Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.

date_field_widget_settings_form in core/modules/date/date.field.inc
Implements hook_field_widget_settings_form().
email_field_widget_settings_form in core/modules/email/email.module
Implements hook_field_widget_settings_form().
field_test_field_widget_settings_form in core/modules/field/tests/field_test/field_test.field.inc
Implements hook_field_widget_settings_form().
file_field_widget_settings_form in core/modules/file/file.field.inc
Implements hook_field_widget_settings_form().
image_field_widget_settings_form in core/modules/image/image.field.inc
Implements hook_field_widget_settings_form().
options_field_widget_settings_form in core/modules/field/modules/options/options.module
Implements hook_field_widget_settings_form().
taxonomy_field_widget_settings_form in core/modules/taxonomy/taxonomy.module
Implements hook_field_widget_settings_form().
text_field_widget_settings_form in core/modules/field/modules/text/text.module
Implements hook_field_widget_settings_form().