backend/native: support for three finger drag
After initially looking at implementing this feature in libinput itself, it was determined that it made more sense for the compositing layer to emulate the functionality.
This patch adds the necessary emulation for the native/Wayland input handling backend in Mutter.
Closes: https://bugzilla.gnome.org/show_bug.cgi?id=768421
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Note that this will only work on Wayland, the X11 implementation is left empty intentionally.
Edited by Florian Müllner