greetd-session: use const pointers for getter functions

This will get rid of some compilation warnings along the way.

src/greetd-session.c

@@ -82,30 +82,30 @@ phog_greetd_session_new (void)
 }
 
 const gchar *
-phog_greetd_session_get_id (PhogGreetdSession *session)
+phog_greetd_session_get_id (const PhogGreetdSession *session)
 {
-    g_return_val_if_fail (PHOG_IS_GREETD_SESSION (session), NULL);
+    g_return_val_if_fail (session, NULL);
     return session->id;
 }
 
 const gchar *
-phog_greetd_session_get_name (PhogGreetdSession *session)
+phog_greetd_session_get_name (const PhogGreetdSession *session)
 {
-    g_return_val_if_fail (PHOG_IS_GREETD_SESSION (session), NULL);
+    g_return_val_if_fail (session, NULL);
     return session->name;
 }
 
 const gchar *
-phog_greetd_session_get_command (PhogGreetdSession *session)
+phog_greetd_session_get_command (const PhogGreetdSession *session)
 {
-    g_return_val_if_fail (PHOG_IS_GREETD_SESSION (session), NULL);
+    g_return_val_if_fail (session, NULL);
     return session->command;
 }
 
 const gchar *
-phog_greetd_session_get_desktop_names (PhogGreetdSession *session)
+phog_greetd_session_get_desktop_names (const PhogGreetdSession *session)
 {
-    g_return_val_if_fail (PHOG_IS_GREETD_SESSION (session), NULL);
+    g_return_val_if_fail (session, NULL);
     return session->desktop_names;
 }
 

src/greetd-session.h

@@ -20,10 +20,10 @@ G_DECLARE_FINAL_TYPE (PhogGreetdSession, phog_greetd_session, PHOG, GREETD_SESSI
 
 GObject     *phog_greetd_session_new (void);
 
-const gchar *phog_greetd_session_get_id (PhogGreetdSession *session);
-const gchar *phog_greetd_session_get_name (PhogGreetdSession *session);
-const gchar *phog_greetd_session_get_command (PhogGreetdSession *session);
-const gchar *phog_greetd_session_get_desktop_names (PhogGreetdSession *session);
+const gchar *phog_greetd_session_get_id (const PhogGreetdSession *session);
+const gchar *phog_greetd_session_get_name (const PhogGreetdSession *session);
+const gchar *phog_greetd_session_get_command (const PhogGreetdSession *session);
+const gchar *phog_greetd_session_get_desktop_names (const PhogGreetdSession *session);
 
 void         phog_greetd_session_set_id (PhogGreetdSession *session, const gchar *id);
 void         phog_greetd_session_set_name (PhogGreetdSession *session, const gchar *name);