It seems that if we ever try to reply to a selection request after
another has been sent by the same requestor (we reply in FIFO order),
the requestor never reads from it, and we end up stalling forever on a
transfer that will never complete.
It appears that `XCB_SELECTION_REQUEST` has some sort of singleton
semantics, and new requests for the same selection are meant to replace
outstanding older ones. I couldn't find a reference for this, but
empirically this does seem to be the case.
Real (contrived) case where we don't currently do this, and things break:
* run fcitx
* run Slack
* wl-copy < <(base64 /opt/firefox/libxul.so) # or some other large file
* focus Slack (no need to paste)
fcitx will send in an `XCB_SELECTION_REQUEST`, and we'll start
processing it. Immediately after, Slack sends its own. fcitx hangs for a
long, long time. In the meantime, Slack retries and sends another
selection request. We now have two pending requests from Slack.
Eventually fcitx gives up (or it can be `pkill`'d), and we start
processing the first request Slack gave us (FIFO). Slack (Electron?)
isn't listening on the other end anymore, and this transfer never
completes. The X11 clipboard becomes unusable until Slack is killed.
After this patch, the clipboard is immediately usable again after fcitx
bails. Also added a bunch of debug-level logging that makes diagnosing
this sort of issue easier.
Refs swaywm/sway#4007.
Fixes#2425.
wlroots can only handle one outgoing transfer at a time, so it keeps a
list of pending selections. The head of the list is the currently-active
selection, and when that transfer completes and is destroyed, the next
one is started.
The trouble is when you have a transfer to some app that is misbehaving.
fcitx is one such application. With really large transfers, fcitx will
hang and never wake up again. So, you can end up with a transfer list
that looks like this:
| T1: started | T2: pending | T3: pending | T4: pending |
The file descriptor for transfer T1 is registered in libwayland's epoll
loop. The rest are waiting in wlroots' list.
As a user, you want your clipboard back, so you `pkill fcitx`. Now
Xwayland sends `XCB_DESTROY_NOTIFY` to let us know to give up. We clean
up T4 first.
Due to a bug in wlroots code, we register the (fd, transfer data
pointer) pair for T1 with libwayland *again*, despite it already being
registered. We do this 2 more times as we remove T3 and T2.
Finally, we remove T1 and `free` all the memory associated with it,
before `close`-ing its transfer file descriptor.
However, we still have 3 copies of T1's file descriptor left in the
epoll loop, since we erroneously added them as part of removing T2/3/4.
When we `close` the file descriptor as part of T1's teardown, we
actually cause the epoll loop to wake up the next time around, saying
"this file descriptor has activity!" (it was closed, so `read`-ing would
normally return 0 to let us know of EOF).
But instead of returning 0, it returns -1 with `EBADF`, because the file
descriptor has already been closed. And finally, as part of error-handling
this, we access the transfer pointer, which was `free`'d. And we crash.
This one was awful to track down, but calls to `wlr_log` with %m have
the errno masked by the `isatty` call in `log_stderr`. Switch them to
`wlr_log_errno` instead.
Cue quality "how can read(2) POSSIBLY be returning ENOTTY?" moments.
This change tracks, for each wlr_seat_client, the most recent serial
numbers which were sent to the client. When the client makes a
selection request, wlroots now verifies that the serial number
associated with the selection request was actually provided to that
specific client. This ensures that the client that was most
recently interacted with always has priority for its copy selection
requests, and that no other clients can incorrectly use a larger serial
value and "steal" the role of having the copy selection.
Also, the code used to determine when a given selection is superseded
by a newer request uses < instead of <= to allow clients to make
multiple selection requests with the same serial number and have the
last one hold.
To limit memory use, a ring buffer is used to store runs of sequential
serial numbers, and all serial numbers earlier than the start of the
ring buffer are assumed to be valid. Faking very old serials is
unlikely to be disruptive.
Assuming all clients are correctly written, the only additional
constraint which this patch should impose is that serial numbers
are now bound to seats: clients may not receive a serial number
from an input event on one seat and then use that to request
copy-selection on another seat.
This supersedes f24e17259e and
04c9ca4198. These commits were manually removing
wlr_data_source destroy handlers when starting a new drag. This is error-prone.
Instead, this commit destroys the previous source whenever we start a new drag.
This makes compositors able to block and/or customize set_selection requests
coming from clients. For instance, it's possible for a compositor to disable
rich selection content (by removing all MIME types except text/plain). This
commit implements the design proposed in [1].
Two new events are added to wlr_seat: request_set_selection and
request_set_primary_selection. Compositors need to listen to these events and
either destroy the source or effectively set the selection.
Fixes https://github.com/swaywm/wlroots/issues/1138
[1]: https://github.com/swaywm/wlroots/issues/1367#issuecomment-442403454
This is a common interface that can be used for all primary selection
protocols, as discussed in [1]. A new function wlr_seat_set_primary_selection
is added to set the primary selection for all protocols.
The seat now owns again the source, and resets the selection to NULL when
destroyed.
[1]: https://github.com/swaywm/wlroots/issues/1367#issuecomment-442403454
This commits completely refactors wlr_gtk_primary_selection. The goal is to
remove gtk-primary-selection state from the seat and better handle inert
resources where it makes sense.
wlr_seat_client.primary_selection_devices has been removed and replaced by
wlr_gtk_primary_selection_device. This allows us to make offers inert when the
current selection is replaced.
wlr_seat_set_primary_selection has been removed because it relied on wlr_seat
instead of wlr_gtk_primary_selection_device_manager. A new function,
wlr_gtk_primary_selection_device_manager_set_selection (candidate for the
longest function name in wlroots) has been added. It doesn't take a serial
anymore as serial checking only makes sense for set_selection requests coming
from Wayland clients (serial checking is now done in the Wayland interface
implementation).
Since wlr_gtk_primary_selection_device_manager is now required to set the
selection, a new function wlr_xwayland_set_gtk_primary_selection_device_manager
(candidate number two for longest function name) has been added.
Devices are now made inert when the seat goes away.
Future work includes removing the last primary selection bits from the seat,
mainly wlr_seat.primary_selection_source and wlr_seat.events.primary_selection,
replacing those with new fields in wlr_gtk_primary_selection_device. Or maybe
we could keep those in the seat and replace them with a re-usable interface
(for future zwp_primary_selection_v1 support). We need to think how we'll sync
these three protocols (GTK, X11 and wayland-protocols).
See https://github.com/swaywm/wlroots/issues/1388
This unbreaks the build on armhf that otherwise fails like
../xwayland/selection/incoming.c: In function 'xwm_data_source_write':
../include/wlr/util/log.h:34:17: error: format '%ld' expects argument of type 'long int', but argument 6 has type 'ssize_t {aka int}' [-Werror=format=]
_wlr_log(verb, "[%s:%d] " fmt, wlr_strip_path(__FILE__), __LINE__, ##__VA_ARGS__)
^
../xwayland/selection/incoming.c:34:2: note: in expansion of macro 'wlr_log'
wlr_log(L_DEBUG, "wrote %zd (chunk size %ld) of %d bytes",
^~~~~~~
../xwayland/selection/incoming.c:34:44: note: format string is defined here
wlr_log(L_DEBUG, "wrote %zd (chunk size %ld) of %d bytes",
~~^
%d
