Here is some very basic logic that implements a slideshow in SV Pro 1.8. I've kept my example simple -- no new buttons or controls are used -- by modifying a fairly standard install of SV. Hopefully it's easy enough to get you started and not so simple to be of no use.
You'll start by modifying the ImageArea.as file. We want the init() function. Right after this line of code (~ line 107)
and before the function's closing brace ( } ) you want to insert this line of code
mIntervalId = setInterval( Delegate.create( this, onClickNext ), mSlideShowDuration );
This guy does the work. It's a timer that calls onClickNext, but it depends on variables we've not yet set. So let's set 'em...
The beginning of the ImageArea class is where all our variables are defined. (Well, it's where you ought to define them if you enjoy tidy code.) Look for a suitable blank spot, say line 47 or so, and insert 2 lines
private var mSlideShowDuration:Number = 3000;
public var mIntervalId:Number;
Now we have a public reference to our timer, mIntervalId, and we have a private reference to the duration between calls, mSlideShowDuration. (The duration is in milliseconds.) You'll notice all the other variables here are private. We're making mIntervalId public in order to be able to call it from outside of the ImageArea class.
The slideshow would work now. It would start as soon as your first image displayed and continue until the final image was shown. But we need a way to disable it. I've chosen to disable the show as soon as any thumbnail is clicked.
To do this, we need to edit the Thumb.as file and look for private function onRelease(). (You might find the function declared around line 212.) On the last line of the function (before the closing brace) insert this code
clearInterval( mImageArea.mIntervalId );
to stop the slideshow. Now when a thumbnail is selected (a click, a dragout, etc) the reference to our timer is cleared and the slideshow stops.