In Cooperative Scrolling, the user procedure step and CA Gen cooperate to perform scrolling. When the user places the viewport anywhere within the boundaries of the data view, then the CA Gen software performs the scrolling operation. Scroll action commands are not passed to the procedure step.
However, when the user moves the viewport entirely outside of the data view boundaries, then the procedure step is called. The command entered by the user is translated to a common scroll action command, which is then passed to the procedure step for processing.
The scrolling command can be dialect specific. It is associated with a standard scroll operation that is presented to the procedure steps. This way, the screen procedure step logic does not have to be duplicated, or sensitive to, dialect specific scroll commands. As a result, scrolling support can be constructed without regard to the dialect defined for a screen.
After the viewport origin is relocated, it is evaluated to make sure it is within the data view. If the viewport has been moved entirely outside of the data view boundaries either prior or beyond it, then the common command is passed to the procedure step.
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