I was working to a flex project, I need a canvas where I have to put some elements on a big surface, so I really need to have scrollbars. That’s fine. If I move an object to the right-bottom corner it’s working great, if the object goes out of working space, will go under scrollbars, and other object that are on the stage.

But if we drag an object to left-top corner of our working space this will move over the other elements, because the mask it’s not active until scrollbars are active. Don’t try to activate your self, it’s not working .

I try to activate scrollbars when I create my canvas … and nothing … I search into manual and …. let me quote this : “The mask. This property may be undefined if no scroll bars are currently displayed or in some subclasses which have a different masking mechanism. A mask defined the viewable area of a displayable object. Thus this mask is used to hide the portions of the content that are not currently viewable. In general you do not access this property directly. Manipulation of the horizontalScrollPolicy, verticalScrollPolicy, horizontalScrollPosition, and verticalScrollPosition properties should provide sufficient control over the mask. “.

As a observation controlling horizontalScrollPolicy, verticalScrollPolicy, horizontalScrollPosition, and verticalScrollPosition properties it’s not activating ScrollBase mask always.