Mozilla has released another alpha of the next Firefox (either 3.7 as the nightlies name suggest, or 4.0 like most people expect), conservatively labeled Mozilla Developer Preview.
On Windows at least, besides the new toolbar icons introduced in Alpha 3, there is now an option to place the tab bar above the navigation bar (right-click on a toolbar), which combined with the option to hide the menu bar (introduced in Firefox 3.6), brings Firefox UI closer to the planned Firefox 4.0 theme update. Aero Glass for the toolbars was available for a while in the nightlies (and looked great) then pulled back, but it should be ready for the next alpha or beta.
Awesome bar suggestions that are already open in a tab, are identified with a tab icon. I wish matching pages in current tabs were listed at the top, so it could be used as an easy way to search among tabs, but it’s not the case right now.
A nice addition is text area resize. With it, you get a resize handler for most text areas you will see on the web, so you can set it the right size for you. It needs polishing however. For example, if you try to resize the Facebook status update text area, the resize handler follows the mouse cursor when in reality, you can’t change the text area’s width. So you end with the resize handler in the middle of the text area.
There are also very important enhancements in the performance area. Thanks to the inclusion of Direct2D, Microsoft’s hardware accelerated 2D rendering API, and DirectWrite, its new text-layout and glyph-rendering API.
The benefits of the new APIs are better understood on this short video of a recent nightly running a graphics stress tool, compared with Chrome 4, Safari 4, Opera 10.5, and a nightly with Direct2D off.
Note that Direct2D and DirectWrite are available for Windows 7 and Windows 2008 Server R2. Windows Vista and Windows Server 2008 users will need to apply the Platform Update.
Also, Direct2D is disabled by default, as it is not stable enough yet. To turn it on, access the advanced preferences via about:config, and set gfx.font_rendering.directwrite.enabled to true, and mozilla.widget.render-mode to 6. The latter uses Direct2D for Firefox user interface as well. If you noticed the jagged Back button in the first screenshot in this post it is because of this (still buggy) setting.
Out of process plugins which debuted in public earlier this week in Firefox Lorentz beta, goes a step further here, allowing to run the Flash Player plugin on its own process on Mac OS X, with some hard restrictions: only Flash 10.1 RC on Mac OS X 10.6.
Due to a lot of optimization, exiting Firefox is now lightning fast (97% faster), so you won’t have to think twice to perform restart Firefox for an update or a new extension.
Mozilla Developer Preview Alpha 4 release notes, including download links.