dbus interface for control channel

[Antoine Martin]

Some of the server's features could be exposed via dbus, this would complement the "xpra control" interface.
r9773 + r9774 already moved the dbus bits to their own module.

The service name should contain the display number to ensure it is unique, which also makes it less discoverable...

Some good pointers:

• ​Very simple python-dbus server/client in same process
• ​Python Dbus : How to export Interface property
• ​Adding methods to a dbus object in python
• ​How to write a dbus service for linux (in python)

[Antoine Martin]

See #476

• ​Create DBus signal dynamically in python
• ​How dynamically export methods to dbus using python, without static decorator?

[Antoine Martin]

Stub with 4 methods added in r10734.

[Antoine Martin]

More improvements in r10735, r10736 and r10738.
Note the namespace is changed in r10738 from /org/xpra/ServerNNN to /org/xpra/Server/NNN.

This could / should eventually replace the "xpra control" interface.

You can see the services using tools like d-feet:

And you can query things using qdbus:

$ qdbus --session org.xpra.Server
/
/org
/org/xpra
/org/xpra/Server/13

Finds the server started on display 13, then we can list all the methods:

$ qdbus --session org.xpra.Server /org/xpra/Server/13
method QString org.freedesktop.DBus.Introspectable.Introspect()
method QDBusVariant org.freedesktop.DBus.Properties.Get(QString property_name)
method QVariantMap org.freedesktop.DBus.Properties.GetAll(QDBusVariant interface_name)
signal void org.freedesktop.DBus.Properties.PropertiesChanged(QString interface_name, QVariantMap changed_properties, QStringList invalidated_properties)
method void org.freedesktop.DBus.Properties.Set(QString interface_name, QString property_name, QDBusVariant new_value)
method void org.xpra.Server.DisableDebug(QString category)
method void org.xpra.Server.EnableDebug(QString category)
method void org.xpra.Server.Focus(int wid)
method void org.xpra.Server.KeyPress(QString keycode)
method void org.xpra.Server.KeyRelease(QString keycode)
method QDBusVariant org.xpra.Server.ListWindows()
method void org.xpra.Server.MoveWindowToWorkspace(int wid, int workspace)
method void org.xpra.Server.RefreshAllWindows()
method void org.xpra.Server.RefreshWindow(int wid)
method void org.xpra.Server.RefreshWindows(QDBusRawType::ai window_ids)
method void org.xpra.Server.Resume()
method void org.xpra.Server.SetWindowEncoding(int wid, QString encoding)
method void org.xpra.Server.SetWindowScaling(int wid, QString scaling)
method void org.xpra.Server.SetWindowScalingControl(int wid, int scaling_control)
method void org.xpra.Server.Start(QString command)
method void org.xpra.Server.StartChild(QString command)
method void org.xpra.Server.Suspend()
method void org.xpra.Server.Ungrab()

With dbus-send, it's a bit too verbose but here it is:

$ dbus-send --session --print-reply --type=method_call --dest='org.xpra.Server' '/org/xpra/Server/13' org.xpra.Server.ListWindows
method return sender=:1.551 -> dest=:1.562 reply_serial=2
   variant       array [
         dict entry(
            int32 2
            string "antoine@desktop:~/projects/Xpra/trunk/src"
         )
      ]

Sending a refresh all:

• with dbus-send:

  dbus-send --session --type=method_call \
      --dest='org.xpra.Server' '/org/xpra/Server/13' \
      org.xpra.Server.RefreshAllWindows
  

• with qdbus:

  qdbus --session org.xpra.Server /org/xpra/Server/13 \
      org.xpra.Server.RefreshAllWindows
  

@afarr: this is mostly a FYI, unless you can find problems with it or suggest improvements, please close.

[alas]

Trying to run just for more of a sense, it looks like there's some details required to set up the dbus server, or at least name it 'org.xpra.Server' (or whatever) which isn't set up as a default.

I assume these will be configured/used later on.

Running qdbus --session org.xpra.Server /org/xpra/Server/13 from an ssh connection into a vm running a server, I get the response:

Could not connect to D-Bus server: org.freedesktop.DBus.Error.NotSupported: Unable to autolaunch a dbus-daemon without a $DISPLAY for X11

When I try the same command from an xterm within the session, I just get the message Service 'org.xpra.Server' does not exist.

I suppose I'll need to learn more about using dbus...

In the meantime, I'll close this.

[Antoine Martin]

d-feet shows our new dbus server - updated picture with new namespace

[Antoine Martin]

Trying to run just for more of a sense, it looks like there's some details required to set up the dbus server

I have clarified this in the FAQ, start your server with:

dbus-launch xpra start ...

(but you probably have that already - that's not the problem, see below)

Could not connect to D-Bus server .. without a $DISPLAY for X11

You must tell it where to find the dbus server, either by running from within the xpra session or by setting the environment variables manually to point to that particular session if you are connecting via ssh or a console. (DISPLAY and/or DBUS_SESSION_BUS_ADDRESS depending on the tool used)

Running qdbus --session org.xpra.Server /org/xpra/Server/13
..
When I try the same command from an xterm within the session, I just get the message Service 'org.xpra.Server' does not exist.

Sorry about that. That's because I forgot to update this ticket, there were fixes and updates in: r10746, r10745, r10741, r10740, r11102.

In order to support multiple servers on the same system, we have to use a different service name for each server (but we can then use the same paths for each server). The number appended is the display number.
Try:

qdbus --session org.xpra.Server13 /org/xpra/Server
qdbus --session org.xpra.Server13 /org/xpra/Client1

I have updated the examples in comment:4 - you may need to force reload the page to get the update screenshot.
You can always use d-feet for exploring without needing to remember the service name, just search for "xpra" on the session bus.

Finally, it's worth mentioning that there is a new debug category for this: -d dbus.

[J. Max Mena]

• Using a Fedora 20 trunk r11211 client against a Fedora 21 r11211 Server:

• dbus commands appear to be working through d-feet (as best I can hand them arguments)
  • StartChild() will launch children fine
  • MoveWindowToWorkspace() also works. It was entertaining to move Firefox about. (Apparently I am easily entertained)

• However, I cannot figure out how to assign a display properly to get it working through SSH.
  • I've been attempting unsuccessfully with:

    [max@schlafanzug ~]$ export DISPLAY=:13
    [max@schlafanzug ~]$ qdbus --session org.xpra.Server13 /org/xpra/Server
    Service 'org.xpra.Server13' does not exist.
    

Update:

• Added a DBUS_SESSION_BUS_ADDRESS (gotten from d-feet)
• Found the session.

[Antoine Martin]

Other possible ways of finding the value you need to use for DBUS_SESSION_BUS_ADDRESS:

• env | grep DBUS_SESSION_BUS_ADDRESS from within the session
• xpra info | grep DBUS_SESSION_BUS_ADDRESS

(there may be more I can't think of)

[Antoine Martin]

See #486: we now have much better namespace support, so the data will come through in a much more structured format (needed fix in r12300), we also have a GetInfo which takes a subsystem as argument to reduce the amount of data returned

[Antoine Martin]

fix in r16067 for MouseClick, which can be used with:

gdbus call --session --dest org.xpra.Server1  --object-path /org/xpra/Server  --method org.xpra.Server.MouseClick 1 4 true 800 350 []
gdbus call --session --dest org.xpra.Server1  --object-path /org/xpra/Server  --method org.xpra.Server.MouseClick 1 4 false 800 350 []

This will send a scroll-up to window 1, with the mouse position at 800x350.

Beware:

• my server is called "Server1" because it is on display 1
• this dbus command must be executed from the session environment (or you would need to point it to the correct dbus instance)
• each command may print some output, which can cause the xterm to scroll (and make it look like it failed to cause any scrolling)

[Antoine Martin]

As of 16074, the dbus interface for MouseClick is simplified:

MouseClick(button, pressed)

ie:

gdbus call --session --dest org.xpra.Server1  --object-path /org/xpra/Server  --method org.xpra.Server.MouseClick 4 true
gdbus call --session --dest org.xpra.Server1  --object-path /org/xpra/Server  --method org.xpra.Server.MouseClick 4 false

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/904