Compute a concrete size for the `GdkPaintable`.
Applies the sizing algorithm outlined in the [CSS Image spec](https://drafts.csswg.org/css-images-3/default
-sizing) to the
given this. See that link for more details.
It is not necessary to call this function when both specified_width
and specified_height
are known, but it is
useful to call this function in GtkWidget:measure implementations to compute the other dimension when only one dimension is given.
this |
a `GdkPaintable` |
specified_width |
the width this could be drawn into or 0.0 if unknown |
specified_height |
the height this could be drawn into or 0.0 if unknown |
default_width |
the width this would be drawn into if no other constraints were given |
default_height |
the height this would be drawn into if no other constraints were given |
concrete_width |
will be set to the concrete width computed |
concrete_height |
will be set to the concrete height computed |