tools: libinput-record: add support for printing libinput events

Collect libinput events together with the evdev events and print them to the
log. This makes it possible to debug the full behavior of a user's machine
rather than having to replay it with potential different race conditions/side
effects.

Example event output:
  - evdev:
    - [  2, 314443,   4,   4,    57] # EV_MSC / MSC_SCAN               57
    - [  2, 314443,   1,  57,     1] # EV_KEY / KEY_SPACE               1
    - [  2, 314443,   0,   0,     0] # ------------ SYN_REPORT (0) ---------- +87ms
    libinput:
    - {time: 2.314443, type: KEYBOARD_KEY, key: 57, state: pressed}
  - evdev:
    - [  2, 377203,   4,   4,    57] # EV_MSC / MSC_SCAN               57
    - [  2, 377203,   1,  57,     0] # EV_KEY / KEY_SPACE               0
    - [  2, 377203,   0,   0,     0] # ------------ SYN_REPORT (0) ---------- +63ms
    libinput:
    - {time: 2.377203, type: KEYBOARD_KEY, key: 57, state: released}

Note that the only way to know that events are within the same frame is to
check the timestamp. libinput keeps those intact which means we can tell that
if we just had an evdev frame with timestamp T and get a pointer motion with
timestamp T, that frame caused the motion event.

So far, only key, pointer and touch events are printed. We also
hardcode-enable tapping where available until we have options to enable this
on the commandline just because that's useful to have.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/tools/libinput-record.man b/tools/libinput-record.man
index 5ff263ad..dbe581a1 100644
--- a/tools/libinput-record.man
+++ b/tools/libinput-record.man
@@ -52,6 +52,13 @@ Record multiple devices at once, see section
 This option requires that a
 \fB\-\-output-file\fR is specified and that all devices to be recorded are
 given on the commandline.
+.TP 8
+.B \-\-with-libinput
+Record libinput events alongside device events.
+.B THIS FEATURE IS EXPERIMENTAL.
+See section
+.B RECORDING LIBINPUT EVENTS
+for more details.
 
 .SH RECORDING MULTIPLE DEVICES
 Sometimes it is necessary to record the events from multiple devices
@@ -70,6 +77,25 @@ invocation is:
 Note that when recording multiple devices, only the first device is printed
 immediately, all other devices and their events are printed on exit.
 
+.SH RECORDING LIBINPUT EVENTS
+When the \fB\-\-with-libinput\fR switch is provided, \fBlibinput\-record\fR
+initializes a libinput context for the devices being recorded. Events from
+these contexts are printed alongside the evdev events.
+.B THIS FEATURE IS EXPERIMENTAL.
+.PP
+The primary purpose of this feature is debugging and event analysis, no
+caller may rely on any specific format of the events.
+.PP
+Note that while libinput and \fBlibinput\-record\fR see the same events from
+the device nodes, no guarantee can be given about the correct order of
+events. libinput events may come in earlier or later than the events from
+the device nodes and for some devices, libinput may internally alter the
+event stream before processing.
+.PP
+Note that the libinput context created by \fBlibinput\-record\fR does not
+affect the running desktop session and does not (can not!) copy any
+configuration options from that session.
+
 .SH FILE FORMAT
 The output file format is in YAML and intended to be both human-readable and
 machine-parseable. Below is a short example YAML file, all keys are detailed