logind: rework display counting when detecting whether the system is docked

Previously, we'd just count connected displays, and if there was 2 or
more we assumed a "docked" state.

With this change we now:

- Only count external displays, ignore internal ones (which we detect by
  checking the connector name against a whitelist of known external plug
  types)

- We ignore connectors which are explicitly disabled

- We then compare the count with >= 1 rather than >= 2 as before

This new logic has the benefit that systems that disconnect the internal
display when the lid is closed are better supported. Also, explicitly
disabled ports do not confuse the algorithm anymore.

This new algorithm has been suggested here:

http://lists.freedesktop.org/archives/intel-gfx/2015-June/068821.html

This also makes two functions static, that are not used outside of their
.c files.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index e6f9ec7845..8ebcd3f5ca 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -258,7 +258,7 @@ static int property_get_docked(
         assert(reply);
         assert(m);
 
-        return sd_bus_message_append(reply, "b", manager_is_docked_or_multiple_displays(m));
+        return sd_bus_message_append(reply, "b", manager_is_docked_or_external_displays(m));
 }
 
 static int method_get_session(sd_bus_message *message, void *userdata, sd_bus_error *error) {