/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "imgINotificationObserver.idl"

%{C++
#include "mozilla/Maybe.h"
#include "Visibility.h"
%}

interface imgIRequest;
interface nsIChannel;
interface nsIStreamListener;
interface nsIURI;
interface nsIFrame;

[ref] native MaybeOnNonvisible(const mozilla::Maybe<mozilla::OnNonvisible>);
native Visibility(mozilla::Visibility);

/**
 * 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.
 *
 * Please make sure to update the MozImageLoadingContent WebIDL
 * mixin to mirror this interface when changing it.
 */

// We can't make this interface noscript yet, because there is JS code doing
// "instanceof Ci.nsIImageLoadingContent" and using the nsIImageLoadingContent
// constants.
[scriptable, builtinclass, uuid(0357123d-9224-4d12-a47e-868c32689777)]
interface nsIImageLoadingContent : imgINotificationObserver
{
  /**
   * 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".
   */
  const long UNKNOWN_REQUEST = -1;
  const long CURRENT_REQUEST = 0;
  const long PENDING_REQUEST = 1;

  /**
   * setLoadingEnabled 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.
   */
  [notxpcom, nostdcall] void setLoadingEnabled(in boolean aEnabled);

  /**
   * 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.
   *
   * @param aObserver the observer to register
   */
  [notxpcom, nostdcall] void addNativeObserver(in imgINotificationObserver aObserver);

  /**
   * Used to unregister an image decoder observer.
   *
   * @param aObserver the observer to unregister
   */
  [notxpcom, nostdcall] void removeNativeObserver(in imgINotificationObserver aObserver);

  /**
   * Accessor to get the image requests
   *
   * @param aRequestType a value saying which request is wanted
   *
   * @return the imgIRequest object (may be null, even when no error
   * is thrown)
   *
   * @throws NS_ERROR_UNEXPECTED if the request type requested is not
   * known
   */
  [noscript] imgIRequest getRequest(in long aRequestType);

  /**
   * Used to notify the image loading content node that a frame has been
   * created.
   */
  [notxpcom] void frameCreated(in nsIFrame aFrame);

  /**
   * Used to notify the image loading content node that a frame has been
   * destroyed.
   */
  [notxpcom] void frameDestroyed(in nsIFrame aFrame);

  /**
   * Used to find out what type of request one is dealing with (eg
   * which request got passed through to the imgINotificationObserver
   * interface of an observer)
   *
   * @param aRequest the request whose type we want to know
   *
   * @return an enum value saying what type this request is
   *
   * @throws NS_ERROR_UNEXPECTED if aRequest is not known
   */
  [noscript] long getRequestType(in imgIRequest aRequest);

  /**
   * 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.
   */
  [noscript, infallible] readonly attribute nsIURI currentURI;

  /**
   * Gets the sync-decoding hint set by the decoding attribute.
   */
  [noscript, infallible] readonly attribute boolean syncDecodingHint;

  /**
   * loadImageWithChannel allows data from an existing channel to be
   * used as the image data for this content node.
   *
   * @param aChannel the channel that will deliver the data
   *
   * @return a stream listener to pump the image data into
   *
   * @see imgILoader::loadImageWithChannel
   *
   * @throws NS_ERROR_NULL_POINTER if aChannel is null
   */
  [noscript] nsIStreamListener loadImageWithChannel(in nsIChannel aChannel);

  /**
   * Called by layout to announce when the frame associated with this content
   * has changed its visibility state.
   *
   * @param aNewVisibility    The new visibility state.
   * @param aNonvisibleAction A requested action if the frame has become
   *                          nonvisible. If Nothing(), no action is
   *                          requested. If DISCARD_IMAGES is specified, the
   *                          frame is requested to ask any images it's
   *                          associated with to discard their surfaces if
   *                          possible.
   */
  [noscript, notxpcom] void onVisibilityChange(in Visibility aNewVisibility,
                                               in MaybeOnNonvisible aNonvisibleAction);
};