The OPTIONS section of ThumbGrid's parameters include a few miscellaneous behavioral options for thumbnails.
Off by default, "Active Focus" is an option whereby ThumbGrid engages and disengages an interactivity timer keep end-users from losing their place. When on, ThumbGrid waits for the user to stop interacting with the component. When they do, a five second timer starts. When the five seconds are up, ThumbGrid moves the interface back to the thumbnail group containing the currently loaded thumbnail (so it can be seen in the ThumbGrid interface).
On by default, "Active highlight" controls whether the "...Active" parameters in THUMB STYLE are applied to the thumbnail that is "active" and currently in view in the SlideShowPro player. Turning this off will prevent "...Active" style settings from being applied.
This parameter works in conjunction with the THUMB IMAGES/Scale parameter. When scale is set to "Proportional", THUMB BEHAVIOR/Resize controls whether the thumbnail element's background resizes itself to conform to the proportionally scaled image (thus giving it a uniform padded appearance around its perimeter.