Firefox 28 for developers
Firefox 28 was released on March 18, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
Changes for Web developers
console.exceptionproperty has been added (Firefox bug 922214).
console.assertproperty has been added (Firefox bug 760193).
- App Manager: a new Manifest Editor was added.
- App Manager: the toolbox used for debugging apps is now embedded in the app manager UI.
- Web Console: added a "split console" mode - press Escape to quickly open the console in any other tool.
- Web Console: added a dark theme for the output.
- Debugger: hover over any variable or click on it to bring up a pop-up that displays the current value.
- Inspector: added a color picker in rules view and various tooltips.
- Browser Toolbox: allows add-on and platform developers to use almost all of the developer tools while targeting the browser itself.
More details in this post.
- Support for multi-line flexbox has been added (Firefox bug 939901).
- Longhand East Asian counter styles have been implemented (Firefox bug 934072).
- Experimental support for the
background-blend-modeproperty has been added, but is disabled by default (Firefox bug 841601).
nonevalue has been added to
font-variant-ligatures(Firefox bug 913264).
- Support for the
:hoveruser action pseudo-class on pseudo-elements has been implemented (Firefox bug 922669).
<input type=number>have been implemented, disabled by default.
- ECMAScript 2015 implementation continues:
Arraymethods have been implemented:
Array.prototype.keys()(Firefox bug 894658).
- A bug causing that
Object.getOwnPropertyNames()did not see unresolved properties of
Errorobjects has been fixed (Firefox bug 724768).
maybe. (Firefox bug 884275).
DocumentFragment.getElementById()method has been implemented. E.g.
document.createDocumentFragment().getElementById()(Firefox bug 933193).
KeyboardEvent.repeatattribute has been implemented (Firefox bug 600117).
new File(["foo"], "foo.txt")has been implemented. (Firefox bug 819900).
navigator.pluginsis no more enumerable, for privacy reasons (Firefox bug 757726).
- The two attributes
Window.screenYnow return CSS pixels (and no more device pixels) (Firefox bug 943668).
- The two methods
CanvasRenderingContext2D.drawCustomFocusRing()have been implemented. The preference
canvas.focusring.enabledmust be set to
trueto activate both (Firefox bug 540456).
willReadFrequentlycontext attribute for "
2d" canvas contexts has been implemented (see
HTMLCanvasElement.getContext()) (Firefox bug 884226).
- The following attributes and methods of
NavigatorIDhave been implemented on
WorkerNavigatorto allow their use in workers:
taintEnabled()(Firefox bug 925847).
nextElementSiblingproperties has been removed from
DocumentType, because of compatibility problems (Firefox bug 932501).
- Support of the
mathvariantattribute has been added (Firefox bug 114365).
- Opus in WebM is now supported (Firefox bug 887978).
- The VP9 video decoder is now supported (Firefox bug 833023).
- Support of
SPDY/2has been removed.
Changes for addon and Mozilla developers
- The interface of DeferredTask.jsm has been changed, and the
cancel()methods have been removed (Firefox bug 940408).
- CSP was not enforced in sandboxed iframes. This has been fixed (Firefox bug 886164).
- The CSP 1.1 experimental
script-noncedirective has been implemented. The preference
security.csp.experimentalEnabledshould be set to
trueto enable this functionality (Firefox bug 855326).
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