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.
Our only use-case where we use this utility is for keymaps. Those have
to be MAP_PRIVATE in wayland's wl_seat version 8 so let's do the same to make
make sure we're compatible.
From the documentation:
"The x/y coordinate must be within the device's regions or the event is
silently discarded."
libei discards it but if it somehow makes it through anyway, let's
discard it again.
The check is currently missing from a number of libeis APIs but in most
cases we can blame the EIS implementation and say "don't do this".
Device removal is an exception since that is still required.
With the planned switch to a protocol supporting multiple interfaces
(a la wayland), a single version number is no longer useful. Remove this
API, we can add something more specific later if we need to.
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)
In various places, including the DBUS calls which can take some time, if
a SIGALRM triggers, the call will fail.
To prevent this from happening, use the wrappers when possible and make
sure to block the SIGALRM signal when issuing DBUS calls.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Change the signal-blocking helper to take a vararg list of signals to
block and provide a magic macro that works like python's context
manager, using attribute(cleanup).
In our for loop we create a new struct with the old sigmask and a
boolean that's always true. We enter the body of the loop once and
set that boolean to false on the second run, i.e. we never do more than
one run. On loop exit, the destroy function for our struct restores the
previous signal mask.
Most system calls will fail if interrupted by a SIGALRM. Make sure we
block SIGALRM prior to do the syscall, and restore the set of signals
afterwards.
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
libei used to have direct portal support code (see the git history) but:
- that code was a custom proposed portal that never went anywhere
- libei has slowly changed to be more an input event transport layer since
it is now also used sending events *to* a libei context
- a number of libei users will never need the DBus code, either because they
don't want it or because they talk Dbus themselves na ddon't need this
abstraction.
Luckily, it's quite easy to move this into a separate library with a
simple API that does, effectively, the same trick as the old portal backend.
This API is aiming to be as simple as possible because the tools that
require anything more complex should talk to DBus directly.
An example tool that uses the API to retrieve an EIS fd over the
RemoteDesktop portal is included in this patch.
"Öffis" is a German word meaning public transport. It also sounds like the
French Œuf, the word for egg.
Co-authored-by: Olivier Fourdan <ofourdan@redhat.com>
The original idea here was that we would have an EmulatedInput portal
that allows the application to connect directly to the EIS
implementation to exchange input events - instead of ping-ponging DBus
events through the xdg-desktop-portal as the RemoteDesktop portal
requires.
This is no longer accurate, there are suggested PRs open to add
RemoteDesktop.ConnectToEIS to achieve the same through the existing
RemoteDesktop interface [1] and to add a new InputCapture portal
to allow for events to be sent to a libei receiver context [2].
The example EmulatedInput portal is thus superfluous and can be removed
from here.
We could switch the ei_setup_backend_portal() code to use RemoteDesktop
or InputCapture, depending on the context type, the utility of this is
questionable. Interaction with portals is complex, one needs to
implement the Session/Request interfaces correctly and in the case of
InputCapture also handle the complex zones/pointer barrier setup.
libportal does some of this (or it will, anyway) so it's more useful for
an application to use libportal and then just pass the received fd to
libei.
If there is a future need for this to be handled as part of libei, we
can (re)implement this, but for now it's best to just purge all of this.
[1] https://github.com/flatpak/xdg-desktop-portal/pull/762
[2] https://github.com/flatpak/xdg-desktop-portal/pull/714
