clipboard support for OSX and win32

[Antoine Martin]

Some pointers which may be useful:

• ​windows-clipboard-viewer
• ​win32clipboard
• ​Build a Shared Clipboard Utility in Python
• ​MS Windows Clipboard (comp.lang.python)

• ​manipulate-mac-os-clipboard (python)
• ​OSX NSPasteBoard
• ​Pasteboard Manager
• ​Copying and pasting in Python on Mac OS X

Notes: it doesn't look like OSX supports events... Carbon.Scrap.InfoScrap() has a serial number, so maybe we can poll/compare that?

[Antoine Martin]

Added partial support for win32 in r241 (see commit message)

Still need to:

• add more transformation code for X11 atoms to strings and back
• maybe allow win32 user to choose which clipboard it shares with? ("PRIMARY" vs "SECONDARY" vs "CLIPBOARD"..)

OSX support is just really tedious, the GTK stuff does not work:

self.selection_owner_set(self._selection):
Failed to acquire local clipboard CLIPBOARD;
will not be able to pass local apps contents of remote clipboard

The ​apple pasteboards doc seems to have sync methods, but none that would call back to us whenever the clipboard's contents changes so we may have to poll it whenever we get a clipboard message from the server or when the application becomes (in)active. (via NSApplicationWillResignActive / NSApplicationDidBecomeActive)
See ​PasteboardSynchronize and ​SetPromiseKeeper.
The only python code I can find that does anything remotely similar is clipboard/carbon.py (now dead link) which uses pyglet.. not keen on adding yet-another-dependency, but may have to.

[Antoine Martin]

Note that there are already problems with the clipboard code and its nested main loop, see #52 and #8, and also:

xpra/platform/clipboard_base.py:232: GtkWarning: IA__gdk_x11_atom_to_xatom_for_display: assertion 
                 `ATOM_TO_INDEX (atom) < virtual_atom_array->len' failed
   gtk.Invisible.do_selection_request_event(self, event)

So it may be worth re-working the whole thing using deferred (ala twisted)

[Antoine Martin]

Much improved support (support for gdk atoms on non-X11 platforms) in r1274

The fix for the GtkWarning: IA__gdk_x11_atom_to_xatom_for_display warning was already in r1230 + r1234

Still some work needed on win32, testing on osx (what selections are available there?)

[Antoine Martin]

• r1278 fixes keyboard targets for non-X11 systems
• r1279 allows win32 users to choose which remote keyboard to sync with via a nice UI menu

As for OSX... it doesn't look like GTK is going to get the fix anytime soon. So if we wanted to support it, we would need to write the code ourselves - yuk.

[Antoine Martin]

Closing this outdated ticket:

• win32 info can be found in #272
• osx (still TODO) in #318
• better links an summary in wiki/Clipboard

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/11