Sort Keys

When creating the cursor initially with e_book_client_get_cursor(), a list of EContactFields must be provided to define the sort order for the newly created cursor. Only contact fields of type G_TYPE_STRING can potentially be used to define a cursor's sort order.

Backends which support cursors may refuse to create a cursor based on the fields specified as sort keys, if this happens then an E_CLIENT_ERROR_INVALID_QUERY error will be reported by e_book_client_get_cursor().

The default SQLite backend provided with Evolution Data Server only supports EContactFields that are specified as summary information to be used as sort keys. Whether a contact field is configured to be part of the summary for your addressbook can be verified with e_source_backend_summary_setup_get_summary_fields().

The order of sort keys given to e_book_client_get_cursor() defines which sort key will be the primary sort key and which keys will serve as tie breakers where the previous sort keys are exact matches. In the following example we create a typical cursor sorted with E_CONTACT_FAMILY_NAME as the primary sort key and E_CONTACT_GIVEN_NAME as a tie breaker.

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EBookClientCursor *cursor = NULL;
EContactField sort_fields[] = { E_CONTACT_FAMILY_NAME, E_CONTACT_GIVEN_NAME };
EBookCursorSortType sort_types[] = { E_BOOK_CURSOR_SORT_ASCENDING, E_BOOK_CURSOR_SORT_ASCENDING };
GError *error = NULL;

if (e_book_client_get_cursor_sync (book_client, // EBookClient
                                   NULL,        // Search Expression
                                   sort_fields, // Sort Keys
                                   sort_types,  // Ascending / Descending
                                   2,           // Number of keys
                                   &cursor,     // Return location for cursor
                                   NULL,        // GCancellable
                                   &error)) {
        // Now we have a cursor ...
}

Sort order is immutable, if you need to browse content in a different order, then you need to create a separate cursor.

Understanding cursor state

At any given time in a cursor's life cycle, a cursor's internal state will refer to a relative position in a sorted list.

There are three basic varieties of cursor states:

Cursor position and total

The “position” and “total” attributes provide feedback about a cursor's position in relation to the addressbook provided the cursor's sort order.

The total reflects that total amount of contacts in the addressbook given the cursor's Search Expression. The position is defined as the number of contacts leading up to the cursor position inclusive of the cursor position.

To help illustrate how the total and position attributes relate to a sorted list of contacts, we've provided the diagram below.

The above diagram shows two representations of a sorted contact list, using E_CONTACT_FAMILY_NAME as the primary sort key and E_CONTACT_GIVEN_NAME as a secondary sort key. On either side we can see the symbolic positions E_BOOK_CURSOR_ORIGIN_BEGIN and E_BOOK_CURSOR_ORIGIN_END.

For a given cursor state, the position value will be equal to the total number of contacts leading up to the current cursor state inclusive of the cursor state itself. In the left hand side of the above diagram the cursor points to the fourth contact and the cursor position is also 4. An exception to this is when the cursor state refers to the E_BOOK_CURSOR_ORIGIN_END position. When the cursor state refers to the end of list, the position property will have a value of (total + 1).

Another thing the above diagram illustrates is the effect that an asynchronous addressbook modification has on the cursor. The right hand side of the diagram portrays the result of deleting "Mickey Mouse" from the original list on the left.

The cursor state at this time still litteraly refers to "Mickey Mouse", however the number of contacts leading up to "Mickey Mouse" is now 3 instead of 4. As one might have guessed, any addition of a contact which is considered to be less than or equal to "Mickey Mouse" at this point, will cause the position to increase again. In this way, asynchronous addressbook modification might cause the cursor's position and total values to change, but never effect the cursor's state and it's actual position in relation to other contacts in the sorted list.

The position and total can be useful for various tasks such as determining "Forward" / "Back" button sensitivity in a browser interface, or displaying some indication of the view window's position in the full contact list.

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gint position, total;
gdouble percent;

// Fetch the position & total
position = e_book_client_cursor_get_position (cursor);
total    = e_book_client_cursor_get_total (cursor);

// The position can be total + 1 if we're at the end of the
// list, let's ignore that for this calculation.
position = CLAMP (position, 0, total);

// Calculate the percentage.
percent = position * 1.0F / (total - N_DISPLAY_CONTACTS);

// Let the user know the percentage of contacts in the list
// which are positioned before the view position (the
// percentage of the addressbook which the user has seen so far).
update_percentage_of_list_browsed (user_interface, percent);

These total and position values are guaranteed to always be coherent, they are updated synchronously upon successful completion of any of the asynchronous cursor API calls, and also updated asynchronously whenever the addressbook changes and a “refresh” signal is delivered.

Change notifications are guaranteed to only ever be delivered in the GMainContext which was the thread default main context at cursor creation time.

Search Expressions

The list of contacts associated to a given cursor can be filtered with a search expression generated by e_book_query_to_string(). Since this effects how the data will be traversed in the backend, seach expressions come with the same limitation as sort keys. Backends will report E_CLIENT_ERROR_INVALID_QUERY for contact fields which are not supported. For the default local addressbook, any fields which are configured in the summary can be used to filter cursor results.

Changing the search expression can be done at any time using e_book_client_cursor_set_sexp(). The cursor position and total values will be updated synchronously after successfully setting the search expression at which time you might refresh the current view, displaying the new filtered list of contacts at the same cursor position.

Iteration with the cursor API

The cursor API allows you to iterate through a sorted list of contacts without keeping a potentially large collection of contacts loaded in memory.

Iterating through the contact list is done with e_book_client_cursor_step(), this function allows one to move the cursor and fetch the results following the current cursor position.

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GError *error = NULL;
GSList *results = NULL;
gint n_results;

// Move the cursor forward by 10 contacts and fetch the results.
n_results = e_book_client_cursor_step_sync (cursor,
                                            E_BOOK_CURSOR_STEP_MOVE |
                                            E_BOOK_CURSOR_STEP_FETCH,
                                            E_BOOK_CURSOR_ORIGIN_CURRENT,
                                            10,
                                            &results,
                                            NULL,
                                            &error);

if (n_results < 0)
  {
    if (g_error_matches (error,
                         E_CLIENT_ERROR,
                         E_CLIENT_ERROR_OUT_OF_SYNC))
      {
        // The addressbook has been modified at the same time as
        // we asked to step. The appropriate thing to do is wait
        // for the "refresh" signal before trying again.
        handle_out_of_sync_condition (cursor);
      }
    else if (g_error_matches (error,
                              E_CLIENT_ERROR,
                              E_CLIENT_ERROR_QUERY_REFUSED))
      {
        // We asked for 10 contacts but were already positioned
        // at the end of the list (or we asked for -10 contacts
        // and were positioned at the beginning).
        handle_end_of_list_condition (cursor);
      }
    else
      {
        // Some error actually occurred
        handle_error_condition (cursor, error);
      }

    g_clear_error (&error);
  }
else if (n_results < 10)
  {
    // Cursor did not traverse as many contacts as requested.
    //
    // This is not an error but rather an indication that
    // the end of the list was reached. The next attempt to
    // move the cursor in the same direction will result in
    // an E_CLIENT_ERROR_QUERY_REFUSED error.
  }

In the above example we chose E_BOOK_CURSOR_ORIGIN_CURRENT as our EBookCursorOrigin so the above call will traverse 10 contacts following the cursor's current position. One can also choose the E_BOOK_CURSOR_ORIGIN_BEGIN or E_BOOK_CURSOR_ORIGIN_END origin to start at the beginning or end of the results at any time.

We also specified both of the flags E_BOOK_CURSOR_STEP_MOVE and E_BOOK_CURSOR_STEP_FETCH, this means we want to receive results from the addressbook and we also want to modify the current cursor state (move the cursor), these operations can however be done completely independantly of eachother, which is often what is desired for a contact browsing user interface. It is however recommended to move and fetch results in a single pass wherever that makes sense in your application.

Because the addressbook might be modified at any time by another application, it's important to handle the E_CLIENT_ERROR_OUT_OF_SYNC error. This error will occur at any time that the cursor detects an addressbook change while trying to step. Whenever an out of sync condition arises, the cursor should be left alone until the next “refresh” signal. The “refresh” signal is triggered any time that the addressbook changes and is the right place to refresh the currently loaded content, it is also guaranteed to be triggered after any E_CLIENT_ERROR_OUT_OF_SYNC error.

The diagram below illustrates some scenarios of how the cursor state is updated in calls to e_book_client_cursor_step().

Alphabetic Indexes

The cursor permits navigation of the sorted contact list in terms of alphabetic positions in the list, allowing one to jump from one letter to the next in the active alphabet.

The active alphabet itself is represented as an array of UTF-8 strings which are suitable to display a given glyph or alphabetic position in the user's active alphabet. This array of alphabetic position labels is exposed via the “alphabet” property and can always be fetched with e_book_client_cursor_get_alphabet().

As shown below, each index in the active alphabet array is a potential cursor state which refers to a position before, after or in between contacts in the sorted contact list. Most of the positions in the active alphabet array refer to alphabetic glyhps or positions, however the the 'underflow', 'inflow' and 'overflow' positions represent positions for contacts which sort outside the bounderies of the active alphabet.

The active alphabet is dynamically resolved from the system locale at startup time and whenever a system locale change notification is delivered to Evolution Data Server. If ever the system locale changes at runtime then a change notification will be delivered for the “alphabet” property, this is a good time to refresh the list of alphabetic positions available in a user interface.

Using the active alphabet, one can build a user interface which allows the user to navigate to a specific letter in the results. To set the cursor's position directly before any results starting with a specific letter, one can use e_book_client_cursor_set_alphabetic_index().

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GError *error = NULL;
gint index = currently_selected_index (user_interface);

// At this point 'index' must be a numeric value corresponding
// to one of the positions in the array returned by
// e_book_client_cursor_get_alphabet().
if (!e_book_client_cursor_set_alphabetic_index_sync (cursor,
                                                     index,
                                                     NULL,
                                                     &error))
  {
    if (g_error_matches (error,
                         E_CLIENT_ERROR,
                         E_CLIENT_ERROR_OUT_OF_SYNC))
      {
        // The system locale has changed at the same time
        // as we were setting an alphabetic cursor position.
        handle_out_of_sync_condition (cursor);
      }
    else
      {
        // Some error actually occurred
        handle_error_condition (cursor, error);
      }

    g_clear_error (&error);
  }

After setting the alphabetic index successfully, you can go ahead and use e_book_client_cursor_step() to load some contacts at the beginning of the given letter.

This API can result in an E_CLIENT_ERROR_OUT_OF_SYNC error. This error will occur at any time that the cursor tries to set the alphabetic index whilst the addressbook is changing its active locale setting. In the case of a dynamic locale change, a change notification will be delivered for the “alphabet” property at which point the application should reload anything related to the alphabet (a “refresh” signal will also be delivered at this point).

While moving through the cursor results using e_book_client_cursor_step(), it can be useful to know which alphabetic position a given contact sorts under. This can be useful if your user interface displays an alphabetic label indicating where the first contact in your view is positioned in the alphabet.

One can determine the appropriate index for a given EContact by calling e_book_client_cursor_get_contact_alphabetic_index() after refreshing the currently displayed contacts in a view.

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EContact *contact;
const gchar * const *alphabet;
gint index;

// Fetch the first displayed EContact in the view
contact = first_contact_in_the_list (user_interface);

// Calculate the position in the alphabet for this contact
index = e_book_client_cursor_get_contact_alphabetic_index (cursor, contact);

// Fetch the alphabet labels
alphabet = e_book_client_cursor_get_alphabet (cursor, &n_labels,
                                              NULL, NULL, NULL);

// Update label in user interface
set_alphabetic_position_feedback_text (user_interface, alphabet[index]);

e_book_client_cursor_ref_client ()

struct _EBookClient *
e_book_client_cursor_ref_client (EBookClientCursor *cursor);

Returns the “client” associated with cursor .

The returned EBookClient is referenced because the cursor does not keep a strong reference to the client.

Unreference the EBookClient with g_object_unref() when finished with it.

Since: 3.12

e_book_client_cursor_get_total ()

gint
e_book_client_cursor_get_total (EBookClientCursor *cursor);

Fetches the total number of contacts in the addressbook which match cursor 's query

Since: 3.12

e_book_client_cursor_get_position ()

gint
e_book_client_cursor_get_position (EBookClientCursor *cursor);

Fetches the number of contacts leading up to the current cursor position, inclusive of the current cursor position.

The position value can be anywhere from 0 to the total number of contacts plus one. A value of 0 indicates that the cursor is positioned before the contact list in the symbolic E_BOOK_CURSOR_ORIGIN_BEGIN state. If the position is greater than the total, as returned by e_book_client_cursor_get_total(), then the cursor is positioned after the last contact in the symbolic E_BOOK_CURSOR_ORIGIN_END position.

Since: 3.12

e_book_client_cursor_set_sexp ()

void
e_book_client_cursor_set_sexp (EBookClientCursor *cursor,
                               const gchar *sexp,
                               GCancellable *cancellable,
                               GAsyncReadyCallback callback,
                               gpointer user_data);

Sets the Search Expression for the cursor.

See: e_book_client_cursor_set_sexp_sync().

This asynchronous call is completed with a call to e_book_client_cursor_set_sexp_finish() from the specified callback .

Since: 3.12

e_book_client_cursor_set_sexp_finish ()

gboolean
e_book_client_cursor_set_sexp_finish (EBookClientCursor *cursor,
                                      GAsyncResult *result,
                                      GError **error);

Completes an asynchronous call initiated by e_book_client_cursor_set_sexp(), reporting whether the new search expression was accepted.

Since: 3.12

e_book_client_cursor_set_sexp_sync ()

gboolean
e_book_client_cursor_set_sexp_sync (EBookClientCursor *cursor,
                                    const gchar *sexp,
                                    GCancellable *cancellable,
                                    GError **error);

Sets the Search Expression for the cursor.

A side effect of setting the search expression is that the

properties will be updated.

If this method is called from the same thread context in which the cursor was created, then the updates to the “position” and “total” properties are guaranteed to be delivered synchronously upon successful completion of setting the search expression. Otherwise, notifications will be delivered asynchronously in the cursor's original thread context.

If the backend does not support the given search expression, an E_CLIENT_ERROR_INVALID_QUERY error will be set.

Since: 3.12

e_book_client_cursor_step ()

void
e_book_client_cursor_step (EBookClientCursor *cursor,
                           EBookCursorStepFlags flags,
                           EBookCursorOrigin origin,
                           gint count,
                           GCancellable *cancellable,
                           GAsyncReadyCallback callback,
                           gpointer user_data);

a maximum of count and fetch the results traversed.

See: e_book_client_cursor_step_sync().

This asynchronous call is completed with a call to e_book_client_cursor_step_finish() from the specified callback .

Since: 3.12

e_book_client_cursor_step_finish ()

gint
e_book_client_cursor_step_finish (EBookClientCursor *cursor,
                                  GAsyncResult *result,
                                  GSList **out_contacts,
                                  GError **error);

Completes an asynchronous call initiated by e_book_client_cursor_step(), fetching any contacts which might have been returned by the call.

Since: 3.12

e_book_client_cursor_step_sync ()

gint
e_book_client_cursor_step_sync (EBookClientCursor *cursor,
                                EBookCursorStepFlags flags,
                                EBookCursorOrigin origin,
                                gint count,
                                GSList **out_contacts,
                                GCancellable *cancellable,
                                GError **error);

a maximum of count and fetch the results traversed.

If count is negative, then the cursor will move backwards.

If cursor reaches the beginning or end of the query results, then the returned list might not contain the amount of desired contacts, or might return no results if the cursor currently points to the last contact. Reaching the end of the list is not considered an error condition. Attempts to step beyond the end of the list after having reached the end of the list will however trigger an E_CLIENT_ERROR_QUERY_REFUSED error.

If E_BOOK_CURSOR_STEP_FETCH is specified in flags, a pointer to a NULL GSList pointer should be provided for the results parameter.

If E_BOOK_CURSOR_STEP_MOVE is specified in flags, then the cursor's state will be modified and the position property will be updated as a result.

If this method is called from the same thread context in which the cursor was created, then the updates to the “position” property are guaranteed to be delivered synchronously upon successful completion of moving the cursor. Otherwise, notifications will be delivered asynchronously in the cursor's original thread context.

If this method completes with an E_CLIENT_ERROR_OUT_OF_SYNC error, it is an indication that the addressbook has been modified and it would be unsafe to move the cursor at this time. Any E_CLIENT_ERROR_OUT_OF_SYNC error is guaranteed to be followed by an “refresh” signal at which point any content should be reloaded.

Since: 3.12

e_book_client_cursor_set_alphabetic_index ()

void
e_book_client_cursor_set_alphabetic_index
                               (EBookClientCursor *cursor,
                                gint index,
                                GCancellable *cancellable,
                                GAsyncReadyCallback callback,
                                gpointer user_data);

Sets the current cursor position to point to an Alphabetic Index.

See: e_book_client_cursor_set_alphabetic_index_sync().

This asynchronous call is completed with a call to e_book_client_cursor_set_alphabetic_index_finish() from the specified callback .

Since: 3.12

e_book_client_cursor_set_alphabetic_index_finish ()

gboolean
e_book_client_cursor_set_alphabetic_index_finish
                               (EBookClientCursor *cursor,
                                GAsyncResult *result,
                                GError **error);

Completes an asynchronous call initiated by e_book_client_cursor_set_alphabetic_index().

Since: 3.12

e_book_client_cursor_set_alphabetic_index_sync ()

gboolean
e_book_client_cursor_set_alphabetic_index_sync
                               (EBookClientCursor *cursor,
                                gint index,
                                GCancellable *cancellable,
                                GError **error);

Sets the cursor to point to an Alphabetic Index.

After setting the alphabetic index, for example the index for letter 'E', then further calls to e_book_client_cursor_step() will return results starting with the letter 'E' (or results starting with the last result in 'D' when navigating through cursor results in reverse).

The passed index must be a valid index into the alphabet parameters returned by e_book_client_cursor_get_alphabet().

If this method is called from the same thread context in which the cursor was created, then the updates to the “position” property are guaranteed to be delivered synchronously upon successful completion of moving the cursor. Otherwise, notifications will be delivered asynchronously in the cursor's original thread context.

If this method completes with an E_CLIENT_ERROR_OUT_OF_SYNC error, it is an indication that the addressbook has been set into a new locale and it would be unsafe to set the alphabetic index at this time. If you receive an out of sync error from this method, then you should wait until a “alphabet” property change notification is delivered and then proceed to load the new alphabet before trying to set any alphabetic index.

Since: 3.12

e_book_client_cursor_get_contact_alphabetic_index ()

gint
e_book_client_cursor_get_contact_alphabetic_index
                               (EBookClientCursor *cursor,
                                EContact *contact);

Checks which alphabetic index contact would be sorted into according to cursor .

So long as the active “alphabet” does not change, the returned index will be a valid position in the array of labels returned by e_book_client_cursor_get_alphabet().

If the index returned by this function is needed for any extended period of time, it should be recalculated whenever the “alphabet” changes.

Since: 3.12

struct EBookClientCursor

struct EBookClientCursor;

Contains only private data.

Since: 3.12

struct EBookClientCursorClass

struct EBookClientCursorClass {
	/* Signals */
	void		(* refresh) (EBookClientCursor *cursor);
};

The cursor class structure.

Since: 3.12

The “alphabet” property

  “alphabet”                 GStrv

The currently active alphabet.

The value is a NULL terminated array of strings, each string is suitable to display a specific letter in the active alphabet.

Indexes from this array can later be used with e_book_client_cursor_set_alphabetic_index().

This property will automatically change if the active locale of the addressbook server changes.

Property change notifications are guaranteed to be delivered in the GMainContext which was the thread default context at cursor creation time.

Flags: Read

Since: 3.12

The “client” property

  “client”                   EBookClient *

The EBookClient which this cursor was created for

Flags: Read / Write / Construct Only

Since: 3.12

The “connection” property

  “connection”               GDBusConnection *

The GDBusConnection to the addressbook server.

Flags: Write / Construct Only

Since: 3.12

The “context” property

  “context”                  GMainContext *

The GMainContext in which the EBookClient created this cursor.

Flags: Write / Construct Only

Since: 3.12

The “direct-cursor” property

  “direct-cursor”            EDataBookCursor *

The direct handle to the EDataBookCursor for direct read access mode.

Flags: Write / Construct Only

Since: 3.12

The “object-path” property

  “object-path”              gchar *

The D-Bus object path to find the server side cursor object.

Flags: Write / Construct Only

Default value: NULL

Since: 3.12

The “position” property

  “position”                 gint

The current cursor position in the cursor's result list.

More specifically, the cursor position is defined as the number of contacts leading up to the current cursor position, inclusive of the current cursor position.

If the position value is 0, then the cursor is positioned before the contact list in the symbolic E_BOOK_CURSOR_ORIGIN_BEGIN position. If the position value is greater than “total”, this indicates that the cursor is positioned after the contact list in the symbolic E_BOOK_CURSOR_ORIGIN_END position.

Property change notifications are guaranteed to be delivered in the GMainContext which was the thread default context at cursor creation time.

Flags: Read

Allowed values: >= 0

Default value: 0

Since: 3.12

The “sort-fields” property

  “sort-fields”              GStrv

The EContactField names to sort this cursor with

Flags: Write / Construct Only

Since: 3.12

The “total” property

  “total”                    gint

The total number of contacts which satisfy the cursor's query.

Property change notifications are guaranteed to be delivered in the GMainContext which was the thread default context at cursor creation time.

Flags: Read

Allowed values: >= 0

Default value: 0

Since: 3.12

The “refresh” signal

void
user_function (EBookClientCursor *cursor,
               gpointer           user_data)

Indicates that the addressbook has been modified and that any content currently being displayed from the current cursor position should be reloaded.

This signal is guaranteed to be delivered in the GMainContext which was the thread default context at cursor creation time.

Flags: Run Last

Since: 3.12