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Easy Access to the Applications Folder from a Disk Image

by Ben Artin

Disk images in Mac OS X provide developers with a powerful mechanism for packaging and delivering software on the internet. They enable developers to make a good first impression with users. A well-crafted disk image shows attention to detail, and signals that the software is designed well and with the user in mind.

In Mac OS X 10.2.3, Apple added support for internet-enabled disk images, which automatically replace themselves with their contents. While they have gained some acceptance, most software is not distributed this way, partly because internet-enabled disk images prevent the developer from making a strong first impression or including an introductory document with the application.

For all their strengths, disk images still have a remarkably annoying behavior. The one thing most users want to do with a disk image is drag something from it to the Applications folder, but most disk images provide no easy way to get at the Applications folder. For example, an early version of the Fetch 5 disk image looked like this:

figure 1
Figure 1. A disk image with no easy access to the Applications folder

Even with the installation instructions right in the disk image background, this method can be problematic. Accessing the Applications folder in the Finder may obscure the disk image window, move parts of it off the screen, or make it too small to show its entire content. For example, on some disk images, the application icon is so close to the right edge of the window that showing the Finder sidebar causes the application icon to move beyond the right edge, requiring the user to use the scroll bar to find the application.

In designing the disk image for Fetch 5, we considered these options and found only one way to guarantee easy access to the Applications folder. Namely, we included an item (on the disk image itself) to which the user can drag our application in order to install it:

figure 2
Figure 2. A disk image providing easy access to the Applications folder

To provide the drag target on the disk image, we used a symbolic link to the /Applications folder. The symbolic link can be created in multiple ways.

  • To create a symbolic link in the Finder, first install SymbolicLinker. After relaunching the Finder, as per the SymbolicLinker install instructions, open the top level of your startup disk, Control-click the Applications folder, and choose Make Symbolic Link from the contextual menu. The symbolic link will be created on your desktop and named Applications symlink.
  • To create a symbolic link from Terminal, use:
    ln -s /Applications ~/Desktop
    The symbolic link will be created on your desktop and named Applications.

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Once you've created the symbolic link, you need to include it on your disk image as you would any other item. We use MindVision FileStorm to create our disk images, and I highly recommend it for its ease of use and ability to consistently create high-quality disk images. In FileStorm, adding the symbolic link is as easy as dragging it into the project window and positioning it as desired.

We had originally thought that the written instructions and the small arrow that's a part of the symbolic link icon would be sufficient to guide our users. After initial user testing, we decided to also provide a large arrow pointing from the application to the Applications folder symbolic link as an additional visual cue indicating what the user is supposed to do. This arrow is part of the disk image's background picture.

Our users' feedback so far indicates that the technique is effective and intuitive. Users who were confused by our disk image typically would have been equally confused if the disk image had not contained the Applications folder symbolic link. This leads us to believe that some of our users are unfamiliar with disk images, but that this technique improved usability for others.

Adding an Applications folder symbolic link to your disk image is a very simple and effective way to make your users' initial experience with your software more enjoyable. As a user who interacts with disk images on an almost daily basis, I look forward to seeing this technique used more widely.

Ben Artin has been a Mac programmer for about a decade. His past accomplishments include two MacHack awards. He has been working on Fetch since 2003 and is enjoying it very much.

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