8 uses of REGIONS_VISIBLE in Drupal 9

BlockController::getVisibleRegionNames in core/modules/block/src/Controller/BlockController.php

Returns the human-readable list of regions keyed by machine name.

BlockDeleteForm::getDeletionMessage in core/modules/block/src/Form/BlockDeleteForm.php

Gets the message to display to the user after deleting the entity.

BlockDeleteForm::getQuestion in core/modules/block/src/Form/BlockDeleteForm.php

BlockForm::form in core/modules/block/src/BlockForm.php

Gets the actual form array to be built.

BlockForm::themeSwitch in core/modules/block/src/BlockForm.php

Handles switching the available regions based on the selected theme.

BlockListBuilder::buildBlocksForm in core/modules/block/src/BlockListBuilder.php

Builds the main "Blocks" portion of the form.

block_theme_initialize in core/modules/block/block.module

Assigns an initial, default set of blocks for a theme.

system_default_region in core/modules/system/system.module

Gets the name of the default region for a given theme.