Firefox 6, based on Gecko 6.0, was released on August 16, 2011. This article provides links to information about the changes that affect developers in this release.
<progress> element, which lets you create a progress bar, is now supported.<track> element, which specifies text tracks for media elements, is now supported. This element should appear in the DOM now, though its behavior is still not implemented.<iframe> element is now clipped correctly by its container when the container's corners have been rounded using the border-radius property.<form> elements' text <input> fields no longer support the XUL maxwidth property; this was never intentional, and is in violation of the HTML specification. You should instead use the size attribute to set the maximum width of input fields.<canvas> CanvasRenderingContext2d properties fillStyle and strokeStyle used to ignore garbage included after a valid color definition; now this is correctly treated as an error. For example, "red blue" as a color used to be treated as "red", when it should have been ignored.<canvas> elements can now properly be set to 0px; previously, these were getting arbitrarily set to 300px when you tried to do that.element.dataset property allows to access them.<textarea> element receives focus, the text insertion point is now placed, by default, at the beginning of the text rather than at the end. This makes Firefox's behavior consistent with other browsers.-moz-text-decoration-color-moz-text-decoration-line-moz-text-decoration-style-moz-hyphens-moz-orient<progress>).::-moz-progress-bar<progress> element representing the completed portion of a task.@-moz-document property has a new regexp() function, which lets you match the document's URL to a regular expression.azimuth CSS property is no longer supported, as we have removed what little code we had for the aural media group. It was never significantly implemented, so it made more sense to remove the crufty implementation for the time being rather than try to patch it up.:hover pseudoclass was not applied to class selectors when in quirks mode; for example, .someclass:hover did not work. This quirk has been removed.:indeterminate pseudo-class can be applied to <progress> elements. This is non-standard, but we hope it will be adopted by other browsers, because it will be useful.-moz-win-exclude-glass value has been added to the -moz-appearance CSS property in order to exclude opaque regions in Aero Glass glaze effects on Windows systems.bug 658949 changed how the hash (#) symbol is treated in data URIs which may break CSS stylesheets which contain such a symbol if it is not escaped.
window.matchMedia() method and the MediaQueryList interface.navigator.securityPolicy, which has returned an empty string for a long time, has been removed outright.BlobBuilder is now implemented, although for now it's prefixed (so you need to use MozBlobBuilder).document.height and document.width have been removed. bug 585877DocumentType object's entities and notations properties, which were never implemented and always returned null, have been removed, since they've been removed from the specification anyway.DOMConfiguration interface and the document.domConfig property that used it have both been removed; they were never supported and have since been removed from the DOM specification.hashchange event now correctly includes the newURL and oldURL fields.FileReader interface's abort() method now throws an exception when used if no file read is in progress.window.postMessage() method now uses the structured clone algorithm to let you pass JavaScript objects instead of just strings from one window to another.window.history API now uses the structured clone algorithm to serialize the objects you pass to the pushState() and replaceState() methods; this lets you use more complex objects (including those that contain cyclic graphs of references).beforeprint and afterprint events.document.strictErrorChecking property has been removed, since it was never implemented and was removed from the DOM specification.event.defaultPrevented property is now supported; you should use this instead of the non-standard getPreventDefault() method to detect whether or not event.preventDefault() was called on the event.window.top property is now properly read only.EventTarget function addEventListener()'s useCapture parameter is now optional, as it is in WebKit (and as per the latest version of the specification).mozResponseArrayBuffer property of the XMLHttpRequest object has been replaced with the responseType and response properties.element.dataset property has been added to the HTMLElement interface allowing access to the data-* global attributes of an element.CustomEvent interface has been implemented. (see bug 427537)data: and javascript: URIs no longer inherit the security context of the current page when the user enters them in the location bar; instead, a new, empty, security context is created. This means that script loaded by entering javascript: URIs in the location bar no longer has access to DOM methods and the like, for example. These URIs continue to work as before when used by script, however.new operator on several built-in functions (eval, parseInt, Date.parse...) that should not have allowed it, according to the specification. This behavior is no longer supported. Using the new operator in this way was never officially supported and was not widely done, so it's unlikely that this change affects you.pathLength attribute is now supported.data: URLs.<mstyle> has been corrected.aria-busy changes.aria-sort occurs.WebSocket object has been renamed to MozWebSocket to prevent it from incorrectly being used to detect the availability of unprefixed WebSockets.Content-Disposition header has been fixed to properly interpret backslash-escaped ASCII characters as just that character itself. Previously it was incorrectly replacing that character with an underscore ("_").Set-Cookie headers is now interpreted correctly when quotes are used; previously, they were being treated as part of the path string instead of as delimiters. This change may affect compatibility with some web sites, so authors should check their code.Upgrade request header is now supported; you can request an upgrade of an HTTP channel to another protocol by calling nsIHttpChannelInternal.HTTPUpgrade().OES_texture_float extension.console.trace() method has been added to the ConsoleAPI (see bug 585956).For an overview of the changes you may need to make in order to make your add-on compatible with Firefox 6, see Updating add-ons for Firefox 6.
openSafeFileOutputStream() method now opens files with the DEFER_OPEN behavior flag instead of attempting to open them immediately.importRelative() method lets you load one JavaScript code module from a path relative to the path of another JavaScript code module. This makes it easier to build modules that depend on each other.nsCOMArray<T> now has a RemoveObjectsAt() method for removing multiple objects at once from the array.File constructor now supports specifying a local pathname string when used from chrome. In addition, you can also specify the file to access using the DOM File API using an nsIFile object.nsINavHistoryQueryOptions now supports sorting in frecency order using the new SORT_BY_FRECENCY_ASCENDING and SORT_BY_FRECENCY_DESCENDING constants.nsIFilePicker has a new nsIFilePicker.addToRecentDocs attribute, which lets you indicate that the selected file should be added to the user's "recent documents" list if there is one. This attribute has no effect when in private browsing mode.nsINavBookmarkObserver methods with item ID parameters now require a GUID as well.nsIPrefBranch.clearUserPref() no longer throws an exception if the specified preference doesn't exist or has no user-set value. Instead, it simply does nothing.nsIMemoryReporter interface now provides support for indicating the kind of memory being described (mapped, heap, or other).nsISHEntry stateData attribute now returns a nsIStructuredCloneContainer.nsIURI has a new nsIURI.ref attribute, which returns the reference portion (the part after the "#") of the URI. It also has new methods nsIURI.cloneIgnoringRef() which clones the nsIURI without the ref member and nsIURI.equalsExceptRef() which compares to another nsIURI ignoring the ref member.mozIAsyncFaviconsnsIEventSourcensIGSettingsCollectionnsIGSettingsServicensIHttpUpgradeListenernsIHttpChannelInternal.HTTPUpgrade() method.nsIStructuredCloneContainernsITelemetrynsITimedChannelnsIWebSocketListenernsIWebSocketProtocolThe following interfaces were implementation details that are no longer needed:
nsIDOMDocumentEvent (see bug 655517)nsIDOMDocumentTraversal (see bug 655514)nsIDOMDocumentRange (see bug 655513)IWeaveCrypto (see bug 651596)nsIDOM3DocumentEvent (see bug 481863)nsIDOMAbstractViewnsILiveTitleNotificationSubjectnsIPlugin (see bug 637253)nsIPluginInstance (see bug 637253)nsIHTMLEditRules (see bug 633750)nsIXSLTProcessorObsolete (see bug 649534)