Hot on the heels of the SquirrelFish news, Apple released Safari 4 Developer Preview to anyone with a free ADC account. It includes a recent WebKit framework and a newer Safari binary wrapper with a few new features.

The one people are writing home about the most is “Save as Web Application…” item in the File menu. This uses a copy of a specially prebuilt binary and wraps the current page up in the .plist along with an icon representing a screen capture of the page. This allows actual “.app” style applications that can be added to left side the Dock or restricted using the Parental Controls or any other thing you can do with them. The only difference in a regular web site and that site as a web app is that the Safari menu bar and toolbars are gone. There’s hardly a border to the window at all, just titlebar and contents. I can see this being useful for two scenarios: the very locked down corporate environment or public kiosk where all care is taken to keep people in a sandbox, and for personal use when you need to focus on work and not be tempted to look through bookmarks or go to a new URL.

The other features I’ve noticed so far are an option to include your home page preference as the default for new tabs, only noticed because it was on by default and interrupted my “Cmd-T, type address” reflex, and a new page zoom style. The entire page, including images, will zoom, meaning images get pixelated but fonts stay sharp and crisp. I’m not really sure I like this option. The only times I use the zoom toolbar button are when text is too small or too large, and I’ve never needed that for images. In fact, zooming images rearranges the page elements far more than text enlarging. I suspect the default behavior is somewhere in the plist.

UPDATE: In com.apple.Safari.plist, WebKitDebugFullPageZoomPreferenceKey a value of -1 (default) enables full page zooming. Setting it to 0 reverts to the old way.

The Web Inspector is also seeing some improvements, but I believe that’s been noticeably so in the WebKit nightlies for awhile now. The Inspector is an invaluable tool especially for CSS work, but I just keep forgetting it’s there.