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NSScreen Class Reference

Inherits from
Conforms to
Framework
/System/Library/Frameworks/AppKit.framework
Availability
Available in Mac OS X v10.0 and later.
Companion guide
Declared in
NSScreen.h
Related sample code

Overview

An NSScreen object describes the attributes of a computer’s monitor, or screen. An application may use an NSScreen object to retrieve information about a screen and use this information to decide what to display upon that screen. For example, an application may use the deepestScreen method to find out which of the available screens can best represent color and then may choose to display all of its windows on that screen.

The application object should be created before you use the methods in this class, so that the application object can make the necessary connection to the window system. You can make sure the application object exists by invoking the sharedApplication method of NSApplication. If you created your application with Xcode, the application object is automatically created for you during initialization.

Note: The NSScreen class is for getting information about the available displays only. If you need additional information or want to change the attributes relating to a display, you must use Quartz Services. For more information, see Quartz Display Services Reference.

Tasks

Getting NSScreen Objects

Getting Screen Information

Class Methods

deepestScreen

Returns an NSScreen object representing the screen that can best represent color.

+ (NSScreen *)deepestScreen

Return Value

The screen with the highest bit depth.

Discussion

This method always returns an object, even if there is only one screen and it is not a color screen.

Availability
Declared In
NSScreen.h

mainScreen

Returns the NSScreen object containing the window with the keyboard focus.

+ (NSScreen *)mainScreen

Return Value

The main screen object.

Discussion

The main screen is not necessarily the same screen that contains the menu bar or has its origin at (0, 0). The main screen refers to the screen containing the window that is currently receiving keyboard events. It is the main screen because it is the one with which the user is most likely interacting.

The screen containing the menu bar is always the first object (index 0) in the array returned by the screens method.

Availability
See Also
Related Sample Code
Declared In
NSScreen.h

screens

Returns an array of NSScreen objects representing all of the screens available on the system.

+ (NSArray *)screens

Return Value

An array of the NSScreen objects available on the current system or nil if the screen information could not be obtained from the window system.

Discussion

The screen at index 0 in the returned array corresponds to the primary screen of the user’s system. This is the screen that contains the menu bar and whose origin is at the point (0, 0). In the case of mirroring, the first screen is the largest drawable display; if all screens are the same size, it is the screen with the highest pixel depth. This primary screen may not be the same as the one returned by the mainScreen method, which returns the screen with the active window.

The array should not be cached. Screens can be added, removed, or dynamically reconfigured at any time. When the display configuration is changed, the default notification center sends a NSApplicationDidChangeScreenParametersNotification notification.

Availability
Declared In
NSScreen.h

Instance Methods

depth

Returns the receiver’s current bit depth and colorspace information.

- (NSWindowDepth)depth

Return Value

The window depth information. This value cannot be used directly. You must pass it to a function such as NSBitsPerPixelFromDepth or NSColorSpaceFromDepth to obtain a concrete value for the desired information.

Availability
Declared In
NSScreen.h

deviceDescription

Returns the device dictionary for the screen.

- (NSDictionary *)deviceDescription

Return Value

A dictionary containing the attributes of the receiver's screen. For the list of keys you can use to retrieve values from the returned dictionary, see Display Device—Descriptions.

Discussion

In addition to the display device constants described in NSWindow Class Reference, you can also retrieve the CGDirectDisplayID value associated with the screen from this dictionary. To access this value, specify the Objective-C string @"NSScreenNumber" as the key when requesting the item from the dictionary. The value associated with this key is an NSNumber object containing the display ID value. This string is only valid when used as a key for the dictionary returned by this method.

Availability
Declared In
NSScreen.h

frame

Returns the dimensions and location of the receiver.

- (NSRect)frame

Return Value

The full screen rectangle at the current resolution. This rectangle includes any space currently occupied by the menu bar and dock.

Availability
See Also
Related Sample Code
Declared In
NSScreen.h

supportedWindowDepths

Returns a zero-terminated array of the window depths supported by the receiver.

- (const NSWindowDepth *)supportedWindowDepths

Return Value

A C-style array of window depths. The returned values cannot be used directly. You must pass each one to a function such as NSBitsPerPixelFromDepth or NSColorSpaceFromDepth to obtain a concrete value for the desired screen.

Availability
Declared In
NSScreen.h

userSpaceScaleFactor

Returns the scaling factor from user space to device space on the screen represented by the receiver.

- (CGFloat)userSpaceScaleFactor

Return Value

The scaling factor, measured in pixels per point, where a point is always equal to 1/72 of an inch. For example, a scaling factor of 2.0 indicates the display has a resolution 2 pixels per point or 144 pixels-per-inch.

Availability
Declared In
NSScreen.h

visibleFrame

Returns the current location and dimensions of the visible screen.

- (NSRect)visibleFrame

Return Value

The rectangle defining the portion of the screen in which it is currently safe to draw your application content.

Discussion

The returned rectangle is always based on the current user-interface settings and does not include the area currently occupied by the dock and menu bar. Because it is based on the current user -interface settings, the returned rectangle can change between calls and should not be cached.

Note: Even when dock hiding is enabled, the rectangle returned by this method may be smaller than the full screen. The system uses a small boundary area to determine when it should display the dock.

Availability
See Also
Related Sample Code
Declared In
NSScreen.h

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© 2009 Apple Inc. All Rights Reserved. (Last updated: 2009-01-06)

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