DisplayConfig: Add an optional 'is_underscanning' monitor property

Add a 'is_underscanning' entry to the properties map, if the monitor
supports underscanning. The client should assume a monitor does not
support underscanning if no property was added.

https://bugzilla.gnome.org/show_bug.cgi?id=777732

src/backends/meta-monitor-manager.c

@@ -1209,6 +1209,7 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
       MetaMonitorMode *current_mode;
       MetaMonitorMode *preferred_mode;
       GVariantBuilder modes_builder;
+      GVariantBuilder properties_builder;
       GList *k;
 
       current_mode = meta_monitor_get_current_mode (monitor);
@@ -1240,13 +1241,23 @@ meta_monitor_manager_handle_get_current_state (MetaDBusDisplayConfig *skeleton,
                                  flags);
         }
 
+      g_variant_builder_init (&properties_builder, G_VARIANT_TYPE ("a{sv}"));
+      if (meta_monitor_supports_underscanning (monitor))
+        {
+          gboolean is_underscanning = meta_monitor_is_underscanning (monitor);
+
+          g_variant_builder_add (&properties_builder, "{sv}",
+                                 "is_underscanning",
+                                 g_variant_new_boolean (is_underscanning));
+        }
+
       g_variant_builder_add (&monitors_builder, MONITOR_FORMAT,
                              monitor_spec->connector,
                              monitor_spec->vendor,
                              monitor_spec->product,
                              monitor_spec->serial,
                              &modes_builder,
-                             NULL);
+                             &properties_builder);
     }
 
   for (l = manager->logical_monitors; l; l = l->next)

src/backends/meta-monitor.c

@@ -186,6 +186,16 @@ meta_monitor_is_primary (MetaMonitor *monitor)
   return output->is_primary;
 }
 
+gboolean
+meta_monitor_supports_underscanning (MetaMonitor *monitor)
+{
+  MetaOutput *output;
+
+  output = meta_monitor_get_main_output (monitor);
+
+  return output->supports_underscanning;
+}
+
 gboolean
 meta_monitor_is_underscanning (MetaMonitor *monitor)
 {

src/backends/meta-monitor.h

@@ -91,6 +91,8 @@ MetaOutput * meta_monitor_get_main_output (MetaMonitor *monitor);
 
 gboolean meta_monitor_is_primary (MetaMonitor *monitor);
 
+gboolean meta_monitor_supports_underscanning (MetaMonitor *monitor);
+
 gboolean meta_monitor_is_underscanning (MetaMonitor *monitor);
 
 gboolean meta_monitor_is_laptop_panel (MetaMonitor *monitor);

src/org.gnome.Mutter.DisplayConfig.xml

@@ -313,6 +313,9 @@
 	* a{sv} properties: optional properties, including:
 	    - "width_mm" (i): physical width of monitor in millimeters
 	    - "height_mm" (i): physical height of monitor in millimeters
+	    - "is_underscanning" (b): whether underscanning is enabled
+				      (absence of this means underscanning
+				      not being supported)
 
         Possible mode flags:
 	  1 : preferred mode
@@ -337,7 +340,6 @@
 
 	@max_screen_size represents the maximum size the screen may have, or 0x0 if no
 	such limit is known.
-
     -->
     <method name="GetCurrentState">
       <arg name="serial" direction="out" type="u" />