Lower obj to the bottom of its layer.
obj will, then, be the lowest one in the layer it belongs to. Objects on other layers won't get touched.
See also Efl.Gfx.Stack.stack_above(), Efl.Gfx.Stack.stack_below() and Efl.Gfx.Stack.raise_to_top()
Since 1.22
Overridden from Efl.Gfx.Stack.lower_to_bottom.
lower_to_bottom @pure_virtual {}
void efl_gfx_stack_lower_to_bottom(Eo *obj);