Splitting this from ticket:1461#comment:15. Reproducible with Firefox on any platform.
This sounds like Capturing a Paste Event in Firefox: The paste event has been supported in major browsers for some time now, but interestingly Firefox doesn’t trigger the event unless the user’s cursor is currently focussed in an editable region.
Unfortunately, the Firefox bug is meant to have been fixed already and sprinkling contenteditable=true in every div doesn't make any difference. Neither does listening for clipboard events on all contenteditable elements as suggested here: https://stackoverflow.com/a/19269040/428751.
More answers here: JavaScript get clipboard data on paste event (Cross browser)
page similar to the client, clipboard works here...
r17537 fixes this by not using jquery for keyboard events, which somehow fixes the clipboard with Firefox (yes, it did take me a while to figure that out)
Maybe we should try to not use jquery quite so much: #1712.
A few improvements were made along the way:
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1689