Dragging an icon in gtk4
First reported in issue #3642 (closed).
I've found several problems with drag-and-drop in gtk4. My system uses the X11 backend. I found these problems in demos and example programs in gtkmm and gtkmm-documentation. They also occur in similar programs in gtk.
In gtk3 it's possible to drag an icon from demos/icon-browser/gtk3-icon-browser to LibreOffice Writer. That's not possible to do from demos/icon-browser/gtk4-icon-browser in gtk4. The icon is dragged, but LibreOffice Writer rejects the drop.