Refresh Issue of OpenGL graph

Version: 2020b

Type: Features

Category: Graphing

Subcategory: General

Jira: ORG-20972

A new system variable @RUGT is added to control whether a graph should redraw when uncover. @RUGT is in milliseconds, if a graph spends less than that time to finish drawing, then it will redraw itself when being uncovered (regardless of the @NPP). Otherwise, the @NPP would still be effective.