Apple's U.S. Patent No. 8,230,366 for a "Dynamically Changing Cursor for User Interface" was first filed for in 2003 and covers the familiar contextualized Mac cursor perhaps most well known for its "spinning beach-ball of death" mode.
The utility patent describes functionality similar to that of Windows PC counterparts that turn the GUI's cursor into an hour glass when a program is "busy," but goes further by integrating system status information and functions like noting the number of files being moved in drag-and drop operations.
This "hybrid cursor," defined as a pointer arrow with a tail, not only serves the basic need of identifying on-screen location but also provides valuable information regarding the task at hand.
From the '366 patent abstract:
A dynamic cursor for a computer graphical user interface changes according to the processing state of applications over which the cursor is located, or with respect to an operating system element. A normal cursor is displayed when either the operating system element, or an application over which the cursor is located, can be accessed in a normal manner. A standard wait cursor is displayed over busy applications that require a user to wait until interacting with the application, when the application is active in the foreground of the computer system. When the application is busy and operating in the background, a hybrid wait cursor is displayed that indicates to the user the busy state of the application and the user's ability to interact with operating system elements or other applications regardless of this busy state. Other forms of hybrid cursors are disclosed that indicate the results of a drag operation, and quantitative data pertaining to objects being dragged.
Illustration of possible hybrid cursor embodiments. | Source: USPTO
As noted in the patent's background literature, a system-wide dynamically changing cursor can offer a great deal more information to a user than one that shifts appearance based on simple application cues such as filling in a text box. Apple's invention provides feedback in a number of situations where, in some cases, the tail portion of the cursor changes appearance to reflect various operations or operating status.
The patent supports a "tail section" which displays contextual data in numbers, geometric shapes and colors, among other graphical assets.
In the most recent versions of Apple's desktop operating system, namely OS X, the dynamic cursor has a modified hybrid design which overlays the arrow's tail on top of contextualized content.