Author Archives: Jonathan Sampson

Simple Throttle Function

When you’re handling events like window resize, keystrokes, mouse movement, and scrolling you need to be careful how many times you call heavy-handed functions. For instance, if you’re leveraging JavaScript to create responsive UIs in legacy browsers you probably don’t want to run complicated DOM-altering handlers 10 times a second when far fewer runs would be sufficient. Enter throttling.

Throttling is a means by which we can limit the number of times a function can be called in a given period. For instance, we may have a method that should be called no more than 5 times per second.

function callback () {
    console.count("Throttled");
}

window.addEventListener("resize", throttle( callback, 200 ));

In the above, our throttle function takes a callback, and a rate limiter. It will fire the callback at most once every 200 milliseconds, or at most 5 times per second. So what does the actual implementation of the throttle function look like?

function throttle (callback, limit) {
    var wait = false;                 // Initially, we're not waiting
    return function () {              // We return a throttled function
        if (!wait) {                  // If we're not waiting
            callback.call();          // Execute users function
            wait = true;              // Prevent future invocations
            setTimeout(function () {  // After a period of time
                wait = false;         // And allow future invocations
            }, limit);
        }
    }
}

The above is fairly straight forward, but let’s discuss it briefly anyway.

The overall solution is to replace the user’s function with our own function. This allows us to add extra logic to the mix, such as how frequently the function can be invoked. This is why our throttle function inevitably returns a new function.

We manage our state with a variable called wait. When wait is true, our door is closed. When wait is false, our door is open. So by switching this value from true to false, we can allow the user’s function to be invoked. And by switching wait from false to true, we prevent any calls to the user function.

Anytime we switch this, we setup a timeout that will toggle it back to false after a period of time. This is where the 200 milliseconds comes in – we’re allowing the user to determine the length of time our door should be shut.

You should also use throttling for function that get called dozens, or hundreds of times. It’s rare that you actually want things to be called that often. The implementation in this post is fairly simple (I was shooting for conciseness), but more complicated solutions exist such as those in lo-dash, underscore, and more.

I created a fiddle with a throttled and and non-throttled callback. Tying this to the window resize event, I adjusted my window width/height briefly and let the number of calls speak for themselves:

Throttled results vs Non-throttled results

Throttled results vs Non-throttled results

Emulation Accuracy in Internet Explorer

Early preview versions of Internet Explorer 11 lacked Emulation features that we saw in Internet Explorer 9 and 10. When Windows 8.1 shipped, Internet Explorer 11 was found to have the Emulation features shipped with it. These tools are helpful, though they can be misleading at times.

My general workflow in the past when using these tools goes like this: A user reports an issue in Internet Explorer x. I instruct the latest version of Internet Explorer to emulate the reported version. If I encounter the same issue, I can debug using the modern version of Internet Explorer. If emulation does not reveal the same issue, I need to load up a virtual machine, or use a service like BrowserStack.

The problem with these tools is that it’s not entirely clear where the line of reliability resides. To what degree this emulation replicates the native experience is unknown (to me, at least). Due to this, I’ve decided to do a deep dive into Emulation and see just how reliable it is, and in which areas.

Computed Styles

The first dive wasinto Computed Styles. Does Internet Explorer generate the same computed styles as IE10 and IE9 when it is emulating those versions? Surprisingly, yes. Granted, I’m running instances of IE10 and IE9 in a Virtual Machine (compliments of modern.ie), so that should be considered. Also other important thing to note is that this pass-through assumes Standards Mode.

The comparison tables are being maintained in a Google Docs spreadsheet. Click the preview below for the full view.

comparison.table

Window Object

My next focus was on cycling over enumerable properties on the window object and laying those out for comparison. A cursory glance of this next table will reveal that Internet Explorer 11 emulates the window object from IE9 and IE10 very well. Granted, there are some very clear examples of where it brought along a couple extra methods and properties.

comparison.table.window

It’s worth noting that this particular table had to be done a couple of times. Some of these members don’t attach themselves to the window object until certain actions are performed. For instance, this table is front-loaded with a bunch of BROWSERTOOLS members that are pushed onto the window object when various portions of the developer tools are opened. Other members, such as $0, don’t exist until you perform an action like selecting an element in the DOM Explorer.

More on GIFs and Painting in Internet Explorer

About a week ago I wrote a post demonstrating the use of UI Responsiveness functionality in Internet Explorer 11 to determine how the browser handles animated GIFs in various states. This post was a fairly well-received so I wanted to expand a bit more upon it and cover a few more scenarios.

For the most recent round of testing, I setup a simple interval to change the className of the body element every few seconds. This, in turn, affects the placement and layout of a single image element within the document.

(function () {

  "use strict";

  var states = ["", "opacity", "visibility", "offscreen", "perpendicular"],
      container  = document.body,
      cycles = 0,
      nextState;

  function advanceState () {
    // Advance to next array index, or return to start
    nextState = states[++cycles % states.length];
    // Indicate a new performance mark in our developer tools
    performance.mark(nextState ? "Starting " + nextState : "Restarting");
    // Update the body class to affect rendering of image
    container.className = nextState;
  }

  setInterval(advanceState, 3000);

}());

I used the performance.mark method to add my own indicators in the performance graphs to help me identify when the demo was transitioning into a new state. These performance marks are represented in Internet Explorer by small upside-down orange triangles.

performance.ticks

Let’s walk through each of these triangles left to right, discussing the state they represent.

GIF Untouched

This state is represented by all activity to the left of the first performance mark. Not much needs to be said – Internet Explorer continued to paint the GIF as it sat animated on the screen.

performance.ticks.0

Setting GIF Opacity

This step is represented by all activity between the first and second performance marks. In this step, the image element has its opacity property set to 0. Even though the image is no longer visible, the browser continued repainting the region occupied by the image element.

performance.ticks.1

Setting GIF Visibility

This step is represented by all activity between the second and third performance marks. In this step, the image element has its visibility property set to hidden. Once the visibility property was set to hidden, the browser made one final repaint (presumably to hide the element) and no further paint events took place during the duration of this state.

Of relevance here is that the hidden attribute on the image itself has the same effect. When this attribute is present on the element, Internet Explorer will cease to repaint that elements occupied region.

performance.ticks.2

Setting GIF Outside of View

This step is represented by all activity between the third and fourth performance marks. In this step, the image element is positioned absolutely at top -100% left -100%. In spite of the fact the element is positioned outside of the viewport itself, the browser continued to run paint cycles.

performance.ticks.3

Setting GIF Orientation Perpendicular to Viewport

This step is represented by all activity between the fourth and fifth performance marks (the fifth mark is the ‘Restarting’ mark). In this step, the image is rotated using the transform property so as to set it at a right angle to the viewport, effectively hiding its content from the viewer. This orientation did not affect the browser paint cycle, and Internet Explorer continued repainting the region occupied by the image element.

performance.ticks.4

Conclusion

As a general rule, it appears Internet Explorer will run paint cycles for every animated GIF in the document, unless that element has its visibility property set to hidden. This is fairly reasonable, since setting visibility to hidden is the only explicit way to tell the browser not to render the element. Keep this in mind when performance is of key importance.

After running through and investigating this further I was curious what the same test would reveal in Chrome. I was pleased to see that Chrome would cease to paint for the opacity, visibility, and offscreen configurations. No performance marks are revealed in Chrome’s developer tools, but you can identify the timer functions by the presence of a small orange mark.

performance.ticks.chrome

Tracking GIF Repaints with UI Responsiveness

I recently came across Paul Lewis’ article Avoiding Unnecessary Paints: Animated GIF Edition on HTML5 Rocks and wanted to contribute a bit to the message. If you aren’t a regular reader or HTML5 Rocks I would definitely encourage you to visit often.

The summary of Lewis’ post is that animated GIFs can cause repaints even when obscured by other elements. So even though you may not see the GIF, the browser may continue to repaint every frame of it.

As far as browsers go, Lewis shared with us the “Show paint rectangles” feature in Chrome. When enabled, this feature will visually outline regions that are being repainted. This obviously makes it very easy to determine whether paints are happening on obscured elements. Chrome, Safari, and Opera all repaint. Firefox does not.

In his discussion of various browsers, Lewis calls Internet Explorer 11 a “black box,” suggesting it gives “no indication whether repaints are happening or not.” As a result, no statement was made speculating whether Internet Explorer was in the camp of Chrome, Safari, and Opera, or Firefox.

I quickly did a scan of the comments to see if anybody addressed these words regarding Internet Explorer, but at the time nobody had. I saw this as a great opportunity to introduce my friends to the new UI Responsiveness tool in Internet Explorer 11.

The UI Responsiveness tool in Internet Explorer’s Developer Tools will actually give us pretty granular information about frame-rates, script timing, styling changes, rendering, and even repaints. Given the novelty of this feature in Internet Explorer, I felt it would be good to provide a quick example of how Internet Explorer 11 can indeed tell you whether obscured GIFs cause repaints or not.

A Single Visible GIF

My first experiment consisted of nothing more than a single GIF in the body of my document. By profiling the page for a few seconds I could see that there was constant repainting. This was expected of course, after all there’s a GIF on my screen spinning.

Below is one second of activity. As you can see, constant repainting.

gif.1

Toggling Visibility of a Single GIF

Next up, toggle the visibility of the GIF by way of its display property. I setup a interval to flip the visibility every second. The results were also as expected. For roughly one second, we had constant repainting. Following this we saw a set style event, followed by a single repaint (to hide the element). At this point, it was silence for a second before the element became visible again, and thus began causing additional repaints.

gif.2

Routinely Obscuring a Single GIF

The last experiment was to add another element, a div with a solid background-color in this case, and obscure the animated GIF on an interval. This was done by positioning both the div and the image absolutely within the body, and giving the div a higher z-index.

As can be seen in the image below, repainting did not cease even when the layout was adjusted every second. This demonstrates that when obscured, animated GIFs will continue to cause repaints in Internet Explorer 11. Whether this will be the case for future versions of Internet Explorer remains to be seen.

gif.3

Conclusion

So as we can see in these examples above, Internet Explorer 11 is capable of sharing vital information about costly repaints. Additionally, IE falls into the Chrome, Safari, and Opera camp. It sure would be nice if all browsers followed Firefox’s lead here and stopped repaints on obscured GIFs, but perhaps there is a good reason they haven’t, who knows.

I hope you can see the enormous value the UI Responsiveness panel in Internet Explorer 11’s Developer Tools brings to the debugging experience and use it to make your projects more responsive and performant in the future. The team behind Internet Explorer really have been doing amazing work lately, and the UI Responsiveness functionality is but one example of this.

UPDATE: More on GIFs and Painting in Internet Explorer

Hacking Windows 8 Snapped Mode

I recently updated four machines of mine to Windows 8.1. Love it, not a thing I would change (talking high-level here). But one of my favorite features continues to give me a slight headache.

In Windows 8 you have the ability to “snap” a web-browser to either side of your screen. This is great if you’re trying to keep documentation up, an in-browser chat visible, or even some productivity tools that are browser-based.

Sadly, many of the sites I snap wind up getting reduced so badly that I can no longer make out what is on them – kinda like how browsing the web is when you’re on a small mobile device, and the site you’re viewing isn’t “responsive” in a cross-browser compat way.

As an example, here I am trying to use wunderlist (awesome service) on my Acer Aspire R7.

Wunderlist in Snapped Mode.

Wunderlist in Snapped Mode.

Ideally I would just contact Wunderlist and have them fix their site for IE in Snapped Mode, but that isn’t always easy. Fortunately, there happens to exist a feature in IE that we can leverage – custom accessibility stylesheets.

In order to find this setting, click the Gear icon (or press alt to reveal your toolbar, and then click “Tools”) > Internet Options > General [tab] > Accessibility [button]. Alternatively, you can press the Gear icon

Internet Explorer on Windows 8 uses the same settings whether you’re in the Desktop mode or the Immersive (“Metro”) mode. As such, all we need to do is create our own custom stylesheet that will be applied to every website we visit. With this, we can set the new viewport size on our own.

Setting custom stylesheet in Internet Explorer.

Setting custom stylesheet in Internet Explorer.

I should note here that after setting (or updating) your stylesheet, you will need to close and re-open Internet Explorer (That’s a feature I’d like to see changed). This was really bugging me since I would make changes, and refresh, only to see no changes at all.

In the screenshot above you can see that I tossed in a basic media query to set the viewport to 320px wide anytime the browser itself was 400px or less in size. The result is immediately seen when you re-open Internet Explorer and pull up Wunderlist.

Wunderlist, with our custom stylesheet in place.

Wunderlist, with our custom stylesheet in place.

The end result is a far better user experience, and something I can now use in parallel to my daily work. I hope this works for you, and you find the Snapped Mode as enjoyable as I do.

You may have to add a bit more to your stylesheet to target certain websites, etc. This basic example was meant to address one site only. A real-world application would be ever-changing to accommodate sites and services you come across in your daily routine.

Hack on, hackers.

Milestone Hangout 0.2.0 Reached

For months I’ve been doing weekly Hangouts where I walk through the HTML Specification, and most recently the CSS 2.1 Specification. This has served as a means by which I can help others get a better understanding of the core technologies behind solid web development, as well as an opportunity for myself to retrace some of the forgotten roots of these ubiquitous languages.

Recently I wrapped up episode 20, or 0.2.0, which covered Counters, Automatic Numbering, Lists, and Backgrounds in CSS. It was a great episode since I had never actually used counters in CSS to begin with. This was one of the benefits of retracing those old roots – there is a surprisingly amount of stuff that isn’t common enough that I ever learned about it in the past.

After roughly 21 hours of live hangouts I am about to start a series of JavaScript hangouts. These will take place at the same standard time, Thursday evenings at 7:30pm Eastern. If you’re new to web development, or don’t feel all that confident with JavaScript, please feel free to attend. You can login with your Twitter handle and ask questions in realtime.

If you want to drop through some of the older hangouts, they’re organized in two playlists:

Browsers – Broken By Design

I set out a few hours ago to write about a problem I had experienced in Safari, Chrome, Firefox, and Internet Explorer. Opera worked as I expected, which had me convinced the other vendors merely dropped the ball, and shipped partial implementations for the :visited and :link pseudo-classes.

My CSS was very simple:

:link {
    color: white;
    background: red;
}

:link::before {
    content: "Pseudo: ";
}

A color set for unvisited links, followed by some content in the ::before pseudo element on all unvisited links. So when I dropped in two links (one visited, one not) I expected to see the following:

image00 copy

Instead, what I saw was a litter of inconsistent results between Chrome, Safari, Internet Explorer, Firefox, and Opera. The above image came from Opera. It performed exactly as I suspected. The others, not so much.

Chrome and Firefox gave similar results; both set “Pseudo” as a virtual first-child of both anchors (though I only asked to have it on unvisited links), and leaked the background color from :link into :visited.

Internet Explorer did better than Chrome and Firefox; it preserved the “pseudo” text, but left the background of the visited link untouched. I was still very perplexed as to why it was spilling values from :link over into :visited.

You can observe something interesting in Internet Explorer – :visited links start visually identical to :link links, but are transitioned into their :visited state immediately thereafter. Setting a transition on all links reveals the change when the document loads:

a {
    transition: background 10s;
}

You’ll see the :link links remain unchanged but :visited links slowly adopt their end style. This is not the case for Chrome, Firefox, Opera, or Safari.

Safari appeared to be the most broken of them all. It duplicated everything. Further, I attempted to set additional styles to :visited, and it completely ignored them.

Discovering History

I found it incredible that all of these browsers, with the exception of Opera, would get this so wrong. So like any good developer I took to the web to see who else might be complaining about this, which is when I came across a Stack Overflow post suggesting this was somehow related to security concerns.

This offered another search vector; security issues. That was the needed catalyst for opening up a fascinating story about yet another creative attempt by developers to put their nose where it may not belong – in the client browser’s history.

Browsers typically style links with a default color to indicate whether it is a visited link or not. We’ve all seen those blue and purple links before – they’ve become quite at home on the web. Somebody got the (seriously) brilliant idea to create anchors ad hoc, and use getComputedStyle to see if the links represented visited or unvisited locations.

Mozilla reports that you could test more than 200,000 urls every minute with this approach. As such, you could – with a great deal of accuracy – fingerprint the user visiting your site based on the other urls they have visited; and browser history runs deep.

Scorched Earth Solution

The solution implemented by Firefox (and apparently others) was to greatly reduce the presence of visited links. They started by instructing functions like getComputedStyle and querySelectorAll to lie (their words, not mine) about their results. Sure enough, a simple check confirms that though my :visited links have a different font color than :link links, getComputedStyle says they’re the same rgb value.

Mozilla’s Christopher Blizzard continues with a very key point (emphasis added):

You will still be able to visually style visited links, but you’re severely limited in what you can use. We’re limiting the CSS properties that can be used to style visited links to color, background-color, border-*-color, and outline-color and the color parts of the fill and stroke properties. For any other parts of the style for visited links, the style for unvisited links is used instead. In addition, for the list of properties you can change above, you won’t be able to set rgba() or hsla() colors or transparent on them.

And there it was, the explanation that tied all of the seemingly broken pieces together. The browser would instruct :visited to share property values with :link. The browsers aren’t broken; they were designed to fail.

Test Confirmations

I wanted to explore the now-understood implementation a bit further, so I tried a few things. Querying the DOM for :visited links (expecting 1 of 2) was my first decision. I also queried the DOM for :link as well – expecting 2 due to the new security:

Browser Number of :visited Number of :link
Chrome 0 2
Firefox 0 2
Internet Explorer 0 2
Safari 0 2
Opera 1 2

Nearly all of the browsers report no :visited link, with the exception of Opera. All browsers report a total of 2 links when querying :link.

So it seems like you can still get a list of visited sites in Opera. Internet Explorer, Firefox, Chrome, and Safari all prevented the exploit from being carried out. But one thing about Internet Explorer intrigued me; remember the transitioning I spoke of earlier?

Internet Explorer Still Vulnerable?

I noticed that if I set transition: background 10s on anchors in Internet Explorer you would slowly see all visited links slowly tween into their end state. Transitions fire the transitionend event when they complete, so could we still get the user’s visited links in Internet Explorer?

The CSS to test this is very simple:

a { transition: background .01s }
:link { background: red }

And the following JavaScript:

/* Anchor var, fragment, and array of guesses */
var anchor;
var fragment = document.createDocumentFragment();
var websites = [
    'http://bing.com',
    'http://google.com',
    'http://jquery.com',
    'http://appendto.com',
    'http://stackoverflow.com'
];

/* Listen for completed transitions */
document.addEventListener("transitionend", function (event){
    console.log(event.target.href);
}, false);

/* Create a link for each url */
websites.forEach(function(url){
    anchor = document.createElement("a");
    anchor.setAttribute("href", url);
    anchor.innerHTML = url;
    fragment.appendChild( anchor );
});

/* Add our document fragment to our DOM */
document.body.appendChild(fragment);

Immediately upon being added to the DOM our :visited anchors will start to transition away from looking like a :link anchor. Once that transition is complete, we learn what the URL is, and confirm that the user has visited that site.

Closing Thoughts

I was reminded today just how exciting our industry is. People are constantly experimenting, learning new things, and sharing that knowledge. Industry experts, developers, designers, and browser vendors are always working to shift and adjust in light of the ever-evolving web.

Although the CSS2.1 Specification says something, that doesn’t make it so – even if the feature is 15 years old. If the ends justify the means, browser vendors will (and did) fire-bomb their own code-base to protect the end user.

Finally, we’re all in this together; we ought to work together. Microsoft launched the @IEDevChat twitter account not too long ago to assist developer’s who are attempting to follow web-standards. Then even organized a group of developers who wanted to volunteer and help build a better web; you can find (and join) it online at http://useragents.ie.

I’m sure there’s more history here that I’ve yet to discover, but what I have seen is enough to pique my interest. If you have anything else to share, or can contribute to the vulnerability test approach above, please leave a comment below. I may swing back around and check out the other browsers later on.

Designing with Pseudo Elements in IE10

Pseudo Elements in IE10

When Internet Explorer 10 came onto the scene as one of the first desktop browsers engineered for touch, it brought with it a few upgrades to many form elements. Input fields began, overnight, to render with their own clear buttons, causing some anguish among designers who had already provided similar functionality on their own.

image05

It wasn’t long until Stack Overflow, and other communities, began hearing the groans of web designers wanting to know how they can turn off these new progressive enhancements. But what initially appeared to be a nuisance is actually a great opportunity. These new pseudo elements give us more control than ever before.

Quick Brushup

Pseudo elements are parts of the document that are not declared in our markup, but are provided by the browser when rendering certain elements. For instance, pseudo-elements exist that represent the ::first-line of text in a paragraph. This requires no additional markup to function, but gives us great control over how things look.

image06

I would like to cover nearly 20 pseudo elements in the remainder of this article, demonstrating with each what type of effect(s) we can achieve in our presentation.

Here’s a list of what we’re going to cover:

::after ::before
::first-letter ::first-line
::-ms-browse ::-ms-value
::-ms-check ::-ms-clear
::-ms-expand ::-ms-fill
::-ms-fill-lower ::-ms-fill-upper
::-ms-reveal ::-ms-thumb
::-ms-ticks-after ::-ms-ticks-before
::-ms-tooltip ::-ms-track
::selection

Before and After Pseudo Elements

The ::before and ::after pseudo elements create virtual children within the container (like an invisible <span> element). These appear before all other children, and after all other children, respectively. You can use these to achieve many great effects, such as fading an image out and adding text over the top of it.

image02

The HTML for the above is very simple. It’s nothing more than an image within a figure element.

<figure>
    <img src=”jonathan-sampson.jpg">
</figure>

In the CSS we’re using ::after (::before is used the same way) to add a positioned element over the top of our image, give it a gradient background, and some text content.

figure {
    position: relative;
}

figure::after {
    /* Text and Color */
    color: white;
    font: 1em "Segoe UI";
    content: "@jonathansampson";
    text-shadow: 0 .1em .2em #004D71;
    /* Size and Placement */
    left: 0; bottom: 0;
    width: 100%; padding: 2em 0;
    display: block; position: absolute; 
    /* Background */
    background: linear-gradient(to top, white 1em, transparent);
}

First Line and Letter Pseudo Elements

By using the ::first-line and ::first-letter pseudo elements we can target the first line of text in a text block, as well as the first letter in that line, and modify their styles independently of their surroundings. By combining both of these, we can achieve an effect like the following:

image03

The above consists of nothing more than a simple paragraph, as far as markup is concerned.

<p>When Internet Explorer 10 came onto the scene...</p>

The styles too are very concise and easy to understand.

p {
    font: 1em "Segoe UI";
}

p::first-line {
    font-weight: bold;
}

p::first-letter {
    font: 5em "Script";
    float: left;
    line-height: .5em;
    padding: .15em .15em 0;
}

Browse and Value Pseudo Elements

File uploads have always been a pain to style; in the past we didn’t have much access to the button itself. Today with the ::-ms-browse and ::-ms-value pseudo elements we can target individual parts of the file upload control and create a far better presentation than was ever possible before.

image07

The markup here is familiar and short; it’s just a single file input.

<input type="file">

The CSS, on the other hand, is slightly more verbose since we’re targeting the input element, the browse and value pseudo elements collectively, as well as individually.

input {
    background: transparent;
}

::-ms-browse, ::-ms-value {
    border: 0;
    padding: 1em;
    color: rgb(71,194,254);
    background-color: rgb(1,132,195);
    background-image: 
        linear-gradient(to bottom, transparent 1px, rgb(71, 194, 254) 1px, transparent 1em),
        linear-gradient(to top, transparent 1px, rgba(0,0,0,.2) 1px, transparent 2em);
}

::-ms-browse {
    font-weight: bold;
    background-color: rgb(1, 107, 157);
    border-radius: 0 .5em .5em 0;
}

::-ms-value {
    border-radius: .5em 0 0 .5em;
}

Check Pseudo Element

With ::-ms-check we now have access to the inner-part of a radio or checkbox. This means we can now modify its presentation just as easily as we could the rest of the element itself. In the example below we’ve increased padding, changed the background color of the checked-portion, updated the foreground color, and even added a subtle inner glow.

image09

The CSS is very straightforward.

::-ms-check {
    border: 0;
    color: white;
    padding: .25em;
    background-color: rgb(1,132,195);
    box-shadow: inset 0 0 .5em rgb(71, 194, 254),
}

Clear and Reveal Pseudo Elements

This article opened with an example of the new ::-ms-clear pseudo element, and a short description of the frustration it has caused many designers who have already had long-standing functionality in place to clear fields. Often times designers just want it to go away.

::-ms-clear {
    display: none;
}

Easy enough.

Similar to the ::-ms-clear pseudo element is the ::-ms-reveal pseudo element. This is represented as a button in password fields. When pressed, and held, it reveals the password in the text box to which it is associated.

You can also set its display to none if you wish to get rid of it.

Expand Pseudo Element

The ::-ms-expand pseudo element grants you power over the button typically displayed with select menus. By leveraging this pseudo element we can round corners, set gradient backgrounds, and so much more.

image01

I cheated here just a bit and added styles to both the select element, and the ::-ms-expand pseudo element.

select {
    color: #333;
    padding: .25em;
    border-radius: .5em;
    background-color: #f1f1f1;
    background-image:
        linear-gradient(to bottom, white, transparent);
    border: 1px solid rgb(71, 194, 254);
}

::-ms-expand {
    padding: .25em;
    margin-left: .25em;
    border-radius: 50%;
    color: rgba(0, 0, 0, .25);
    background-color: rgb(71, 194, 254);
    background-image: 
        linear-gradient(to bottom, rgba(255, 255, 255, .8), transparent 1em);
    border: 1px solid rgba(71, 194, 254, .5);
}

Fill Pseudo Element

The ::-ms-fill pseudo element works with the <progress> element, which shows an advancement in a set of sequences or length of time. The “filled” portion of the progress bar is exposed to us for additional styling on top of those styles applied directly to the main element itself.

While this element, visually, isn’t as complex as others we can still have some fun with it.

image00

progress {
    border: 0;
    height: 1.5em;
    border-radius: .25em;
    background-color: #f1f1f1;
}

::-ms-fill {
    border: 0;
    background-image:
        linear-gradient(to top, transparent 1px, rgba(255,255,255,.5) 1px, transparent 1em),
        linear-gradient(to left, rgba(0,0,0,.3) 3px, transparent 3px),
        linear-gradient(to right, rgba(0, 0, 0, .3), transparent);
}

Fill Upper/Lower, Ticks Before/After, Thumb, Tooltip, and Track Pseudo Elements

The range control is full of pseudo elements. The right side of the range, the left, the (optionally visible) ticks above or beside the control, the track itself, the popup tooltip, and the handle to change the value. In the following image you can see nearly every pseudo element adjusted in some way, shape, or form (tooltip not visible).

image08

The upper fill was given a slight glimmer while the lower fill was left solid. The ticks before (above the slider) and after (below) were made lighter. The thumb was rounded, given a slight gradient for depth, and a hollow-looking center. Lastly the track pseudo element was given white, semi-opaque, markers.

::-ms-tooltip {
    display: none;
}

::-ms-ticks-before, ::-ms-ticks-after {
    color: #999;
    display: block;
}

::-ms-ticks-before {
    background: linear-gradient(to top, #CCC, transparent 30%);
}

::-ms-ticks-after {
    background: linear-gradient(to top, transparent 70%, #CCC);
}

::-ms-fill-upper {
    background-color: rgb(1, 107, 157);
    background-image: 
        linear-gradient(to bottom, transparent 1px, rgba(255,255,255,.25) 1px, transparent 70%);
}

::-ms-fill-lower {
    background-color: rgb(1,132,195);
}

::-ms-thumb {
    background-color: white;
    background-image: 
        radial-gradient(circle, rgb(1, 107, 157) 20%, transparent 20%),
        linear-gradient(to top, #CCC, white);
    border-radius: 50%;
    border: 0;
}

::-ms-track {
    color: rgba(255, 255, 255, .5);
}

Selection Pseudo Element

The last pseudo element we’re going to look at is the ::selection pseudo element. This represents any selection of text in the document. The control you have over this is extended to the foreground color, and background color of the selection.

image04

By default selected text is white with a blue background. In the example above we have changed the text to black, and the background to hot pink (in true Irish fashion).

::selection {
    color: black;
    background: pink;
}

Conclusion

We’ve looked at nearly every pseudo element available in Internet Explorer 10, as well as a few types of modifications we can make to the UI by leveraging their presence in the document. It’s important to note that different browsers may have different pseudo elements you’ll have to target in order to modify the same (or similar) document elements. This post was merely an exploration of those that presently exist in Internet Explorer.

If you have any questions about the above examples, please feel free to reach out to myself, or any of my fellow IE User Agents. You can do so by leaving a comment below on this post, or tagging your tweet with the #IEUserAgents hashtag (we’re listening). If you have questions about general development and Internet Explorer, follow and interact with @IEDevChat on twitter.

If you would like access to Internet Explorer from your Mac to test these features, you can use BrowserStack, or download a free Virtual Machine from http://modern.ie. I use both methods regularly – I would encourage the virtual machine route if you have the space/memory.

That’s it. Go change the web.