[Nautilus/Nemo/Caja] dragging file with middle mouse button doesn't show "Copy/Move/Link" context menu
Steps to reproduce
- Run Nautilus or one of its forks (Nemo or Caja)
- Switch to icon view (if it's not selected already)
- Drag a file using middle mouse button
The current behavior is the same as when dragging a file using left mouse button. The cursor that is shown is the d-n-d cursor with small arrow on it. If you release the button, the file isn't copied or moved, and no context menu appears.
The expected behavior would be the same as when dragging a file with Alt key held. The cursor would be the d-n-d cursor with small question mark on it. If you release the button, a context menu with possible actions (Copy/Move/Link) would appear, prompting you to choose what to do with the file.
GTK+ version: 3.20/3.22/3.24
Distro: tested in Ubuntu 18.04, Debian Stable, Debian Testing
Nautilus version: reproducible with 3.22, 3.26, 3.30
Original report about Nautilus: https://bugzilla.gnome.org/772797
Original report about Caja: https://github.com/mate-desktop/caja/issues/753
Mention of the same issue in Nemo: https://github.com/linuxmint/nemo/issues/1289#issuecomment-247057387
I suspect the problem appeared due to a change in GTK+ between 3.18 and 3.20: bfee45e6
It seems like it always determines the suggested action (e.g. copy, move or ask user) for the primary mouse button. This can explain why it behaves the same with the middle button.