1. Quit/Relaunch Finder using the Force Quit menu
2. Open Terminal
3. Paste (or type) the following command: defaults write com.apple.Finder QLEnableXRayFolders 1
4. Relaunch Finder

TUAW reader David wrote us to ask how he could view .erb files (Rails development) in Quick Look. The fact is, there are a lot of plain-text files with extensions that Quick Look doesn't recognize. It's relatively straightforward to tell Quick Look to treat these files like any other text file and preview them as plain text; it does require diving into plist files and possibly breaking an application, so don't dive in unless you're comfortable and fully backed up. Read on for a short tour of Quick Look hacking basics ...

1. Identify files on remote machines. I've been using Remote Desktop at my day job for a couple of years now. With a few clicks, I can observe or control a remote Mac. Leopard brings this convenience to home users with Screen Sharing. It's useful, but files appear quite tiny when viewed on this screen-within-a-screen (and titles even smaller). Fortunately, Quick Look makes things much more legible.
2. Preview the contents of Zip files (plug-in required). BetterZip and the Zip Quick Look Plug-in both let you view the contents of a zipped file with Quick Look. In fact, Zip Quick Look's display is dependent on a HTML file which you may alter to your liking. Here's how to install Quick Look plug-ins.
3. Preview the contents of a folder (plug-in required). Much like BetterZip and Zip Quick Look, the Folder List plug-in lets you preview the contents of a folder. You can also customize its HTML-powered display and show or hide hidden files or time stamps.
4. Examine snippets of code with syntax highlighting intact. Here's another tip that requires a plug-in. Qlcolorcode lets you preview your code with all the helpful highlighting you expect.
5. Examine files in the trash. Until Leopard, the Finder's trash would keep its contents to itself. Anything you wanted to examine had to be moved back to the desktop. Fortunately, Quick Look lets you preview trashed items. Now you know precisely which item to yank out of there.
6. Prep your iWork documents for use with Quick Look. When you create a document with Numbers, Pages or Keynote, you can ensure that its preview will display the proper formatting by selecting the Include Preview in Document check box whey you save (or turn this feature on by default in the general preference pane).
7. Enhance TextMate. TextMate is the editor that geeks everywhere love (including the geeks at TUAW). Ciarán Walsh has written two Quick Look plug-ins for TextMate that let you preview items in a project or render Quick Look previews (for certain file types) using the TextMate syntax highlighter, respectively.
8. Preview fonts. Open a Finder window, select Cover Flow view and navigate to the font you're interested in. Click the space bar and presto! Instant preview.
9. Quick Look and Cover Flow. I love the combination of Cover Flow and Quick Look. Open a bulging folder in the Finder and select Cover Flow view. Tap the space bar to preview the 1st file and then use the arrow keys to move the next one and so on. You'll stay in Quick Look mode! Very cool.
10. Send images to iPhoto. When viewing an image with Quick Look - either from the Finder or attached to a Mail message - you'll see a tiny iPhoto icon at the bottom of the window. Click it to send that image to iPhoto.

• First is nice little tip from Mac OS X Hints about zooming in Quick Look. If you invoke Quick Look with the spacebar you can actually zoom in on the image in a couple of ways. You can hold down the option key and use your mouse's scrollwheel/ball (or two-finder scrolling on a touchpad) to zoom in and out. You can also zoom in by holding down the option key and clicking on the image, or zoom out by holding shift-option. While zoomed in you can also click and drag to pan the image. Strangely, the same shortcuts don't work with PDFs, but you can still zoom in and out with ? + and ? - (command plus/minus) with the Quick Look HUD selected.
  
• The second is that you can use Quick Look with more than one file at a time. So if you select several files in the Finder by command-clicking and then invoke Quick Look with the spacebar, you can scroll between the images with the arrow keys. However, there's also a nifty index sheet icon at the bottom that will bring up a kind of contact sheet with the selected files (as above).
• Finally, I know some folks had complained that the slideshow option has disappeared from the Finder's contextual menu. But if you select a group of files in the Finder and then invoke Quick Look you'll also see a play button that runs a slideshow in the Quick Look HUD.

TUAW reader Shaun Haber sent us a link to his personal blog with a great post about using Leopard's Quick Look from the command line, which is wonderfully handy for anyone who spends a chunk of their day in Terminal. The qlmanage utility gives you direct access to many Quick Look functions; of specific interest is the -p flag. This option displays the Quick Look generated preview for any file. So if you tell it to qlmanage -p foo.png, the image immediately pops up in a Quick Look pane.

Even better, Quick Look supports slide shows. So if you cd into a folder of images and run qlmanage -p *.jpg, you'll be rewarded with a full-on presentation of your pictures.

Other qlmanage flags of interest include -h (displays a help message) -t (thumbnail generation) and -f (a zoom factor to display with).

The downside of qlmanage is that it's full of NSLog-style messages. Haber recommends you pipe the output into /dev/null as follows: qlmanage -p *.jpg >& /dev/null.