Changes in 1.4.0:

* Added a [TDLib build instructions generator](https://tdlib.github.io/td/build.html), covering in details
  TDLib building on the most popular operating systems.
* Added an example of TDLib building and usage from a browser.
  See https://github.com/tdlib/td/blob/master/example/web/ for more details.
* Allowed to pass NULL pointer to `td_json_client_execute` instead of a previously created JSON client.
  Now you can use synchronous TDLib methods through a JSON interface before creating a TDLib JSON client.
* Added support for media streaming by allowing to download any part of a file:
  - Added the `offset` parameter to `downloadFile` which specifies the starting position
    from which the file should be downloaded.
  - Added the `limit` parameter to `downloadFile` which specifies how many bytes should be downloaded starting from
    the `offset` position.
  - Added the field `download_offset` to the class `localFile` which contains the current download offset.
  - The field `downloaded_prefix_size` of the `localFile` class now contains the number of available bytes
    from the position `download_offset` instead of from the beginning of the file.
  - Added the method `getFileDownloadedPrefixSize` which can be used to get the number of locally available file bytes
    from a given offset without actually changing the download offset.
* Added the parameter `synchronous` to `downloadFile` which causes the request to return the result only after
  the download is completed.
* Added support for native polls in messages:
  - Added `messagePoll` to the types of message content; contains a poll.
  - Added the classes `poll` and `pollOption` describing a poll and a poll answer option respectively.
  - Added `inputMessagePoll` to the types of new input message content; can be used to send a poll.
  - Added the method `setPollAnswer` which can be used for voting in polls.
  - Added the method `stopPoll` which can be used to stop polls. Use the `Message.can_be_edited` field to check whether
    this method can be called on a message.
  - Added the update `updatePoll` for bots only. Ordinary users receive poll updates through `updateMessageContent`.
* Added a Notification API. See article https://core.telegram.org/tdlib/notification-api for a detailed description.
  - Added the class `pushReceiverId` which contains a globally unique identifier of the push notification subscription.
  - Changed the return type of the method `registerDevice` to `pushReceiverId` to allow matching of push notifications
    with TDLib instances.
  - Removed the fields `disable_notification` and `contains_mention` from `updateNewMessage`.
  - Renamed the class `deviceTokenGoogleCloudMessaging` to `deviceTokenFirebaseCloudMessaging`.
  - Added the field `encrypt` to classes `deviceTokenApplePushVoIP` and `deviceTokenFirebaseCloudMessaging`
    which allows to subscribe for end-to-end encrypted push notifications.
  - Added the option `notification_group_count_max` which can be used to enable the Notification API and set
    the maximum number of notification groups to be shown simultaneously.
  - Added the option `notification_group_size_max` which can be used to set the maximum number of simultaneously shown
    notifications in a group.
  - Added the synchronous method `getPushReceiverId` for matching a push notification with a TDLib instance.
  - Added the method `processPushNotification` for handling of push notifications.
  - Removed the method `processDcUpdate` in favor of the general `processPushNotification` method.
  - Added the update `updateNotificationGroup`, sent whenever a notification group changes.
  - Added the update `updateNotification`, sent whenever a notification changes.
  - Added the update `updateActiveNotifications` for syncing the list of active notifications on startup.
  - Added the update `updateHavePendingNotifications` which can be used to improve lifetime handling of
    the TDLib instance.
  - Added the possibility to disable special handling of notifications about pinned messages via the new settings
    `use_default_disable_pinned_message_notifications`, `disable_pinned_message_notifications` in
    the class `chatNotificationSettings` and the new setting `disable_pinned_message_notifications` in
    the class `scopeNotificationSettings`.
  - Added the possibility to disable special handling of notifications about mentions and replies via the new settings
    `use_default_disable_mention_notifications`, `disable_mention_notifications` in
    the class `chatNotificationSettings` and the new setting `disable_mention_notifications` in
    the class `scopeNotificationSettings`.
  - Added the class `PushMessageContent` describing the content of a notification, received through
    a push notification.
  - Added the class `NotificationType` describing a type of a notification.
  - Added the class `notification` containing information about a notification.
  - Added the class `NotificationGroupType` describing a type of a notification group.
  - Added the class `notificationGroup` describing a state of a notification group.
  - Added the methods `removeNotification` and `removeNotificationGroup` for handling notifications removal
    by the user.
  - Added the separate notification scope `notificationSettingsScopeChannelChats` for channel chats.
* Added support for pinned notifications in basic groups and Saved Messages:
  - Added the field `pinned_message_id` to the class `chat`.
  - Removed the field `pinned_message_id` from the class `supergroupFullInfo` in favor of `Chat.pinned_message_id`.
  - Added the update `updateChatPinnedMessage`.
  - The right `can_pin_messages` is now applicable to both basic groups and supergroups.
  - Replaced the method `pinSupergroupMessage` with `pinChatMessage` which can be used for any chat type.
  - Replaced the method `unpinSupergroupMessage` with `unpinChatMessage` which can be used for any chat type.
* Added new synchronous methods for managing TDLib internal logging. The old functions are deprecated and
  will be removed in TDLib 2.0.0.
  - Added the synchronous method `setLogStream` for changing the stream to which the TDLib internal log is written.
  - Added the synchronous method `getLogStream` for getting information about the currently used log stream.
  - Added the classes `logStreamDefault`, `logStreamFile` and `logStreamEmpty` describing different supported kinds of
    log streams.
  - Added the class `logVerbosityLevel` containing the verbosity level of the TDLib internal log.
  - Added the class `logTags` containing a list of available TDLib internal log tags.
  - Added the synchronous method `setLogVerbosityLevel` for changing verbosity level of logging.
  - Added the synchronous method `getLogVerbosityLevel` for getting the current verbosity level of logging.
  - Added the synchronous method `getLogTags` returning all currently supported log tags.
  - Added the synchronous method `setLogTagVerbosityLevel` for changing the verbosity level of logging for
    some specific part of the code.
  - Added the synchronous method `getLogTagVerbosityLevel` for getting the current verbosity level for a specific part
    of the code.
  - Added the synchronous method `addLogMessage` for using the TDLib internal log by the application.
* Added support for Instant View 2.0:
  - Replaced the field `has_instant_view` in class `webPage` with the `instant_view_version` field.
  - Added the field `version` to the class `webPageInstantView`.
  - Added the class `pageBlockCaption`.
  - Changed the type of `caption` fields in `pageBlockAnimation`, `pageBlockAudio`, `pageBlockPhoto`, `pageBlockVideo`,
    `pageBlockEmbedded`, `pageBlockEmbeddedPost`, `pageBlockCollage` and `pageBlockSlideshow` from
    `RichText` to `pageBlockCaption`.
  - Added the class `pageBlockListItem` and replaced the content of the `pageBlockList` class with a list of
    `pageBlockListItem`.
  - Added 6 new kinds of `RichText`: `richTextSubscript`, `richTextSuperscript`, `richTextMarked`,
    `richTextPhoneNumber`, `richTextIcon` and `richTextAnchor`.
  - Added new classes `pageBlockRelatedArticle`, `PageBlockHorizontalAlignment`, `PageBlockVerticalAlignment` and
    `pageBlockTableCell`.
  - Added new block types `pageBlockKicker`, `pageBlockRelatedArticles`, `pageBlockTable`, `pageBlockDetails` and
    `pageBlockMap`.
  - Added the flag `is_rtl` to `webPageInstantView` object.
  - Renamed the field `caption` in classes `pageBlockBlockQuote` and `pageBlockPullQuote` to `credit`.
  - Dimensions in `pageBlockEmbedded` can now be unknown.
  - Added the field `url` to `pageBlockPhoto` which contains a URL that needs to be opened when the photo is clicked.
  - Added the field `url` to `webPageInstantView` which must be used for the correct handling of anchors.
* Added methods for confirmation of the 2-step verification recovery email address:
  - Added the method `checkRecoveryEmailAddressCode` for checking the verification code.
  - Added the method `resendRecoveryEmailAddressCode` for resending the verification code.
  - Replaced the field `unconfirmed_recovery_email_address_pattern` in the class `passwordState` with
    the `recovery_email_address_code_info` field containing full information about the code.
  - The necessity of recovery email address confirmation in `setPassword` and `setRecoveryEmailAddress` methods
    is now returned by the corresponding `passwordState` and not by the error `EMAIL_UNCONFIRMED`.
* Improved the `MessageForwardInfo` class and added support for hidden original senders:
  - Removed the old `messageForwardedPost` and `messageForwardedFromUser` classes.
  - Added the class `messageForwardInfo` which contains information about the origin of the message, original sending
    date and identifies the place from which the message was forwarded the last time for messages forwarded to
    Saved Messages.
  - Added the classes `messageForwardOriginUser`, `messageForwardOriginHiddenUser` and `messageForwardOriginChannel`
    which describe the exact origins of a message.
* Improved getting the list of user profile photos:
  - Added the class `userProfilePhoto`, containing `id`, `added_date` and `sizes` of a profile photo.
  - Changed the type of the field `photos` in `userProfilePhotos` to a list of `userProfilePhoto` instead of
    a list of `photo`. `getUserProfilePhotos` now returns a date for each profile photo.
  - Removed the field `id` from the class `photo` (this field was only needed in the result of `getUserProfilePhotos`).
* Added the possibility to get a Telegram Passport authorization form before asking the user for a password:
  - Removed the parameter `password` from the method `getPassportAuthorizationForm`.
  - Moved the fields `elements` and `errors` from the class `passportAuthorizationForm` to
    the new class `passportElementsWithErrors`.
  - Added the method `getPassportAuthorizationFormAvailableElements` that takes the user's password and
    returns previously uploaded Telegram Passport elements and errors in them.
* Added the field `file_index` to the classes `passportElementErrorSourceFile` and
  `passportElementErrorSourceTranslationFile`.
* Added the method `getCurrentState` returning all updates describing the current `TDLib` state. It can be used to
  restore the correct state after connecting to a running TDLib instance.
* Added the class `updates` which contains a list of updates and is returned by the `getCurrentState` method.
* Added the update `updateChatOnlineMemberCount` which is automatically sent for open group chats if the number of
  online members in a group changes.
* Added support for custom language packs downloaded from the server:
  - Added the fields `base_language_pack_id`` to the `languagePackInfo` object. Strings from the base language pack
    must be used for untranslated keys from the chosen language pack.
  - Added the fields `plural_code`, `is_official`, `is_rtl`, `is_beta`, `is_installed`, `total_string_count`,
    `translated_string_count`, `translation_url` to the `languagePackInfo` object.
  - Added the method `addCustomServerLanguagePack` which adds a custom server language pack to the list of
    installed language packs.
  - Added the method `getLanguagePackInfo` which can be used for handling `https://t.me/setlanguage/...` links.
  - Added the method `synchronizeLanguagePack` which can be used to fetch the latest versions of all strings from
    a language pack.
    The method doesn't need to be called explicitly for the current used/base language packs.
  - The method `deleteLanguagePack` now also removes the language pack from the list of installed language packs.
* Added the method `getChatNotificationSettingsExceptions` which can be used to get chats with
  non-default notification settings.
* Added the parameter `hide_via_bot` to `sendInlineQueryResultMessage` which can be used for
  `getOption("animation_search_bot_username")`, `getOption("photo_search_bot_username")` and
  `getOption("venue_search_bot_username")` bots to hide that the message was sent via the bot.
* Added the class `chatReportReasonChildAbuse` which can be used to report a chat for child abuse.
* Added the method `getMessageLocally` which returns a message only if it is available locally without
  a network request.
* Added the method `writeGeneratedFilePart` which can be used to write a generated file if there is no direct access to
  TDLib's file system.
* Added the method `readFilePart` which can be used to read a file from the TDLib file cache.
* Added the class `filePart` to represent the result of the new `readFilePart` method.
* Added the field `log_size` to the `storageStatisticsFast` class which contains the size of the TDLib internal log.
  Previously the size was included into the value of the `database_size` field.
* Added the field `language_pack_database_size` to the `storageStatisticsFast` class which contains the size of the
  language pack database.
* Added the field `is_support` to the class `user` which can be used to identify Telegram Support accounts.
* Added the class `HttpUrl` encapsulating an HTTP URL.
* Added the method `getMessageLink` which can be used to create a private link (which works only for members) to
  a message in a supergroup or channel.
* Added support for channel statistics (coming soon):
  - Added the field `can_view_statistics` to the `supergroupFullInfo` class.
  - Added the method `getChatStatisticsUrl` which returns a URL with the chat statistics.
* Added support for server-side peer-to-peer calls privacy:
  - Added the class `userPrivacySettingAllowPeerToPeerCalls` for managing privacy.
  - Added the field `allow_p2p` to `callStateReady` class which must be used to determine whether
    a peer-to-peer connection can be used.
* Added the option `ignore_background_updates` which allows to skip all updates received while the TDLib instance was
  not running. The option does nothing if the database or secret chats are used.
* Added the read-only option `expect_blocking`, suggesting whether Telegram is blocked for the user.
* Added the read-only option `enabled_proxy_id`, containing the ID of the enabled proxy.
* Added the ability to identify password pending sessions (where the code was entered but not
  the two-step verification password) via the flag `is_password_pending` in the `session` class.
  TDLib guarantees that the sessions will be returned by the `getActiveSessions` method in the correct order.
* Added the classes `JsonValue` and `jsonObjectMember` which represent a JSON value and
  a member of a JSON object respectively as TDLib API objects.
* Added the synchronous methods `getJsonValue` and `getJsonString` for simple conversion between
  a JSON-encoded string and `JsonValue` TDLib API class.
* Added the methods `getApplicationConfig` and `saveApplicationLogEvent` to be used for testing purposes.
* Added the temporarily class `databaseStatistics` and the method `getDatabaseStatistics` for rough estimations of
  database tables size in a human-readable format.
* Made the method `Client.Execute` static in .NET interface.
* Removed the `on_closed` callback virtual method from low-level C++ ClientActor interface.
  Callback destructor can be used instead.
* Updated dependencies in the prebuilt TDLib for Android:
  - Updated SDK to SDK 28 in which helper classes was moved from `android.support.` to `androidx.` package.
  - Updated NDK to r19c, which dropped support for Android versions up to 4.0.4, so the minimum supported version is
    Android 4.1.
  - Updated OpenSSL to version 1.1.1.
  - Added x86_64 libraries.
* Added out of the box `FreeBSD` support.
* Significantly improved TDLib compilation time and decreased compiler RAM usage:
  - In native C++ interface `td_api::object_ptr` is now a simple homebrew const-propagating class instead of
    `std::unique_ptr`.
  - Added the script `SplitSource.php`, which can be used to split some source code files before building
    the library to reduce maximum RAM usage per file at the expense of increased build time.
* The update `updateOption` with the `version` option is now guaranteed to come before all other updates.
  It can now be used to dynamically discover available methods.
* Added the ability to delete incoming messages in private chats and revoke messages without a time limit:
  - Added the parameter `revoke` to the method `deleteChatHistory`; use it to delete chat history for all chat members.
  - Added the fields `can_be_deleted_only_for_self` and `can_be_deleted_for_all_users` to `Chat` object
    which can be used to determine for whom the chat can be deleted through the `deleteChatHistory` method.
  - The fields `Message.can_be_deleted_only_for_self` and `Message.can_be_deleted_for_all_users` can still be used
    to determine for whom the message can be deleted through the `deleteMessages` method.
* Added support for server-generated notifications about newly registered contacts:
  - Setting the option `disable_contact_registered_notifications` now affects all user sessions.
    When the option is enabled, the client will still receive `messageContactRegistered` message in the private chat,
    but there will be no notification about the message.
  - `getOption("disable_contact_registered_notifications")` can be used to fetch the actual value of the option,
    the option will not be updated automatically after a change from another device.
* Decreased the maximum allowed first name and last name length to 64, chat title length to 128,
  matching the new server-side limits.
* Decreased the maximum allowed value of the `forward_limit` parameter of the `addChatMember` method from 300 to 100,
  matching the new server-side limit.
* Added protection from opening two TDLib instances with the same database directory from one process.
* Added copying of notification settings of new secret chats from notification settings of
  the corresponding private chat.
* Excluded the sponsored chat (when using sponsored proxies) from unread counters.
* Allowed to pass decreased local_size in `setFileGenerationProgress` to restart the generation from the beginning.
* Added a check for modification time of original file in `inputFileGenerated` whenever possible.
  If the original file was changed, then TDLib will restart the generation.
* Added the destruction of MTProto keys on the server during log out.
* Added support for hexadecimal-encoded and decimal-encoded IPv4 proxy server addresses.
* Improved the behavior of `changeImportedContacts` which now also deletes contacts of users without Telegram accounts
  from the server.
* Added the ability to call `getStorageStatistics` before authorization.
* Allowed to pass `limit` = -`offset` for negative offset in the `getChatHistory` method.
* Changed the recommended `inputThumbnail` size to be at most 320x320 instead of the previous 90x90.
* Disabled building by default of the native C interface. Use `cmake --build . --target tdc` to build it.
* Numerous optimizations and bug fixes:
  - Network implementation for Windows was completely rewritten to allow a literally unlimited number of
    simultaneously used TDLib instances.
  - TDLib instances can now share working threads with each other. Only a limited number of threads will be created
    even if there are thousands of TDLib instances in a single process.
  - Removed the restriction on the size of update or response result in JSON interface.
  - Fixed pinning of the 5th chat when there is a sponsored chat.
  - Fixed IPv6 on Windows.
  - Improved network connections balancing, aliveness checks and overall stability.
  - Various autogenerated documentation fixes and improvements.