On Mon, Jun 20, 2022 at 2:46 PM Marc-André Lureau < marcandre.lur...@gmail.com> wrote:
> Hi > > On Mon, Jun 20, 2022 at 6:09 PM Nick Couchman <vn...@apache.org> wrote: > >> Hello, everyone, >> I've posted here, before, with some questions during my journey of trying >> to add support for the SPICE protocol to the Guacamole project. The good >> news is that I've actually made measurable progress in the implementation - >> I can now connect to a SPICE server, and the basics work (mouse and >> keyboard - mostly anyway), so I'm moving on to the extra stuff - clipboard, >> audio, file transfer, etc. >> >> In working on the clipboard integration, I'm currently running into an >> issue with a couple of the callback functions, specifically the clipboard >> grab/release functions, where the number of arguments seems to be >> mismatched. According to the documentation, these callbacks should be >> called with the following arguments: >> >> gboolean >> user_function (SpiceMainChannel *main, >> guint selection, >> gpointer types, >> guint ntypes, >> gpointer user_data) >> >> > types is actually guint32*, but that's not the problem here. > Okay, I'll update that. > > >> void >> user_function (SpiceMainChannel *main, >> guint selection, >> gpointer user_data) >> >> I've implemented the callbacks with those arguments, as follows: >> >> void guac_spice_clipboard_selection_grab_handler(SpiceMainChannel channel, >> guint selection, gpointer types, guint ntypes, guac_client* >> client) >> >> void guac_spice_clipboard_selection_release_handler(SpiceMainChannel >> channel, >> guint selection, guac_client* client) >> > > It looks correct. Can you point to your code connecting the signals with > the handlers? > Sure - source code is here: https://github.com/necouchman/guacamole-server/tree/working/spice-basic Here's the section in the src/protocol/spice/client.c file that registers the callbacks: /* Register clipboard handlers. */ g_signal_connect(channel, SPICE_SIGNAL_MAIN_CLIPBOARD_SELECTION, G_CALLBACK(guac_spice_clipboard_selection_handler), client); g_signal_connect(channel, SPICE_SIGNAL_MAIN_CLIPBOARD_SELECTION_GRAB, G_CALLBACK(guac_spice_clipboard_selection_grab_handler), client); g_signal_connect(channel, SPICE_SIGNAL_MAIN_CLIPBOARD_SELECTION_RELEASE, G_CALLBACK(guac_spice_clipboard_selection_release_handler), client); g_signal_connect(channel, SPICE_SIGNAL_MAIN_CLIPBOARD_SELECTION_REQUEST, G_CALLBACK(guac_spice_clipboard_selection_request_handler), client); link to the full function is here: https://github.com/necouchman/guacamole-server/blob/5e073802a0656e65b1bc8e7e6051831bea0d9508/src/protocols/spice/client.c#L236-L375 > > >> >> and registered them appropriately. However, if I use them as implemented >> above, when the callbacks are triggered, the application segfaults when I >> try to access the "guac_client* client" data structure. I used GDB to try >> to help track this down, and I noticed that the value of "client" was 0x1, >> which looks less like a pointer to a memory location and more like the >> number 1. >> >> So, I decided to add another argument to the callback functions, just >> before the client argument: >> >> void guac_spice_clipboard_selection_grab_handler(SpiceMainChannel channel, >> guint selection, gpointer types, guint ntypes, guint extra, >> guac_client* client) >> >> void guac_spice_clipboard_selection_release_handler(SpiceMainChannel >> channel, >> guint selection, guint extra, guac_client* client) >> >> Strangely, this works - the client data structure can be referenced, >> there are no segfaults (yet), etc. So, I decided to print the values that >> are being passed for all of these parameters, and I get the following: >> >> guacd[100252]: DEBUG: Notifying client of clipboard grab in the guest. >> guacd[100252]: DEBUG: Arg: channel: 0x00000000 >> guacd[100252]: DEBUG: Arg: selection: 1275303536 >> guacd[100252]: DEBUG: Arg: types: 0x00000001 >> guacd[100252]: DEBUG: Arg: ntypes: 1276022924 >> guacd[100252]: DEBUG: Arg: extra: 1 >> >> > Weird > > >> I printed them in the format I thought they should be in based on what >> the arguments are supposed to be - I probably should have just done all >> hex. But, it seems like maybe the "extra" parameter being passed is in >> front of the channel, since the channel is showing up as all zeros? >> >> I was trying to find the code where the callbacks are actually called - >> I'm guessing, since this is clipboard integration, it'll be in the vdagent >> code somewhere - but I was having trouble tracking that down. >> >> > The callbacks are not directly called, since those a GObject signals. The > main channel will call g_signal_emit(). > > Okay. > > >> If anyone has any ideas, I'd appreciate the insight into this - I'm >> puzzled by this apparent mismatch in the number of arguments. Also, if it >> matters, I'm running CentOS 8 Stream, using Xspice to provide a test SPICE >> server, and running spice-vdagentd/spice-vdagent within my X session. Yes, >> I know Xspice is unmaintained, but I just needed something simple and that >> I didn't have to spend a bunch of time building in order to give me a spice >> server to point at, and, so far, this has been pretty reliable. Also, at >> its core, it appears to use the same spice-qxl X driver that x11spice uses, >> just with a simple Python wrapper script for generating an X config file >> and starting the X server/display. So, I think it's still pretty "safe" for >> attempting to develop this Guacamole integration - if for some reason you >> believe me to be wrong about that, please let me know. >> > > Your testing environment shouldn't be a problem, it's really your > client-side code integration with spice-glib that looks broken. > > That's what I was thinking, and maybe I'm just messing up something simple! Thanks, Nick
