content/base/public/nsIImageLoadingContent.idl

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  15  * The Original Code is mozilla.org code.
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  17  * The Initial Developer of the Original Code is
  18  * Boris Zbarsky <bzbarsky@mit.edu>.
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  37
  38 #include "imgIDecoderObserver.idl"
  39
  40 interface imgIRequest;
  41 interface nsIChannel;
  42 interface nsIStreamListener;
  43 interface nsIURI;
  44
  45 /**
  46  * This interface represents a content node that loads images.  The interface
  47  * exists to allow getting information on the images that the content node
  48  * loads and to allow registration of observers for the image loads.
  49  *
  50  * Implementors of this interface should handle all the mechanics of actually
  51  * loading an image -- getting the URI, checking with content policies and
  52  * the security manager to see whether loading the URI is allowed, performing
  53  * the load, firing any DOM events as needed.
  54  *
  55  * An implementation of this interface may support the concepts of a
  56  * "current" image and a "pending" image.  If it does, a request to change
  57  * the currently loaded image will start a "pending" request which will
  58  * become current only when the image is loaded.  It is the responsibility of
  59  * observers to check which request they are getting notifications for.
  60  *
  61  * Observers added in mid-load will not get any notifications they
  62  * missed.  We should NOT freeze this interface without considering
  63  * this issue.  (It could be that the image status on imgIRequest is
  64  * sufficient, when combined with the imageBlockingStatus information.)
  65  */
  66
  67 [scriptable, uuid(7744c6d3-5c60-4b7b-a526-4fe9d5ac7e97)]
  68 interface nsIImageLoadingContent : imgIDecoderObserver
  69 {
  70   /**
  71    * Request types.  Image loading content nodes attempt to do atomic
  72    * image changes when the image url is changed.  This means that
  73    * when the url changes the new image load will start, but the old
  74    * image will remain the "current" request until the new image is
  75    * fully loaded.  At that point, the old "current" request will be
  76    * discarded and the "pending" request will become "current".
  77    */
  78   const long UNKNOWN_REQUEST = -1;
  79   const long CURRENT_REQUEST = 0;
  80   const long PENDING_REQUEST = 1;
  81
  82   /**
  83    * loadingEnabled is used to enable and disable loading in
  84    * situations where loading images is unwanted.  Note that enabling
  85    * loading will *not* automatically trigger an image load.
  86    */
  87   attribute boolean loadingEnabled;
  88
  89   /**
  90    * Returns the image blocking status (@see nsIContentPolicy).  This
  91    * will always be an nsIContentPolicy REJECT_* status for cases when
  92    * the image was blocked.  This status always refers to the
  93    * CURRENT_REQUEST load.
  94    */
  95   readonly attribute short imageBlockingStatus;
  96
  97   /**
  98    * Used to register an image decoder observer.  Typically, this will
  99    * be a proxy for a frame that wants to paint the image.
 100    * Notifications from ongoing image loads will be passed to all
 101    * registered observers.  Notifications for all request types,
 102    * current and pending, will be passed through.
 103    *
 104    * @param aObserver the observer to register
 105    *
 106    * @throws NS_ERROR_OUT_OF_MEMORY
 107    */
 108   void addObserver(in imgIDecoderObserver aObserver);
 109
 110   /**
 111    * Used to unregister an image decoder observer.
 112    *
 113    * @param aObserver the observer to unregister
 114    */
 115   void removeObserver(in imgIDecoderObserver aObserver);
 116
 117   /**
 118    * Accessor to get the image requests
 119    *
 120    * @param aRequestType a value saying which request is wanted
 121    *
 122    * @return the imgIRequest object (may be null, even when no error
 123    * is thrown)
 124    *
 125    * @throws NS_ERROR_UNEXPECTED if the request type requested is not
 126    * known
 127    */
 128   imgIRequest getRequest(in long aRequestType);
 129
 130   /**
 131    * Used to find out what type of request one is dealing with (eg
 132    * which request got passed through to the imgIDecoderObserver
 133    * interface of an observer)
 134    *
 135    * @param aRequest the request whose type we want to know
 136    *
 137    * @return an enum value saying what type this request is
 138    *
 139    * @throws NS_ERROR_UNEXPECTED if aRequest is not known
 140    */
 141   long getRequestType(in imgIRequest aRequest);
 142
 143   /**
 144    * Gets the URI of the current request, if available.
 145    * Otherwise, returns the last URI that this content tried to load, or
 146    * null if there haven't been any such attempts.
 147    */
 148   readonly attribute nsIURI currentURI;
 149
 150   /**
 151    * loadImageWithChannel allows data from an existing channel to be
 152    * used as the image data for this content node.
 153    *
 154    * @param aChannel the channel that will deliver the data
 155    *
 156    * @return a stream listener to pump the image data into
 157    *
 158    * @see imgILoader::loadImageWithChannel
 159    *
 160    * @throws NS_ERROR_NULL_POINTER if aChannel is null
 161    */
 162   nsIStreamListener loadImageWithChannel(in nsIChannel aChannel);
 163
 164   /**
 165    * forceReload forces reloading of the image pointed to by currentURI
 166    *
 167    * @throws NS_ERROR_NOT_AVAILABLE if there is no current URI to reload
 168    */
 169   void forceReload();
 170 };