Sets the minimum size of the toplevel.
The minimum size corresponds to the limitations the toplevel can be shrunk to, without resulting in incorrect painting. A user of a `GdkToplevel` should calculate these given both the existing size, and the bounds retrieved from the `GdkToplevelSize` object.
The minimum size should be within the bounds (see [[email protected]_bounds]).
| this |
a `GdkToplevelSize` |
| min_width |
the minimum width |
| min_height |
the minimum height |