Greeter Interface: LightDM Reference Manual

## Greeter Interface Greeter Interface — Make a connection to the LightDM daemon and authenticate users |

## Functions

void | (*show_message) ()
void | (*show_prompt) ()
void | (*authentication_complete) ()
void | (*autologin_timer_expired) ()
void | (*idle) ()
void | (*reset) ()
LightDMGreeter * | lightdm_greeter_new ()
void | lightdm_greeter_set_resettable ()
void | lightdm_greeter_connect_to_daemon ()
gboolean | lightdm_greeter_connect_to_daemon_finish ()
gboolean | lightdm_greeter_connect_to_daemon_sync ()
void | lightdm_greeter_ensure_shared_data_dir ()
gchar * | lightdm_greeter_ensure_shared_data_dir_finish ()
gchar * | lightdm_greeter_ensure_shared_data_dir_sync ()
const gchar * | lightdm_greeter_get_default_session_hint ()
const gchar * | lightdm_greeter_get_hint ()
gboolean | lightdm_greeter_get_lock_hint ()
gboolean | lightdm_greeter_get_has_guest_account_hint ()
gboolean | lightdm_greeter_get_hide_users_hint ()
gboolean | lightdm_greeter_get_show_manual_login_hint ()
gboolean | lightdm_greeter_get_show_remote_login_hint ()
const gchar * | lightdm_greeter_get_select_user_hint ()
gboolean | lightdm_greeter_get_select_guest_hint ()
const gchar * | lightdm_greeter_get_autologin_user_hint ()
gboolean | lightdm_greeter_get_autologin_guest_hint ()
gint | lightdm_greeter_get_autologin_timeout_hint ()
void | lightdm_greeter_set_language ()
void | lightdm_greeter_cancel_autologin ()
void | lightdm_greeter_authenticate ()
void | lightdm_greeter_authenticate_as_guest ()
void | lightdm_greeter_authenticate_autologin ()
void | lightdm_greeter_authenticate_remote ()
void | lightdm_greeter_respond ()
void | lightdm_greeter_cancel_authentication ()
gboolean | lightdm_greeter_get_in_authentication ()
gboolean | lightdm_greeter_get_is_authenticated ()
const gchar * | lightdm_greeter_get_authentication_user ()
void | lightdm_greeter_start_session ()
gboolean | lightdm_greeter_start_session_finish ()
gboolean | lightdm_greeter_start_session_sync ()

## Types and Values

enum | LightDMMessageType
enum | LightDMPromptType

## Includes

    #include <lightdm.h>

## Description

LightDMGreeter is an object that manages the connection to the LightDM server and provides common greeter functionality.

Example 1. Example Greeter

    int main ()
    {
        GMainLoop *main_loop;
        LightDMGreeter *greeter
        main_loop = g_main_loop_new ();
        greeter = lightdm_greeter_new ();
        g_object_connect (greeter, "show-prompt", G_CALLBACK (show_prompt_cb), NULL);
        g_object_connect (greeter, "authentication-complete", G_CALLBACK (authentication_complete_cb), NULL);
        // Connect to LightDM daemon
        if (!lightdm_greeter_connect_to_daemon_sync (greeter, NULL))
            return EXIT_FAILURE;
        // Start authentication
        lightdm_greeter_authenticate (greeter, NULL);
        g_main_loop_run (main_loop);
        return EXIT_SUCCESS;
    }
    static void show_prompt_cb (LightDMGreeter *greeter, const char *text, LightDMPromptType type)
    {
        // Show the user the message and prompt for some response
        gchar *secret = prompt_user (text, type);
        // Give the result to the user
        lightdm_greeter_respond (greeter, response);
    }
    static void authentication_complete_cb (LightDMGreeter *greeter)
    {
        // Start the session
        if (!lightdm_greeter_get_is_authenticated (greeter) ||
            !lightdm_greeter_start_session_sync (greeter, NULL))
        {
            // Failed authentication, try again
            lightdm_greeter_authenticate (greeter, NULL);
        }
    }

## Functions

### show_message ()

    void
    (*show_message) (LightDMGreeter *greeter,
                     const gchar *text,
                     LightDMMessageType type);

### show_prompt ()

    void
    (*show_prompt) (LightDMGreeter *greeter,
                    const gchar *text,
                    LightDMPromptType type);

### authentication_complete ()

    void
    (*authentication_complete) (LightDMGreeter *greeter);

### autologin_timer_expired ()

    void
    (*autologin_timer_expired) (LightDMGreeter *greeter);

### idle ()

    void
    (*idle) (LightDMGreeter *greeter);

### reset ()

    void
    (*reset) (LightDMGreeter *greeter);

### lightdm_greeter_new ()

    LightDMGreeter *
    lightdm_greeter_new (void);

Create a new greeter.

#### Returns

the new LightDMGreeter

### lightdm_greeter_set_resettable ()

    void
    lightdm_greeter_set_resettable (LightDMGreeter *greeter,
                                    gboolean resettable);

Set whether the greeter will be reset instead of killed after the user logs in. This must be called before lightdm_greeter_connect is called.

#### Parameters

greeter | A LightDMGreeter |
resettable | Whether the greeter wants to be reset instead of killed after the user logs in |

### lightdm_greeter_connect_to_daemon ()

    void
    lightdm_greeter_connect_to_daemon (LightDMGreeter *greeter,
                                       GCancellable *cancellable,
                                       GAsyncReadyCallback callback,
                                       gpointer user_data);

Asynchronously connects the greeter to the display manager.

When the operation is finished, `callback` will be invoked. You can then call `lightdm_greeter_connect_to_daemon_finish()` to get the result of the operation.

See `lightdm_greeter_connect_to_daemon_sync()` for the synchronous version.

#### Parameters

greeter | The greeter to connect |
cancellable | A GCancellable or `NULL`. | [allow-none]
callback | A GAsyncReadyCallback to call when completed or `NULL`. | [allow-none]
user_data | data to pass to the `callback` or `NULL`. | [allow-none]

### lightdm_greeter_connect_to_daemon_finish ()

    gboolean
    lightdm_greeter_connect_to_daemon_finish
                                   (LightDMGreeter *greeter,
                                    GAsyncResult *result,
                                    GError **error);

Finishes an operation started with `lightdm_greeter_connect_to_daemon()`.

#### Parameters

greeter | The greeter the the request was done with |
result | A GAsyncResult. |
error | return location for a GError, or `NULL` |

#### Returns

TRUE if successfully connected

### lightdm_greeter_connect_to_daemon_sync ()

    gboolean
    lightdm_greeter_connect_to_daemon_sync
                                   (LightDMGreeter *greeter,
                                    GError **error);

Connects the greeter to the display manager. Will block until connected.

#### Parameters

greeter | The greeter to connect |
error | return location for a GError, or `NULL` |

#### Returns

TRUE if successfully connected

### lightdm_greeter_ensure_shared_data_dir ()

    void
    lightdm_greeter_ensure_shared_data_dir
                                   (LightDMGreeter *greeter,
                                    const gchar *username,
                                    GCancellable *cancellable,
                                    GAsyncReadyCallback callback,
                                    gpointer user_data);

Ensure that a shared data dir for the given user is available. Both the greeter user and `username` will have write access to that folder. The intention is that larger pieces of shared data would be stored there (files that the greeter creates but wants to give to a user -- like camera photos -- or files that the user creates but wants the greeter to see -- like contact avatars).

LightDM will automatically create these if the user actually logs in, so greeters only need to call this method if they want to store something in the directory themselves.

#### Parameters

greeter | A LightDMGreeter |
username | A username |
cancellable | A GCancellable or `NULL`. | [allow-none]
callback | A GAsyncReadyCallback to call when completed or `NULL`. | [allow-none]
user_data | data to pass to the `callback` or `NULL`. | [allow-none]

### lightdm_greeter_ensure_shared_data_dir_finish ()

    gchar *
    lightdm_greeter_ensure_shared_data_dir_finish
                                   (LightDMGreeter *greeter,
                                    GAsyncResult *result);

Function to call from lightdm_greeter_ensure_shared_data_dir callback.

#### Parameters

greeter | A LightDMGreeter |
result | A GAsyncResult. |

#### Returns

The path to the shared directory, free with g_free.

### lightdm_greeter_ensure_shared_data_dir_sync ()

    gchar *
    lightdm_greeter_ensure_shared_data_dir_sync
                                   (LightDMGreeter *greeter,
                                    const gchar *username);

Ensure that a shared data dir for the given user is available. Both the greeter user and `username` will have write access to that folder. The intention is that larger pieces of shared data would be stored there (files that the greeter creates but wants to give to a user -- like camera photos -- or files that the user creates but wants the greeter to see -- like contact avatars).

LightDM will automatically create these if the user actually logs in, so greeters only need to call this method if they want to store something in the directory themselves.

#### Parameters

greeter | A LightDMGreeter |
username | A username |

#### Returns

The path to the shared directory, free with g_free.

### lightdm_greeter_get_default_session_hint ()

    const gchar *
    lightdm_greeter_get_default_session_hint
                                   (LightDMGreeter *greeter);

Get the default session to use.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

The session name

### lightdm_greeter_get_hint ()

    const gchar *
    lightdm_greeter_get_hint (LightDMGreeter *greeter,
                              const gchar *name);

Get a hint.

#### Parameters

greeter | A LightDMGreeter |
name | The hint name to query. |

#### Returns

The value for this hint or NULL if not set.

[nullable]

### lightdm_greeter_get_lock_hint ()

    gboolean
    lightdm_greeter_get_lock_hint (LightDMGreeter *greeter);

Check if the greeter is acting as a lock screen.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the greeter was triggered by locking the seat.

### lightdm_greeter_get_has_guest_account_hint ()

    gboolean
    lightdm_greeter_get_has_guest_account_hint
                                   (LightDMGreeter *greeter);

Check if guest sessions are supported.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if guest sessions are supported.

### lightdm_greeter_get_hide_users_hint ()

    gboolean
    lightdm_greeter_get_hide_users_hint (LightDMGreeter *greeter);

Check if user accounts should be shown. If this is TRUE then the list of accounts should be taken from LightDMUserList and displayed in the greeter for the user to choose from. Note that this list can be empty and it is recommended you show a method for the user to enter a username manually.

If this option is shown the greeter should only allow these users to be chosen for login unless the manual login hint is set.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the available users should not be shown.

### lightdm_greeter_get_show_manual_login_hint ()

    gboolean
    lightdm_greeter_get_show_manual_login_hint
                                   (LightDMGreeter *greeter);

Check if a manual login option should be shown. If set the GUI should provide a way for a username to be entered manually. Without this hint a greeter which is showing a user list can limit logins to only those users.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if a manual login option should be shown.

### lightdm_greeter_get_show_remote_login_hint ()

    gboolean
    lightdm_greeter_get_show_remote_login_hint
                                   (LightDMGreeter *greeter);

Check if a remote login option should be shown. If set the GUI should provide a way for a user to log into a remote desktop server.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if a remote login option should be shown.

### lightdm_greeter_get_select_user_hint ()

    const gchar *
    lightdm_greeter_get_select_user_hint (LightDMGreeter *greeter);

Get the user to select by default.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

A username or `NULL` if no particular user should be selected.

[nullable]

### lightdm_greeter_get_select_guest_hint ()

    gboolean
    lightdm_greeter_get_select_guest_hint (LightDMGreeter *greeter);

Check if the guest account should be selected by default.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the guest account should be selected by default.

### lightdm_greeter_get_autologin_user_hint ()

    const gchar *
    lightdm_greeter_get_autologin_user_hint
                                   (LightDMGreeter *greeter);

Get the user account to automatically log into when the timer expires.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

The user account to automatically log into or `NULL` if none configured.

[nullable]

### lightdm_greeter_get_autologin_guest_hint ()

    gboolean
    lightdm_greeter_get_autologin_guest_hint
                                   (LightDMGreeter *greeter);

Check if the guest account should be automatically logged into when the timer expires.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the guest account should be automatically logged into.

### lightdm_greeter_get_autologin_timeout_hint ()

    gint
    lightdm_greeter_get_autologin_timeout_hint
                                   (LightDMGreeter *greeter);

Get the number of seconds to wait before automaitcally logging in.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

The number of seconds to wait before automatically logging in or 0 for no timeout.

### lightdm_greeter_set_language ()

    void
    lightdm_greeter_set_language (LightDMGreeter *greeter,
                                  const gchar *language);

Set the language for the currently authenticated user.

#### Parameters

greeter | A LightDMGreeter |
language | The language to use for this user in the form of a locale specification (e.g. "de_DE.UTF-8"). |

### lightdm_greeter_cancel_autologin ()

    void
    lightdm_greeter_cancel_autologin (LightDMGreeter *greeter);

Cancel the automatic login.

#### Parameters

greeter | A LightDMGreeter |

### lightdm_greeter_authenticate ()

    void
    lightdm_greeter_authenticate (LightDMGreeter *greeter,
                                  const gchar *username);

Starts the authentication procedure for a user.

#### Parameters

greeter | A LightDMGreeter |
username | A username or NULL to prompt for a username. | [allow-none]

### lightdm_greeter_authenticate_as_guest ()

    void
    lightdm_greeter_authenticate_as_guest (LightDMGreeter *greeter);

Starts the authentication procedure for the guest user.

#### Parameters

greeter | A LightDMGreeter |

### lightdm_greeter_authenticate_autologin ()

    void
    lightdm_greeter_authenticate_autologin
                                   (LightDMGreeter *greeter);

Starts the authentication procedure for the automatic login user.

#### Parameters

greeter | A LightDMGreeter |

### lightdm_greeter_authenticate_remote ()

    void
    lightdm_greeter_authenticate_remote (LightDMGreeter *greeter,
                                         const gchar *session,
                                         const gchar *username);

Start authentication for a remote session type.

#### Parameters

greeter | A LightDMGreeter |
session | The name of a remote session |
username | A username of NULL to prompt for a username. | [allow-none]

### lightdm_greeter_respond ()

    void
    lightdm_greeter_respond (LightDMGreeter *greeter,
                             const gchar *response);

Provide response to a prompt. May be one in a series.

#### Parameters

greeter | A LightDMGreeter |
response | Response to a prompt |

### lightdm_greeter_cancel_authentication ()

    void
    lightdm_greeter_cancel_authentication (LightDMGreeter *greeter);

Cancel the current user authentication.

#### Parameters

greeter | A LightDMGreeter |

### lightdm_greeter_get_in_authentication ()

    gboolean
    lightdm_greeter_get_in_authentication (LightDMGreeter *greeter);

Checks if the greeter is in the process of authenticating.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the greeter is authenticating a user.

### lightdm_greeter_get_is_authenticated ()

    gboolean
    lightdm_greeter_get_is_authenticated (LightDMGreeter *greeter);

Checks if the greeter has successfully authenticated.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

TRUE if the greeter is authenticated for login.

### lightdm_greeter_get_authentication_user ()

    const gchar *
    lightdm_greeter_get_authentication_user
                                   (LightDMGreeter *greeter);

Get the user that is being authenticated.

#### Parameters

greeter | A LightDMGreeter |

#### Returns

The username of the authentication user being authenticated or NULL if no authentication in progress.

[nullable]

### lightdm_greeter_start_session ()

    void
    lightdm_greeter_start_session (LightDMGreeter *greeter,
                                   const gchar *session,
                                   GCancellable *cancellable,
                                   GAsyncReadyCallback callback,
                                   gpointer user_data);

Asynchronously start a session for the authenticated user.

When the operation is finished, `callback` will be invoked. You can then call `lightdm_greeter_start_session_finish()` to get the result of the operation.

See `lightdm_greeter_start_session_sync()` for the synchronous version.

#### Parameters

greeter | A LightDMGreeter |
session | The session to log into or NULL to use the default. | [allow-none]
cancellable | A GCancellable or `NULL`. | [allow-none]
callback | A GAsyncReadyCallback to call when completed or `NULL`. | [allow-none]
user_data | data to pass to the `callback` or `NULL`. | [allow-none]

### lightdm_greeter_start_session_finish ()

    gboolean
    lightdm_greeter_start_session_finish (LightDMGreeter *greeter,
                                          GAsyncResult *result,
                                          GError **error);

Start a session for the authenticated user.

#### Parameters

greeter | A LightDMGreeter |
result | A GAsyncResult. |
error | return location for a GError, or `NULL` |

#### Returns

TRUE if the session was started.

### lightdm_greeter_start_session_sync ()

    gboolean
    lightdm_greeter_start_session_sync (LightDMGreeter *greeter,
                                        const gchar *session,
                                        GError **error);

Start a session for the authenticated user.

#### Parameters

greeter | A LightDMGreeter |
session | The session to log into or NULL to use the default. | [allow-none]
error | return location for a GError, or `NULL` |

#### Returns

TRUE if the session was started.

## Types and Values

### enum LightDMMessageType

#### Members

LIGHTDM_MESSAGE_TYPE_INFO | Informational message. |
LIGHTDM_MESSAGE_TYPE_ERROR | Error message. |

### enum LightDMPromptType

#### Members

LIGHTDM_PROMPT_TYPE_QUESTION | Prompt is a question. The information can be shown as it is entered. |
LIGHTDM_PROMPT_TYPE_SECRET | Prompt is for secret information. The entered information should be obscured so it can't be publically visible. |