In our continued efforts to demonstrate different ways to use Core Animation, we have noticed different effects you see in OS X itself that present an interesting challenge to duplicate. In a previous post, we demonstrated how to shake a login window similar to the way that OS X shakes the login window when the user enters the wrong password. This time, we’re going to demonstrate how to do what we’ve dubbed the Dashboard Effect.
I’m not sure this is the best name for it as some people may think we mean the ripple effect you see when you drop a new Dashboard widget on the screen, but what we mean is the way in which the Dashboard widgets that are already employed in Dashboard fly in and out of view when you enable and disable Dashboard. Enable Dashboard now and watch your widgets fly in from offscreen. Then disable it and watch the widgets fly out again. This is what we mean by the Dashboard effect and this is what we set out to duplicate.
In my first post I wrote about using NSOperation to grab an image of the current frame of a QuickTime movie while it was playing and save it out to the filesystem. Considering the excitement that is surrounding Core Animation these days, I thought it might be interesting to take that project and change it to instead grab the current frame and animate it across the screen using a Core Animation layer (CALayer). I had to employ a few tricks to get it to work, but the end result, while completely useless, is quite excellent.
A question that I have seen pop up a few times is how to build a Wizard in Cocoa. Having thought about that question a bit I realized that a better answer to it is — how to build a wizard in Cocoa using Core Animation.
The basic concept behind this project is to present a window to the user that will walk them through a list of options. To accomplish this task, I created a number of NSViews that will be presented to the user in order so that they can make the decisions needed. To make this a little easier, I have extended NSView to create MSZLinkedView. The added functionality in this subclass is that the view has a reference to the previous and next views in the wizard. These references are set in interface builder directly so that I do not have to worry about them in code.
Core Animation is really the buzz among Cocoa developers these days and we are no different from the rest. Learning to do simple fades and frame movement is trivial, but figuring out the more complex effects is quite a challenge. We decided to venture out and try to create some really concise examples of effects you might find used in Leopard. And while these effects may not be done with Core Animation where they are found in the OS, we’ve set out to duplicate them in Core Animation regardless. Our first challenge? Shaking a login window.