From 94bce5a00f73139dfb74db1511bcc34912f76314 Mon Sep 17 00:00:00 2001
From: Cosimo Cecchi <cosimoc@gnome.org>
Date: Wed, 1 Jul 2015 17:42:46 -0700
Subject: [PATCH] monitor-manager: add a property to discover if underscan is
 supported

So that clients such as the control center can decide to hide an
underscanning checkbutton when the output does not support it.

Support in the KMS / native backend to come later...
---
 src/backends/meta-monitor-manager-private.h   |  1 +
 src/backends/meta-monitor-manager.c           |  2 +
 .../x11/meta-monitor-manager-xrandr.c         | 46 +++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/src/backends/meta-monitor-manager-private.h b/src/backends/meta-monitor-manager-private.h
index d21888ed6..e73aec976 100644
--- a/src/backends/meta-monitor-manager-private.h
+++ b/src/backends/meta-monitor-manager-private.h
@@ -145,6 +145,7 @@ struct _MetaOutput
   gboolean is_primary;
   gboolean is_presentation;
   gboolean is_underscanning;
+  gboolean supports_underscanning;
 
   gpointer driver_private;
   GDestroyNotify driver_notify;
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 21ab21583..4fe971720 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -647,6 +647,8 @@ meta_monitor_manager_handle_get_resources (MetaDBusDisplayConfig *skeleton,
                              g_variant_new_string (get_connector_type_name (output->connector_type)));
       g_variant_builder_add (&properties, "{sv}", "underscanning",
                              g_variant_new_boolean (output->is_underscanning));
+      g_variant_builder_add (&properties, "{sv}", "supports-underscanning",
+                             g_variant_new_boolean (output->supports_underscanning));
 
       edid_file = manager_class->get_edid_file (manager, output);
       if (edid_file)
diff --git a/src/backends/x11/meta-monitor-manager-xrandr.c b/src/backends/x11/meta-monitor-manager-xrandr.c
index 13010b022..86d24b511 100644
--- a/src/backends/x11/meta-monitor-manager-xrandr.c
+++ b/src/backends/x11/meta-monitor-manager-xrandr.c
@@ -246,6 +246,51 @@ output_get_underscanning_xrandr (MetaMonitorManagerXrandr *manager_xrandr,
   return (strcmp (str, "on") == 0);
 }
 
+static gboolean
+output_get_supports_underscanning_xrandr (MetaMonitorManagerXrandr *manager_xrandr,
+                                          MetaOutput               *output)
+{
+  Atom atom, actual_type;
+  int actual_format, i;
+  unsigned long nitems, bytes_after;
+  g_autofree unsigned char *buffer = NULL;
+  XRRPropertyInfo *property_info;
+  Atom *values;
+  gboolean supports_underscanning = FALSE;
+
+  atom = XInternAtom (manager_xrandr->xdisplay, "underscan", False);
+  XRRGetOutputProperty (manager_xrandr->xdisplay,
+                        (XID)output->winsys_id,
+                        atom,
+                        0, G_MAXLONG, False, False, XA_ATOM,
+                        &actual_type, &actual_format,
+                        &nitems, &bytes_after, &buffer);
+
+  if (actual_type != XA_ATOM || actual_format != 32 || nitems < 1)
+    return FALSE;
+
+  property_info = XRRQueryOutputProperty (manager_xrandr->xdisplay,
+                                          (XID) output->winsys_id,
+                                          atom);
+  values = (Atom *) property_info->values;
+
+  for (i = 0; i < property_info->num_values; i++)
+    {
+      /* The output supports underscanning if "on" is a valid value
+       * for the underscan property.
+       */
+      char *name = XGetAtomName (manager_xrandr->xdisplay, values[i]);
+      if (strcmp (name, "on") == 0)
+        supports_underscanning = TRUE;
+
+      XFree (name);
+    }
+
+  XFree (property_info);
+
+  return supports_underscanning;
+}
+
 static int
 normalize_backlight (MetaOutput *output,
                      int         hw_value)
@@ -804,6 +849,7 @@ meta_monitor_manager_xrandr_read_current (MetaMonitorManager *manager)
 	  meta_output->is_primary = ((XID)meta_output->winsys_id == primary_output);
 	  meta_output->is_presentation = output_get_presentation_xrandr (manager_xrandr, meta_output);
 	  meta_output->is_underscanning = output_get_underscanning_xrandr (manager_xrandr, meta_output);
+          meta_output->supports_underscanning = output_get_supports_underscanning_xrandr (manager_xrandr, meta_output);
 	  output_get_backlight_limits_xrandr (manager_xrandr, meta_output);
 
 	  if (!(meta_output->backlight_min == 0 && meta_output->backlight_max == 0))