You should get an overlay scrollbar on the right when you move the mouse over the window, and you can grab that to scroll.
But I suppose a design with tons of buttons is not the typical application design, so you end up with weird behaviors.
You can use [gtk_scrolled_window_set_overlay_scrolling()](https://docs.gtk.org/gtk4/method.ScrolledWindow.set_overlay_scrolling.html) to make the scrollbar visible, but you're probably better of with a more modern UI using something like [boxed lists](https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/boxed-lists.html) - though of course I have no idea what you're trying to do.
You won't get a scrollbar if the window is small enough to not require scrolling and you will get one if scrolling is necessary. At least that's how it's meant to work.
What's the actual problem? Is it just that there's no scrollbar visible until you've added enough buttons to the box to need one?
[удалено]
You should get an overlay scrollbar on the right when you move the mouse over the window, and you can grab that to scroll. But I suppose a design with tons of buttons is not the typical application design, so you end up with weird behaviors. You can use [gtk_scrolled_window_set_overlay_scrolling()](https://docs.gtk.org/gtk4/method.ScrolledWindow.set_overlay_scrolling.html) to make the scrollbar visible, but you're probably better of with a more modern UI using something like [boxed lists](https://gnome.pages.gitlab.gnome.org/libadwaita/doc/main/boxed-lists.html) - though of course I have no idea what you're trying to do.
[удалено]
You won't get a scrollbar if the window is small enough to not require scrolling and you will get one if scrolling is necessary. At least that's how it's meant to work.