HOW-TO: Make a customized RSS screensaver in Tiger

By Engadget staff

posted May 17th 2005 2:55PM

Allright, we all know a bunch of you OS X users got Tiger and went "Yipee!" over the RSS screensavers. Well they are pretty cool, but Apple news gets boring...so why not make your own for your obviously favorite website? With Tiger's Quartz Composer, you can make both standalone RSS applications and Screensavers which ends up being really useful or at least handy if you're an RSS junkie. Let's get going already. All you need are 2 things: A mac running Tiger (decently fast of course) and Xcode developer tools installed.

We�ll go through the process of making a screensaver first. Go into your Developer folder and open Quartz Composer. Yes, it�s very pretty. That�s what it�s good for, making pretty things. Choose �New Project� from the menu and choose Mac OS X RSS screensaver (see below)
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What this serves as is the starting point for our RSS screen saver. It does the dirty math work for us basically. And when you click it and choose a name to save it as, you�ll see a pretty scrolling Apple RSS screen saver. You will also see the underlying heart of Quartz. It looks like a bunch of squares and cubes hooked together with yellowish hoses. Apple has made it very easy for things to interconnect. You can just drag a hose to an appropriate spot to connect it (it will even light up).

So we don�t want this screen saver right? We want to customize it. Make it our very own creation that you can brag about. There�s 4 main parts when it comes to changing this:
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#1 is our starting point. This is the RSS feed location. You�ll want to click on the dot next to URL and a text box should pop up with Apple�s RSS location in there. Let�s enter something like http://www.engadget.com/rss.xml shall we? Good. You�re done step one. Wait a few seconds and sure enough, Engadget�s RSS feeds start popping up instead of Apple�s!

Technically, if you�re really keen on the glowing background and everything, you could just save it and be done with it right now. But that�s no fun. Let�s keep customizing.

#2 is the background. Double click the box and you�ll go further into the composition and you�ll see an all new set of boxes and hoses. If you want to make the background a static color combo, you can remove the hoses from the pink box that says Gradient. Choose your colors with the color wheel and it will remain the same. But what if you want to make the colors/direction/blending change? Easy. Look at that list to the right of all the functions/objects/interpreters etc. Find the one that says LFO. This is going to spit out a ton of random numbers for us thus giving us a dynamic variable (read: always-changing) background. Clicking �Type� allows you to mess around with what kind of mathematics it will use, but what you want to do is click on the dot next to Result. Drag your hose over to a variable on the Gradient. Say, Direction. Voila. Direction now will be a constantly changing thing. Or why not do a color? You can randomly bust out the hot colors like it�s nobody�s business. When done, look at the hierarchy tree above and go back to the root. You�ll be back at our numbered chart section again.

#3 is the article title. The one we see in the middle. Double click the box and you�ll be inside the guts of that. In the words of Teenage Mutant Ninja Turtles, �Whoa dudes!� theres a lot inside here! Don�t worry. Interpolation is the same as LFO, it busts out a slew of mathematical functions which means randomization. Grab another LFO from the side menu and throw it somewhere. Double click on where it says Repeat Mode and choose �Mirrored Loop�. This will make a nice back and forth transition with whatever we�re doing instead of it going all nuts like a normal loop would. It�s kind of like a seesaw. With this you can really have some fun. Drag the hose over to either of the Billboard boxes and hook it up to Rotation. Ooh! Look! It�s moving back and forth and floating! Mess around with all kinda of variables and what not. Just remember, if you hook it up to something like X-Position, know the following:

What you�re looking at is an X/Y graph. Thus, X-Position that�s negative goes to the left, positive to the right. With Y-Position, negative is down, positive goes up. Remember math class from middle school? Good. You�re putting it to good use now. Quartz is really scaled so use decimals, not whole numbers. Ex: 0.8339 or -0.52252 instead of 4.5 or 8.5.

#4 applies just the same to #3 except it deals with the floating article content in the background. You can just delete the box entirely if you don�t like it, or you can mess around with it, make it fade in and out and what not. You should have the hang of it by now.

When you�re done your creation, it�s time to save. Save it and quit, open your screen saver preferences and choose the one you just made in Quartz. Tada! Go you.

Now if you wanted to take it a step further (read: people/developers familiar with Xcode, Cocoa, and Interface Builder), you can start a new Cocoa Application in Xcode, edit MainMenu.nib, import the Quartz Preference Pane into IB, load your composition in, add a button or two, edit the menus, save it, and build it, you�d have a standalone RSS application that�s pretty! Also useful if you spend a lot of time waiting for RSS to update! Now get out there and start messing around with Quartz! There�s much more to be created�iTunes plug-ins anyone?

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