For most interfaces, the client announcing its supported version is
sufficient - the objects are all created server-side. For some
interfaces (ei_connection_setup and ei_callback right now) the client
needs to know the server-supported version.
So let's switch the current ei_connection_setup.version event (used to
negotiate ei_connection_setup's version) to a generic
`interface_version` event. This way our EIS implementation can
eventually send a version for ei_callback as well.
The Target was specific to libei/libeis, it resolved to "ei" or
"eis_client" depending on which component we were building. But that's
specific to our C implementation here, so let's push it into our C
implementation templates.
Leave the ei_callback as-is and instead add ei_pingpong for the same
thing initiated by the server. The interface is otherwise identical but
for the direction it is supposed to flow.
This reduces the possibility of a client accidentally sending a
request when it is supposed to handle an event or vice versa.
This is effectively the same as connection.sync, but goes the other way.
This adds the ei_callback.done request.
In libeis this is (currently) enforced immediately after sending the
connection object. Not required there and makes the code a bit messier
but this way we can ensure that any client library handles that part of
the code.
This event is to notify the client that an object used in a request was
unknown. This allows the client to work around race conditions like
binding to a seat that was removed.
This is currently the server-side only which is probably enough for now.
The only client-side created objects we have are the callbacks.
On the first run we extract the interfaces only, on the second run all
the rest. This allows us to pass the interface to the Argument where
appropriate.
This changes the initial connection negotiation to have the
ei_connection_setup as the pre-existing object id 0. Once the client has
sent all the data to set up the connection, the EIS implementation
replies with a new object ID that is the ei_connection protocol object,
i.e. the main object.
This allows for version negotiation of our main protocol object.
This allows us to have a device support multiple interfaces and evolve
those interfaces individually, e.g. add things to the keyboard interface
without having to bump the touchscreen interface.
Note that due to a name clash with the existing struct ei_touch public
API the protocol interface is named touchscreen.
The idea here is that the client announces the interfaces it can support
and their version (including the core ei_connection). The server can
then send the various bits based on those versions, where applicable.
This replaces the connect/connect_done and version/get_version requests.
Immediately after connecting, the server sends an ei_protocol_setup
event to the client with the ID of the object and the server's highest
supported version number (of this object).
This is a one-shot object that the client can use to configure its name
and whether it is a sender or receiver context. Once .done is sent, the
object is discarded.
The server version is sent along to the client to allow for requests to
be added to this object in the future.
As a fixme left: the client now assumes to be connected as soon as the
.done request is sent and the following sync event is received. The
EIS implementation will not have actually eis_client_connect()ed the
client yet, but it's good enough for now.
Arguably, the CONNECTED event is superfluous anyway since *any* event
other than DISCONNECTED indicates connected status. CONNECTED is a
leftover from when the client created devices and needed to know if it's
worth doing so.
Directly copied from wayland. Note that while the wayland protocol
specifies the data is the last event serial in our case here it's just
0 since we don't have any event serials (yet).
The sync request is currently triggered after connection, merely to
ensure it works, it's not actually needed.
In the protocol this is a simple rename but in the implementation we can
now separate the protocol object out from the ei/ei-client context
itself by having the ei_connection objects.
This protocol is wayland-like though it uses a slightly different
message format. The XML file uses the same structure, except for the
"fixed" type which is "float" here.
The scanner uses a jinja template to generate source and header files
for ei and eis which are now used instead of the protobuf-generated
objects. Note that the scanner is a minimal working version, some
features like enum value checks are not yet implemented.
Unlike wayland we do not need to generate the libwayland-like library,
we only need the wire protocol parser - some shortcuts can thus be taken.
To keep the changes simple, the protocol currently is a flat protocol
with only one interface and all messages copied over from the previous
ei.proto file. In future commits, this will be moved to the respective
interfaces instead.
This makes it easier to correlate a particular input transaction
(whether there are events or not) with out-of-band information like the
planned portal InputCapture::Activated signal's "activation-id".
The primary use-case for these properties in libei itself was to send
some fixed information (pid, cmdline and conection type). In the portal
case, these can be obtained out-of-band via the portal. In the
non-portal case these can be obtained from the socket itself (fetch pid,
look up /proc/pid/cmdline) which is just as reliable as trusting
whatever libei sends.
The only other use-case for the properties was the activation id in the
InputCapture::Activated portal signal. This can be achieved with a
serial in the START_EMULATING event.
libreis was intended for an intermediary to set some information that
the libei client cannot be entrusted with. In particular this was the
application name, the allowed capabilities, and some properties that -
once set - the client could no longer change (appid as probably the only
really useful one). The price for this was a rather complicated version
negotiation dance before the initial CONNECT request.
Now that we have a clear view of what's going to happen -
RemoteDesktop.ConnectToEIS and the InputCapture portal - there is no
longer any need for libreis. The extra information that libreis would've
sent is communicated out-of-band in both portals and are known to the
compositor at the time the connection is being established.
So we can simply drop this, it's no longer required and dropping it
makes the protocol significantly simpler anyway.
We need some sort of length field to be able to know how long the next
message is. But for simplicity, we might as well just write that
explicitly on the wire instead of wrapping our messages into yet another
message. This makes the wire format slightly simpler since the first 4
bytes are now always the length, without the previous 0x0d prefix
caused by the protobuf encoding.
0x0d == (field number << 3) | wire_type == 1 << 3 | 5
(see https://protobuf.dev/programming-guides/encoding/#structure)
uint32 in protobuf is encoded as VARINT (roughly similar to UTF-8 but
for numbers). Thats useful when you're sending lots of messages over the
net but in our case having a simple fixed-size protocol message format
is better.
This is primarily for namespacing: where a portal sets some properties
it needs to do so *before* the Connect event. By moving this out to a
different namespace we can separate this easier, avoiding a portal
accidentally sending a property event after it has already passed the fd
to the client.
Fixes#23
The same socket is used for pre-connection configuration by a portal and
for the actual client that then uses the data. The portal and the client
may need different protocol versions *and* there may be different REIS
intermediaries.
So let's allow version negotiation for the configuration through
transactions: a REIS intermediary must start/finish a transaction with a
given version number.
This is only partially implemented in libreis right now: each API call
is wrapped in a transaction. Since we support version 1 only anyway,
there's no need to do anything but send our version down the wire. In
the future where we actually need to negotiate, libreis will need a
reis_dispatch() so we can wait for the server version to arrive, parse
it, etc. before sending ConfigureVersion down the wire. It's likely this
will never be needed.
Let the client set the version number it wants on Connect. There is new
public API to query the client/server's version as set once the connect
finished (eis_client_get_version() and ei_get_version()) but there is
currently no public API for the client to select the version it actually
wants, other than whatever both support. IOW, it's not possible for the
client to say "I want version 8 but if that's not supported, use version
5".
