This is a generic function with methods for grob and gTree objects.
The grob and gTree methods automatically push any viewports in a
vp
slot and automatically apply any gpar
settings
in a gp
slot. In addition, the gTree method pushes and
ups any viewports in a childrenvp
slot and automatically
calls grid.draw
for any grobs in a children
slot.
The methods for grob and gTree call the generic hook functions
preDrawDetails
, drawDetails
, and postDrawDetails
to allow classes derived from grob or gTree to perform
additional viewport pushing/popping and produce additional
output beyond the default behaviour for grobs and gTrees.