Today, three months after the release of Firefox 4, we release Firefox 5, thanks to our new development cycle. Developers will be able to create richer animations using CSS3 Animations. This release comes with various improvements, performance optimization and bug fixes.

CSS3 Animations

CSS Animations (check out the documentation) are a new way to create animations using CSS. Like CSS Transitions, they are efficient and run smoothly (see David Baron’s article), and the developers have a better controls over the intermediate steps (keyframes), and can now create much more complex animations.

Notable changes

You can now pass an image as a parameter to createImageDatato copy its dimensions.

setTimeout and setInterval will only be able to execute callbacks once per second in inactive tabs. This follows the behavior of requestAnimationFrame to save CPU and power consumption.

Other Bug Fixes and Performance Improvements:

Canvas improvements The <canvas> 2D drawing context now supports specifying an ImageData object as the input to the createImageData() method; this creates a new ImageData object initialized with the same dimensions as the specified object, but still with all pixels preset to transparent black.

2D drawing context now supports specifying an object as the input to the method; this creates a new object initialized with the same dimensions as the specified object, but still with all pixels preset to transparent black. Specifying non-finite values when adding color stops through a call to the CanvasGradient method addColorStop() now correctly throws INDEX_SIZE_ERR instead of SYNTAX_ERR .

method now correctly throws instead of . The HTMLCanvasElement method toDataURL() now correctly lower-cases the specified MIME type before matching.

method now correctly lower-cases the specified MIME type before matching. getImageData() now correctly accepts rectangles that extend beyond the bounds of the canvas; pixels outside the canvas are returned as transparent black.

now correctly accepts rectangles that extend beyond the bounds of the canvas; pixels outside the canvas are returned as transparent black. drawImage() and createImageData() now handle negative arguments in accordance with the specification, by flipping the rectangle around the appropriate axis.

and now handle negative arguments in accordance with the specification, by flipping the rectangle around the appropriate axis. Specifying non-finite values when calling createImageData() now properly throws a NOT_SUPPORTED_ERR exception.

now properly throws a exception. createImageData() and getImageData() now correctly return at least one pixel’s worth of image data if a rectangle smaller than one pixel is specified.

and now correctly return at least one pixel’s worth of image data if a rectangle smaller than one pixel is specified. Specifying a negative radius when calling createRadialGradient() now correctly throws INDEX_SIZE_ERR .

now correctly throws . Specifying a null or undefined image when calling createPattern() or drawImage() now correctly throws a TYPE_MISMATCH_ERR exception.

or image when calling or now correctly throws a exception. Specifying invalid values for globalAlpha no longer throws a SYNTAX_ERR exception; these are now correctly silently ignored.

no longer throws a exception; these are now correctly silently ignored. Specifying invalid values when calling translate() , transform() , rect() , clearRect() , fillRect() , strokeRect() , lineTo() , moveTo() , quadraticCurveTo() , or arc() no longer throws an exception; these calls are now correctly silently ignored.

, , , , , , , , , or no longer throws an exception; these calls are now correctly silently ignored. Setting the value of shadowOffsetX , shadowOffsetY , or shadowBlur to an invalid value is now silently ignored.

, , or to an invalid value is now silently ignored. Setting the value of rotate or scale to an invalid value is now silently ignored.

CSS Support for CSS animations has been added, using the -moz- prefix for now.

DOM The selection object’s modify() method has been changed so that the “word” selection granularity no longer includes trailing spaces; this makes it more consistent across platforms and matches the behavior of WebKit’s implementation.

object’s method has been changed so that the “word” selection granularity no longer includes trailing spaces; this makes it more consistent across platforms and matches the behavior of WebKit’s implementation. The window.setTimeout() method now clamps to send no more than one timeout per second in inactive tabs. In addition, it now clamps nested timeouts to the smallest value allowed by the HTML5 specification: 4 ms (instead of the 10 ms it used to clamp to).

method now clamps to send no more than one timeout per second in inactive tabs. In addition, it now clamps nested timeouts to the smallest value allowed by the HTML5 specification: 4 ms (instead of the 10 ms it used to clamp to). Similarly, the window.setInterval() method now clamps to no more than one interval per second in inactive tabs.

method now clamps to no more than one interval per second in inactive tabs. XMLHttpRequest now supports the loadend event for progress listeners. This is sent after any transfer is finished (that is, after the abort , error , or load event). You can use this to handle any tasks that need to be performed regardless of success or failure of a transfer.

now supports the event for progress listeners. This is sent after any transfer is finished (that is, after the , , or event). You can use this to handle any tasks that need to be performed regardless of success or failure of a transfer. The Blob and, by extension, the File objects’ slice() method has been removed and replaced with a new, proposed syntax that makes it more consistent with Array.slice() and String.slice() methods in JavaScript. This method is named mozSlice() for now.

and, by extension, the objects’ method has been removed and replaced with a new, proposed syntax that makes it more consistent with and methods in JavaScript. This method is named for now. The value of window.navigator.language is now determined by looking at the value of the Accept-Language HTTP header.

JavaScript Regular expressions are no longer callable as if they were functions; this change has been made in concert with the WebKit team to ensure compatibility (see WebKit bug 28285).

The Function.prototype.isGenerator() method is now supported; this lets you determine if a function is a generator.

SVG The class SVG attribute can now be animated.

SVG attribute can now be animated. The following SVG-related DOM interfaces representing lists of objects are now indexable and can be accessed like arrays; in addition, they have a length property indicating the number of items in the lists: SVGLengthList , SVGNumberList , SVGPathSegList , and SVGPointList .

HTTP Firefox no longer sends the “Keep-Alive” HTTP header; we weren’t formatting it correctly, and it was redundant since we were also sending the Connection: or Proxy-Connection: header with the value “keep-alive” anyway.

or header with the value “keep-alive” anyway. The HTTP transaction model has been updated to be more intelligent about reusing connections in the persistent connection pool; instead of treating the pool as a FIFO queue, Necko now attempts to sort the pool with connections with the largest congestion window (CWND) first. This can reduce the round-trip time (RTT) of HTTP transactions by avoiding the need to grow connections’ windows in many cases.

Firefox now handles the Content-Disposition HTTP response header more effectively if both the filename and filename* parameters are provided; it looks through all provided names, using the filename* parameter if one is available, even if a filename parameter is included first. Previously, the first matching parameter would be used, thereby preventing a more appropriate name from being used. See bug 588781 .

MathML Support for embellished operators