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nsIImageLoadingContent

IID:7744c6d3-5c60-4b7b-a526-4fe9d5ac7e97
Inherits From:imgIDecoderObserver

This interface represents a content node that loads images. The interface exists to allow getting information on the images that the content node loads and to allow registration of observers for the image loads.

Implementors of this interface should handle all the mechanics of actually loading an image -- getting the URI, checking with content policies and the security manager to see whether loading the URI is allowed, performing the load, firing any DOM events as needed.

An implementation of this interface may support the concepts of a "current" image and a "pending" image. If it does, a request to change the currently loaded image will start a "pending" request which will become current only when the image is loaded. It is the responsibility of observers to check which request they are getting notifications for.

Observers added in mid-load will not get any notifications they missed. We should NOT freeze this interface without considering this issue. (It could be that the image status on imgIRequest is sufficient, when combined with the imageBlockingStatus information.)

This interface is implemented by the following components:

Constants

Request types. Image loading content nodes attempt to do atomic image changes when the image url is changed. This means that when the url changes the new image load will start, but the old image will remain the "current" request until the new image is fully loaded. At that point, the old "current" request will be discarded and the "pending" request will become "current".
PRInt32 UNKNOWN_REQUEST = -1
PRInt32 CURRENT_REQUEST = 0
PRInt32 PENDING_REQUEST = 1

Properties

readonly nsIURI currentURI

Gets the URI of the current request, if available. Otherwise, returns the last URI that this content tried to load, or null if there haven't been any such attempts.

readonly PRInt16 imageBlockingStatus

Returns the image blocking status (@see nsIContentPolicy). This will always be an nsIContentPolicy REJECT_* status for cases when the image was blocked. This status always refers to the CURRENT_REQUEST load.

PRBool loadingEnabled

LoadingEnabled is used to enable and disable loading in situations where loading images is unwanted. Note that enabling loading will *not* automatically trigger an image load.

Methods

void addObserver ( imgIDecoderObserver observer ) void forceReload ( ) imgIRequest getRequest ( PRInt32 requestType ) PRInt32 getRequestType ( imgIRequest request ) nsIStreamListener loadImageWithChannel ( nsIChannel channel ) void removeObserver ( imgIDecoderObserver observer )

void addObserver ( imgIDecoderObserver observer )

Used to register an image decoder observer. Typically, this will be a proxy for a frame that wants to paint the image. Notifications from ongoing image loads will be passed to all registered observers. Notifications for all request types, current and pending, will be passed through.

Arguments:
observer: the observer to register

void forceReload ( )

ForceReload forces reloading of the image pointed to by currentURI

imgIRequest getRequest ( PRInt32 requestType )

Accessor to get the image requests

Arguments:
requestType: a value saying which request is wanted
Returns:
imgIRequest object (may be null, even when no error is thrown)

PRInt32 getRequestType ( imgIRequest request )

Used to find out what type of request one is dealing with (eg which request got passed through to the imgIDecoderObserver interface of an observer)

Arguments:
request: the request whose type we want to know
Returns:
an enum value saying what type this request is

nsIStreamListener loadImageWithChannel ( nsIChannel channel )

LoadImageWithChannel allows data from an existing channel to be used as the image data for this content node.

Arguments:
channel: the channel that will deliver the data
Returns:
a stream listener to pump the image data into

void removeObserver ( imgIDecoderObserver observer )

Used to unregister an image decoder observer.

Arguments:
observer: the observer to unregister

Reference documentation is generated from Mozilla's source.