Synchronously invokes the <link linkend="gdbus-method-org-freedesktop-cbd.
OpenMessages">OpenMessages</link> D-Bus method on this. The calling thread is
blocked until a reply is received.
See call_open_messages for the asynchronous version of this method.
| this |
A DBusCbdProxy. |
| out_result |
Return location for return parameter or null to ignore. |
| cancellable |
A Cancellable or null. |
|
true if the call succeeded, false if throws is set. |