Create a new shape attribute.
A shape is used to impose a particular ink and logical rectangle on the result of shaping a particular glyph. This might be used, for instance, for embedding a picture or a widget inside a `PangoLayout`.
ink_rect |
ink rectangle to assign to each character |
logical_rect |
logical rectangle to assign to each character |
the newly allocated `PangoAttribute`, which should be freed with [[email protected]] |