pdf: Reimplement 'de facto' tooltip feature keeping the ABI

Structs in EvForm are not opaque, and
Commit e2ad8611 introduced a ABI change
4 jobs for wip/gpoo/make-struct-priv in 3 minutes and 12 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
failed #803173
flatpak
flatpak

00:03:12

manual #803170
allowed to fail manual
master
failed #803171
meson

00:00:44

manual #803172
allowed to fail manual
meson-gtk-doc
 
Name Stage Failure
failed
flatpak Build
Running after_script
Uploading artifacts for failed job
Uploading artifacts...
WARNING: org.gnome.Evince.flatpak: no matching files
WARNING: repo.tar: no matching files
.flatpak-builder/build/evince/_flatpak_build/meson-logs/meson-log.txt: found 1 matching files

WARNING: .flatpak-builder/build/evince/_flatpak_build/meson-logs/testlog.txt: no matching files
Uploading artifacts to coordinator... ok
id=803173 responseStatus=201 Created token=qzUybbd7
ERROR: Job failed: exit code 1
failed
meson Build
libdocument/meson.build:5:0: ERROR: File ev-form-field-private.h does not exist.

A full log can be found at /builds/GNOME/evince/_build/meson-logs/meson-log.txt
Running after_script
Uploading artifacts for failed job
Uploading artifacts...
_build/meson-logs/meson-log.txt: found 1 matching files

Uploading artifacts to coordinator... ok
id=803171 responseStatus=201 Created token=xz36g_dW
ERROR: Job failed: exit code 1