New hook functions, makeContext() and makeContent(), have been added to the grid graphics package. These functions allow an alternative approach to developing custom grobs when a grob can only decide what to draw at drawing time rather than when the grob is created. For custom grobs that are based on this new approach, the
grid.force() function provides access to low-level grobs that are otherwise invisible because they are only generated at drawing time.
These functions lead to greater flexibility in the development of custom grobs and more power to modify the result after drawing is complete.