By Graham K. Rogers

In OS X 10.10, Yosemite, System Preferences has seen changes with the design of the interface, while some panels have seen changes, some remain unchanged. Extensions is a new panel. This controls the way these additional control files are used by the Mac, including those from 3rd-party developers.

Extensions for Apple operating systems have existed since before OS X: indeed, the name of this site and the column I write for the Bangkok Post came from this and the new emphasis (then) on the X of OS X: OS Ten, not OS x. These small files add functions to applications: extending their normal capabilities. Some other functions are already available by using the Services menu for each application.

When demonstrated at the World Wide Developers Conference in June 2014, an image captured from Safari was added to an email and then Markup was used to add information and comments to the photograph. Markup is one of the extensions already available and works in many apps that already mix text and images, such as TextEdit and Stickies. Not all apps have such extensibility. Preview incorporates similar functions as part of its tool-set.

As a new feature, there is still some learning to be done; and as more developers (or Apple) increase the availability of extensions so more functions will be added to those apps that are able to use such new features. Links to articles written on the feature are available below.

The single panel has two parts: to the left the types of extensions: All, Actions, Finder, Share Menu, Today. Below each extension type, is a summary (in grey) of what is available. When one of the types is highlighted, any extensions are shown in the main panel to the right.

• All - All third-party extensions. On my Mac, this currently shows Dropbox and a checkbox, with Finder alongside. As Dropbox synchronises from my iOS devices and other computer via the Finder, there is a relationship (See also Finder extension, below)

• Actions - Markup. As Markup is the only action extension installed so far, it is shown in this section. A checkbox alongside indicates that it is active. If the checkbox is deselected, Markup is immediately unavailable in apps. When the box is checked again, it is available right away. Markup has a number of ways to make comments or annotations on an image used in an application that allows this, including the use of a signature.

• Finder - currently my installation only has Dropbox shown (see All, above) with a checkbox. As future applications are developed to provide such interoperability, we should expect to see more.

• Share Menu - this includes a list of several applications from which it is already possible to export or otherwise share data. These include Apple developed applications (including Mail, Messages and AirDrop) as well as a number of 3rd party ones, such as Facebook, Twitter and Flickr. Those that are currently in use, have their boxes checked. A number of other extensions that are installed, but are not used, are unchecked.

• Today is the other half of the Notifications Center panel in which a user may display icons that access specific functions or display certain information. The Notifications half is controlled in System Preferences > Notifications.

  In my "Today" display I use Social (allowing links to sites like Facebook and Twitter if wanted), Stocks, World Clock, Weather and other such data displays. Other extensions that are installed, but are not used, are unchecked.

The extensions here are installed for system-wide use, so those installed specifically for Safari (for example) are not shown here. It is expected that more extensions will appear, but will be part of new applications (or updates to already-installed applications).

As more information becomes available, or if changes are made, this page will be updated.

Useful Links:

• Action extensions in OS X Yosemite: Explained (Peter Cohen, iMore)

• An In-Depth Look at App Extensions in iOS 8 and Yosemite (Juli Clover, MacRumors)

• OS X 10.10 Yosemite: The Ars Technica Review - Extensions in Yosemite (John Siracusa, Ars Technica) - All 25 pages of John Siracusa's Yosemite Review are worth reading

• OS X Yosemite: What's new in Mail, Messages, and Calendars (Jason Snell, MacWorld)

• Accessibility
• App Store
• Bluetooth
• CDs & DVDs
• Date & Time
• Desktop & Screensaver
• Dictation & Speech
• Displays
• Dock
• General
• Mission Control

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand where he is also Assistant Dean. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs.