TweetFollow Us on Twitter

Creating a Dashboard Widget that Processes an RSS Feed

Volume Number: 24 (2008)
Issue Number: 07
Column Tag: Dashboard Widget

Creating a Dashboard Widget that Processes an RSS Feed

What is an RSS feed and how do I process it from within a Dashboard Widget?

by Mihalis Tsoukalos

Article Overview

A Dashboard Widget, named "GetRSS'' Widget, that uses the RSS technology, is going to be programmed in this article using JavaScript, CSS and HTML code as well as some PNG image files. The "GetRSS'' Widget uses the XMLHttpRequest object from the JavaScript programming language to get data from the MacTech RSS feed and present it in a Dashboard Widget fashion.

Because of the unknown amount of the incoming RSS data, this Widget needs to include a scroll bar–a forthcoming article is going to fully present the scroll bar technique. For the purposes of this article, only RSS-related material is going to be explained.

Also, the presented Widget has a backside! Combining two or more techniques is relatively simple as long as you already know how to use each one of them in isolation.

What is RSS?

RSS (Really Simple Syndication) is a Web content syndication format. RSS is a dialect of XML (Extensible Markup Language) and all RSS files must conform to the XML 1.0 specification. It is extensively used by news websites, weblogs and podcasting. The RSS protocol transfers information in an XML file format that is called RSS feed, RSS stream, webfeed or RSS channel.

Two most important advantages of RSS are that the RSS information is transferred as plain text, and that you can use a news aggregator to automatically get the updated information.

A news aggregator is a category of software that can get RSS feed information and present it to the user. Aggregators trim down the time and effort required for frequently checking the websites you want for updates. Using an aggregator you can subscribe to an RSS feed that it will check for new content at user-determined intervals, and retrieve the new content without further human intervention.

The following is a small part of RSS code, taken from MacTech's News RSS: (

<?xml version="1.0" encoding="UTF-8"?>
<!— generator="wordpress/1.5" —>
<rss version="2.0" 
   <title>MacTech News</title>
   [[link]][[?php bloginfo_rss('url') ?]][[/link]]
   <description>MacTech News is the source of news, information, updates and special offers specifically for the Mac technical community.</description>
   <pubDate>Fri, 14 Mar 2008 14:30:31 -0800</pubDate>
      <title>OWC Announces Mercury Elite-AL Pro Firewire+USB2 1TB Drives</title>
      <pubDate>Fri, 14 Mar 2008 06:30:31 -0800</pubDate>
   <category>Breaking News</category>
=46ast, Economical FireWire+USB 2.0 Combo External Drive Solutions Feature
New Oxford 934 Chipset and the Latest SATA Technology
Woodstock, IL, March 14, [...]]]></description>
      <title>New Take Control Ebook Helps Switch from PC to Mac</title>

The listing above will help you understand the RSS feed format. The first line dictates that you are using XML version 1.0 with UTF-8 Unicode character encoding. The second and third line tells that you are using RSS version 2.0 code that is created using the WordPress semantic personal publishing software (line 2). The other lines tell you where you can find the definitions of the various standards. You can also find out that each entry (or record) is included inside the <item> tag and consists of the following tags: <title>, <link>, <comments>, <pubDate>, <dc:creator>, <category>, <guid>, <description> and <wfw:commentRSS>. You will later have to decide which of the information you want to include inside your Widget's output.

Which files compose the complete GetRSS Widget?

The files that compose the GetRSS Widget are the following:

1. Info.plist: a file necessary for every Widget.

2. GetRSS.html: the main HTML file for the "GetRSS" Widget.

3. GetRSS.js: the JavaScript code needed for the "GetRSS" Widget.

4. GetRSS.css: the CSS file needed for formatting the Widget.

5. Two image files called Default.png and Icon.png. Every Dashboard Widget has these two graphics files. The Icon.png file should be 82x82 pixels and is displayed in the Dashboard Widget Bar.

6. Some other files and directories that will be shown later on.

The Info.plist file

The contents of the Info.plist file are the following:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN"
<plist version="1.0">

The GetRSS.html file

The contents of the GetRSS.html can be found in the archive for this article at It should be noted that the GetRSS.html file acts as the glue that connects all the other Widget files. It is also easy to understand that the GetRSS.html file contains uncomplicated HTML code. Most of its code is typical and is included in every Widget that uses certain Dashboard features.

The GetRSS.css File

The contents of the GetRSS.css file can be found in the source archive for this column found at The CSS code may look big and complex, but this is not the case. Most of the CSS code is standard for widgets, and is repeated in every widget that has a backside and a scroll bar.

The GetRSS.js File

The GetRSS.js file is the most important file of the whole Widget. A small mistake in it and the Widget will either misbehave or not work at all. Its contents are also in the archive for this article. Later in, "Explaining the Technique," will further explain the technique and you will better understand the JavaScript code.

Before continuing with the rest of the article, I will have to tell you a little problem that I had with this particular Widget. I first wrote this Widget using Mac OS X 10.4 and it worked fine. When I got the Mac OS X 10.5 DVD and first tried the Widget, it did not work as expected. When I pressed on a link, the link was not working. The following JavaScript code (the output of the diff UNIX utility) shows a small modification that I made for the Widget to work:

<       widget.openURL (div.the_link);
<    } else document.location = div.the_link;
>       widget.openURL(div.getAttribute('the_link'));
>    } 
>    else
>       document.location = div.getAttribute('the_link');

It turns out that the div.the_link code was not working as expected in Leopard. I had to use div.getAttribute('the_link') instead for the Widget to work. In Tiger, those notations were, more or less, equivalent.

The full list of the "GetRSS" Widget files

The following is the full list of the files that compose the "GetRSS" Widget.

drwxr-xr-x   AppleClasses
-rw-r—r—   Default.png
-rw-r—r—   GetRSS.css
-rw-r—r—   GetRSS.html
-rw-r—r—   GetRSS.js
-rw-r—r—   Icon.png
drwxr-xr-x   Images
-rw-r—r—   Info.plist

NOTE: You can find the JavaScript files contained in the AppleClasses directory of the Widget inside the /System/Library/WidgetResources/AppleClasses/ directory. You will also find the ./AppleClasses/Images directory along with its contents there.

Figure 1 shows the image files that can be found inside the ./Images directory of the Widget.

Figure 1: The images of the ./Images directory

The files found inside the AppleClasses/Images directory of the Widget are provided by Apple and can be found in /Developer/Applications/ on a Leopard system–provided that you have Dashcode installed.

Explaining the technique

The most challenging part of this Widget is the GetRSS.js JavaScript file. The following function, called load() does the necessary initializations of the JavaScript objects.

function load()
    scrollbar = new
    scrollArea = new
    AppleScrollArea(document.getElementById("contents"), scrollbar);
    scrollArea.scrollsHorizontally = false;
    scrollArea.singlepressScrollPixels = 15;
whiteInfoButton = new AppleInfoButton(document.getElementById("flipper"),
    document.getElementById("front"), "white", "white", showBack);
glassButton = new AppleGlassButton(document.getElementById("doneButton"),
"Done", showFront);
    window.onfocus = function () { scrollArea.focus(); }
    window.onblur = function () { scrollArea.blur(); }
    if (!window.widget)

An attention-grabbing JavaScript function is the show() function which is defined as follows:

function show ()
    var now = (new Date).getTime();
    // only check if 15 minutes have passed
    if ((now - last_updated) > 900000)
        if (xml_request != null)
            xml_request = null;
        xml_request = new XMLHttpRequest();
        xml_request.onload = function(e) {xml_loaded(e, xml_request);}
        xml_request.overrideMimeType("text/xml");"GET", feed.url);
        xml_request.setRequestHeader("Cache-Control", "no-cache");

The 900000 time value–it represents the minimum refresh time value–is in milliseconds and is therefore equivalent to 15 minutes (900000/1000 = 900 seconds. 900 / 60 = 15 minutes). Then, a new XMLHttpRequest() object is defined. This object holds the RSS feed data after is processed by the xml_loaded(e, request) function. The xml_loaded(e, request) function extracts the data from the required RSS feed fields using the following JavaScript code:

for( var item = channel.firstChild; item != null; item = item.nextSibling)
    if( item.nodeName == 'item' )
        var title = findChild (item, 'title');
        // we have to have the title to include the item in the list
        if( title != null )
            var link = findChild (item, 'link');
            var pubDate = findChild (item, 'pubDate');
            results[results.length] = {,
                link:(link != null ? : null),
                date:new Date(Date.parse(

The above JavaScript code parses the RSS feed and mines the wanted information. It only looks for the <item>, <title>, <link> and <pubDate> tags and their respective data.

Figure 2: The "GetRSS" Widget look

Figure 3: The backside of the Widget

It is also both interesting and educational to look at the clickOnTitle(event, div) function definition that introduces the widget.openURL() function.

function clickOnTitle(event, div)
   if (window.widget)
      document.location = div.getAttribute('the_link');

The widget.openURL() method opens the given URL in the (default) web browser which resides outside Dashboard.

Inside the JavaScript code you saw some alert() function calls which are the best technique for debugging Widgets. alert() output is written to the Console. Please remember to remove your alert() function calls when you finish debugging or otherwise your Console logs may become too crowded.


Using a Widget to read RSS feeds is a very valuable technique, especially now that Widgets are getting more and more popular. It is also an efficient way of keeping a close eye on an RSS feed without having to open a dedicated browser window. Finally, please note: The RSS-related code of this article is heavily based on the "Sample RSS" Widget code that is provided by Apple in the "/Developer/Examples/Dashboard/Sample RSS" directory of a Tiger system. Strangely enough, Leopard does not have the "/Developer/Examples/Dashboard" directory with the Widget examples. Also note that the "Sample RSS" Widget does not have a backside.

Bibliography and References

1. RSS:

2. RSS 2.0.1 specification:

3. XML 1.0:

4. WordPress software:

5. The XMLHttpRequest object:

6. XMLHttpRequest object:

7. Ben Hammersley, Developing Feeds with RSS and Atom, O'Reilly & Associates, 2005

8. Leslie M. Orchard, Hacking RSS and Atom. John Wiley & Sons, 2005

9. Elliote Rusty Harold and W. Scott Means, XML in a nutshell, O'Reilly & Associates, 2002

Mihalis Tsoukalos lives in Greece with his wife Eugenia and enjoys digital photography and writing articles. He is the author of the "Programming Dashboard Widgets" eBook. You can reach him at


Community Search:
MacTech Search:

Software Updates via MacUpdate

OfficeTime 1.8.2 - Easy time and expense...
OfficeTime is time and expense tracking that is easy, elegant and focused. Other time keepers are clumsy or oversimplified. OfficeTime balances features and ease of use, allowing you to easily track... Read more
Dash 4.1.6 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Quicken 5.5.6 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Civilization VI 1.1.0 - Next iteration o...
Sid Meier’s Civilization VI is the next entry in the popular Civilization franchise. Originally created by legendary game designer Sid Meier, Civilization is a strategy game in which you attempt to... Read more
Network Radar 2.3.3 - $17.99
Network Radar is an advanced network scanning and managing tool. Featuring an easy-to-use and streamlined design, the all-new Network Radar 2 has been engineered from the ground up as a modern Mac... Read more
Printopia 3.0.8 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
ForkLift 3.2.1 - Powerful file manager:...
ForkLift is a powerful file manager and ferociously fast FTP client clothed in a clean and versatile UI that offers the combination of absolute simplicity and raw power expected from a well-executed... Read more
BetterTouchTool 2.417 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more

Latest Forum Discussions

See All

Construction Simulator 2 reaches its fir...
Construction Simulator 2 debuted iOS and Android devices exactly one year ago, and publisher Astragon is marking the game’s first anniversary with a range of time-limited discounts. It’s been a successful debut for the civil engineering sim, which... | Read more »
All the best games on sale for iPhone an...
This week's list of games on sale for the iPhone and iPad isn't too bad really. There's some gems on here, as well as some games that have had their prices cut low enough that you can look past the rough edges and questionable decisions. [Read... | Read more »
The best games that came out for iPhone...
It's not a huge surprise that there's not a massive influx of new, must-buy games on the App Store this week. After all, GDC is happening, so everyone's busy at parties and networking and dying from a sinister form of jetlag. That said, there are... | Read more »
Destiny meets its mobile match - Everyth...
Shadowgun Legends is the latest game in the Shadowgun series, and it's taking the franchise in some interesting new directions. Which is good news. The even better news is that it's coming out tomorrow, so if you didn't make it into the beta you... | Read more »
How PUBG, Fortnite, and the battle royal...
The history of the battle royale genre isn't a long one. While the nascent parts of the experience have existed ever since players first started killing one another online, it's really only in the past six years that the genre has coalesced into... | Read more »
Around the Empire: What have you missed...
Oh hi nice reader, and thanks for popping in to check out our weekly round-up of all the stuff that you might have missed across the Steel Media network. Yeah, that's right, it's a big ol' network. Obviously 148Apps is the best, but there are some... | Read more »
All the best games on sale for iPhone an...
It might not have been the greatest week for new releases on the App Store, but don't let that get you down, because there are some truly incredible games on sale for iPhone and iPad right now. Seriously, you could buy anything on this list and I... | Read more »
Everything You Need to Know About The Fo...
In just over a week, Epic Games has made a flurry of announcements. First, they revealed that Fortnite—their ultra-popular PUBG competitor—is coming to mobile. This was followed by brief sign-up period for interested beta testers before sending out... | Read more »
The best games that came out for iPhone...
It's not been the best week for games on the App Store. There are a few decent ones here and there, but nothing that's really going to make you throw down what you're doing and run to the nearest WiFi hotspot in order to download it. That's not to... | Read more »
Death Coming (Games)
Death Coming Device: iOS Universal Category: Games Price: $1.99, Version: (iTunes) Description: --- Background Story ---You Died. Pure and simple, but death was not the end. You have become an agent of Death: a... | Read more »

Price Scanner via

Thursday roundup of the best 13″ MacBook Pro...
B&H Photo has new 2017 13″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only. Their prices are the lowest available for... Read more
Sale: 9.7-inch 2017 WiFi iPads starting at $2...
B&H Photo has 9.7″ 2017 WiFi Apple iPads on sale for $40 off MSRP for a limited time. Shipping is free, and pay sales tax in NY & NJ only: – 32GB iPad WiFi: $289, $40 off – 128GB iPad WiFi: $... Read more
Roundup of Certified Refurbished iPads, iPad...
Apple has Certified Refurbished 9.7″ WiFi iPads available for $50-$80 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free: – 9″ 32GB WiFi iPad: $... Read more
Back in stock! Apple’s full line of Certified...
Save $300-$300 on the purchase of a 2017 13″ MacBook Pro today with Certified Refurbished models at Apple. Apple’s refurbished prices are the lowest available for each model from any reseller. A... Read more
Wednesday deals: Huge sale on Apple 15″ MacBo...
Adorama has new 2017 15″ MacBook Pros on sale for $250-$300 off MSRP. Shipping is free, and Adorama charges sales tax in NJ and NY only: – 15″ 2.8GHz Touch Bar MacBook Pro Space Gray (MPTR2LL/A): $... Read more
Apple offers Certified Refurbished Series 3 A...
Apple has Certified Refurbished Series 3 Apple Watch GPS models available for $50, or 13%, off the cost of new models. Apple’s standard 1-year warranty is included, and shipping is free. Numerous... Read more
12″ 1.2GHz Space Gray MacBook on sale for $11...
B&H Photo has the Space Gray 12″ 1.2GHz MacBook on sale for $100 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 12″ 1.2GHz Space Gray MacBook: $1199 $... Read more
Mac minis available for up to $150 off MSRP w...
Apple has restocked Certified Refurbished Mac minis starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Back in stock: 13-inch 2.5GHz MacBook Pro (Ce...
Apple has Certified Refurbished 13″ 2.5GHz MacBook Pros (MD101LL/A) available for $829, or $270 off original MSRP. Apple’s one-year warranty is standard, and shipping is free: – 13″ 2.5GHz MacBook... Read more
Apple restocks Certified Refurbished 2017 13″...
Apple has Certified Refurbished 2017 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: – 13″ 1.8GHz/8GB/128GB MacBook Air (... Read more

Jobs Board

Payments Counsel - *Apple* Pay (payments, c...
# Payments Counsel - Apple Pay (payments, credit/debit) Job Number: 112941729 Santa Clara Valley, California, United States Posted: 26-Feb-2018 Weekly Hours: 40.00 Read more
Firmware Engineer - *Apple* Accessories - A...
# Firmware Engineer - Apple Accessories Job Number: 113452350 Santa Clara Valley, California, United States Posted: 28-Feb-2018 Weekly Hours: 40.00 **Job Summary** Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 113501424 Norman, Oklahoma, United States Posted: 15-Feb-2018 Weekly Hours: 40.00 **Job Summary** Are you passionate about Read more
*Apple* Inc. Is Look For *Apple* Genius Te...
Apple Inc. Is Look For Apple Genius Technical Customer Service Minneapolis Mn In Minneapolis - Apple , Inc. Apple Genius Technical Customer Service Read more
*Apple* Genius Technical Customer Service Co...
Apple Genius Technical Customer Service Columbus Oh Apple Inc. - Apple , Inc. Apple Genius Technical Customer Service Columbus Oh - Apple , Inc. Job Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.