I need to write interactive live wallpaper for Mac OS X Lion on C/C++. What type of application (target in terms of xcode) it must be? plugin? Cocoa application? etc? Please help me with some tutorials, maybe working source code.
This is a little tricky but can be done. You will have to use two windows for this. Create one that spans the whole screen and has a level of kCGDesktopWindowLevel. This window will be layered above the standard desktop picture but below the desktop icons. In there you can render your custom desktop with any available drawing technologies.
The user can not interact with this window though because the finder layers the actual desktop (icons and so on) above this level and catches all events so that they don’t reach your background window.
So you have to create another window for each interactive region that is layered slightly below kCGNormalWindowLevel. You will have to experiment with the exact value.