## EBookMetaBackend

EBookMetaBackend — An EBookBackend descendant for book backends

## Functions

EBookMetaBackendInfo * | e_book_meta_backend_info_new ()
EBookMetaBackendInfo * | e_book_meta_backend_info_copy ()
void | e_book_meta_backend_info_free ()
const gchar * | e_book_meta_backend_get_capabilities ()
void | e_book_meta_backend_set_ever_connected ()
gboolean | e_book_meta_backend_get_ever_connected ()
void | e_book_meta_backend_set_connected_writable ()
gboolean | e_book_meta_backend_get_connected_writable ()
gchar * | e_book_meta_backend_dup_sync_tag ()
void | e_book_meta_backend_set_cache ()
EBookCache * | e_book_meta_backend_ref_cache ()
gboolean | e_book_meta_backend_inline_local_photos_sync ()
gboolean | e_book_meta_backend_store_inline_photos_sync ()
gboolean | e_book_meta_backend_empty_cache_sync ()
void | e_book_meta_backend_schedule_refresh ()
gboolean | e_book_meta_backend_refresh_sync ()
gboolean | e_book_meta_backend_ensure_connected_sync ()
gboolean | e_book_meta_backend_split_changes_sync ()
gboolean | e_book_meta_backend_process_changes_sync ()
gboolean | e_book_meta_backend_connect_sync ()
gboolean | e_book_meta_backend_disconnect_sync ()
gboolean | e_book_meta_backend_get_changes_sync ()
gboolean | e_book_meta_backend_list_existing_sync ()
gboolean | e_book_meta_backend_load_contact_sync ()
gboolean | e_book_meta_backend_save_contact_sync ()
gboolean | e_book_meta_backend_remove_contact_sync ()
gboolean | e_book_meta_backend_search_sync ()
gboolean | e_book_meta_backend_search_uids_sync ()
gboolean | e_book_meta_backend_requires_reconnect ()
gboolean | e_book_meta_backend_get_ssl_error_details ()

## Properties

EBookCache * | cache | Read / Write

## Signals

void | refresh-completed | Run Last
void | source-changed | Run Last

## Types and Values

struct | EBookMetaBackend
struct | EBookMetaBackendClass

## Object Hierarchy

        GBoxed
        ╰── EBookMetaBackendInfo
        GObject
        ╰── EBackend
            ╰── EBookBackend
                ╰── EBookBackendSync
                    ╰── EBookMetaBackend

## Includes

    #include <libedata-book/libedata-book.h>

## Description

The EBookMetaBackend is an abstract EBookBackend descendant which aims to implement all evolution-data-server internals for the backend itself and lefts the backend do as minimum work as possible, like loading and saving contacts, listing available contacts and so on, thus the backend implementation can focus on things like converting (possibly) remote data into vCard objects and back.

As the EBookMetaBackend uses an EBookCache, the offline support is provided by default.

The structure is thread safe.

## Functions

### e_book_meta_backend_info_new ()

    EBookMetaBackendInfo *
    e_book_meta_backend_info_new (const gchar *uid,
                                  const gchar *revision,
                                  const gchar *object,
                                  const gchar *extra);

Creates a new EBookMetaBackendInfo prefilled with the given values.

#### Parameters

uid | a contact UID; cannot be `NULL` |
revision | the contact revision; can be `NULL`. | [nullable]
object | the contact object as a vCard string; can be `NULL`. | [nullable]
extra | extra backend-specific data; can be `NULL`. | [nullable]

#### Returns

A new EBookMetaBackendInfo. Free it with `e_book_meta_backend_info_free()`, when no longer needed.

[transfer full]

Since: 3.26

### e_book_meta_backend_info_copy ()

    EBookMetaBackendInfo *
    e_book_meta_backend_info_copy (const EBookMetaBackendInfo *src);

#### Parameters

src | a source EBookMetaBackendInfo to copy, or `NULL`. | [nullable]

#### Returns

Copy of the given `src` . Free it with `e_book_meta_backend_info_free()` when no longer needed. If the `src` is `NULL`, then returns `NULL` as well.

[transfer full][nullable]

Since: 3.26

### e_book_meta_backend_info_free ()

    void
    e_book_meta_backend_info_free (gpointer ptr);

Frees the `ptr` structure, previously allocated with `e_book_meta_backend_info_new()` or `e_book_meta_backend_info_copy()`.

#### Parameters

ptr | an EBookMetaBackendInfo. | [nullable]

Since: 3.26

### e_book_meta_backend_get_capabilities ()

    const gchar *
    e_book_meta_backend_get_capabilities (EBookMetaBackend *meta_backend);

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

an “capabilities” property to be used by the descendant in conjunction to the descendant's capabilities in the result of `e_book_backend_get_backend_property()` with CLIENT_BACKEND_PROPERTY_CAPABILITIES.

Since: 3.26

### e_book_meta_backend_set_ever_connected ()

    void
    e_book_meta_backend_set_ever_connected
                                   (EBookMetaBackend *meta_backend,
                                    gboolean value);

Sets whether the `meta_backend` ever made a successful connection to its destination.

This is used by the `meta_backend` itself, during the opening phase, when it had not been connected yet, then it does so immediately, to eventually report settings error easily.

#### Parameters

meta_backend | an EBookMetaBackend |
value | value to set |

Since: 3.26

### e_book_meta_backend_get_ever_connected ()

    gboolean
    e_book_meta_backend_get_ever_connected
                                   (EBookMetaBackend *meta_backend);

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

Whether the `meta_backend` ever made a successful connection to its destination.

Since: 3.26

### e_book_meta_backend_set_connected_writable ()

    void
    e_book_meta_backend_set_connected_writable
                                   (EBookMetaBackend *meta_backend,
                                    gboolean value);

Sets whether the `meta_backend` connected to a writable destination. This value has meaning only if `e_book_meta_backend_get_ever_connected()` is `TRUE`.

This is used by the `meta_backend` itself, during the opening phase, to set the backend writable or not also in the offline mode.

#### Parameters

meta_backend | an EBookMetaBackend |
value | value to set |

Since: 3.26

### e_book_meta_backend_get_connected_writable ()

    gboolean
    e_book_meta_backend_get_connected_writable
                                   (EBookMetaBackend *meta_backend);

This value has meaning only if `e_book_meta_backend_get_ever_connected()` is `TRUE`.

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

Whether the `meta_backend` connected to a writable destination.

Since: 3.26

### e_book_meta_backend_dup_sync_tag ()

    gchar *
    e_book_meta_backend_dup_sync_tag (EBookMetaBackend *meta_backend);

Returns the last known synchronization tag, the same as used to call `e_book_meta_backend_get_changes_sync()`.

Free the returned string with `g_free()`, when no longer needed.

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

The last known synchronization tag, or `NULL`, when none is stored.

[transfer full][nullable]

Since: 3.28

### e_book_meta_backend_set_cache ()

    void
    e_book_meta_backend_set_cache (EBookMetaBackend *meta_backend,
                                   EBookCache *cache);

Sets the `cache` as the cache to be used by the `meta_backend` . By default, a cache.db in EBookBackend::cache-dir is created in the constructed method. This function can be used to override the default.

Note the `meta_backend` adds its own reference to the `cache` .

#### Parameters

meta_backend | an EBookMetaBackend |
cache | an EBookCache to use |

Since: 3.26

### e_book_meta_backend_ref_cache ()

    EBookCache *
    e_book_meta_backend_ref_cache (EBookMetaBackend *meta_backend);

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

Referenced EBookCache, which is used by `meta_backend` . Unref it with `g_object_unref()`, when no longer needed.

[transfer full]

Since: 3.26

### e_book_meta_backend_inline_local_photos_sync ()

    gboolean
    e_book_meta_backend_inline_local_photos_sync
                                   (EBookMetaBackend *meta_backend,
                                    EContact *contact,
                                    GCancellable *cancellable,
                                    GError **error);

Changes all URL photos and logos which point to a local file in `contact` to inline type, aka adds the file content into the `contact` . This is called automatically before `e_book_meta_backend_save_contact_sync()`.

The reverse operation is `e_book_meta_backend_store_inline_photos_sync()`.

#### Parameters

meta_backend | an EBookMetaBackend |
contact | an EContact to work with |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_store_inline_photos_sync ()

    gboolean
    e_book_meta_backend_store_inline_photos_sync
                                   (EBookMetaBackend *meta_backend,
                                    EContact *contact,
                                    GCancellable *cancellable,
                                    GError **error);

Changes all inline photos and logos to URL type in `contact` , which will point to a local file instead, beside the cache file. This is called automatically after `e_book_meta_backend_load_contact_sync()`.

The reverse operation is `e_book_meta_backend_inline_local_photos_sync()`.

#### Parameters

meta_backend | an EBookMetaBackend |
contact | an EContact to work with |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_empty_cache_sync ()

    gboolean
    e_book_meta_backend_empty_cache_sync (EBookMetaBackend *meta_backend,
                                          GCancellable *cancellable,
                                          GError **error);

Empties the local cache by removing all known contacts from it and notifies about such removal any opened views.

#### Parameters

meta_backend | an EBookMetaBackend |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_schedule_refresh ()

    void
    e_book_meta_backend_schedule_refresh (EBookMetaBackend *meta_backend);

Schedules refresh of the content of the `meta_backend` . If there's any already scheduled, then the function does nothing.

Use `e_book_meta_backend_refresh_sync()` to refresh the `meta_backend` immediately.

#### Parameters

meta_backend | an EBookMetaBackend |

Since: 3.26

### e_book_meta_backend_refresh_sync ()

    gboolean
    e_book_meta_backend_refresh_sync (EBookMetaBackend *meta_backend,
                                      GCancellable *cancellable,
                                      GError **error);

Refreshes the `meta_backend` immediately. To just schedule refresh operation call `e_book_meta_backend_schedule_refresh()`.

#### Parameters

meta_backend | an EBookMetaBackend |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_ensure_connected_sync ()

    gboolean
    e_book_meta_backend_ensure_connected_sync
                                   (EBookMetaBackend *meta_backend,
                                    GCancellable *cancellable,
                                    GError **error);

Ensures that the `meta_backend` is connected to its destination.

#### Parameters

meta_backend | an EBookMetaBackend |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_split_changes_sync ()

    gboolean
    e_book_meta_backend_split_changes_sync
                                   (EBookMetaBackend *meta_backend,
                                    GSList *objects,
                                    GSList **out_created_objects,
                                    GSList **out_modified_objects,
                                    GSList **out_removed_objects,
                                    GCancellable *cancellable,
                                    GError **error);

Splits `objects` into created/modified/removed lists according to current local cache content. Only the `out_removed_objects` can be `NULL`, others cannot. The function modifies `objects` by moving its 'data' to corresponding out lists and sets the `objects` 'data' to `NULL`.

Each output GSList should be freed with g_slist_free_full (objects, e_book_meta_backend_info_free); when no longer needed.

The caller is still responsible to free `objects` as well.

#### Parameters

meta_backend | an EBookMetaBackend |
objects | a GSList of EBookMetaBackendInfo object infos to split. | [inout][element-type EBookMetaBackendInfo]
out_created_objects | a GSList of EBookMetaBackendInfo object infos which had been created. | [out][element-type EBookMetaBackendInfo][transfer full]
out_modified_objects | a GSList of EBookMetaBackendInfo object infos which had been modified. | [out][element-type EBookMetaBackendInfo][transfer full]
out_removed_objects | a GSList of EBookMetaBackendInfo object infos which had been removed; it can be `NULL`, to not gather list of removed object infos. | [out][element-type EBookMetaBackendInfo][transfer full][nullable]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_process_changes_sync ()

    gboolean
    e_book_meta_backend_process_changes_sync
                                   (EBookMetaBackend *meta_backend,
                                    const GSList *created_objects,
                                    const GSList *modified_objects,
                                    const GSList *removed_objects,
                                    GCancellable *cancellable,
                                    GError **error);

Processes given changes by updating local cache content accordingly. The `meta_backend` processes the changes like being online and particularly requires to be online to load created and modified objects when needed.

#### Parameters

meta_backend | an EBookMetaBackend |
created_objects | a GSList of EBookMetaBackendInfo object infos which had been created. | [element-type EBookMetaBackendInfo][nullable]
modified_objects | a GSList of EBookMetaBackendInfo object infos which had been modified. | [element-type EBookMetaBackendInfo][nullable]
removed_objects | a GSList of EBookMetaBackendInfo object infos which had been removed. | [element-type EBookMetaBackendInfo][nullable]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_connect_sync ()

    gboolean
    e_book_meta_backend_connect_sync (EBookMetaBackend *meta_backend,
                                      const ENamedParameters *credentials,
                                      ESourceAuthenticationResult *out_auth_result,
                                      gchar **out_certificate_pem,
                                      GTlsCertificateFlags *out_certificate_errors,
                                      GCancellable *cancellable,
                                      GError **error);

This is called always before any operation which requires a connection to the remote side. It can fail with an E_CLIENT_ERROR_REPOSITORY_OFFLINE error to indicate that the remote side cannot be currently reached. Other errors are propagated to the caller/client side. This method is not called when the backend is offline.

The descendant should also call `e_book_backend_set_writable()` after successful connect to the remote side. This value is stored for later use, when being opened offline.

The `credentials` parameter consists of the previously used credentials. It's always `NULL` with the first connection attempt. To get the credentials, just set the `out_auth_result` to `E_SOURCE_AUTHENTICATION_REQUIRED` for the first time and the function will be called again once the credentials are available. See the documentation of ESourceAuthenticationResult for other available results.

The out parameters are passed to `e_backend_schedule_credentials_required()` and are ignored when the descendant returns `TRUE`, aka they are used only if the connection fails. The `out_certificate_pem` and `out_certificate_errors` should be used together and they can be left untouched if the failure reason was not related to certificate. Use `out_auth_result` `E_SOURCE_AUTHENTICATION_UNKNOWN` to indicate other error than `credentials` error, otherwise the `error` is used according to `out_auth_result` value.

It is mandatory to implement this virtual method by the descendant.

#### Parameters

meta_backend | an EBookMetaBackend |
credentials | an ENamedParameters with previously used credentials, or `NULL`. | [nullable]
out_auth_result | an ESourceAuthenticationResult with an authentication result. | [out]
out_certificate_pem | a PEM encoded certificate on failure, or `NULL`. | [out][transfer full]
out_certificate_errors | a GTlsCertificateFlags on failure, or 0. | [out]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_disconnect_sync ()

    gboolean
    e_book_meta_backend_disconnect_sync (EBookMetaBackend *meta_backend,
                                         GCancellable *cancellable,
                                         GError **error);

This is called when the backend goes into offline mode or when the disconnect is required. The implementation should not report any error when it is called and the `meta_backend` is not connected.

It is mandatory to implement this virtual method by the descendant.

#### Parameters

meta_backend | an EBookMetaBackend |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_get_changes_sync ()

    gboolean
    e_book_meta_backend_get_changes_sync (EBookMetaBackend *meta_backend,
                                          const gchar *last_sync_tag,
                                          gboolean is_repeat,
                                          gchar **out_new_sync_tag,
                                          gboolean *out_repeat,
                                          GSList **out_created_objects,
                                          GSList **out_modified_objects,
                                          GSList **out_removed_objects,
                                          GCancellable *cancellable,
                                          GError **error);

Gathers the changes since the last check which had been done on the remote side.

The `last_sync_tag` can be used as a tag of the last check. This can be `NULL`, when there was no previous call or when the descendant doesn't store any such tags. The `out_new_sync_tag` can be populated with a value to be stored and used the next time.

The `out_repeat` can be set to `TRUE` when the descendant didn't finish read of all the changes. In that case the `meta_backend` calls this function again with the `out_new_sync_tag` as the `last_sync_tag` , but also notifies about the found changes immediately. The `is_repeat` is set to `TRUE` as well in this case, otherwise it's `FALSE`.

The descendant can populate also EBookMetaBackendInfo::object of the `out_created_objects` and `out_modified_objects` , if known, in which case this will be used instead of loading it with `e_book_meta_backend_load_contact_sync()`.

It is optional to implement this virtual method by the descendant. The default implementation calls `e_book_meta_backend_list_existing_sync()` and then compares the list with the current content of the local cache and populates the respective lists appropriately.

Each output GSList should be freed with g_slist_free_full (objects, e_book_meta_backend_info_free); when no longer needed.

#### Parameters

meta_backend | an EBookMetaBackend |
last_sync_tag | optional sync tag from the last check. | [nullable]
is_repeat | set to `TRUE` when this is the repeated call |
out_new_sync_tag | new sync tag to store on success. | [out][transfer full]
out_repeat | whether to repeat this call again; default is `FALSE`. | [out]
out_created_objects | a GSList of EBookMetaBackendInfo object infos which had been created since the last check. | [out][element-type EBookMetaBackendInfo][transfer full]
out_modified_objects | a GSList of EBookMetaBackendInfo object infos which had been modified since the last check. | [out][element-type EBookMetaBackendInfo][transfer full]
out_removed_objects | a GSList of EBookMetaBackendInfo object infos which had been removed since the last check. | [out][element-type EBookMetaBackendInfo][transfer full]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_list_existing_sync ()

    gboolean
    e_book_meta_backend_list_existing_sync
                                   (EBookMetaBackend *meta_backend,
                                    gchar **out_new_sync_tag,
                                    GSList **out_existing_objects,
                                    GCancellable *cancellable,
                                    GError **error);

Used to get list of all existing objects on the remote side. The descendant can optionally provide `out_new_sync_tag` , which will be stored on success, if not `NULL`. The descendant can populate also EBookMetaBackendInfo::object of the `out_existing_objects` , if known, in which case this will be used instead of loading it with `e_book_meta_backend_load_contact_sync()`.

It is mandatory to implement this virtual method by the descendant, unless it implements its own `EBookMetaBackendClass.get_changes_sync()`.

The `out_existing_objects` GSList should be freed with g_slist_free_full (objects, e_book_meta_backend_info_free); when no longer needed.

#### Parameters

meta_backend | an EBookMetaBackend |
out_new_sync_tag | optional return location for a new sync tag. | [out][transfer full]
out_existing_objects | a GSList of EBookMetaBackendInfo object infos which are stored on the remote side. | [out][element-type EBookMetaBackendInfo][transfer full]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_load_contact_sync ()

    gboolean
    e_book_meta_backend_load_contact_sync (EBookMetaBackend *meta_backend,
                                           const gchar *uid,
                                           const gchar *extra,
                                           EContact **out_contact,
                                           gchar **out_extra,
                                           GCancellable *cancellable,
                                           GError **error);

Loads a contact from the remote side.

It is mandatory to implement this virtual method by the descendant.

The returned `out_contact` should be freed with `g_object_unref()`, when no longer needed.

The returned `out_extra` should be freed with `g_free()`, when no longer needed.

#### Parameters

meta_backend | an EBookMetaBackend |
uid | a contact UID |
extra | optional extra data stored with the contact, or `NULL`. | [nullable]
out_contact | a loaded contact, as an EContact. | [out][transfer full]
out_extra | an extra data to store to EBookCache with this contact. | [out][transfer full]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_save_contact_sync ()

    gboolean
    e_book_meta_backend_save_contact_sync (EBookMetaBackend *meta_backend,
                                           gboolean overwrite_existing,
                                           EConflictResolution conflict_resolution,
                                           EContact *contact,
                                           const gchar *extra,
                                           guint32 opflags,
                                           gchar **out_new_uid,
                                           gchar **out_new_extra,
                                           GCancellable *cancellable,
                                           GError **error);

Saves one contact into the remote side. When the `overwrite_existing` is `TRUE`, then the descendant can overwrite an object with the same UID on the remote side (usually used for modify). The `conflict_resolution` defines what to do when the remote side had made any changes to the object since the last update.

The `contact` has already converted locally stored photos and logos into inline variants, thus it's not needed to call `e_book_meta_backend_inline_local_photos_sync()` by the descendant.

The `out_new_uid` can be populated with a UID of the saved contact as the server assigned it to it. This UID, if set, is loaded from the remote side afterwards, also to see whether any changes had been made to the contact by the remote side.

The `out_new_extra` can be populated with a new extra data to save with the contact. Left it `NULL`, to keep the same value as the `extra` .

The descendant can use an E_CLIENT_ERROR_OUT_OF_SYNC error to indicate that the save failed due to made changes on the remote side, and let the `meta_backend` resolve this conflict based on the `conflict_resolution` on its own. The E_CLIENT_ERROR_OUT_OF_SYNC error should not be used when the descendant is able to resolve the conflicts itself.

It is mandatory to implement this virtual method by the writable descendant.

#### Parameters

meta_backend | an EBookMetaBackend |
overwrite_existing | `TRUE` when can overwrite existing contacts, `FALSE` otherwise |
conflict_resolution | one of EConflictResolution, what to do on conflicts |
contact | an EContact to save |
extra | extra data saved with the contacts in an EBookCache. | [nullable]
opflags | bit-or of EBookOperationFlags |
out_new_uid | return location for the UID of the saved contact. | [out][transfer full]
out_new_extra | return location for the extra data to store with the contact. | [out][transfer full]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_remove_contact_sync ()

    gboolean
    e_book_meta_backend_remove_contact_sync
                                   (EBookMetaBackend *meta_backend,
                                    EConflictResolution conflict_resolution,
                                    const gchar *uid,
                                    const gchar *extra,
                                    const gchar *object,
                                    guint32 opflags,
                                    GCancellable *cancellable,
                                    GError **error);

Removes a contact from the remote side. The `object` is not `NULL` when it's removing locally deleted object in offline mode. Being it `NULL`, the descendant can obtain the object from the EBookCache.

It is mandatory to implement this virtual method by the writable descendant.

#### Parameters

meta_backend | an EBookMetaBackend |
conflict_resolution | an EConflictResolution to use |
uid | a contact UID |
extra | extra data being saved with the contact in the local cache, or `NULL`. | [nullable]
object | corresponding vCard object, as stored in the local cache, or `NULL`. | [nullable]
opflags | bit-or of EBookOperationFlags |
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_search_sync ()

    gboolean
    e_book_meta_backend_search_sync (EBookMetaBackend *meta_backend,
                                     const gchar *expr,
                                     gboolean meta_contact,
                                     GSList **out_contacts,
                                     GCancellable *cancellable,
                                     GError **error);

Searches `meta_backend` with given expression `expr` and returns found contacts as a GSList of EContact `out_contacts` . Free the returned `out_contacts` with g_slist_free_full (contacts, g_object_unref); when no longer needed. When the `expr` is `NULL`, all objects are returned. To get UID-s instead, call `e_book_meta_backend_search_uids_sync()`.

It is optional to implement this virtual method by the descendant. The default implementation searches `meta_backend` 's cache. It's also not required to be online for searching, thus `meta_backend` doesn't ensure it.

#### Parameters

meta_backend | an EBookMetaBackend |
expr | a search expression, or `NULL`. | [nullable]
meta_contact | `TRUE`, when return EContact filled with UID and REV only, `FALSE` to return full contacts |
out_contacts | return location for the found contacts as EContact. | [out][transfer full][element-type EContact]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_search_uids_sync ()

    gboolean
    e_book_meta_backend_search_uids_sync (EBookMetaBackend *meta_backend,
                                          const gchar *expr,
                                          GSList **out_uids,
                                          GCancellable *cancellable,
                                          GError **error);

Searches `meta_backend` with given expression `expr` and returns found contact UID-s as a GSList `out_contacts` . Free the returned `out_uids` with g_slist_free_full (uids, g_free); when no longer needed. When the `expr` is `NULL`, all UID-s are returned. To get EContact(s) instead, call `e_book_meta_backend_search_sync()`.

It is optional to implement this virtual method by the descendant. The default implementation searches `meta_backend` 's cache. It's also not required to be online for searching, thus `meta_backend` doesn't ensure it.

#### Parameters

meta_backend | an EBookMetaBackend |
expr | a search expression, or `NULL`. | [nullable]
out_uids | return location for the found contact UID-s. | [out][transfer full][element-type utf8]
cancellable | optional GCancellable object, or `NULL` |
error | return location for a GError, or `NULL` |

#### Returns

Whether succeeded.

Since: 3.26

### e_book_meta_backend_requires_reconnect ()

    gboolean
    e_book_meta_backend_requires_reconnect
                                   (EBookMetaBackend *meta_backend);

Determines, whether current source content requires reconnect of the backend.

It is optional to implement this virtual method by the descendant. The default implementation compares `E_SOURCE_EXTENSION_AUTHENTICATION` and `E_SOURCE_EXTENSION_WEBDAV_BACKEND`, if existing in the source, with the values after the last successful connect and returns `TRUE` when they changed. It always return `TRUE` when there was no successful connect done yet.

#### Parameters

meta_backend | an EBookMetaBackend |

#### Returns

`TRUE`, when reconnect is required, `FALSE` otherwise.

Since: 3.26

### e_book_meta_backend_get_ssl_error_details ()

    gboolean
    e_book_meta_backend_get_ssl_error_details
                                   (EBookMetaBackend *meta_backend,
                                    gchar **out_certificate_pem,
                                    GTlsCertificateFlags *out_certificate_errors);

It is optional to implement this virtual method by the descendants. It is used to receive SSL error details when any online operation returns E_CLIENT_ERROR, E_CLIENT_ERROR_TLS_NOT_AVAILABLE error.

#### Parameters

meta_backend | an EBookMetaBackend |
out_certificate_pem | SSL certificate encoded in PEM format. | [out]
out_certificate_errors | bit-or of GTlsCertificateFlags claiming the certificate errors. | [out]

#### Returns

`TRUE`, when the SSL error details had been available and the out parameters populated, `FALSE` otherwise.

Since: 3.28

## Types and Values

### struct EBookMetaBackend

    struct EBookMetaBackend;

Contains only private data that should be read and manipulated using the functions below.

Since: 3.26

### struct EBookMetaBackendClass

    struct EBookMetaBackendClass {
    };

Class structure for the EBookMetaBackend class.

Since: 3.26

## Property Details

### The `“cache”` property

      “cache”                    EBookCache *

The EBookCache being used for this meta backend.

Owner: EBookMetaBackend

Flags: Read / Write

## Signal Details

### The `“refresh-completed”` signal

    void
    user_function (EBookMetaBackend *ebookmetabackend,
                   gpointer          user_data)

Flags: Run Last

### The `“source-changed”` signal

    void
    user_function (EBookMetaBackend *ebookmetabackend,
                   gpointer          user_data)

This signal is emitted whenever the underlying backend ESource changes. Unlike the ESource's 'changed' signal this one is tight to the EBookMetaBackend itself and is emitted from a dedicated thread, thus it doesn't block the main thread.

#### Parameters

user_data | user data set when the signal handler was connected. |

Flags: Run Last

Since: 3.26