GtkWindow::set_default_size
void set_default_size(int width, int height);
set_default_size() sets the
default opening size of a window, in pixels. This can be overridden
by size requests from the window's child widget exceeding the default
size of the window, or by actively setting the resizing policy of the
window so that the window always shrink-wraps its child.
Note that a smaller child widget whose size has not been set or
otherwise restricted by the programmer will generally expand to fit
the default size of the parent window.
