Other combinations work fine:
Found that this is a regression by trying the old 0.14.x LTS as server. Bisection:
So the problem is
XPRA_REPARENT_ROOT which was changed to enabled by default in r13690.
More details in #770, now re-opened.
So r15216 disables it again in the v1.0.x branch (v2.0 has not been changed so far because it doesn't support centos6), which means that drag and drop will not work in the next update... we have to choose one or the other.
r15262 is a better fix: we undo a hackish change so that we can keep reparent-to-root (and therefore drag-n-drop support). r15263 for v1.x branch. Will follow up in #469.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1453