Your application determines the initial size and position of a window, which is called the standard state. If the user changes a window’s size or location by at least 7 points, the new size and location is the called the user state. The user can toggle between the standard state and the user state by clicking the zoom button in the title bar. Follow the guidelines in this section so that users can have the zoom experience they expect.
Choose a standard state that is best suited for the tasks your app enables. A document window, for example, should show as much as possible of the document’s content. Don’t assume that the standard state should be as large as the current display permits; instead, determine a size that makes it convenient for users to use your app. If appropriate, you can allow users to take some app windows full screen if they want more space.
Adjust the standard state when appropriate. The user can’t change the standard state that defines a window’s initial position and size, but your app can do so, based on other settings. For example, a word processor might define a standard that accommodates the display of a document whose width is specified in the Page Setup dialog.
Respond appropriately when the user zooms. When the user zooms a window that is in the user state, your app should make sure that size defined by the standard state is appropriate in the current context. Specifically, move the window as little as possible to make it the standard size, while at the same time keeping the entire window on the screen. The zoom button should not cause the window to fill the entire screen unless that was the last state the user set.
If the user zooms a window in a multidisplay system, the standard state should be on the display that contains the largest portion of the window, not necessarily on the display that contains the menu bar. This means that if the user moves a window between displays, the window’s position in the standard state could be on different displays at different times. The standard state for any window must always be fully contained on a single display.
Don’t allow a zoomed window to overlap the Dock. You always want to make sure that users have full use of both your windows and the Dock. For more information about the Dock, see “The Dock.”
http://developer.apple.com/library/mac/#documentation/UserEx...