Defines in what direction a surface should be positioned, relative to
the anchor point of the parent surface. If two orthogonal gravities are
specified (e.g. 'bottom' and 'right'), then the child surface will be
placed in the specified direction; otherwise, the child surface will be
centered over the anchor point on any axis that had no gravity
specified.
If two parallel gravities are specified (e.g. 'left' and 'right'), the
invalid_input error is raised.
set child surface gravity
Defines in what direction a surface should be positioned, relative to the anchor point of the parent surface. If two orthogonal gravities are specified (e.g. 'bottom' and 'right'), then the child surface will be placed in the specified direction; otherwise, the child surface will be centered over the anchor point on any axis that had no gravity specified.
If two parallel gravities are specified (e.g. 'left' and 'right'), the invalid_input error is raised.