nsIWebProgressListener

IID:570F39D1-EFD0-11d3-B093-00A024FFC08C
Inherits From:nsISupports
Status:FROZEN

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.

This interface is implemented by the following components:


Constants

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.

PRUint32 STATE_START = 1
PRUint32 STATE_REDIRECTING = 2
PRUint32 STATE_TRANSFERRING = 4
PRUint32 STATE_NEGOTIATING = 8
PRUint32 STATE_STOP = 16
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 its 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.

PRUint32 STATE_IS_REQUEST = 65536
PRUint32 STATE_IS_DOCUMENT = 131072
PRUint32 STATE_IS_NETWORK = 262144
PRUint32 STATE_IS_WINDOW = 524288
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.

PRUint32 STATE_RESTORING = 16777216
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.

PRUint32 STATE_IS_INSECURE = 4
PRUint32 STATE_IS_BROKEN = 1
PRUint32 STATE_IS_SECURE = 2
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.

PRUint32 STATE_SECURE_HIGH = 262144
PRUint32 STATE_SECURE_MED = 65536
PRUint32 STATE_SECURE_LOW = 131072

Methods

void onLocationChange ( nsIWebProgress webProgress , nsIRequest request , nsIURI location ) void onProgressChange ( nsIWebProgress webProgress , nsIRequest request , PRInt32 curSelfProgress , PRInt32 maxSelfProgress , PRInt32 curTotalProgress , PRInt32 maxTotalProgress ) void onSecurityChange ( nsIWebProgress webProgress , nsIRequest request , PRUint32 state ) void onStateChange ( nsIWebProgress webProgress , nsIRequest request , PRUint32 stateFlags , nsresult status ) void onStatusChange ( nsIWebProgress webProgress , nsIRequest request , nsresult status , PRUnichar* message )

void onLocationChange ( nsIWebProgress webProgress , nsIRequest request , nsIURI location )

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.

Arguments:
webProgress: The nsIWebProgress instance that fired the notification.
request: The associated nsIRequest. This may be null in some cases.
location: The URI of the location that is being loaded.

void onProgressChange ( nsIWebProgress webProgress , nsIRequest request , PRInt32 curSelfProgress , PRInt32 maxSelfProgress , PRInt32 curTotalProgress , PRInt32 maxTotalProgress )

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

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.

Arguments:
webProgress: The nsIWebProgress instance that fired the notification.
request: The nsIRequest that has new progress.
curSelfProgress: The current progress for request.
maxSelfProgress: The maximum progress for request.
curTotalProgress: The current progress for all requests associated with webProgress.
maxTotalProgress: The total progress for all requests associated with webProgress.

void onSecurityChange ( nsIWebProgress webProgress , nsIRequest request , PRUint32 state )

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.

Arguments:
webProgress: The nsIWebProgress instance that fired the notification.
request: The nsIRequest that has new security state.
state: A value composed of the Security State Flags and the Security Strength Flags listed above. Any undefined bits are reserved for future use.

void onStateChange ( nsIWebProgress webProgress , nsIRequest request , PRUint32 stateFlags , nsresult status )

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

Arguments:
webProgress: The nsIWebProgress instance that fired the notification
request: The nsIRequest that has changed state.
stateFlags: 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.
status: Error status code associated with the state change. This parameter should be ignored unless stateFlags includes the STATE_STOP bit. The status code indicates success or failure of the request associated with the state change. NOTE: status may be a success code even for server generated errors, such as the HTTP 404 error. In such cases, the request itself should be queried for extended error information (e.g., for HTTP requests see nsIHttpChannel).

void onStatusChange ( nsIWebProgress webProgress , nsIRequest request , nsresult status , PRUnichar* message )

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).

Arguments:
webProgress: The nsIWebProgress instance that fired the notification.
request: The nsIRequest that has new status.
status: 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.
message: Localized text corresponding to status.

References

This interface is the type of the following properties:

nsIWebBrowserPersist.progressListener

This interface is passed as an argument to the following methods:

nsIAbLDAPProcessReplicationData.init, nsIAbLDAPReplicationQuery.init, nsIAbLDAPReplicationService.startReplication, nsIContentViewerFile.printWithParent, nsIMsgProgress.registerListener, nsIMsgProgress.unregisterListener, nsIPrintProgress.registerListener, nsIPrintProgress.unregisterListener, nsIPrintingPrompt.showProgress, nsIPrintingPromptService.showProgress, nsIWebBrowserPrint.print, nsIWebBrowserPrint.printPreview, nsIWebProgress.addProgressListener, nsIWebProgress.removeProgressListener

Reference documentation is generated from Mozilla's source.

Add a note User Contributed Notes
July 12, 2005, 12:54 pm dfields at pluck dot com
There's an example of using nsIWebProgressListener for watching location changes at FirefoxDeveloper.com

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