I'm implementing D&D to move nodes in VirtualTreeView and I think I've encountered a bug on both Linux and Windows when I set "DragType" to "dtVCL" and "Right click select" to "true".
On windows, right click sometimes does not work. Nothing happens. Some time, you have to double right click to select a node and show popup. On Linux(Ubuntu at least), it is bit worse. Right click some times triggers dragging. On Mac, it is similar to Ubuntu but, since Cocoa interface is currently unstable, other things did not work properly either. So I did not test it further on Mac.
I am aware dtVCL is sort of a deprecated option for the original VirtualTreeview. However, since there is no ActiveX for Linux, dtVCL is the only way to drag nodes around.
I've created the simplest project file to recreate the behavior.
VT-Test.zip (3.3 kB)
https://forum.lazarus.freepascal.org/index.php?action=dlattach;topic=40061.0;attach=25252
Windows 10:
Lazarus 1.8.0 r56594 FPC 3.0.4 x86_64-win64-win32/win64
Ubuntu 17.10:
Lazarus 1.8.0 rc4+dfsg-1 FPC 3.0.2 x86_64-linux-gtk2
MacOS 10.13.3 High Sierra:
Lazarus 1.8.0 rexported FPC 3.0.4 i386-darwin-carbon