AppleInsider reports that an Apple patent filling revealed this week shows a single scroll bar user interface for controlling windows with more than one scrollable panel.

“Panels move in lock-step with one another at certain times, but not at other times, depending on whether the lock-step scrolling would cause blank areas to be displayed,” Apple said in the filing.

Illustrations show multi-panel scrolling in actionIllustrations show multi-panel scrolling in action

“If the user’s scroll commands would result in a blank area of a panel being displayed, the scroll command is not performed; rather, the panel remains frozen in its current position, even while other panel(s) do scroll.”

The idea being to ensure useful content is displayed at all times, making sure no screen estate is wasted.

The patent could be implemented in a “conventional personal computer system, such as a Macintosh, running an operating system such as Mac OS X.”