Make xwidget-events special and document xwidget callbacks

Users have always been supposed to use callbacks for handling
xwidget events, but for some reason this has not been
documented until now.

* doc/lispref/commands.texi (Xwidget Events): Document xwidget
callbacks and the special status of `xwidget-event's.

* doc/lispref/display.texi (Xwidgets): Add xwidget property
list functions to the concept index.

* lisp/xwidget.el: Make xwidget events special.
0 jobs for master
Child pipeline (parent) yaml invalid error

Found errors in your .gitlab-ci.yml:

  • jobs test-lib-src-inotify config should implement a script: or a trigger: keyword
You can also test your .gitlab-ci.yml in CI Lint