This files describes API changes in core libraries and APIs,
information provided here is intended especially for developers.

=== 2.8.8 ===

* The actionmenu hideMenu() function now expects an EventFacade object to be passed to it,
  i.e. a call to M.core.actionmenu.instance.hideMenu() can be changed to M.core.actionmenu.instance.hideMenu(e) to ensure good
  behaviour when using custom action menus.
* Users of the text editor API to manually create a text editor should call set_text before calling use_editor. See MDL-51179.
* In the html_editors (tinyMCE, Atto), the manage files button can be hidden by changing the 'enable_filemanagement' option to false.

=== 2.8.7 ===

* New methods grade_grade::get_grade_max() and get_grade_min() must be used rather than directly the public properties rawgrademax and rawgrademin.
* New method grade_item::is_aggregate_item() indicates when a grade_item is an aggreggated type grade.
* \webservice_xmlrpc_client now respects proxy server settings. If your XMLRPC server is available on your local network and not via your proxy server, you may need to add it to the list of proxy
  server exceptions in $CFG->proxybypass. See MDL-39353 for details.

=== 2.8.4 ===

* The authorization procedure in the mdeploy.php script has been improved. The script
  now relies on the main config.php when deploying an available update.

=== 2.8.2 ===

* \core_component::fetch_subsystems() now returns a valid path for completion component instead of null.

=== 2.8 ===

* Gradebook grade category option "aggregatesubcats" has been removed completely.
  This means that the database column is removed, the admin settings are removed and
  the properties from the grade_category object have been removed. If any courses were
  found to be using this setting, a warning to check the grades will be shown in the
  course grader report after upgrading the site. The same warning will be shown on
  courses restored from backup that had this setting enabled (see MDL-47503).
* lib/excelllib.class.php has been updated. The class MoodleExcelWorkbook will now only produce excel 2007 files.
* renderers: We now remove the suffix _renderable when looking for a render method for a renderable.
  If you have a renderable class named like "blah_renderable" and have a method on a renderer named "render_blah_renderable"
  you will need to change the name of your render method to "render_blah" instead, as renderable at the end is no longer accepted.
* New functions get_course_and_cm_from_cmid($cmorid, $modulename) and
  get_course_and_cm_from_instance($instanceorid, $modulename) can be used to
  more efficiently load these basic data objects at the start of a script.
* New function cm_info::create($cm) can be used when you need a cm_info
  object, but have a $cm which might only be a standard database record.
* $CFG->enablegroupmembersonly no longer exists.
* Scheduled tasks have gained support for syntax to introduce variability when a
  task will run across installs. When a when hour or minute are defined as 'R'
  they will be installed with a random hour/minute value.
* Several classes grade_edit_tree_column_xxx were removed since grades setup page
  has been significantly changed. These classes should not be used outside of
  gradebook or developers can copy them into their plugins from 2.7 branch.
* Google APIs Client Library (lib/google/) has been upgraded to 1.0.5-beta and
  API has changed dramatically without backward compatibility. Any code accessing
  it must be amended. It does not apply to lib/googleapi.php. See MDL-47297
* Added an extra parameter to the function get_formatted_help_string() (default null) which is used to specify
  additional string parameters.
* User settings node and course node in navigation now support callbacks from admin tools.
* grade_get_grades() optional parameteres $itemtype, $itemmodule, $iteminstance are now required.

DEPRECATIONS:
* completion_info->get_incomplete_criteria() is deprecated and will be removed in Moodle 3.0.
* grade_category::aggregate_values() is deprecated and will be removed in Moodle 3.0.
* groups_filter_users_by_course_module_visible() is deprecated; replace with
  core_availability\info::filter_user_list. Will be removed in Moodle 3.0.
* groups_course_module_visible() is deprecated; replace with $cm->uservisible.
* cm_info property $cm->groupmembersonly is deprecated and always returns 0.
  Use core_availability\info::filter_user_list if trying to determine which
  other users can see an activity.
* cm_info method $cm->is_user_access_restricted_by_group() is deprecated and
  always returns false. Use $cm->uservisible to determine whether the user can
  access the activity.
* Constant FEATURE_GROUPMEMBERSONLY (used in module _supports functions) is
  deprecated.
* cohort_get_visible_list() is deprecated. There is a better function cohort_get_available_cohorts()
  that respects user capabilities to view cohorts.
* enrol_cohort_get_cohorts() and enrol_cohort_search_cohorts() are deprecated since
  functionality is removed. Please use cohort_get_available_cohorts()
* enrol_cohort_enrol_all_users() is deprecated; enrol_manual is now responsible for this action
* enrol_cohort_can_view_cohort() is deprecated; replace with cohort_can_view_cohort()

=== 2.6.4 / 2.7.1 ===

* setnew_password_and_mail() and update_internal_user_password() will trigger
  \core\event\user_password_updated. Previously they used to generate
  \core\event\user_updated event.
* update_internal_user_password() accepts optional boolean $fasthash for fast
  hashing.
* user_update_user() and user_create_user() api's accept optional param
  $triggerevent to avoid respective events to be triggred from the api's.

=== 2.7 ===

* PHPUnit cannot be installed via PEAR any more, please use composer package manager instead.
* $core_renderer->block_move_target() changed to support more verbose move-block-here descriptions.

Events and Logging:
* Significant changes in Logging API. For upgrading existing events_trigger() and
  add_to_log() see http://docs.moodle.org/dev/Migrating_logging_calls_in_plugins
  For accessing logs from plugins see http://docs.moodle.org/dev/Migrating_log_access_in_reports
* The validation of the following events is now stricter (see MDL-45445):
    - \core\event\blog_entry_created
    - \core\event\blog_entry_deleted
    - \core\event\blog_entry_updated
    - \core\event\cohort_member_added
    - \core\event\cohort_member_removed
    - \core\event\course_category_deleted
    - \core\event\course_completed
    - \core\event\course_content_deleted
    - \core\event\course_created
    - \core\event\course_deleted
    - \core\event\course_restored
    - \core\event\course_section_updated (see MDL-45229)
    - \core\event\email_failed
    - \core\event\group_member_added
    - \core\event\group_member_removed
    - \core\event\note_created
    - \core\event\note_deleted
    - \core\event\note_updated
    - \core\event\role_assigned
    - \core\event\role_deleted
    - \core\event\role_unassigned
    - \core\event\user_graded
    - \core\event\user_loggedinas
    - \core\event\user_profile_viewed
    - \core\event\webservice_token_created

DEPRECATIONS:
* $module uses in mod/xxx/version.php files is now deprecated. Please use $plugin instead. It will be removed in Moodle 2.10.
* Update init methods in all event classes - "level" property was renamed to "edulevel", the level property is now deprecated.
* Abstract class \core\event\course_module_instances_list_viewed is deprecated now, use \core\event\instances_list_viewed instead.
* Abstract class core\event\content_viewed has been deprecated. Please extend base event or other relevant abstract class.
* mod_book\event\instances_list_viewed has been deprecated. Please use mod_book\event\course_module_instance_list_viewed instead.
* mod_chat\event\instances_list_viewed has been deprecated. Please use mod_chat\event\course_module_instance_list_viewed instead.
* mod_choice\event\instances_list_viewed has been deprecated. Please use mod_choice\event\course_module_instance_list_viewed instead.
* mod_feedback\event\instances_list_viewed has been deprecated. Please use mod_feedback\event\course_module_instance_list_viewed instead.
* mod_page\event\instances_list_viewed has been deprecated. Please use mod_page\event\course_module_instance_list_viewed instead.
* The constants FRONTPAGECOURSELIST, FRONTPAGETOPICONLY & FRONTPAGECOURSELIMIT have been removed.
* Conditional availability API has moved and changed. The condition_info class is
  replaced by \core_availability\info_module, and condition_info_section by
  \core_availability\info_section. (Code that uses the old classes will generally
  still work.)
* coursemodule_visible_for_user() has been deprecated but still works - replaced
  by a new static function \core_availability\info_module::is_user_visible()
* cm_info::is_user_access_restricted_by_conditional_access has been deprecated
  but still works (it has never done what its name suggests, and is
  unnecessary).
* cm_info and section_info property showavailability has been deprecated, but
  still works (with the caveat that this information is now per-user).
* cm_info and section_info properties availablefrom and availableuntil have been
  deprecated and always return zero (underlying data doesn't have these values).
* section_info property groupingid has been deprecated and always returns zero,
  same deal.
* Various cm_info methods have been deprecated in favour of their read-only properties (get_url(), get_content(), get_extra_classes(),
  get_on_click(), get_custom_data(), get_after_link, get_after_edit_icons)
* The ajaxenabled function has been deprecated and always returns true. All code should be fully functional in Javascript.
* count_login_failures() has been deprecated, use user_count_login_failures() instead. Refer MDL-42891 for details.

Conditional availability (activities and sections):
* New conditional availability API in /availability, including new availability
  condition plugins in /availability/condition. The new API is very similar with
  regard to checking availability, but any code that modifies availability settings
  for an activity or section is likely to need substantial changes.

YUI:
  * The lightbox attribute for moodle-core-notification-dialogue has been
    deprecated and replaced by the modal attribute. This was actually
    changed in Moodle 2.2, but has only been marked as deprecated now. It
    will be removed in Moodle 2.9.
  * When destroying any type of dialogue based on moodle-core-notification, the relevant content is also removed from
    the DOM. Previously it was left orphaned.

JavaSript:
    * The findChildNodes global function has been deprecated. Y.all should
      be used instead.
    * The callback argument to confirm_action and M.util.show_confirm_dialog has been deprecated. If you need to write a
      confirmation which includes a callback, please use moodle-core-notification-confirmation and attach callbacks to the
      events provided.

* New locking api and admin settings to configure the system locking type.
* New "Time spent waiting for the database" performance metric displayed along with the
  other MDL_PERF vars; the change affects both the error logs and the vars displayed in
  the page footer.
* Changes in the tag API. The component and contextid are now saved when assigning tags to an item. Please see
  tag/upgrade.txt for more information.

=== 2.6 ===

* Use new methods from core_component class instead of get_core_subsystems(), get_plugin_types(),
  get_plugin_list(), get_plugin_list_with_class(), get_plugin_directory(), normalize_component(),
  get_component_directory() and get_plugin_list_with_file(). The names of the new methods are
  exactly the same, the only differences are that core_component::get_plugin_types() now always returns
  full paths and core_component::get_plugin_list() does not accept empty parameter any more.
* Use core_text::* instead of textlib:: and also core_collator::* instead of collatorlib::*.
* Use new function moodleform::mock_submit() to simulate form submission in unit tests (backported).
* New $CFG->localcachedir setting useful for cluster nodes. Admins have to update X-Sendfile aliases if used.
* MS SQL Server drivers are now using NVARCHAR(MAX) instead of NTEXT and VARBINARY(MAX) instead of IMAGE,
  this change should be fully transparent and it should help significantly with add-on compatibility.
* The string manager classes were renamed. Note that they should not be modified or used directly,
  always use get_string_manager() to get instance of the string manager.
* The ability to use an 'insecure' rc4encrypt/rc4decrypt key has been removed.
* Use $CFG->debugdeveloper instead of debugging('', DEBUG_DEVELOPER).
* Use set_debugging(DEBUG_xxx) when changing debugging level for current request.
* Function moveto_module() does not modify $mod argument and instead now returns the new module visibility value.
* Use behat_selectors::get_allowed_text_selectors() and behat_selectors::get_allowed_selectors() instead of
  behat_command::$allowedtextselectors and behat_command::$allowedselectors
* Subplugins are supported in admin tools and local plugins.
* file_packer/zip_packer API has been modified so that key functions support a new file_progress interface
  to report progress during long operations. Related to this, zip_archive now supports an estimated_count()
  function that returns an approximate number of entries in the zip faster than the count() function.
* Class cm_info no longer extends stdClass. All properties are read-only and calculated on first request only.
* Class course_modinfo no longer extends stdClass. All properties are read-only.
* Database fields modinfo and sectioncache in table course are removed. Application cache core/coursemodinfo
  is used instead. Course cache is still reset, rebuilt and retrieved using function rebuild_course_cache() and
  get_fast_modinfo(). Purging all caches and every core upgrade purges course modinfo cache as well.
  If function get_fast_modinfo() is called for multiple courses make sure to include field cacherev in course
  object.
* Internal (noreply and support) user support has been added for sending/receiving message.
  Use core_user::get_noreply_user() and core_user::get_support_user() to get noreply and support user's respectively.
  Real users can be used as noreply/support users by setting $CFG->noreplyuserid and $CFG->supportuserid
* New function readfile_allow_large() in filelib.php for use when very large files may need sending to user.
* Use core_plugin_manager::reset_caches() when changing visibility of plugins.
* Implement new method get_enabled_plugins() method in subplugin info classes.
* Each plugin should include version information in version.php.
* Module and block tables do not contain version column any more, use get_config('xx_yy', 'version') instead.
* $USER->password field is intentionally unset so that session data does not contain password hashes.
* Use core_shutdown_manager::register_function() instead of register_shutdown_function().
* New file packer for .tar.gz files; obtain by calling get_file_packer('application/x-gzip'). Intended initially
  for use in backup/restore only, as there are limitations on supported filenames. Also new packer for
  backups which supports both compression formats; get_file_packer('application/vnd.moodle.backup').
* New optional parameter to stored_file::get_content_file_handle to open file handle with 'gzopen' instead
  of 'fopen' to read gzip-compressed files if required.
* update_internal_user_password() and setnew_password_and_mail() now trigger user_updated event.
* Add thirdpartylibs.xml file to plugins that bundle any 3rd party libraries.
* New class introduced to help auto generate zIndex values for modal dialogues. Class "moodle-has-zindex"
  should set on any element which uses a non-default zindex and needs to ensure it doesn't show above a
  dialogue.
* $CFG->filelifetime is now used consistently for most file serving operations, the default was lowered
  to 6 hours from 24 hours because etags and x-sendfile support should make file serving less expensive.
* Date format locale charset for windows server will come from calendar type and for gregorian it will use
  lang file.
* The library to interact with Box.net (class boxclient) is only compatible with their APIv1 which
  reaches its end of life on the 14th of Dec. You should migrate your scripts to make usage of the
  new class boxnet_client(). Note that the method names and return values have changed.
* Settings pages are now possible for Calendar type plugins. Calendar type plugins that require a settings page to
  work properly will need to set their requires version to a number that is equal to or grater than the 2.6.1 release version.
* The admin/tool/generator tool was overhauled to use testing data generators and the previous interface to create
  test data was removed (it was not working correctly anyway). If you were using this tool you will probably need to
  update your code.

DEPRECATIONS:
Various previously deprecated functions have now been altered to throw DEBUG_DEVELOPER debugging notices
and will be removed in a future release (target: 2.8), a summary follows:

Accesslib:
    * get_context_instance()                ->  context_xxxx::instance()
    * get_context_instance_by_id()          ->  context::instance_by_id($id)
    * get_system_context()                  ->  context_system::instance()
    * context_moved()                       ->  context::update_moved()
    * preload_course_contexts()             ->  context_helper::preload_course()
    * context_instance_preload()            ->  context_helper::preload_from_record()
    * context_instance_preload_sql()        ->  context_helper::get_preload_record_columns_sql()
    * get_contextlevel_name()               ->  context_helper::get_level_name()
    * create_contexts()                     ->  context_helper::create_instances()
    * cleanup_contexts()                    ->  context_helper::cleanup_instances()
    * build_context_path()                  ->  context_helper::build_all_paths()
    * print_context_name()                  ->  $context->get_context_name()
    * mark_context_dirty()                  ->  $context->mark_dirty()
    * delete_context()                      ->  $context->delete_content() or context_helper::delete_instance()
    * get_context_url()                     ->  $context->get_url()
    * get_course_context()                  ->  $context->get_course_context()
    * get_parent_contexts()                 ->  $context->get_parent_context_ids()
    * get_parent_contextid()                ->  $context->get_parent_context()
    * get_child_contexts()                  ->  $context->get_child_contexts()
    * rebuild_contexts()                    ->  $context->reset_paths()
    * get_user_courses_bycap()              ->  enrol_get_users_courses()
    * get_courseid_from_context()           ->  $context->get_course_context(false)
    * get_role_context_caps()               ->  (no replacement)
    * load_temp_role()                      ->  (no replacement)
    * remove_temp_roles()                   ->  (no replacement)
    * get_related_contexts_string()         ->  $context->get_parent_context_ids(true)
    * get_recent_enrolments()               ->  (no replacement)

Enrollment:
    * get_course_participants()             -> get_enrolled_users()
    * is_course_participant()               -> is_enrolled()

Output:
    * current_theme()                       -> $PAGE->theme->name
    * skip_main_destination()               -> $OUTPUT->skip_link_target()
    * print_container()                     -> $OUTPUT->container()
    * print_container_start()               -> $OUTPUT->container_start()
    * print_container_end()                 -> $OUTPUT->container_end()
    * print_continue()                      -> $OUTPUT->continue_button()
    * print_header()                        -> $PAGE methods
    * print_header_simple()                 -> $PAGE methods
    * print_side_block()                    -> $OUTPUT->block()
    * print_arrow()                         -> $OUTPUT->arrow()
    * print_scale_menu_helpbutton()         -> $OUTPUT->help_icon_scale($courseid, $scale)
    * print_checkbox()                      -> html_writer::checkbox()

Navigation:
    * print_navigation()                    -> $OUTPUT->navbar()
    * build_navigation()                    -> $PAGE->navbar methods
    * navmenu()                             -> (no replacement)
    * settings_navigation::
          get_course_modules()              -> (no replacement)

Files and repositories:
    * stored_file::replace_content_with()   -> stored_file::replace_file_with()
    * stored_file::set_filesize()           -> stored_file::replace_file_with()
    * stored_file::get_referencelifetime()  -> (no replacement)
    * repository::sync_external_file()      -> see repository::sync_reference()
    * repository::get_file_by_reference()   -> repository::sync_reference()
    * repository::
          get_reference_file_lifetime()     -> (no replacement)
    * repository::sync_individual_file()    -> (no replacement)
    * repository::reset_caches()            -> (no replacement)

Calendar:
    * add_event()                           -> calendar_event::create()
    * update_event()                        -> calendar_event->update()
    * delete_event()                        -> calendar_event->delete()
    * hide_event()                          -> calendar_event->toggle_visibility(false)
    * show_event()                          -> calendar_event->toggle_visibility(true)

Misc:
    * filter_text()                         -> format_text(), format_string()...
    * httpsrequired()                       -> $PAGE->https_required()
    * detect_munged_arguments()             -> clean_param([...], PARAM_FILE)
    * mygroupid()                           -> groups_get_all_groups()
    * js_minify()                           -> core_minify::js_files()
    * css_minify_css()                      -> core_minify::css_files()
    * course_modinfo::build_section_cache() -> (no replacement)
    * generate_email_supportuser()          -> core_user::get_support_user()

Sessions:
    * session_get_instance()->xxx()         -> \core\session\manager::xxx()
    * session_kill_all()                    -> \core\session\manager::kill_all_sessions()
    * session_touch()                       -> \core\session\manager::touch_session()
    * session_kill()                        -> \core\session\manager::kill_session()
    * session_kill_user()                   -> \core\session\manager::kill_user_sessions()
    * session_gc()                          -> \core\session\manager::gc()
    * session_set_user()                    -> \core\session\manager::set_user()
    * session_is_loggedinas()               -> \core\session\manager::is_loggedinas()
    * session_get_realuser()                -> \core\session\manager::get_realuser()
    * session_loginas()                     -> \core\session\manager::loginas()

User-agent related functions:
    * check_browser_operating_system()      -> core_useragent::check_browser_operating_system()
    * check_browser_version()               -> core_useragent::check_browser_version()
    * get_device_type()                     -> core_useragent::get_device_type()
    * get_device_type_list()                -> core_useragent::get_device_type_list()
    * get_selected_theme_for_device_type()  -> core_useragent::get_device_type_theme()
    * get_device_cfg_var_name()             -> core_useragent::get_device_type_cfg_var_name()
    * set_user_device_type()                -> core_useragent::set_user_device_type()
    * get_user_device_type()                -> core_useragent::get_user_device_type()
    * get_browser_version_classes()         -> core_useragent::get_browser_version_classes()

YUI:
    * moodle-core-notification has been deprecated with a recommendation of
      using its subclasses instead. This is to allow for reduced page
      transport costs. Current subclasses include:
      * dialogue
      * alert
      * confirm
      * exception
      * ajaxexception

Event triggering and event handlers:
    * All existing events and event handlers should be replaced by new
      event classes and matching new event observers.
    * See http://docs.moodle.org/dev/Event_2 for more information.
    * The following events will be entirely removed, though they can still
      be captured using handlers, but they should not be used any more.
      * groups_members_removed          -> \core\event\group_member_removed
      * groups_groupings_groups_removed -> (no replacement)
      * groups_groups_deleted           -> \core\event\group_deleted
      * groups_groupings_deleted        -> \core\event\grouping_deleted
    * edit_module_post_actions() does not trigger events any more.

=== 2.5.1 ===

* New get_course() function for use when obtaining the course record from database. Will
  reuse existing $COURSE or $SITE globals if possible to improve performance.

=== 2.5 ===

* The database drivers (moodle_database and subclasses) aren't using anymore the ::columns property
  for caching database metadata. MUC (databasemeta) is used instead. Any custom DB driver should
  apply for that change.
* The cron output has been changed to include time and memory usage (see cron_trace_time_and_memory()),
  so any custom utility relying on the old output may require modification.
* Function get_max_file_sizes now returns an option for (for example) "Course limit (500MB)" or
  "Site limit (200MB)" when appropriate with the option set to 0. This function no longer returns
  an option for 0 bytes. Existing code that was replacing the 0 option in the return
  from this function with a more sensible message, can now use the return from this function directly.
* Functions responsible for output in course/lib.php are deprecated, the code is moved to
  appropriate renderers: print_section(), print_section_add_menus(), get_print_section_cm_text(),
  make_editing_buttons()
  See functions' phpdocs in lib/deprecatedlib.php
* Function get_print_section_cm_text() is deprecated, replaced with methods in cm_info
* zip_packer may create empty zip archives, there is a new option to ignore
  problematic files when creating archive
* The function delete_course_module was deprecated and has been replaced with
  course_delete_module. The reason for this was because the function delete_course_module
  only partially deletes data, so wherever it was called extra code was needed to
  perform the whole deletion process. The function course_delete_module now takes care
  of the whole process.
* curl::setopt() does not accept constant values any more. As it never worked properly,
  we decided to make the type check stricter. Now, the keys of the array pass must be a string
  corresponding to the curl constant name.
* Function get_users_listing now return list of users except guest and deleted users. Previously
  deleted users were excluded by get_users_listing. As guest user is not expected while browsing users,
  and not included in get_user function, it will not be returned by get_users_listing.
* The add_* functions in course/dnduploadlib.php have been deprecated. Plugins should be using the
  MODNAME_dndupload_register callback instead.
* The signature of the add() method of classes implementing the parentable_part_of_admin_tree
  interface (such as admin_category) has been extended. The new parameter allows the caller
  to prepend the new node before an existing sibling in the admin tree.
* condition_info:get_condition_user_fields($formatoptions) now accepts the optional
  param $formatoptions, that will determine if the field names are processed by
  format_string() with the passed options.
* remove all references to $CFG->gdversion, GD PHP extension is now required
* Formslib will now throw a developer warning if a PARAM_ type hasn't been set for elements which
  need it. Please set PARAM_RAW explicitly if you do not want any cleaning.
* Functions responsible for managing and accessing course categories are moved to class coursecat
  in lib/coursecatlib.php, functions responsible for rendering courses and categories lists are
  moved to course/renderer.php. The following global functions are deprecated: make_categories_list(),
  category_delete_move(), category_delete_full(), move_category(), course_category_hide(),
  course_category_show(), get_course_category(), create_course_category(), get_all_subcategories(),
  get_child_categories(), get_categories(), print_my_moodle(), print_remote_course(),
  print_remote_host(), print_whole_category_list(), print_category_info(), get_course_category_tree(),
  print_courses(), print_course(), get_category_courses_array(), get_category_courses_array_recursively(),
  get_courses_wmanagers()
  See http://docs.moodle.org/dev/Courses_lists_upgrade_to_2.5
* $core_renderer->block_move_target() changed to support more verbose move-block-here descriptions.
* Additional (optional) param $onlyactive has been added to get_enrolled_users, count_enrolled_users
  functions to get information for only active (excluding suspended enrolments) users. Included two
  helper functions extract_suspended_users, get_suspended_userids to extract suspended user information.
* The core_plugin_manager class now provides two new helper methods for getting information
  about known plugins: get_plugins_of_type() and get_subplugins_of_plugin().
* The get_uninstall_url() method of all subclasses of \core\plugininfo\base class is now expected
  to always return moodle_url. Subclasses can use the new method is_uninstall_allowed()
  to control the availability of the 'Uninstall' link at the Plugins overview page (previously
  they would do it by get_uninstall_url() returning null). By default, URL to a new general plugin
  uninstall tool is returned. Unless the plugin type needs extra steps that can't be handled by
  plugininfo_xxx::uninstall() method or xmldb_xxx_uninstall() function, this default URL should
  satisfy all plugin types.

Database (DML) layer:
* $DB->sql_empty() is deprecated, you have to use sql parameters with empty values instead,
  please note hardcoding of empty strings in SQL queries breaks execution in Oracle database.
* Indexes must not be defined on the same columns as keys, this is now reported as fatal problem.
  Please note that internally we create indexes instead of foreign keys.

YUI changes:
* M.util.help_icon has been deprecated. Code should be updated to use moodle-core-popuphelp
  instead. To do so, remove any existing JS calls to M.util.help_icon from your PHP and ensure
  that your help link is placed in a span which has the class 'helplink'.

=== 2.4 ===

* Pagelib: Numerous deprecated functions were removed as classes page_base, page_course
  and page_generic_activity.
* use $CFG->googlemapkey3 instead of removed $CFG->googlemapkey and migrate to Google Maps API V3
* Function settings_navigation::add_course_editing_links() is completely removed
* function global_navigation::format_display_course_content() is removed completely (the
  functionality is moved to course format class)
* in the function global_navigation::load_generic_course_sections() the argument $courseformat is
  removed
* New component and itemid columns in groups_members table - this allows plugin to create protected
  group memberships using 'xx_yy_allow_group_member_remove' callback and there is also a new restore
  callback 'xx_yy_restore_group_member()'.
* New general role assignment restore plugin callback 'xx_yy_restore_role_assignment()'.
* functions get_generic_section_name(), get_all_sections(), add_mod_to_section(), get_all_mods()
  are deprecated. See their phpdocs in lib/deprecatedlib.php on how to replace them

YUI changes:
* moodle-enrol-notification has been renamed to moodle-core-notification
* YUI2 code must now use 2in3, see http://yuilibrary.com/yui/docs/yui/yui-yui2.html
* M.util.init_select_autosubmit() and M.util.init_url_select() have been deprecated. Code using this should be updated
  to use moodle-core-formautosubmit

Unit testing changes:
* output debugging() is not sent to standard output any more,
  use $this->assertDebuggingCalled(), $this->assertDebuggingNotCalled(),
  $this->getDebuggingMessages() or $this->assertResetDebugging() instead.

=== 2.3 ===

Database layer changes:
* objects are not allowed in paramters of DML functions, use explicit casting to strings if necessary

Note:
* DDL and DML methods which were deprecated in 2.0 have now been removed, they will no longer produce
debug messages and will produce fatal errors

API changes:

* send_stored_file() has changed its interface
* deleted several resourcelib_embed_* functions from resourcelib.php

=== 2.2 ===

removed unused libraries:
* odbc, base32, CodeSniffer, overlib, apd profiling, kses, Smarty, PEAR Console, swfobject, cssshover.htc, md5.js

API changes:
* new admin/tool plugin type
* new context API - old API is still available
* deleted users do not have context any more
* removed global search


=== 2.1 ===

API changes:
* basic suport for restore from 1.9
* new mobile devices API
* new questions API


=== 2.0 ===

API changes:
* new DML API - http://docs.moodle.org/dev/DML_functions
* new DDL API - http://docs.moodle.org/dev/DDL_functions
* new file API - http://docs.moodle.org/dev/File_API
* new $PAGE and $OUTPUT API
* new navigation API
* new theme API - http://docs.moodle.org/dev/Theme_changes_in_2.0
* new javascript API - http://docs.moodle.org/dev/JavaScript_usage_guide
* new portfolio API
* new local plugin type
* new translation support - http://lang.moodle.org
* new web service API
* new cohorts API
* new messaging API
* new rating API
* new comment API
* new sessions API
* new enrolment API
* new backup/restore API
* new blocks API
* new filters API
* improved plugin support (aka Frankenstyle)
* new registration and hub API
* new course completion API
* new plagiarism API
* changed blog API
* new text editor API
* new my moodle and profiles API
