Return the subplot grid positions allowing for variable inter-subplot spacing and using physical units for the spacing terms. The resulting positions include “hidden” panel rows and columns.
The physical units for positioning grid cells are converted from em-widths to inches when the
GridSpecis instantiated. This means that subsequent changes to
rc['font.size']will have no effect on the spaces. This is consistent with
rc['font.size']having no effect on already-instantiated figures.