nsIScreen 编辑

widget/nsIScreen.idlScriptable This interface provides information about a display screen. Inherits from: nsISupports Last changed in Gecko 13.0 (Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10)

Use nsIScreenManager to obtain references to screens.

Implemented by: @mozilla.org/gfx/screenmanager;1 as a service:

var screen = Components.classes["@mozilla.org/gfx/screenmanager;1"]
             .getService(Components.interfaces.nsIScreen);

Method overview

void GetAvailRect(out long left, out long top, out long width, out long height);

void GetRect(out long left, out long top, out long width, out long height);

void lockMinimumBrightness(in unsigned long brightness);

void unlockMinimumBrightness(in unsigned long brightness);

Attributes

Attribute	Type	Description
colorDepth	long	The screen's color depth; this is the number of bits used to represent a color. Read only.
pixelDepth	long	The screen's pixel depth; this is the number of bits used to represent a pixel. Read only.
rotation	unsigned long	The screen's current rotation; you may set this to any of the values listed in Screen rotation constants. This will only have an effect on platforms that support screen rotation.

Gecko 1.9.2 note Starting in Gecko 1.9.2, Gecko running on Microsoft Windows reports 24 bits per pixel instead of 32 bits per pixel on 8-bits per color component displays, since this is typically what the caller is actually looking for.

Constants

Screen rotation constants

Screen brightness constants

Constant	Value	Description
BRIGHTNESS_DIM	0	The screen is fully dimmed (that is, off).
BRIGHTNESS_FULL	1	The screen is at full brightness.
BRIGHTNESS_LEVELS	2	The number of different brightness levels.

Requires Gecko 13.0(Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10)

Constant	Value	Description
ROTATION_0_DEG	0	0° of rotation (that is, no rotation, or default orientation).
ROTATION_90_DEG	1	90° of rotation.
ROTATION_180_DEG	2	180° of rotation.
ROTATION_270_DEG	3	270° of rotation.

Methods

GetAvailRect()

Returns a rectangle indicating the portion of the screen that is available for use.

Note: This returns a rectangle representing the region of the screen that is available for application use. For example, this would exclude the area occupied by the menu bar and Dock on Mac OS X.

void GetAvailRect(
  out long left,
  out long top,
  out long width,
  out long height
);

Parameters

left

The left edge of the available screen rectangle.

top

The top edge of the available screen rectangle.

width

The width of the available screen rectangle.

height

The height edge of the available screen rectangle.

GetRect()

Returns a rectangle indicating the entire screen's coordinate space.

void GetRect(
  out long left,
  out long top,
  out long width,
  out long height
);

Parameters

left

The left edge of the screen's rectangle.

top

The top edge of the screen's rectangle.

width

The width of the screen's rectangle.

height

The height edge of the screen's rectangle.

lockMinimumBrightness()

Locks the minimum brightness of the screen, preventing it from becoming any dimmer than that brightness level. Each call to this method must eventually be followed by a corresponding call to unlockMinimumBrightness() with the same value for the brightness parameter.

void lockMinimumBrightness(
  in unsigned long brightness
);

Parameters

brightness

The new minimum brightness level; this must be one of the values specified in Screen brightness constants.

unlockMinimumBrightness()

Releases a lock on the minimum brightness of the screen, which was previously established through a corresponding call to lockMinimumBrightness().

void unlockMinimumBrightness(
  in unsigned long brightness
);

Parameters

brightness

The brightness level to release; this must be one of the values specified in Screen brightness constants.

Example

var screenMan = Components.classes["@mozilla.org/gfx/screenmanager;1"]
                .getService(Components.interfaces.nsIScreenManager);
var left = {}, top = {}, width = {}, height = {};
screenMan.primaryScreen.GetRect(left, top, width, height);
print([left.value, top.value, width.value, height.value]);

See also

• nsIScreenManager
• Working with out parameters