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Callback functions are based on the event dispatcher pattern. You can register
one or more callbacks for a certain event and when the event is triggered, the
callback functions are being executed. Callbacks allow you to customize the
program flow of the Contao core engine.
||Is executed when the DataContainer object is initialized. Allows you to
e.g. check permissions or to modify the Data Container Array dynamically
||Is executed when a back end form is submitted. Allows you to e.g. modify
the form data before it is written to the database (used to calculate
intervals in the calendar extension).
||Is executed before a record is removed from the database.
||Is executed after a record has been moved to a new position.
||Is executed after a record has been duplicated.
||Allows for individual paste buttons and is e.g. used in the site structure
to disable buttons depending on the user's permissions (requires an
additional command check via load_callback).
||Defines how child elements are rendered in "parent view".
||Allows for individual group headers in the listing.
||Allows for individual labels in the listing and is e.g. used in the user
module to add status icons.
||Allows for individual navigation icons and is e.g. used in the site
structure to disable buttons depending on the user's permissions (requires
an additional command check via load_callback).
||Allows you to define an individual function to load data into a drop-down
menu or checkbox list. Useful e.g. for conditional
||Allows for the creation of individual form fields and is e.g. used in the
back end module "personal data" to generate the "purge data" widget.
Attention: the field is not saved automatically!
||Is executed when a form field is initialized and can e.g. be used to load
a default value.
||Is executed when a field is submitted and can e.g. be used to add an
individual validation routine.