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-button.c b/src/login/logind-button.c
index 8079d0b5aa..210b889c4f 100644
--- a/src/login/logind-button.c
+++ b/src/login/logind-button.c
@@ -100,7 +100,7 @@ static void button_lid_switch_handle_action(Manager *manager, bool is_edge) {
         assert(manager);
 
         /* If we are docked, handle the lid switch differently */
-        if (manager_is_docked_or_multiple_displays(manager))
+        if (manager_is_docked_or_external_displays(manager))
                 handle_action = manager->handle_lid_switch_docked;
         else
                 handle_action = manager->handle_lid_switch;