Meta Configuration of Package perl-Event

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Meta Configuration of Package perl-Event

<package name="perl-Event" project="openSUSE:Backports:SLE-15-SP5">
  <title>Event loop processing</title>
  <description>ALERT: Marc Lehmann may have taken over the future of event loops in Perl.
  Check out his libev library and EV Perl module. 25 Aug 2009

The Event module provide a central facility to watch for various types of
  events and invoke a callback when these events occur. The idea is to delay
  the handling of events so that they may be dispatched in priority order
  when it is safe for callbacks to execute.

Events (in the ordinary sense of the word) are detected by *watchers*,
  which reify them as *events* (in the special Event module sense). For
  clarity, the former type of events may be called "source events", and the
  latter "target events". Source events, such as signals arriving, happen
  whether or not they are being watched. If a source event occurs which a
  watcher is actively watching then the watcher generates a corresponding
  target event. Target events are only created by watchers. If several
  watchers are interested in the same source event then each will generate
  their own target event. Hence, any particular source event may result in
  zero, one, two, or any number of target events: the same as the number of
  watchers which were actively watching for it.

Target events are queued to be processed in priority order (priority being
  determined by the creating watcher) and in FIFO order among events of the
  same priority. Queued ("pending") events can, in some cases, be cancelled
  before being processed. A queued event is processed by being passed to the
  callback function (or method on a particular object or class) which was
  specified to the watcher.

A watcher, once created, operates autonomously without the Event user
  having to retain any reference to it. However, keeping a reference makes it
  possible to modify most of the watcher's characteristics. A watcher can be
  switched between active and inactive states. When inactive, it does not
  generate target events.

Some types of source event are not reified as target events immediately.
  Signals received, for example, are counted initially. The counted signals
  are reified at certain execution points. Hence, signal events may be
  processed out of order, and if handled carelessly, on the wrong side of a
  state change in event handling. A useful way to view this is that
  occurrence of the source event is not actually the arrival of the signal
  but is triggered by the counting of the signal.

Reification can be forced when necessary. The schedule on which some other
  events are created is non-obvious. This is especially the case with
  watchers that watch for a condition rather than an event. In some cases,
  target events are generated on a schedule that depends on the operation of
  the event loop.</description>
</package>

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