\n';
}
var bytes = new air.ByteArray();
bytes.writeUTFBytes(packet);
fileStream.open(store, air.FileMode.WRITE);
fileStream.writeBytes(bytes, 0, bytes.length);
fileStream.close();
}
One important thing to mention here is that we check if the store is a directory first. The reason we do this goes back to our browseForSave call. If the user cancels the dialog without selecting a file first, then the store points to the documentsDirectory that we set it to initially. Since we haven’t specified a file, there’s no place to save the list.
Hopefully by this point, you’ve been thinking of some cool ways to pimp out your list. Now we need to package this up so that we can let other people use it, too.
Creating a Package
Now that we’ve created our application, we need to package it up so that we can distribute it. This is a two step process. The first step is to create a code signing certificate (or you can pay for one from Thawte which will help authenticate you as an AIR application developer).
To create a self-signed certificate, run the following command. This will create a PFX file that you’ll use to sign your application.
adt -certificate -cn todo24ways 1024-RSA todo24ways.pfx mypassword
After you’ve done that, you’ll need to create the package with the certificate
adt -package -storetype pkcs12 -keystore todo24ways.pfx todo24ways.air application.xml .
The important part to mention here is the period at the end of the command. We’re telling it to package up all files in the current directory.
After that, just run the AIR file, which will install your application and run it.
Important things to remember about AIR
When developing an HTML application, the rendering engine is Webkit. You’ll thank your lucky stars that you aren’t struggling with cross-browser issues. (My personal favourites are multiple backgrounds and border radius!)
Be mindful of memory leaks. Things like Ajax calls and event binding can cause applications to slowly leak memory over time. Web pages are normally short lived but desktop applications are often open for hours, if not days, and you may find your little desktop application taking up more memory than anything else on your machine!
The WebKit runtime itself can also be a memory hog, usually taking about 15MB just for itself. If you create multiple HTML windows, it’ll add another 15MB to your memory footprint. Our little to-do list application shouldn’t be much of a concern, though.
The other important thing to remember is that you’re still essentially running within a Flash environment. While you probably won’t notice this working in small applications, the moment you need to move to multiple windows or need to accomplish stuff beyond what HTML and JavaScript can give you, the need to understand some of the Flash-based elements will become more important.
Lastly, the other thing to remember is that HTML links will load within the AIR application. If you want a link to open in the users web browser, you’ll need to capture that event and handle it on your own. The following code takes the HREF from a clicked link and opens it in the default web browser.
air.navigateToURL(new air.URLRequest(this.href));
Only the beginning
Of course, this is only the beginning of what you can do with Adobe AIR. You don’t have the same level of control as building a native desktop application, such as being able to launch other applications, but you do have more control than what you could have within a web application. Check out the Adobe AIR Developer Center for HTML and Ajax for tutorials and other resources.
Now, go forth and create your desktop applications and hopefully you finish all your shopping before Christmas!
Download the example files. |
2007 |
Jonathan Snook |
jonathansnook |
2007-12-19T00:00:00+00:00 |
https://24ways.org/2007/christmas-is-in-the-air/ |
code |
| 152 |
CSS for Accessibility |
CSS is magical stuff. In the right hands, it can transform the plainest of (well-structured) documents into a visual feast. But it’s not all fur coat and nae knickers (as my granny used to say). Here are some simple ways you can use CSS to improve the usability and accessibility of your site.
Even better, no sexy visuals will be harmed by the use of these techniques. Promise.
Nae knickers
This is less of an accessibility tip, and more of a reminder to check that you’ve got your body background colour specified.
If you’re sitting there wondering why I’m mentioning this, because it’s a really basic thing, then you might be as surprised as I was to discover that from a sample of over 200 sites checked last year, 35% of UK local authority websites were missing their body background colour.
Forgetting to specify your body background colour can lead to embarrassing gaps in coverage, which are not only unsightly, but can prevent your users reading the text on your site if they use a different operating system colour scheme.
All it needs is the following line to be added to your CSS file:
body {background-color: #fff;}
If you pair it with
color: #000;
… you’ll be assured of maintaining contrast for any areas you inadvertently forget to specify, no matter what colour scheme your user needs or prefers.
Even better, if you’ve got standard reset CSS you use, make sure that default colours for background and text are specified in it, so you’ll never be caught with your pants down. At the very least, you’ll have a white background and black text that’ll prompt you to change them to your chosen colours.
Elbow room
Paying attention to your typography is important, but it’s not just about making it look nice.
Careful use of the line-height property can make your text more readable, which helps everyone, but is particularly helpful for those with dyslexia, who use screen magnification or simply find it uncomfortable to read lots of text online.
When lines of text are too close together, it can cause the eye to skip down lines when reading, making it difficult to keep track of what you’re reading across.
So, a bit of room is good.
That said, when lines of text are too far apart, it can be just as bad, because the eye has to jump to find the next line. That not only breaks up the reading rhythm, but can make it much more difficult for those using Screen Magnification (especially at high levels of magnification) to find the beginning of the next line which follows on from the end of the line they’ve just read.
Using a line height of between 1.2 and 1.6 times normal can improve readability, and using unit-less line heights help take care of any pesky browser calculation problems.
For example:
p {
font-family: "Lucida Grande", Lucida, Verdana, Helvetica, sans-serif;
font-size: 1em;
line-height: 1.3;
}
or if you want to use the shorthand version:
p {
font: 1em/1.3 "Lucida Grande", Lucida, Verdana, Helvetica, sans-serif;
}
View some examples of different line-heights, based on default text size of 100%/1em.
Further reading on Unitless line-heights from Eric Meyer.
Transformers: Initial case in disguise
Nobody wants to shout at their users, but there are some occasions when you might legitimately want to use uppercase on your site.
Avoid screen-reader pronunciation weirdness (where, for example, CONTACT US would be read out as Contact U S, which is not the same thing – unless you really are offering your users the chance to contact the United States) caused by using uppercase by using title case for your text and using the often neglected text-transform property to fake uppercase.
For example:
.uppercase {
text-transform: uppercase
}
Don’t overdo it though, as uppercase text is harder to read than normal text, not to mention the whole SHOUTING thing.
Linky love
When it comes to accessibility, keyboard only users (which includes those who use voice recognition software) who can see just fine are often forgotten about in favour of screen reader users.
This Christmas, share the accessibility love and light up those links so all of your users can easily find their way around your site.
The link outline
AKA: the focus ring, or that dotted box that goes around links to show users where they are on the site.
The techniques below are intended to supplement this, not take the place of it. You may think it’s ugly and want to get rid of it, especially since you’re going to the effort of tarting up your links.
Don’t.
Just don’t.
The non-underlined underline
If you listen to Jacob Nielsen, every link on your site should be underlined so users know it’s a link.
You might disagree with him on this (I know I do), but if you are choosing to go with underlined links, in whatever state, then remove the default underline and replacing it with a border that’s a couple of pixels away from the text.
The underline is still there, but it’s no longer cutting off the bottom of letters with descenders (e.g., g and y) which makes it easier to read.
This is illustrated in Examples 1 and 2.
You can modify the three lines of code below to suit your own colour and border style preferences, and add it to whichever link state you like.
text-decoration: none;
border-bottom: 1px #000 solid;
padding-bottom: 2px;
Standing out from the crowd
Whatever way you choose to do it, you should be making sure your links stand out from the crowd of normal text which surrounds them when in their default state, and especially in their hover or focus states.
A good way of doing this is to reverse the colours when on hover or focus.
Well-focused
Everyone knows that you can use the :hover pseudo class to change the look of a link when you mouse over it, but, somewhat ironically, people who can see and use a mouse are the group who least need this extra visual clue, since the cursor handily (sorry) changes from an arrow to a hand.
So spare a thought for the non-pointing device users that visit your site and take the time to duplicate that hover look by using the :focus pseudo class.
Of course, the internets being what they are, it’s not quite that simple, and predictably, Internet Explorer is the culprit once more with it’s frustrating lack of support for :focus. Instead it applies the :active pseudo class whenever an anchor has focus.
What this means in practice is that if you want to make your links change on focus as well as on hover, you need to specify focus, hover and active.
Even better, since the look and feel necessarily has to be the same for the last three states, you can combine them into one rule.
So if you wanted to do a simple reverse of colours for a link, and put it together with the non-underline underlines from before, the code might look like this:
a:link {
background: #fff;
color: #000;
font-weight: bold;
text-decoration: none;
border-bottom: 1px #000 solid;
padding-bottom: 2px;
}
a:visited {
background: #fff;
color: #800080;
font-weight: bold;
text-decoration: none;
border-bottom: 1px #000 solid;
padding-bottom: 2px;
}
a:focus, a:hover, a:active {
background: #000;
color: #fff;
font-weight: bold;
text-decoration: none;
border-bottom: 1px #000 solid;
padding-bottom: 2px;
}
Example 3 shows what this looks like in practice.
Location, Location, Location
To take this example to it’s natural conclusion, you can add an id of current (or something similar) in appropriate places in your navigation, specify a full set of link styles for current, and have a navigation which, at a glance, lets users know which page or section they’re currently in.
Example navigation using location indicators.
and the source code
Conclusion
All the examples here are intended to illustrate the concepts, and should not be taken as the absolute best way to format links or style navigation bars – that’s up to you and whatever visual design you’re using at the time.
They’re also not the only things you should be doing to make your site accessible.
Above all, remember that accessibility is for life, not just for Christmas. |
2007 |
Ann McMeekin |
annmcmeekin |
2007-12-13T00:00:00+00:00 |
https://24ways.org/2007/css-for-accessibility/ |
design |
| 153 |
JavaScript Internationalisation |
or: Why Rudolph Is More Than Just a Shiny Nose
Dunder sat, glumly staring at the computer screen.
“What’s up, Dunder?” asked Rudolph, entering the stable and shaking off the snow from his antlers.
“Well,” Dunder replied, “I’ve just finished coding the new reindeer intranet Santa Claus asked me to do. You know how he likes to appear to be at the cutting edge, talking incessantly about Web 2.0, AJAX, rounded corners; he even spooked Comet recently by talking about him as if he were some pushy web server.
“I’ve managed to keep him happy, whilst also keeping it usable, accessible, and gleaming — and I’m still on the back row of the sleigh! But anyway, given the elves will be the ones using the site, and they come from all over the world, the site is in multiple languages. Which is great, except when it comes to the preview JavaScript I’ve written for the reindeer order form. Here, have a look…”
As he said that, he brought up the textileRef:8234272265470b85d91702:linkStartMarker:“order
form in French”:/examples/javascript-internationalisation/initial.fr.html on the screen. (Same in English).
“Looks good,” said Rudolph.
“But if I add some items,” said Dunder, “the preview appears in English, as it’s hard-coded in the JavaScript. I don’t want separate code for each language, as that’s just silly — I thought about just having if statements, but that doesn’t scale at all…”
“And there’s more, you aren’t displaying large numbers in French properly, either,” added Rudolph, who had been playing and looking at part of the source code:
function update_text() {
var hay = getValue('hay');
var carrots = getValue('carrots');
var bells = getValue('bells');
var total = 50 * bells + 30 * hay + 10 * carrots;
var out = 'You are ordering '
+ pretty_num(hay) + ' bushel' + pluralise(hay) + ' of hay, '
+ pretty_num(carrots) + ' carrot' + pluralise(carrots)
+ ', and ' + pretty_num(bells) + ' shiny bell' + pluralise(bells)
+ ', at a total cost of <strong>' + pretty_num(total)
+ '</strong> gold pieces. Thank you.';
document.getElementById('preview').innerHTML = out;
}
function pretty_num(n) {
n += '';
var o = '';
for (i=n.length; i>3; i-=3) {
o = ',' + n.slice(i-3, i) + o;
}
o = n.slice(0, i) + o;
return o;
}
function pluralise(n) {
if (n!=1) return 's';
return '';
}
“Oh, botheration!” cried Dunder. “This is just so complicated.”
“It doesn’t have to be,” said Rudolph, “you just have to think about things in a slightly different way from what you’re used to. As we’re only a simple example, we won’t be able to cover all possibilities, but for starters, we need some way of providing different information to the script dependent on the language. We’ll create a global i18n object, say, and fill it with the correct language information. The first variable we’ll need will be a thousands separator, and then we can change the pretty_num function to use that instead:
function pretty_num(n) {
n += '';
var o = '';
for (i=n.length; i>3; i-=3) {
o = i18n.thousands_sep + n.slice(i-3, i) + o;
}
o = n.slice(0, i) + o;
return o;
}
“The i18n object will also contain our translations, which we will access through a function called _() — that’s just an underscore. Other languages have a function of the same name doing the same thing. It’s very simple:
function _(s) {
if (typeof(i18n)!='undefined' && i18n[s]) {
return i18n[s];
}
return s;
}
“So if a translation is available and provided, we’ll use that; otherwise we’ll default to the string provided — which is helpful if the translation begins to lag behind the site’s text at all, as at least something will be output.”
“Got it,” said Dunder. “ _('Hello Dunder') will print the translation of that string, if one exists, ‘Hello Dunder’ if not.”
“Exactly. Moving on, your plural function breaks even in English if we have a word where the plural doesn’t add an s — like ‘children’.”
“You’re right,” said Dunder. “How did I miss that?”
“No harm done. Better to provide both singular and plural words to the function and let it decide which to use, performing any translation as well:
function pluralise(s, p, n) {
if (n != 1) return _(p);
return _(s);
}
“We’d have to provide different functions for different languages as we employed more elves and got more complicated — for example, in Polish, the word ‘file’ pluralises like this: 1 plik, 2-4 pliki, 5-21 plików, 22-24 pliki, 25-31 plików, and so on.” (More information on plural forms)
“Gosh!”
“Next, as different languages have different word orders, we must stop using concatenation to construct sentences, as it would be impossible for other languages to fit in; we have to keep coherent strings together. Let’s rewrite your update function, and then go through it:
function update_text() {
var hay = getValue('hay');
var carrots = getValue('carrots');
var bells = getValue('bells');
var total = 50 * bells + 30 * hay + 10 * carrots;
hay = sprintf(pluralise('%s bushel of hay', '%s bushels of hay', hay), pretty_num(hay));
carrots = sprintf(pluralise('%s carrot', '%s carrots', carrots), pretty_num(carrots));
bells = sprintf(pluralise('%s shiny bell', '%s shiny bells', bells), pretty_num(bells));
var list = sprintf(_('%s, %s, and %s'), hay, carrots, bells);
var out = sprintf(_('You are ordering %s, at a total cost of <strong>%s</strong> gold pieces.'),
list, pretty_num(total));
out += ' ';
out += _('Thank you.');
document.getElementById('preview').innerHTML = out;
}
“ sprintf is a function in many other languages that, given a format string and some variables, slots the variables into place within the string. JavaScript doesn’t have such a function, so we’ll write our own. Again, keep it simple for now, only integers and strings; I’m sure more complete ones can be found on the internet.
function sprintf(s) {
var bits = s.split('%');
var out = bits[0];
var re = /^([ds])(.*)$/;
for (var i=1; i<bits.length; i++) {
p = re.exec(bits[i]);
if (!p || arguments[i]==null) continue;
if (p[1] == 'd') {
out += parseInt(arguments[i], 10);
} else if (p[1] == 's') {
out += arguments[i];
}
out += p[2];
}
return out;
}
“Lastly, we need to create one file for each language, containing our i18n object, and then include that from the relevant HTML. Here’s what a blank translation file would look like for your order form:
var i18n = {
thousands_sep: ',',
"%s bushel of hay": '',
"%s bushels of hay": '',
"%s carrot": '',
"%s carrots": '',
"%s shiny bell": '',
"%s shiny bells": '',
"%s, %s, and %s": '',
"You are ordering %s, at a total cost of <strong>%s</strong> gold pieces.": '',
"Thank you.": ''
};
“If you implement this across the intranet, you’ll want to investigate the xgettext program, which can automatically extract all strings that need translating from all sorts of code files into a standard .po file (I think Python mode works best for JavaScript). You can then use a different program to take the translated .po file and automatically create the language-specific JavaScript files for us.” (e.g. German .po file for PledgeBank, mySociety’s .po-.js script, example output)
With a flourish, Rudolph finished editing. “And there we go, localised JavaScript in English, French, or German, all using the same main code.”
“Thanks so much, Rudolph!” said Dunder.
“I’m not just a pretty nose!” Rudolph quipped. “Oh, and one last thing — please comment liberally explaining the context of strings you use. Your translator will thank you, probably at the same time as they point out the four hundred places you’ve done something in code that only works in your language and no-one else’s…”
Thanks to Tim Morley and Edmund Grimley Evans for the French and German translations respectively. |
2007 |
Matthew Somerville |
matthewsomerville |
2007-12-08T00:00:00+00:00 |
https://24ways.org/2007/javascript-internationalisation/ |
code |
| 154 |
Diagnostic Styling |
We’re all used to using CSS to make our designs live and breathe, but there’s another way to use CSS: to find out where our markup might be choking on missing accessibility features, targetless links, and just plain missing content.
Note: the techniques discussed here mostly work in Firefox, Safari, and Opera, but not Internet Explorer. I’ll explain why that’s not really a problem near the end of the article — and no, the reason is not “everyone should just ignore IE anyway”.
Basic Diagnostics
To pick a simple example, suppose you want to call out all holdover font and center elements in a site. Simple: you just add the following to your styles.
font, center {outline: 5px solid red;}
You could take it further and add in a nice lime background or some such, but big thick red outlines should suffice. Now you’ll be able to see the offenders wherever as you move through the site. (Of course, if you do this on your public server, everyone else will see the outlines too. So this is probably best done on a development server or local copy of the site.)
Not everyone may be familiar with outlines, which were introduced in CSS2, so a word on those before we move on. Outlines are much like borders, except outlines don’t affect layout. Eh? Here’s a comparison.
On the left, you have a border. On the right, an outline. The border takes up layout space, pushing other content around and generally being a nuisance. The outline, on the other hand, just draws into quietly into place. In most current browsers, it will overdraw any content already onscreen, and will be overdrawn by any content placed later — which is why it overlaps the images above it, and is overlapped by those below it.
Okay, so we can outline deprecated elements like font and center. Is that all? Oh no.
Attribution
Let’s suppose you also want to find any instances of inline style — that is, use of the style attribute on elements in the markup. This is generally discouraged (outside of HTML e-mails, which I’m not going to get anywhere near), as it’s just another side of the same coin of using font: baking the presentation into the document structure instead of putting it somewhere more manageable. So:
*[style], font, center {outline: 5px solid red;}
Adding that attribute selector to the rule’s grouped selector means that we’ll now be outlining any element with a style attribute.
There’s a lot more that attribute selectors will let use diagnose. For example, we can highlight any images that have empty alt or title text.
img[alt=""] {border: 3px dotted red;}
img[title=""] {outline: 3px dotted fuchsia;}
Now, you may wonder why one of these rules calls for a border, and the other for an outline. That’s because I want them to “add together” — that is, if I have an image which possesses both alt and title, and the values of both are empty, then I want it to be doubly marked.
See how the middle image there has both red and fuchsia dots running around it? (And am I the only one who sorely misses the actual circular dots drawn by IE5/Mac?) That’s due to its markup, which we can see here in a fragment showing the whole table row.
<tr>
<th scope="row">empty title</th>
<td><img src="comic.gif" title="" /></td>
<td><img src="comic.gif" title="" alt="" /></td>
<td><img src="comic.gif" title="" alt="comical" /></td>
</tr>
Right, that’s all well and good, but it misses a rather more serious situation: the selector img[alt=""] won’t match an img element that doesn’t even have an alt attribute. How to tackle this problem?
Not a Problem
Well, if you want to select something based on a negative, you need a negative selector.
img:not([alt]) {border: 5px solid red;}
This is really quite a break from the rest of CSS selection, which is all positive: “select anything that has these characteristics”. With :not(), we have the ability to say (in supporting browsers) “select anything that hasn’t these characteristics”. In the above example, only img elements that do not have an alt attribute will be selected. So we expand our list of image-related rules to read:
img[alt=""] {border: 3px dotted red;}
img[title=""] {outline: 3px dotted fuchsia;}
img:not([alt]) {border: 5px solid red;}
img:not([title]) {outline: 5px solid fuchsia;}
With the following results:
We could expand this general idea to pick up tables who lack a summary, or have an empty summary attribute.
table[summary=""] {outline: 3px dotted red;}
table:not([summary]) {outline: 5px solid red;}
When it comes to selecting header cells that lack the proper scope, however, we have a trickier situation. Finding headers with no scope attribute is easy enough, but what about those that have a scope attribute with an incorrect value?
In this case, we actually need to pull an on-off maneuver. This has us setting all th elements to have a highlight style, and then turn it off for the elements that meet our criteria.
th {border: 2px solid red;}
th[scope="col"], th[scope="row"] {border: none;}
This was necessary because of the way CSS selectors work. For example, consider this:
th:not([scope="col"]), th:not([scope="row"]) {border: 2px solid red;}
That would select…all th elements, regardless of their attrributes. That’s because every th element doesn’t have a scope of col, doesn’t have a scope of row, or doesn’t have either. There’s no escaping this selector o’ doom!
This limitation arises because :not() is limited to containing a single “thing” within its parentheses. You can’t, for example, say “select all elements except those that are images which descend from list items”. Reportedly, this limitation was imposed to make browser implementation of :not() easier.
Still, we can make good use of :not() in the service of further diagnosing. Calling out links in trouble is a breeze:
a[href]:not([title]) {border: 5px solid red;}
a[title=""] {outline: 3px dotted red;}
a[href="#"] {background: lime;}
a[href=""] {background: fuchsia;}
Here we have a set that will call our attention to links missing title information, as well as links that have no valid target, whether through a missing URL or a JavaScript-driven page where there are no link fallbacks in the case of missing or disabled JavaScript (href="#").
And What About IE?
As I said at the beginning, much of what I covered here doesn’t work in Internet Explorer, most particularly :not() and outline. (Oh, so basically everything? -Ed.)
I can’t do much about the latter. For the former, however, it’s possible to hack your way around the problem by doing some layered on-off stuff. For example, for images, you replace the previously-shown rules with the following:
img {border: 5px solid red;}
img[alt][title] {border-width: 0;}
img[alt] {border-color: fuchsia;}
img[alt], img[title] {border-style: double;}
img[alt=""][title],
img[alt][title=""] {border-width: 3px;}
img[alt=""][title=""] {border-style: dotted;}
It won’t have exactly the same set of effects, given the inability to use both borders and outlines, but will still highlight troublesome images.
It’s also the case that IE6 and earlier lack support for even attribute selectors, whereas IE7 added pretty much all the attribute selector types there are, so the previous code block won’t have any effect previous to IE7.
In a broader sense, though, these kinds of styles probably aren’t going to be used in the wild, as it were. Diagnostic styles are something only you see as you work on a site, so you can make sure to use a browser that supports outlines and :not() when you’re diagnosing. The fact that IE users won’t see these styles is irrelevant since users of any browser probably won’t be seeing these styles.
Personally, I always develop in Firefox anyway, thanks to its ability to become a full-featured IDE through the addition of extensions like Firebug and the Web Developer Toolbar.
Yeah, About That…
It’s true that much of what I describe in this article is available in the WDT. I feel there are two advantages to writing your own set of diagnostic styles.
When you write your own styles, you can define exactly what the visual results will be, and how they will interact. The WDT doesn’t let you make its outlines thicker or change their colors.
You can combine a bunch of diagnostics into a single set of rules and add it to your site’s style sheet during the diagnostic portion, thus ensuring they persist as you surf around. This can be done in the WDT, but it isn’t as easy (and, at least for me, not as reliable).
It’s also true that a markup validator will catch many of the errors I mentioned, such as missing alt and summary attributes. For some, that’s sufficient. But it won’t catch everything diagnostic styles can, like empty alt values or untargeted links, which are perfectly valid, syntactically speaking.
Diagnosis Complete?
I hope this has been a fun look at the concept of diagnostic styling as well as a quick introduction into possibly new concepts like :not() and outlines. This isn’t all there is to say, of course: there is plenty more that could be added to a diagnostic style sheet. And everyone’s diagnostics will be different, tuned to meet each person’s unique situation.
Mostly, though, I hope this small exploration triggers some creative thinking about the use of CSS to do more than just lay out pages and colorize text. Given the familiarity we acquire with CSS, it only makes sense to use it wherever it might be useful, and setting up visible diagnostic flags is just one more place for it to help us. |
2007 |
Eric Meyer |
ericmeyer |
2007-12-20T00:00:00+00:00 |
https://24ways.org/2007/diagnostic-styling/ |
process |
| 156 |
Mobile 2.0 |
Thinking 2.0
As web geeks, we have a thick skin towards jargon. We all know that “Web 2.0” has been done to death. At Blue Flavor we even have a jargon bucket to penalize those who utter such painfully overused jargon with a cash deposit. But Web 2.0 is a term that has lodged itself into the conscience of the masses. This is actually a good thing.
The 2.0 suffix was able to succinctly summarize all that was wrong with the Web during the dot-com era as well as the next evolution of an evolving media. While the core technologies actually stayed basically the same, the principles, concepts, interactions and contexts were radically different.
With that in mind, this Christmas I want to introduce to you the concept of Mobile 2.0. While not exactly a new concept in the mobile community, it is relatively unknown in the web community. And since the foundation of Mobile 2.0 is the web, I figured it was about time for you to get to know each other.
It’s the Carriers’ world. We just live in it.
Before getting into Mobile 2.0, I thought first I should introduce you to its older brother. You know the kind, the kid with emotional problems that likes to beat up on you and your friends for absolutely no reason. That is the mobile of today.
The mobile ecosystem is a very complicated space often and incorrectly compared to the Web. If the Web was a freewheeling hippie — believing in freedom of information and the unity of man through communities — then Mobile is the cutthroat capitalist — out to pillage and plunder for the sake of the almighty dollar. Where the Web is relatively easy to publish to and ultimately make a buck, Mobile is wrought with layers of complexity, politics and obstacles.
I can think of no better way to summarize these challenges than the testimony of Jason Devitt to the United States Congress in what is now being referred to as the “iPhone Hearing.” Jason is the co-founder and CEO of SkyDeck a new wireless startup and former CEO of Vindigo an early pioneer in mobile content.
As Jason points out, the mobile ecosystem is a closed door environment controlled by the carriers, forcing the independent publisher to compete or succumb to the will of corporate behemoths.
But that is all about to change.
Introducing Mobile 2.0
Mobile 2.0 is term used by the mobile community to describe the current revolution happening in mobile. It describes the convergence of mobile and web services, adding portability, ubiquitous connectivity and location-aware services to add physical context to information found on the Web.
It’s an important term that looks toward the future. Allowing us to imagine the possibilities that mobile technology has long promised but has yet to deliver. It imagines a world where developers can publish mobile content without the current constraints of the mobile ecosystem.
Like the transition from Web 1.0 to 2.0, it signifies the shift away from corporate or brand-centered experiences to user-centered experiences. A focus on richer interactions, driven by user goals. Moving away from proprietary technologies to more open and standard ones, more akin to the Web. And most importantly (from our perspective as web geeks) a shift away from kludgy one-off mobile applications toward using the Web as a platform for content and services.
This means the world of the Web and the world of Mobile are coming together faster than you can say ARPU (Average Revenue Per User, a staple mobile term to you webbies). And this couldn’t come at a better time. The importance of understanding and addressing user context is quickly becoming a crucial consideration to every interactive experience as the number of ways we access information on the Web increases.
Mobile enables the power of the Web, the collective information of millions of people, inherit payment channels and access to just about every other mass media to literally be overlaid on top of the physical world, in context to the person viewing it.
Anyone who can’t imagine how the influence of mobile technology can’t transform how we perform even the simplest of daily tasks needs to get away from their desktop and see the new evolution of information.
The Instigators
But what will make Mobile 2.0 move from idillic concept to a hardened market reality in 2008 will be four key technologies. Its my guess that you know each them already.
1. Opera
Opera is like the little train that could. They have been a driving force on moving the Web as we know it on to mobile handsets. Opera technology has proven itself to be highly adaptable, finding itself preloaded on over 40 million handsets, available on televisions sets through Nintendo Wii or via the Nintendo DS.
2. WebKit
Many were surprised when Apple chose to use KHTML instead of Gecko (the guts of Firefox) to power their Safari rendering engine. But WebKit has quickly evolved to be a powerful and flexible browser in the mobile context. WebKit has been in Nokia smartphones for a few years now, is the technology behind Mobile Safari in the iPhone and the iPod Touch and is the default web technology in Google’s open mobile platform effort, Android.
3. The iPhone
The iPhone has finally brought the concepts and principles of Mobile 2.0 into the forefront of consumers minds and therefore developers’ minds as well. Over 500 web applications have been written specifically for the iPhone since its launch. It’s completely unheard of to see so many applications built for the mobile context in such a short period of time.
4. CSS & Javascript
Web 2.0 could not exist without the rich interactions offered by CSS and Javascript, and Mobile 2.0 is no different. CSS and Javascript support across multiple phones historically has been, well… to put it positively… utter crap.
Javascript finally allows developers to create interesting interactions that support user goals and the mobile context. Specially, AJAX allows us to finally shed the days of bloated Java applications and focus on portable and flexible web applications. While CSS — namely CSS3 — allows us to create designs that are as beautiful as they are economical with bandwidth and load times.
With Leaflets, a collection of iPhone optimized web apps we created, we heavily relied on CSS3 to cache and reuse design elements over and over, minimizing download times while providing an elegant and user-centered design.
In Conclusion
It is the combination of all these instigators that is significantly decreasing the bar to mobile publishing. The market as Jason Devitt describes it, will begin to fade into the background. And maybe the world of mobile will finally start looking more like the Web that we all know and love.
So after the merriment and celebration of the holiday is over and you look toward the new year to refresh and renew, I hope that you take a seriously consider the mobile medium.
By this time next year, it is predicted that one-third of humanity will be using mobile devices to access the Web. |
2007 |
Brian Fling |
brianfling |
2007-12-21T00:00:00+00:00 |
https://24ways.org/2007/mobile-2-0/ |
business |
| 162 |
Conditional Love |
“Browser.” The four-letter word of web design.
I mean, let’s face it: on the good days, when things just work in your target browsers, it’s marvelous. The air smells sweeter, birds’ songs sound more melodious, and both your design and your code are looking sharp.
But on the less-than-good days (which is, frankly, most of them), you’re compelled to tie up all your browsers in a sack, heave them into the nearest river, and start designing all-imagemap websites. We all play favorites, after all: some will swear by Firefox, Opera fans are allegedly legion, and others still will frown upon anything less than the latest WebKit nightly.
Thankfully, we do have an out for those little inconsistencies that crop up when dealing with cross-browser testing: CSS patches.
Spare the Rod, Hack the Browser
Before committing browsercide over some rendering bug, a designer will typically reach for a snippet of CSS fix the faulty browser. Historically referred to as “hacks,” I prefer Dan Cederholm’s more client-friendly alternative, “patches”.
But whatever you call them, CSS patches all work along the same principle: supply the proper property value to the good browsers, while giving higher maintenance other browsers an incorrect value that their frustrating idiosyncratic rendering engine can understand.
Traditionally, this has been done either by exploiting incomplete CSS support:
#content {
height: 1%; // Let's force hasLayout for old versions of IE.
line-height: 1.6;
padding: 1em;
}
html>body #content {
height: auto; // Modern browsers get a proper height value.
}
or by exploiting bugs in their rendering engine to deliver alternate style rules:
#content p {
font-size: .8em;
/* Hide from Mac IE5 \*/
font-size: .9em;
/* End hiding from Mac IE5 */
}
We’ve even used these exploits to serve up whole stylesheets altogether:
@import url("core.css");
@media tty {
i{content:"\";/*" "*/}} @import 'windows-ie5.css'; /*";}
}/* */
The list goes on, and on, and on. For every browser, for every bug, there’s a patch available to fix some rendering bug.
But after some time working with standards-based layouts, I’ve found that CSS patches, as we’ve traditionally used them, become increasingly difficult to maintain. As stylesheets are modified over the course of a site’s lifetime, inline fixes we’ve written may become obsolete, making them difficult to find, update, or prune out of our CSS. A good patch requires a constant gardener to ensure that it adds more than just bloat to a stylesheet, and inline patches can be very hard to weed out of a decently sized CSS file.
Giving the Kids Separate Rooms
Since I joined Airbag Industries earlier this year, every project we’ve worked on has this in the head of its templates:
<link rel="stylesheet" href="-/css/screen/main.css" type="text/css" media="screen, projection" />
<!--[if lt IE 7]>
<link rel="stylesheet" href="-/css/screen/patches/win-ie-old.css" type="text/css" media="screen, projection" />
<![endif]-->
<!--[if gte IE 7]>
<link rel="stylesheet" href="-/css/screen/patches/win-ie7-up.css" type="text/css" media="screen, projection" />
<![endif]-->
The first element is, simply enough, a link element that points to the project’s main CSS file. No patches, no hacks: just pure, modern browser-friendly style rules. Which, nine times out of ten, will net you a design that looks like spilled eggnog in various versions of Internet Explorer.
But don’t reach for the mulled wine quite yet. Immediately after, we’ve got a brace of conditional comments wrapped around two other link elements. These odd-looking comments allow us to selectively serve up additional stylesheets just to the version of IE that needs them. We’ve got one for IE 6 and below:
<!--[if lt IE 7]>
<link rel="stylesheet" href="-/css/screen/patches/win-ie-old.css" type="text/css" media="screen, projection" />
<![endif]-->
And another for IE7 and above:
<!--[if gte IE 7]>
<link rel="stylesheet" href="-/css/screen/patches/win-ie7-up.css" type="text/css" media="screen, projection" />
<![endif]-->
Microsoft’s conditional comments aren’t exactly new, but they can be a valuable alternative to cooking CSS patches directly into a master stylesheet. And though they’re not a W3C-approved markup structure, I think they’re just brilliant because they innovate within the spec: non-IE devices will assume that the comments are just that, and ignore the markup altogether.
This does, of course, mean that there’s a little extra markup in the head of our documents. But this approach can seriously cut down on the unnecessary patches served up to the browsers that don’t need them. Namely, we no longer have to write rules like this in our main stylesheet:
#content {
height: 1%; // Let's force hasLayout for old versions of IE.
line-height: 1.6;
padding: 1em;
}
html>body #content {
height: auto; // Modern browsers get a proper height value.
}
Rather, we can simply write an un-patched rule in our core stylesheet:
#content {
line-height: 1.6;
padding: 1em;
}
And now, our patch for older versions of IE goes in—you guessed it—the stylesheet for older versions of IE:
#content {
height: 1%;
}
The hasLayout patch is applied, our design’s repaired, and—most importantly—the patch is only seen by the browser that needs it. The “good” browsers don’t have to incur any added stylesheet weight from our IE patches, and Internet Explorer gets the conditional love it deserves.
Most importantly, this “compartmentalized” approach to CSS patching makes it much easier for me to patch and maintain the fixes applied to a particular browser. If I need to track down a bug for IE7, I don’t need to scroll through dozens or hundreds of rules in my core stylesheet: instead, I just open the considerably slimmer IE7-specific patch file, make my edits, and move right along.
Even Good Children Misbehave
While IE may occupy the bulk of our debugging time, there’s no denying that other popular, modern browsers will occasionally disagree on how certain bits of CSS should be rendered. But without something as, well, pimp as conditional comments at our disposal, how do we bring the so-called “good browsers” back in line with our design?
Assuming you’re loving the “one patch file per browser” model as much as I do, there’s just one alternative: JavaScript.
function isSaf() {
var isSaf = (document.childNodes && !document.all && !navigator.taintEnabled && !navigator.accentColorName) ? true : false;
return isSaf;
}
function isOp() {
var isOp = (window.opera) ? true : false;
return isOp;
}
Instead of relying on dotcom-era tactics of parsing the browser’s user-agent string, we’re testing here for support for various DOM objects, whose presence or absence we can use to reasonably infer the browser we’re looking at. So running the isOp() function, for example, will test for Opera’s proprietary window.opera object, and thereby accurately tell you if your user’s running Norway’s finest browser.
With scripts such as isOp() and isSaf() in place, you can then reasonably test which browser’s viewing your content, and insert additional link elements as needed.
function loadPatches(dir) {
if (document.getElementsByTagName() && document.createElement()) {
var head = document.getElementsByTagName("head")[0];
if (head) {
var css = new Array();
if (isSaf()) {
css.push("saf.css");
} else if (isOp()) {
css.push("opera.css");
}
if (css.length) {
var link = document.createElement("link");
link.setAttribute("rel", "stylesheet");
link.setAttribute("type", "text/css");
link.setAttribute("media", "screen, projection");
for (var i = 0; i < css.length; i++) {
var tag = link.cloneNode(true);
tag.setAttribute("href", dir + css[0]);
head.appendChild(tag);
}
}
}
}
}
Here, we’re testing the results of isSaf() and isOp(), one after the other. For each function that returns true, then the name of a new stylesheet is added to the oh-so-cleverly named css array. Then, for each entry in css, we create a new link element, point it at our patch file, and insert it into the head of our template.
Fire it up using your favorite onload or DOMContentLoaded function, and you’re good to go.
Scripteat Emptor
At this point, some of the audience’s more conscientious ‘scripters may be preparing to lob figgy pudding at this author’s head. And that’s perfectly understandable; relying on JavaScript to patch CSS chafes a bit against the normally clean separation we have between our pages’ content, presentation, and behavior layers.
And beyond the philosophical concerns, this approach comes with a few technical caveats attached:
Browser detection? So un-133t.
Browser detection is not something I’d typically recommend. Whenever possible, a proper DOM script should check for the support of a given object or method, rather than the device with which your users view your content.
It’s JavaScript, so don’t count on it being available.
According to one site, roughly four percent of Internet users don’t have JavaScript enabled. Your site’s stats might be higher or lower than this number, but still: don’t expect that every member of your audience will see these additional stylesheets, and ensure that your content’s still accessible with JS turned off.
Be a constant gardener.
The sample isSaf() and isOp() functions I’ve written will tell you if the user’s browser is Safari or Opera. As a result, stylesheets written to patch issues in an old browser may break when later releases repair the relevant CSS bugs.
You can, of course, add logic to these simple little scripts to serve up version-specific stylesheets, but that way madness may lie. In any event, test your work vigorously, and keep testing it when new versions of the targeted browsers come out. Make sure that a patch written today doesn’t become a bug tomorrow.
Patching Firefox, Opera, and Safari isn’t something I’ve had to do frequently: still, there have been occasions where the above script’s come in handy. Between conditional comments, careful CSS auditing, and some judicious JavaScript, browser-based bugs can be handled with near-surgical precision.
So pass the ‘nog. It’s patchin’ time. |
2007 |
Ethan Marcotte |
ethanmarcotte |
2007-12-15T00:00:00+00:00 |
https://24ways.org/2007/conditional-love/ |
code |
| 166 |
Performance On A Shoe String |
Back in the summer, I happened to notice the official Wimbledon All England Tennis Club site had jumped to the top of Alexa’s Movers & Shakers list — a list that tracks sites that have had the biggest upturn or downturn in traffic. The lawn tennis championships were underway, and so traffic had leapt from almost nothing to crazy-busy in a no time at all.
Many sites have similar peaks in traffic, especially when they’re based around scheduled events. No one cares about the site for most of the year, and then all of a sudden – wham! – things start getting warm in the data centre. Whilst the thought of chestnuts roasting on an open server has a certain appeal, it’s less attractive if you care about your site being available to visitors. Take a look at this Alexa traffic graph showing traffic patterns for superbowl.com at the beginning of each year, and wimbledon.org in the month of July.
Traffic graph from Alexa.com
Whilst not on the same scale or with such dramatic peaks, we have a similar pattern of traffic here at 24ways.org. Over the last three years we’ve seen a dramatic pick up in traffic over the month of December (as would be expected) and then a much lower, although steady load throughout the year. What we do have, however, is the luxury of knowing when the peaks will be. For a normal site, be that a blog, small scale web app, or even a small corporate site, you often just cannot predict when you might get slashdotted, end up on the front page of Digg or linked to from a similarly high-profile site. You just don’t know when the peaks will be.
If you’re a big commercial enterprise like the Super Bowl, scaling up for that traffic is simply a cost of doing business. But for most of us, we can’t afford to have massive capacity sat there unused for 90% of the year. What you have to do instead is work out how to deal with as much traffic as possible with the modest resources you have.
In this article I’m going to talk about some of the things we’ve learned about keeping 24 ways running throughout December, whilst not spending a fortune on hosting we don’t need for 11 months of each year. We’ve not always got it right, but we’ve learned a lot along the way.
The Problem
To know how to deal with high traffic, you need to have a basic idea of what happens when a request comes into a web server. 24 ways is hosted on a single small virtual dedicated server with a great little hosting company in the UK. We run Apache with PHP and MySQL all on that one server. When a request comes in a new Apache process is started to deal with the request (or assigned if there’s one available not doing anything). Each process takes a bunch of memory, so there’s a finite number of processes that you can run, and therefore a finite number of pages you can serve at once before your server runs out of memory.
With our budget based on whatever is left over after beer, we need to get best performance we can out of the resources available. As the goal is to serve as many pages as quickly as possible, there are several approaches we can take:
Reducing the amount of memory needed by each Apache process
Reducing the amount of time each process is needed
Reducing the number of requests made to the server
Yahoo! have published some information on what they call Exceptional Performance, which is well worth reading, and compliments many of my examples here. The Yahoo! guidelines very much look at things from a user perspective, which is always important.
Server tweaking
If you’re in the position of being able to change your server configuration (our set-up gives us root access to what is effectively a virtual machine) there are some basic steps you can take to maximise the available memory and reduce the memory footprint. Without getting too boring and technical (whole books have been written on this) there are a couple of things to watch out for.
Firstly, check what processes you have running that you might not need. Every megabyte of memory that you free up might equate to several thousand extra requests being served each day, so take a look at top and see what’s using up your resources. Quite often a machine configured as a web server will have some kind of mail server running by default. If your site doesn’t use mail (ours doesn’t) make sure it’s shut down and not using resources.
Secondly, have a look at your Apache configuration and particularly what modules are loaded. The method for doing this varies between versions of Apache, but again, every module loaded increases the amount of memory that each Apache process requires and therefore limits the number of simultaneous requests you can deal with.
The final thing to check is that Apache isn’t configured to start more servers than you have memory for. This is usually done by setting the MaxClients directive. When that limit is reached, your site is going to stop responding to further requests. However, if all else goes well that threshold won’t be reached, and if it does it will at least stop the weight of the traffic taking the entire server down to a point where you can’t even log in to sort it out.
Those are the main tidbits I’ve found useful for this site, although it’s worth repeating that entire books have been written on this subject alone.
Caching
Although the site is generated with PHP and MySQL, the majority of pages served don’t come from the database. The process of compiling a page on-the-fly involves quite a few trips to the database for content, templates, configuration settings and so on, and so can be slow and require a lot of CPU. Unless a new article or comment is published, the site doesn’t actually change between requests and so it makes sense to generate each page once, save it to a file and then just serve all following requests from that file.
We use QuickCache (or rather a plugin based on it) for this. The plugin integrates with our publishing system (Textpattern) to make sure the cache is cleared when something on the site changes. A similar plugin called WP-Cache is available for WordPress, but of course this could be done any number of ways, and with any back-end technology.
The important principal here is to reduce the time it takes to serve a page by compiling the page once and serving that cached result to subsequent visitors. Keep away from your database if you can.
Outsource your feeds
We get around 36,000 requests for our feed each day. That really only works out at about 7,000 subscribers averaging five-and-a-bit requests a day, but it’s still 36,000 requests we could easily do without. Each request uses resources and particularly during December, all those requests can add up.
The simple solution here was to switch our feed over to using FeedBurner. We publish the address of the FeedBurner version of our feed here, so those 36,000 requests a day hit FeedBurner’s servers rather than ours. In addition, we get pretty graphs showing how the subscriber-base is building.
Off-load big files
Larger files like images or downloads pose a problem not in bandwidth, but in the time it takes them to transfer. A typical page request is very quick, a few seconds at the most, resulting in the connection being freed up promptly. Anything that keeps a connection open for a long time is going to start killing performance very quickly.
This year, we started serving most of the images for articles from a subdomain – media.24ways.org. Rather than pointing to our own server, this subdomain points to an Amazon S3 account where the files are held. It’s easy to pigeon-hole S3 as merely an online backup solution, and whilst not a fully fledged CDN, S3 works very nicely for serving larger media files. The roughly 20GB of files served this month have cost around $5 in Amazon S3 charges. That’s so affordable it may not be worth even taking the files back off S3 once December has passed.
I found this article on Scalable Media Hosting with Amazon S3 to be really useful in getting started. I upload the files via a Firefox plugin (mentioned in the article) and then edit the ACL to allow public access to the files. The way S3 enables you to point DNS directly at it means that you’re not tied to always using the service, and that it can be transparent to your users.
If your site uses photographs, consider uploading them to a service like Flickr and serving them directly from there. Many photo sharing sites are happy for you to link to images in this way, but do check the acceptable use policies in case you need to provide a credit or link back.
Off-load small files
You’ll have noticed the pattern by now – get rid of as much traffic as possible. When an article has a lot of comments and each of those comments has an avatar along with it, a great many requests are needed to fetch each of those images. In 2006 we started using Gravatar for avatars, but their servers were slow and were holding up page loads. To get around this we started caching the images on our server, but along with that came the burden of furnishing all the image requests.
Earlier this year Gravatar changed hands and is now run by the same team behind WordPress.com. Those guys clearly know what they’re doing when it comes to high performance, so this year we went back to serving avatars directly from them.
If your site uses avatars, it really makes sense to use a service like Gravatar where your users probably already have an account, and where the image requests are going to be dealt with for you.
Know what you’re paying for
The server account we use for 24 ways was opened in November 2005. When we first hit the front page of Digg in December of that year, we upgraded the server with a bit more memory, but other than that we were still running on that 2005 spec for two years. Of course, the world of technology has moved on in those years, prices have dropped and specs have improved. For the same amount we were paying for that 2005 spec server, we could have an account with twice the CPU, memory and disk space.
So in November of this year I took out a new account and transferred the site from the old server to the new. In that single step we were prepared for dealing with twice the amount of traffic, and because of a special offer at the time I didn’t even have to pay the setup cost on the new server. So it really pays to know what you’re paying for and keep an eye out of ways you can make improvements without needing to spend more money.
Further steps
There’s nearly always more that can be done. For example, there are some media files (particularly for older articles) that are not on S3. We also serve our CSS directly and it’s not minified or compressed. But by tackling the big problems first we’ve managed to reduce load on the server and at the same time make sure that the load being placed on the server can be dealt with in the most frugal way.
Over the last 24 days we’ve served up articles to more than 350,000 visitors without breaking a sweat. On a busy day, that’s been nearly 20,000 visitors in just 24 hours. While in the grand scheme of things that’s not a huge amount of traffic, it can be a lot if you’re not prepared for it. However, with a little planning for the peaks you can help ensure that when the traffic arrives you’re ready to capitalise on it.
Of course, people only visit 24 ways for the wealth of knowledge and experience that’s tied up in the articles here. Therefore I’d like to take the opportunity to thank all our authors this year who have given their time as a gift to the community, and to wish you all a very happy Christmas. |
2007 |
Drew McLellan |
drewmclellan |
2007-12-24T00:00:00+00:00 |
https://24ways.org/2007/performance-on-a-shoe-string/ |
ux |
| 167 |
Back To The Future of Print |
By now we have weathered the storm that was the early days of web development, a dangerous time when we used tables, inline CSS and separate pages for print only versions. We can reflect in a haggard old sea-dog manner (“yarrr… I remember back in the browser wars…”) on the bad practices of the time. We no longer need convincing that print stylesheets are the way to go1, though some of the documentation for them is a little outdated now.
I am going to briefly cover 8 tips and 4 main gotchas when creating print stylesheets in our more enlightened era.
Getting started
As with regular stylesheets, print CSS can be included in a number of ways2, for our purposes we are going to be using the link
element.
<link rel="stylesheet" type="text/css" media="print" href="print.css">
This is still my favourite way of linking to CSS files, its easy to see what files are being included and to what media they are being applied to. Without the media attribute specified the link element defaults to the media type ‘all’ which means that the styles within then apply to print and screen alike. The media type ‘screen’ only applies to the screen and wont be picked up by print, this is the best way of hiding styles from print.
Make sure you include your print styles after all your other CSS, because you will need to override certain rules and this is a lot easier if you are flowing with the cascade than against it!
Another thing you should be thinking is ‘does it need to be printed’. Consider the context3, if it is not a page that is likely to be printed, such as a landing page or a section index then the print styles should resemble the way the page looks on the screen.
Context is really important for the design of your print stylesheet, all the tips and tricks that follow should be taken in the context of the page. If for example you are designing a print stylesheet for an item in a shopping cart, it is irrelevant for the user to know the exact url of the link that takes them to your checkout.
Tips and tricks
During these tip’s we are going to build up print styles for a textileRef:11112857385470b854b8411:linkStartMarker:“simple
example”:/examples/back-to-the-future-of-print/demo-1.html
1. Remove the cruft
First things first, navigation, headers and most page furniture are pretty much useless and dead space in print so they will need to be removed, using display:none;.
2. Linearise your content
Content doesn’t work so well in columns in print, especially if the content columns are long and intend to stretch over multiple columns (as mentioned in the gotcha section below). You might want to consider Lineariseing the content to flow down the page. If you have your source order in correct priority this will make things a lot easier4.
3. Improve your type
Once you have removed all the useless cruft and jiggled things about a bit, you can concentrate more on the typography of the page.
Typography is a complex topic5, but simply put serif-ed fonts such as Georgia work better on print and sans serif-ed fonts such as Verdana are more appropriate for screen use. You will probably want to increase font size and line height and change from px to pt (which is specifically a print measurement).
4. Go wild on links
There are some incredibly fun things you can do with links in print using CSS. There are two schools of thought, one that consider it is best to disguise inline links as body text because they are not click-able on paper. Personally I believe it is useful to know for reference that the document did link to somewhere originally.
When deciding which approach to take, consider the context of your document, do people need to know where they would have gone to? will it help or hinder them to know this information? Also for an alternative to the below, take a look at Aaron Gustafson’s article on generating footnotes for print6.
Using some clever selector trickery and CSS generated content you can have the location of the link generated after the link itself.
HTML:
<p>I wish <a href="http://www.google.com/">Google</a> could find <a href="/photoOfMyKeys.jpg">my keys</a></p>
CSS:
a:link:after,
a:visited:after,
a:hover:after,
a:active:after {
content: " <" attr(href) "> ";
}
But this is not perfect, in the above example the content of the href is just naively plonked after the link text:
I wish Google <http://www.google.com/> would find my keys </photoOfMyKeys.jpg>
As looking back over this printout the user is not immediately aware of the location of the link, a better solution is to use even more crazy selectors to deal with relative links. We can also add a style to the generated content so it is distinguishable from the link text itself.
CSS:
a:link:after,
a:visited:after,
a:hover:after,
a:active:after {
content: " <" attr(href) "> ";
color: grey;
font-style: italic;
font-weight: normal;
}
a[href^="/"]:after {
content: " <http://www.example.com"attr(href)"> ";
}
The output is now what we were looking for (you will need to replace example.com with your own root URL):
I wish Google <http://www.google.com/> would find my keys <http://www.example.com/photoOfMyKeys.jpg>
Using regular expressions on the attribute selectors, one final thing you can do is to suppress the generated content on mailto: links, if for example you know the link text always reflects the email address. Eg:
HTML:
<a href="mailto:me@example.com">me@example.com</a>
CSS:
a[href^="mailto"]:after {
content: "";
}
This example shows the above in action.
Of course with this clever technique, there are the usual browser support issues. While it won’t look as intended in browsers such as Internet Explorer 6 and 7 (IE6 and IE7) it will not break either and will just degrade gracefully because IE cannot do generated content. To the best of my knowledge Safari 2+ and Opera 9.X support a colour set on generated content whereas Firefox 2 & Camino display this in black regardless of the link or inherited text colour.
5. Jazz your headers for print
This is more of a design consideration, don’t go too nuts though; there are a lot more limitations in print media than on screen. For this example we are going to go for is having a bottom border on h2’s and styling other headings with graduating colors or font sizes.
And here is the example complete with jazzy headers.
6. Build in general hooks
If you are building a large site with many different types of page, you may find it useful to build into your CSS structure, classes that control what is printed (e.g. noprint and printonly). This may not be semantically ideal, but in the past I have found it really useful for maintainability of code across large and varied sites
7. For that extra touch of class
When printing pages from a long URL, even if the option is turned on to show the location of the page in the header, browsers may still display a truncated (and thus useless) version.
Using the above tip (or just simply setting to display:none in screen and display:block in print) you can insert the URL of the page you are currently on for print only, using JavaScript’s window.location.href variable.
function addPrintFooter() {
var p = document.createElement('p');
p.className = 'print-footer';
p.innerHTML = window.location.href;
document.body.appendChild(p);
}
You can then call this function using whichever onload or ondomready handler suits your fancy. Here is our familiar demo to show all the above in action
8. Tabular data across pages
If you are using tabled data in your document there are a number of things you can do to increase usability of long tables over several pages. If you use the <thead> element this should repeat your table headers on the next page should your table be split. You will need to set thead {display: table-header-group;} explicitly for IE even though this should be the default value.
Also if you use tr {page-break-inside: avoid;} this should (browser support depending) stop your table row from breaking across two pages. For more information on styling tables for print please see the CSS discuss wiki7.
Gotchas
1. Where did all my content go?
Absolutely the most common mistake I see with print styles is the truncated content bug. The symptom of this is that only the first page of a div’s content will be printed, the rest will look truncated after this.
Floating long columns may still have this affect, as mentioned in Eric Meyer’s article on ‘A List Apart’ article from 20028; though in testing I am no longer able to replicate this. Using overflow:hidden on long content in Firefox however still causes this truncation. Overflow hidden is commonly used to clear floats9.
A simple fix can be applied to resolve this, if the column is floated you can override this with float:none similarly overflow:hidden can be overridden with overflow:visible or the offending rules can be banished to a screen only stylesheet.
Using position:absolute on long columns also has a very similar effect in truncating the content, but can be overridden in print with position:static;
Whilst I only recommend having a print stylesheet for content pages on your site; do at least check other landing pages, section indexes and your homepage. If these are inaccessible in print possibly due to the above gotcha, it might be wise to provide a light dusting of print styles or move the offending overflow / float rules to a screen only stylesheet to fix the issues.
2. Damn those background browser settings
One of the factors of life you now need to accept is that you can’t control the user’s browser settings, no more than you can control whether or not they use IE6. Most browsers by default will not print background colours or images unless explicitly told to by the user.
Naturally this causes a number of problems, for starters you will need to rethink things like branding. At this point it helps if you are doing the print styles early in the project so that you can control the logo not being a background image for example.
Where colour is important to the meaning of the document, for example a status on an invoice, bear in mind that a textural representation will also need to be supplied as the user may be printing in black and white. Borders will print however regardless of setting, so assuming the user is printing in colour you can always use borders to indicate colour.
Check the colour contrast of the text against white, this may need to be altered without backgrounds. You should check how your page looks with backgrounds turned on too, for consistency with the default browser settings you may want to override your background anyway.
One final issue with backgrounds being off is list items. It is relatively common practice to suppress the list-style-type and replace with a background image to finely control the bullet positioning. This technique doesn’t translate to print, you will need to disable this background bullet and re-instate your trusty friend the list-style-type.
3. Using JavaScript in your CSS? … beware IE6
Internet explorer has an issue that when Javascript is used in a stylesheet it applies this to all media types even if only applied to screen. For example, if you happen to be using expressions to set a width for IE, perhaps to mimic min-width, a simple width:100% !important rule can overcome the effects the expression has on your print styles10.
4. De-enhance your Progressive enhancements
Quite a classic “doh” moment is when you realise that, of course paper doesn’t support Javascript. If you have any dynamic elements on the page, for example a document collapsed per section, you really should have been using Progressive enhancement techniques11 and building for browsers without Javascript first, adding in the fancy stuff later.
If this is the case it should be trivial to override your wizzy JS styles in your print stylesheet, to display all your content and make it accessible for print, which is by far the best method of achieving this affect.
And Finally…
I refer you back to the nature of the document in hand, consider the context of your site and the page. Use the tips here to help you add that extra bit of flair to your printed media.
Be careful you don’t get caught out by the common gotchas, keep the design simple, test cross browser and relish in the medium of print.
Further Reading
1 For more information constantly updated, please see the CSS discuss wiki on print stylesheets
2 For more information on media types and ways of including CSS please refer to the CSS discuss wiki on Media Stylesheets
3 Eric Meyer talks to ThinkVitamin about the importance of context when designing your print strategy.
4 Mark Boulton describes how he applies a newspaper like print stylesheet to an article in the Guardian website. Mark also has some persuasive arguments that print should not be left to last
5 Richard Rutter Has a fantastic resource on typography which also applies to print.
6 Aaron Gustafson has a great solution to link problem by creating footnotes at the end of the page.
7 The CSS discuss wiki has more detailed information on printing tables and detailed browser support
8 This ‘A List Apart’ article is dated May 10th 2002 though is still mostly relevant
9 Float clearing technique using ‘overflow:hidden’
10 Autistic Cuckoo describes the interesting insight with regards to expressions specified for screen in IE6 remaining in print
11 Wikipedia has a good article on the definition of progressive enhancement
12 For a really neat trick involving a dynamically generated column to displaying <abbr> and <dfn> meanings (as well as somewhere for the user to write notes), try print previewing on Brian Suda’s site |
2007 |
Natalie Downe |
nataliedowne |
2007-12-09T00:00:00+00:00 |
https://24ways.org/2007/back-to-the-future-of-print/ |
design |