# Yahoo! UI Library

### Container 2.5.2

Yahoo! UI Library > container > YAHOO.widget.Overlay

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## Class YAHOO.widget.Overlay - extends YAHOO.widget.Module

Known Subclasses:
  YAHOO.widget.Panel YAHOO.widget.Menu YAHOO.widget.Tooltip

Overlay is a Module that is absolutely positioned above the page flow. It has convenience methods for positioning and sizing, as well as options for controlling zIndex and constraining the Overlay's position to the current visible viewport. Overlay also contains a dynamicly generated IFRAME which is placed beneath it for Internet Explorer 6 and 5.x so that it will be properly rendered above SELECT elements.

### Constructor

YAHOO.widget.Overlay `( el , userConfig )`

Parameters:
  `el <String>` The element ID representing the Overlay OR
  `el <HTMLElement>` The element representing the Overlay
  `userConfig <Object>` The configuration object literal containing the configuration that should be set for this Overlay. See configuration documentation for more details.

### Properties

#### DEFAULT_CONFIG `- private final Object`

Constant representing the Overlay's configuration properties

#### EVENT_TYPES `- private final Object`

Constant representing the name of the Overlay's events

#### YAHOO.widget.Overlay._initialized `- private Boolean`

A boolean that indicated whether the window resize and scroll events have already been subscribed to.

#### YAHOO.widget.Overlay.BOTTOM_LEFT `- static final String`

Constant representing the top bottom left corner of an element, used for configuring the context element alignment

#### YAHOO.widget.Overlay.BOTTOM_RIGHT `- static final String`

Constant representing the bottom right corner of an element, used for configuring the context element alignment

#### YAHOO.widget.Overlay.CSS_OVERLAY `- static final String`

Constant representing the default CSS class used for an Overlay

#### YAHOO.widget.Overlay.IFRAME_SRC `- static final String`

The URL that will be placed in the iframe
Default Value: 3

#### YAHOO.widget.Overlay.TOP_LEFT `- static final String`

Constant representing the top left corner of an element, used for configuring the context element alignment

#### YAHOO.widget.Overlay.TOP_RIGHT `- static final String`

Constant representing the top right corner of an element, used for configuring the context element alignment

#### YAHOO.widget.Overlay.VIEWPORT_OFFSET `- static final Number`

Number representing the minimum distance an Overlay instance should be positioned relative to the boundaries of the browser's viewport, in pixels.
Default Value: 10

#### Properties inherited from YAHOO.widget.Module:

`body, browser, cfg, contructor, DEFAULT_CONFIG, element, EVENT_TYPES, footer, header, id, imageRoot, isSecure, platform`

### Methods

#### _primeXYFromDOM

`protected void _primeXYFromDOM ( )`
Set's the container's XY value from DOM if not already set. Differs from syncPosition, in that the XY value is only sync'd with DOM if not already set. The method also refire's the XY config property event, so any beforeMove, Move event listeners are invoked.

Returns: `void`

#### align

`void align ( elementAlign , contextAlign )`
Aligns the Overlay to its context element using the specified corner points (represented by the constants TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT, and BOTTOM_RIGHT.

Parameters:
  `elementAlign <String>` The String representing the corner of the Overlay that should be aligned to the context element
  `contextAlign <String>` The corner of the context element that the elementAlign corner should stick to.

Returns: `void`

#### bringToTop

`void bringToTop ( )`
Places the Overlay on top of all other instances of YAHOO.widget.Overlay.

Returns: `void`

#### center

`void center ( )`
Centers the container in the viewport.

Returns: `void`

#### configConstrainToViewport

`void configConstrainToViewport ( type , args , obj )`
The default event handler fired when the "constraintoviewport" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configContext

`void configContext ( type , args , obj )`
The default event handler fired when the "context" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configFixedCenter

`void configFixedCenter ( type , args , obj )`
The default event handler fired when the "fixedcenter" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configHeight

`void configHeight ( type , args , obj )`
The default event handler fired when the "height" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configIframe

`void configIframe ( type , args , obj )`
The default event handler fired when the "iframe" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configVisible

`void configVisible ( type , args , obj )`
The default event handler fired when the "visible" property is changed. This method is responsible for firing showEvent and hideEvent.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configWidth

`void configWidth ( type , args , obj )`
The default event handler fired when the "width" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configX

`void configX ( type , args , obj )`
The default event handler fired when the "x" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configXY

`void configXY ( type , args , obj )`
The default event handler fired when the "xy" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configY

`void configY ( type , args , obj )`
The default event handler fired when the "y" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### configzIndex

`void configzIndex ( type , args , obj )`
The default event handler fired when the "zIndex" property is changed.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### destroy

`void destroy ( )`
Removes the Overlay element from the DOM and sets all child elements to null.

Returns: `void`

#### doCenterOnDOMEvent

`void doCenterOnDOMEvent ( )`
Center event handler used for centering on scroll/resize, but only if the Overlay is visible

Returns: `void`

#### enforceConstraints

`void enforceConstraints ( type , args , obj )`
The default event handler executed when the moveEvent is fired, if the "constraintoviewport" is set to true.

Parameters:
  `type <String>` The CustomEvent type (usually the property name)
  `args <Object[]>` The CustomEvent arguments. For configuration handlers, args[0] will equal the newly applied value for the property.
  `obj <Object>` The scope object. For configuration handlers, this will usually equal the owner.

Returns: `void`

#### getConstrainedXY

`Array getConstrainedXY ( x , y )`
Given x, y coordinate values, returns the calculated coordinates required to position the Overlay if it is to be constrained to the viewport, based on the current element size, viewport dimensions and scroll values.

Parameters:
  `x <Number>` The X coordinate value to be constrained
  `y <Number>` The Y coordinate value to be constrained

Returns: `Array`
  The constrained x and y coordinates at index 0 and 1 respectively;

#### hideIframe

`void hideIframe ( )`
Hides the iframe shim, if it has been enabled.

Returns: `void`

#### hideMacGeckoScrollbars

`void hideMacGeckoScrollbars ( )`
Adds a CSS class ("hide-scrollbars") and removes a CSS class ("show-scrollbars") to the Overlay to fix a bug in Gecko on Mac OS X (https://bugzilla.mozilla.org/show_bug.cgi?id=187435)

Returns: `void`

#### init

`void init ( el , userConfig )`
The Overlay initialization method, which is executed for Overlay and all of its subclasses. This method is automatically called by the constructor, and sets up all DOM references for pre-existing markup, and creates required markup if it is not already present.

Parameters:
  `el <String>` The element ID representing the Overlay OR
  `el <HTMLElement>` The element representing the Overlay
  `userConfig <Object>` The configuration object literal containing the configuration that should be set for this Overlay. See configuration documentation for more details.

Returns: `void`

#### initDefaultConfig

`void initDefaultConfig ( )`
Initializes the class's configurable properties which can be changed using the Overlay's Config object (cfg).

Returns: `void`

#### initEvents

`void initEvents ( )`
Initializes the custom events for Overlay which are fired automatically at appropriate times by the Overlay class.

Returns: `void`

#### moveTo

`void moveTo ( x , y )`
Moves the Overlay to the specified position. This function is identical to calling this.cfg.setProperty("xy", [x,y]);

Parameters:
  `x <Number>` The Overlay's new x position
  `y <Number>` The Overlay's new y position

Returns: `void`

#### onDomResize

`void onDomResize ( e , obj )`
Event handler fired when the resize monitor element is resized.

Parameters:
  `e <DOMEvent>` The resize DOM event
  `obj <Object>` The scope object

Returns: `void`

#### showIframe

`void showIframe ( )`
Shows the iframe shim, if it has been enabled.

Returns: `void`

#### showMacGeckoScrollbars

`void showMacGeckoScrollbars ( )`
Adds a CSS class ("show-scrollbars") and removes a CSS class ("hide-scrollbars") to the Overlay to fix a bug in Gecko on Mac OS X (https://bugzilla.mozilla.org/show_bug.cgi?id=187435)

Returns: `void`

#### stackIframe

`void stackIframe ( )`
Sets the zindex of the iframe shim, if it exists, based on the zindex of the Overlay element. The zindex of the iframe is set to be one less than the Overlay element's zindex.

NOTE: This method will not bump up the zindex of the Overlay element to ensure that the iframe shim has a non-negative zindex. If you require the iframe zindex to be 0 or higher, the zindex of the Overlay element should be set to a value greater than 0, before this method is called.

Returns: `void`

#### syncIframe

`void syncIframe ( )`
Syncronizes the size and position of iframe shim to that of its corresponding Overlay instance.

Returns: `void`

#### syncPosition

`void syncPosition ( )`
Synchronizes the Panel's "xy", "x", and "y" properties with the Panel's position in the DOM. This is primarily used to update position information during drag & drop.

Returns: `void`

#### toString

`String toString ( )`
Returns a String representation of the object.

Returns: `String`
  The string representation of the Overlay.

#### YAHOO.widget.Overlay.windowResizeHandler

`static void YAHOO.widget.Overlay.windowResizeHandler ( e )`
The DOM event handler used to fire the CustomEvent for window resize

Parameters:
  `e <DOMEvent>` The DOM resize event

Returns: `void`

#### YAHOO.widget.Overlay.windowScrollHandler

`static void YAHOO.widget.Overlay.windowScrollHandler ( e )`
The DOM event handler used to fire the CustomEvent for window scroll

Parameters:
  `e <DOMEvent>` The DOM scroll event

Returns: `void`

#### Methods inherited from YAHOO.widget.Module:

`_addToParent, _initResizeMonitor, _supportsCWResize, appendToBody, appendToFooter, appendToHeader, configMonitorResize, configVisible, destroy, hide, init, initDefaultConfig, initEvents, initResizeMonitor, onDomResize, render, setBody, setFooter, setHeader, show, toString`

### Events

#### beforeMoveEvent

`beforeMoveEvent ( x , y )`
CustomEvent fired before the Overlay is moved.

Parameters:
  `x <Number>` x coordinate
  `y <Number>` y coordinate

#### moveEvent

`moveEvent ( x , y )`
CustomEvent fired after the Overlay is moved.

Parameters:
  `x <Number>` x coordinate
  `y <Number>` y coordinate

#### YAHOO.widget.Overlay.windowResizeEvent

`YAHOO.widget.Overlay.windowResizeEvent ( )`
A singleton CustomEvent used for reacting to the DOM event for window resize

#### YAHOO.widget.Overlay.windowScrollEvent

`YAHOO.widget.Overlay.windowScrollEvent ( )`
A singleton CustomEvent used for reacting to the DOM event for window scroll

#### Events inherited from YAHOO.widget.Module:

`appendEvent, beforeHideEvent, beforeInitEvent, beforeRenderEvent, beforeShowEvent, changeBodyEvent, changeContentEvent, changeFooterEvent, changeHeaderEvent, destroyEvent, hideEvent initEvent renderEvent showEvent YAHOO.widget.Module.textResizeEvent`

### Configuration Attributes

#### constraintoviewport `- Boolean`

True if the Overlay should be prevented from being positioned out of the viewport.
Default Value: false

#### context `- Array`

The array of context arguments for context-sensitive positioning. The format is: [id or element, element corner, context corner]. For example, setting this property to ["img1", "tl", "bl"] would align the Overlay's top left corner to the context element's bottom left corner.
Default Value: null

#### fixedcenter `- Boolean`

True if the Overlay should be anchored to the center of the viewport.
Default Value: false

#### height `- String`

CSS height of the Overlay.
Default Value: null

#### iframe `- Boolean`

Boolean indicating whether or not the Overlay should have an IFRAME shim; used to prevent SELECT elements from poking through an Overlay instance in IE6. When set to "true", the iframe shim is created when the Overlay instance is intially made visible.
Default Value: true for IE6 and below, false for all other browsers.

#### width `- String`

CSS width of the Overlay.
Default Value: null

#### x `- Number`

The absolute x-coordinate position of the Overlay
Default Value: null

#### xy `- Number[]`

An array with the absolute x and y positions of the Overlay
Default Value: null

#### y `- Number`

The absolute y-coordinate position of the Overlay
Default Value: null

#### zIndex `- Number`

CSS z-index of the Overlay.
Default Value: null

#### Configuration attributes inherited from YAHOO.widget.Module:

`appendtodocumentbody, effect, monitorresize, visible,`

Copyright © 2007 Yahoo! Inc. All rights reserved.