iCal-like popup window Part II - MAAttachedWindow and CoreAnimation

Looking closely at the iCal dialog it behaves quite differently from my first cut - what it does is to scale an image of the dialog from a single starting point to something slightly bigger than the final size and then back down to final size. There is a movie of this on my previous post. This gives an appearance like it over-scales and snaps back. To me this is really good because that sort of "pop" makes it very noticeable. This happens with the strange (but good) yellow "found text" marker that appears in many Apple apps including Safari, and XCode.

So how to do this type of effect? The basic story seems to be that you need to:

• Get an image of the complete window (as it will be drawn)
• Scale it from the initial start point to the final size (via an oversize) using CoreAnimation.

The animation needs to be hosted in window - if you created a window with no frame (NSBorderlessWindowMask) this would seem to be a good place to host it. Then the animation can be performed either by resizing the view or by trickery on the underlying CALayer. Both would work.

There are as ever many ways to skin the cat. The simplest solution is actually a category of NSWindow that has been opensourced by NoodleSoft great blog can be found here and code is hosted on github.

What Paul Kim (think of him as Mr Noodle) has done is rather clever and wonderfully simple - the recipe is this:

• Get an image of your window as it will be
• Create a new transparent window (NSBorderlessWindowMask)
• Set the content view of the window to be an NSImage - with the image that you want to see (the image of your window)
• Call setFrame:display:animate: with a start and end rectangle
• When the animation is complete destroy your window and show your finished window.

I have tickled his code a little to get the overshoot and pull-back for that "pop" effect - just call setFrame:display:animate: twice once for too big and once for the right size. But it is a tiny tickle. Also, and importantly, as the animation is done in an entirely separate window it will work with Mat Gemmel's MAAttachedWindow.

I attache a movie of this done with a demo version of IShowU