As you know, Creative Flash Scroller acts like a mask to the targeted movie clip. We can adjust the masking behavior from the Mask panel of the Component Inspector.
Adjust the mask options
The first options controls the automasking of Creative Flash Scroller; as I was saying, our component automatically masks the targeted movie clip in order to show only what is behind the scrolling area. You can disable the behavior by enabling this option; in this case, you will still be able to scroll the movie clip, but all of it will be displayed on the stage.
You can create your own custom mask as well; all you have to do is to create a movie clip, place it over the Scroll Area and then write its name in the "Custom mask" text field. What will happen is that the shown content will be only the one behind your custom mask (the movie clip) and it will be possible to scroll only in that area as well.
The following option allows us to decide if we will use a personalised mask or not. For Scroll Area, the None position at "Transparent mask" means that the scroller will appear as default, without any changes. The other two options are "Horizontal" and "Vertical" (masks); this means that the scrolling area will have an alpha gradient aspect, with transparent character in the middle and opaque (white) character on the sides (top and bottom for horizontal, left and right for vertical).
The last parameter, "Transparent zone size", configures the "Vertical" and the "Horizontal" masks; the lowest value (0) means that the visible (transparent) area will be minimum, while the highest value (100) enlarges the visible area to maximum. Nevertheless, the horizontal/vertical mask is kept even for the extreme values (0/100). This parameter is expressed in percent (of the scrolling area).