Last week we wandered about Mountain Lion's Messages application to get a feel for the territory. In today's lesson we'll dig into some of Messages' less obvious features, including screen sharing, initiating remote slideshows and presentations, and viewing past chats.

Messages and screen sharing

When exploring the Mac's sharing features I explained how to share the screen of another Mac on your local network. Through Messages it's possible to do the same thing, but over the Internet.

To do this, each participant must use an AIM, Bonjour, Google Talk, or Jabber account. Screen sharing isn't available through the iMessage protocol (meaning two iCloud accounts) or Yahoo.

To share someone's screen, select their name in your buddy list and from the Buddies menu choose Ask to Share PersonX's Screen (where PersonX is the person you want to interact with). That person will receive an invitation via an alert sound and a dialog box. For them to allow their screen to be shared, they simply click the dialog box. They can also elect to send you a text reply. For example, if they are in the middle of something, they can  just click the Text Reply button and type I can't right this second. Try again in 5 minutes.

You can also elect to share your screen with another person. You do this by selecting your buddy and choosing Buddies > Share My Screen With PersonX. An invitation will be sent and your buddy  can choose to accept it by clicking the dialog box that appears.

When you, as the person whose screen is being shared, wish to end screen sharing, just look in the menu bar and you'll see a flashing orange screen-sharing icon. Click this icon and choose End Screen Sharing. The connection will break. The person who's viewing the other screen remotely can end sharing by clicking the small My Computer window to view their screen and then close the small shared screen window. Alternatively, you can  choose Buddies > End Screen Sharing.

So, in what way is it useful to allow someone to remotely gawk at your Mac's screen? (Or you gawk at theirs?) The beauty of this scheme is that not only can you see the remote screen, but you can also control it. From my end, as the Tech Expert of the Family, this is an invaluable feature because I can troubleshoot a friend or relative's computer from across the country. We share the screen, I ask that they step away from the computer so I can try a few things, and let them know what I'm up to as I'm doing it. As we share, we can also talk to one another using the Mac's microphone and speakers, which saves us the cost of a long-distance call.

You probably know someone who performs a similar service among your circle of friends. If you need help, this is one easy way for them to provide it. And now that you know how to participate, they'll love you all the more.

Or, because each of you can take turns controlling the cursor and screen, this kind of screen sharing can be great for collaboration. Remember, however, that you can't both control the mouse or trackpad at the same time. Try and you'll fight over the thing like a Ouija board possessed by uncooperative spirits.

Sharing slideshows and presentations

In the last lesson I showed you how to conduct video chats using Messages. But I've saved a juicy detail for this week. Within a video chat, you can share images and presentations.

Establish a video chat between you and your buddy as I described last week. (And remember, you must each use the same service--AIM, Bonjour, Google Talk, or Yahoo.) You'll see your image in the smaller window in one of the window's corners (you can drag that window to where you want it) and a larger image that contains your buddy's image as projected by that Mac's camera.

To share an image with the other person, drag it into the video chat window. When you do, you'll see the window divided into two areas. The top reads Send to BuddyX. The bottom says Share With Theater. Drag the image to the window's bottom portion, and it will expand to fill most of each participant's video chat window. You'll still be able to see the other person in a smaller window in one of the corners. This is helpful in that the person sharing the image can narrate and you can respond.

But I mentioned slideshows, right? Correct. If you drag multiple images to the video chat window, Messages will begin a slideshow of those images. The person sharing the images can let the slideshow run, pause it by clicking the Pause button (and restart it by clicking the Play button) and manually click through the images using Back and Forward arrow buttons.

This gets better if you want to share a PowerPoint or Keynote presentation. Let's suppose I was holding a remote meeting with England's Poison Oak Fancier's League and I had a 15-minute presentation on the plant's itch-producing properties that its proponents were dying to see.

All I'd have to do is drag that presentation into the Share With Theater portion of the window. If I do this with a PowerPoint presentation, I'll find Back and Forward buttons that I can use to navigate through the presentation. If I place a Keynote presentation in the window, my copy of Keynote will launch, open the file, and offer a slideshow window that I can use to control my presentation. As with a projected slideshow, those on the other end will see my face in a smaller window in a corner.

This feature is great for families who want to dangle grandchildren in front of distant relatives while speaking at great length of the child's every burp and wiggle. Additionally, it's a tremendous business and collaboration tool. I routinely use the feature to offer remote presentations to business groups.

Capturing your conversations

Unlike those clandestine conversations you hold in the local juke joint, it's possible to keep a copy of your chats. To do so, choose Messages > Preferences, then select the Messages tab, and enable the Save History When Conversations Are Closed option. From this point on, your conversations will be archived.

To locate these archived messages, in the Finder hold down the Option key and choose Go > Library. Within the resulting Library window, open the Messages folder and then look inside the Archive folder. Within this folder is a series of folders named by their dates. Open one of these folders, and you'll find files reflecting any chats you held on that date. You can open these in Messages or you can select one and press the Spacebar to view it in a Quick Look window.

I'm sure everyone you chat with is completely trustworthy and would never use your chats for the purposes of evil. Still, it's useful to know that what you type can be archived. So, as with any other kind of communication, it's best to not put into words what you don't want repeated.

By the way, while you're nosing around in this preference, note that you can change a message's background color, font color, and font (as well as the color, font color, and font of those you chat with). If you like, you can also assign a keyboard shortcut to bring Messages to the front, enable an option that tells Messages to watch for your name in incoming messages (so it can send up an alert when something happens that concerns you), or ask that Messages auto-reply to any incoming message with your Away message.

And that's the lowdown on Messages' finer points.

Next week: Getting some FaceTime