8 uses of REGIONS_VISIBLE

BlockController::getVisibleRegionNames in core/modules/block/src/Controller/BlockController.php
Returns the human-readable list of regions keyed by machine name.
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.
BlockPlaceTest::testPlacingBlocksAdmin in core/modules/block_place/tests/src/Functional/BlockPlaceTest.php
Tests placing blocks as an admin.
block_theme_initialize in core/modules/block/block.module
Assigns an initial, default set of blocks for a theme.
PlaceBlockPageVariant::getVisibleRegionNames in core/modules/block_place/src/Plugin/DisplayVariant/PlaceBlockPageVariant.php
Returns the human-readable list of regions keyed by machine name.
system_default_region in core/modules/system/system.module
Gets the name of the default region for a given theme.

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.