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.

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.

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.

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.

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.