Version: (using KDE Devel) Installed from: Compiled sources An extensive section which covers all developer questions on Drag&Drop must exist(duh). This was recently brought to discussion on kde-core-devel, which probably is a worthy read: http://lists.kde.org/?l=kde-core-devel&m=109446322814352&w=2 It has also been discussed on kde-usability, see the archives. Relevant section in GNOME HIG: http://developer.gnome.org/projects/gup/hig/draft_hig_new/input.html#drag-drop (from a quick glance it doesn't specify what to do when an action, such as copy, is not supported in a query drag) Relevant section in Mac OSX HIG: http://developer.apple.com/documentation/UserExperience/Conceptual/OSXHIGuidelines/
As the issue has been widely discussed on the ML 4 years ago, it seems that the idea to remove the popup after the drag action has been rejected. Is the idea still valid?