nsIWebProgressListener

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[edit] Summary

The nsIWebProgressListener interface is implemented by clients wishing to listen in on the progress associated with the loading of asynchronous requests in the context of a nsIWebProgress instance as well as any child nsIWebProgress instances. nsIWebProgress.idl describes the parent-child relationship of nsIWebProgress instances.

nsIWebProgressListener is defined in uriloader/base/nsIWebProgressListener.idl. It is scriptable and has been frozen since unknown version of Mozilla.

[edit] Interface Code

[scriptable, uuid(570F39D1-EFD0-11d3-B093-00A024FFC08C)]
interface nsIWebProgressListener : nsISupports
{
  const unsigned long STATE_START          = 0x00000001;
  const unsigned long STATE_REDIRECTING    = 0x00000002;
  const unsigned long STATE_TRANSFERRING   = 0x00000004;
  const unsigned long STATE_NEGOTIATING    = 0x00000008;
  const unsigned long STATE_STOP           = 0x00000010;

  const unsigned long STATE_IS_REQUEST     = 0x00010000;
  const unsigned long STATE_IS_DOCUMENT    = 0x00020000;
  const unsigned long STATE_IS_NETWORK     = 0x00040000;
  const unsigned long STATE_IS_WINDOW      = 0x00080000;

  const unsigned long STATE_RESTORING      = 0x01000000;

  const unsigned long STATE_IS_INSECURE     = 0x00000004;
  const unsigned long STATE_IS_BROKEN       = 0x00000001;
  const unsigned long STATE_IS_SECURE       = 0x00000002;

  const unsigned long STATE_SECURE_HIGH     = 0x00040000;
  const unsigned long STATE_SECURE_MED      = 0x00010000;
  const unsigned long STATE_SECURE_LOW      = 0x00020000;


  void onStateChange(in nsIWebProgress aWebProgress,
                     in nsIRequest aRequest,
                     in unsigned long aStateFlags,
                     in nsresult aStatus);

  void onProgressChange(in nsIWebProgress aWebProgress,
                        in nsIRequest aRequest,
                        in long aCurSelfProgress,
                        in long aMaxSelfProgress,
                        in long aCurTotalProgress,
                        in long aMaxTotalProgress);

  void onLocationChange(in nsIWebProgress aWebProgress,
                        in nsIRequest aRequest,
                        in nsIURI aLocation);

  void onStatusChange(in nsIWebProgress aWebProgress,
                      in nsIRequest aRequest,
                      in nsresult aStatus,
                      in wstring aMessage);

  void onSecurityChange(in nsIWebProgress aWebProgress,
                        in nsIRequest aRequest,
                        in unsigned long aState);
};

[edit] Constants

[edit] State Transition Flags

These flags indicate the various states that requests may transition through as they are being loaded. These flags are mutually exclusive.

For any given request, onStateChange is called once with the STATE_START flag, zero or more times with the STATE_TRANSFERRING flag or once with the STATE_REDIRECTING flag, and then finally once with the STATE_STOP flag.

NOTE: For document requests, a second STATE_STOP is generated (see the description of STATE_IS_WINDOW for more details).

STATE_START

This flag indicates the start of a request. This flag is set when a request is initiated. The request is complete when onStateChange is called for the same request with the STATE_STOP flag set.

STATE_REDIRECTING

This flag indicates that a request is being redirected. The request passed to onStateChange is the request that is being redirected. When a redirect occurs, a new request is generated automatically to process the new request. Expect a corresponding STATE_START event for the new request, and a STATE_STOP for the redirected request.

STATE_TRANSFERRING

This flag indicates that data for a request is being transferred to an end consumer. This flag indicates that the request has been targeted, and that the user may start seeing content corresponding to the request.

STATE_NEGOTIATING

This flag is not used.

STATE_STOP

This flag indicates the completion of a request. The aStatus parameter to onStateChange indicates the final status of the request.

[edit] State Type Flags

These flags further describe the entity for which the state transition is occuring. These flags are NOT mutually exclusive (i.e., an onStateChange event may indicate some combination of these flags).

STATE_IS_REQUEST

This flag indicates that the state transition is for a request, which includes but is not limited to document requests. (See below for a description of document requests.) Other types of requests, such as requests for inline content (e.g., images and stylesheets) are considered normal requests.

STATE_IS_DOCUMENT

This flag indicates that the state transition is for a document request. This flag is set in addition to STATE_IS_REQUEST. A document request supports the nsIChannel interface and it's loadFlags attribute includes the nsIChannel::LOAD_DOCUMENT_URI flag.

A document request does not complete until all requests associated with the loading of its corresponding document have completed. This includes other document requests (e.g., corresponding to HTML <iframe> elements). The document corresponding to a document request is available via the DOMWindow attribute of onStateChange's aWebProgress parameter.

STATE_IS_NETWORK

This flag indicates that the state transition corresponds to the start or stop of activity in the indicated nsIWebProgress instance. This flag is accompanied by either STATE_START or STATE_STOP, and it may be combined with other State Type Flags.

Unlike STATE_IS_WINDOW, this flag is only set when activity within the nsIWebProgress instance being observed starts or stops. If activity only occurs in a child nsIWebProgress instance, then this flag will be set to indicate the start and stop of that activity.

For example, in the case of navigation within a single frame of a HTML frameset, a nsIWebProgressListener instance attached to the nsIWebProgress of the frameset window will receive onStateChange calls with the STATE_IS_NETWORK flag set to indicate the start and stop of said navigation. In other words, an observer of an outer window can determine when activity, that may be constrained to a child window or set of child windows, starts and stops.

STATE_IS_WINDOW

This flag indicates that the state transition corresponds to the start or stop of activity in the indicated nsIWebProgress instance. This flag is accompanied by either STATE_START or STATE_STOP, and it may be combined with other State Type Flags.

This flag is similar to STATE_IS_DOCUMENT. However, when a document request completes, two onStateChange calls with STATE_STOP are generated. The document request is passed as aRequest to both calls. The first has STATE_IS_REQUEST and STATE_IS_DOCUMENT set, and the second has the STATE_IS_WINDOW flag set (and possibly the STATE_IS_NETWORK flag set as well - see above for a description of when the STATE_IS_NETWORK flag may be set). This second STATE_STOP event may be useful as a way to partition the work that occurs when a document request completes.

[edit] State Modifier Flags

These flags further describe the transition which is occuring. These flags are NOT mutually exclusive (i.e., an onStateChange event may indicate some combination of these flags).

STATE_RESTORING

This flag indicates that the state transition corresponds to the start or stop of activity for restoring a previously-rendered presentation. As such, there is no actual network activity associated with this request, and any modifications made to the document or presentation when it was originally loaded will still be present.

[edit] State Security Flags

These flags describe the security state reported by a call to the onSecurityChange method. These flags are mutually exclusive.

STATE_IS_INSECURE

This flag indicates that the data corresponding to the request was received over an insecure channel.

STATE_IS_BROKEN

This flag indicates an unknown security state. This may mean that the request is being loaded as part of a page in which some content was received over an insecure channel.

STATE_IS_SECURE

This flag indicates that the data corresponding to the request was received over a secure channel. The degree of security is expressed by STATE_SECURE_HIGH, STATE_SECURE_MED, or STATE_SECURE_LOW.

[edit] Security Strength Flags

These flags describe the security strength and accompany STATE_IS_SECURE in a call to the onSecurityChange method. These flags are mutually exclusive.

These flags are not meant to provide a precise description of data transfer security. These are instead intended as a rough indicator that may be used to, for example, color code a security indicator or otherwise provide basic data transfer security feedback to the user.

STATE_SECURE_HIGH

This flag indicates a high degree of security.

STATE_SECURE_MED

This flag indicates a medium degree of security.

STATE_SECURE_LOW

This flag indicates a low degree of security.

[edit] Methods

[edit] onStateChange

void onStateChange(in nsIWebProgress aWebProgress,
                   in nsIRequest aRequest,
                   in unsigned long aStateFlags,
                   in nsresult aStatus);

Notification indicating the state has changed for one of the requests associated with aWebProgress.

[edit] Parameters

aWebProgress

The nsIWebProgress instance that fired the notification

aRequest

The nsIRequest that has changed state. This parameter may be null. Need more information on what NULL means.

aStateFlags

Flags indicating the new state. This value is a combination of one of the State Transition Flags and one or more of the State Type Flags defined above. Any undefined bits are reserved for future use.

aStatus

Error status code associated with the state change; this indicates whether or not the request was successful. This parameter should be ignored unless aStateFlags includes the STATE_STOP bit.

[edit] onProgressChange

void onProgressChange(in nsIWebProgress aWebProgress,
                      in nsIRequest aRequest,
                      in long aCurSelfProgress,
                      in long aMaxSelfProgress,
                      in long aCurTotalProgress,
                      in long aMaxTotalProgress);

Notification that the progress has changed for one of the requests associated with aWebProgress. Progress totals are reset to zero when all requests in aWebProgress complete (corresponding to onStateChange being called with aStateFlags including the STATE_STOP and STATE_IS_WINDOW flags).

[edit] Parameters

aWebProgress

The nsIWebProgress instance that fired the notification.

aRequest

The nsIRequest that has new progress.

aCurSelfProgress

The current progress for aRequest.

aMaxSelfProgress

The maximum progress for aRequest.

aCurTotalProgress

The current progress for all requests associated with aWebProgress.

aMaxTotalProgress

The total progress for all requests associated with aWebProgress.

NOTE: If any progress value is unknown, or if its value would exceed the maximum value of type long, then its value is replaced with -1.

NOTE: If the object also implements nsIWebProgressListener2 and the caller knows about that interface, this function will not be called. Instead, nsIWebProgressListener2::onProgressChange64 will be called.

[edit] onLocationChange

void onLocationChange(in nsIWebProgress aWebProgress,
                      in nsIRequest aRequest,
                      in nsIURI aLocation);

Called when the location of the window being watched changes. This is not when a load is requested, but rather once it is verified that the load is going to occur in the given window. For instance, a load that starts in a window might send progress and status messages for the new site, but it will not send the onLocationChange until we are sure that we are loading this new page here.

[edit] Parameters

aWebProgress

The nsIWebProgress instance that fired the notification.

aRequest

The associated nsIRequest. This may be null in some cases.

aLocation

The URI of the location that is being loaded.

[edit] onStatusChange

void onStatusChange(in nsIWebProgress aWebProgress,
                    in nsIRequest aRequest,
                    in nsresult aStatus,
                    in wstring aMessage);

Notification that the status of a request has changed. The status message is intended to be displayed to the user (e.g., in the status bar of the browser).

[edit] Parameters

aWebProgress

The nsIWebProgress instance that fired the notification.

aRequest

The nsIRequest that has new status.

aStatus

This value is not an error code. Instead, it is a numeric value that indicates the current status of the request. This interface does not define the set of possible status codes.

NOTE: Some status values are defined by nsITransport and nsISocketTransport.

aMessage

Localized text corresponding to aStatus.

[edit] onSecurityChange

void onSecurityChange(in nsIWebProgress aWebProgress,
                      in nsIRequest aRequest,
                      in unsigned long aState);

Notification called for security progress. This method will be called on security transitions (eg HTTP -> HTTPS, HTTPS -> HTTP, FOO -> HTTPS) and after document load completion. It might also be called if an error occurs during network loading.

NOTE: These notifications will only occur if a security package is installed.

[edit] Parameters

aWebProgress

The nsIWebProgress instance that fired the notification.

aRequest

The nsIRequest that has new security state.

aState

A value composed of the Security State Flags and the Security Strength Flags listed above. Any undefined bits are reserved for future use.