Whenever mpv window gains focus, a new data offer is sent for the
selection. However, mpv currently treats it the same as dnd data
offers, which results in wrong handling. One bug which results from
this is when focus follow mouse is enabled, dropping the dnd file
results in the window being focused and selection offer being sent,
freeing the existing dnd offer. This results in dnd being broken
on at least GTK3.
Fix this by separating selection and dnd offer handling. Since there
is no way to know whether an offer introduced by
data_device_handle_data_offer is a selection or dnd offer, make it
pending, and move them once the identity is confirmed.
nanahi
70e02e7b4e