Sets the minimum size of a widget; that is, the widget's size request will
be width by height. You can use this function to force a widget to be
either larger or smaller than it normally would be.
In most cases, set_default_size() is a better choice for toplevel windows
than this function; setting the default size will still allow users to
shrink the window. Setting the size request will force them to leave the
window at least as large as the size request. When dealing with window
sizes, set_geometry_hints() can be a useful function as well.
Note the inherent danger of setting any fixed size - themes, translations
into other languages, different fonts, and user action can all change the
appropriate size for a given widget. So, it's basically impossible to
hardcode a size that will always be correct.
The size request of a widget is the smallest size a widget can accept while
still functioning well and drawing itself correctly. However in some
strange cases a widget may be allocated less than its requested size, and
in many cases a widget may be allocated more space than it request.
If the size request in a given direction is -1 (unset), then the "natural"
size request of the widget will be used instead.
Widgets can't actually be allocated a size less than 1x1, but you can pass
0,0 to this function to mean "as small as possible".