monitor: Add API to list supported color modes

Available modes are 'default', which is always added, and BT.2100,
which is added if the BT.2020 color space, and the PQ transfer function,
is supported by the output.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4192>

src/backends/meta-monitor.c

@@ -70,6 +70,8 @@ typedef struct _MetaMonitorPrivate
   char *display_name;
 
   gboolean is_for_lease;
+
+  GList *color_modes;
 } MetaMonitorPrivate;
 
 G_DEFINE_TYPE_WITH_PRIVATE (MetaMonitor, meta_monitor, G_TYPE_OBJECT)
@@ -203,6 +205,27 @@ meta_monitor_generate_spec (MetaMonitor *monitor)
   priv->spec = monitor_spec;
 }
 
+static void
+meta_monitor_init_supported_color_modes (MetaMonitor *monitor)
+{
+  MetaMonitorPrivate *priv = meta_monitor_get_instance_private (monitor);
+  const MetaOutputInfo *output_info =
+    meta_monitor_get_main_output_info (monitor);
+
+  priv->color_modes =
+    g_list_append (NULL, GINT_TO_POINTER (META_COLOR_MODE_DEFAULT));
+
+  if ((output_info->supported_color_spaces &
+       (1 << META_OUTPUT_COLORSPACE_BT2020)) &&
+      (output_info->supported_hdr_eotfs &
+       (1 << META_OUTPUT_HDR_METADATA_EOTF_PQ)))
+    {
+      priv->color_modes =
+        g_list_append (priv->color_modes,
+                       GINT_TO_POINTER (META_COLOR_MODE_BT2100));
+    }
+}
+
 static const double known_diagonals[] = {
     12.1,
     13.3,
@@ -588,6 +611,7 @@ meta_monitor_finalize (GObject *object)
   MetaMonitor *monitor = META_MONITOR (object);
   MetaMonitorPrivate *priv = meta_monitor_get_instance_private (monitor);
 
+  g_list_free (priv->color_modes);
   g_hash_table_destroy (priv->mode_ids);
   g_list_free_full (priv->modes, (GDestroyNotify) meta_monitor_mode_free);
   meta_monitor_spec_free (priv->spec);
@@ -837,6 +861,7 @@ meta_monitor_normal_new (MetaMonitorManager *monitor_manager,
   meta_output_set_monitor (output, monitor);
 
   meta_monitor_generate_spec (monitor);
+  meta_monitor_init_supported_color_modes (monitor);
 
   meta_monitor_normal_generate_modes (monitor_normal);
 
@@ -2363,6 +2388,14 @@ meta_monitor_set_hdr_metadata (MetaMonitor            *monitor,
   return TRUE;
 }
 
+GList *
+meta_monitor_get_supported_color_modes (MetaMonitor *monitor)
+{
+  MetaMonitorPrivate *priv = meta_monitor_get_instance_private (monitor);
+
+  return priv->color_modes;
+}
+
 gboolean
 meta_parse_monitor_mode (const char *string,
                          int        *out_width,

src/backends/meta-monitor.h

@@ -355,4 +355,6 @@ void meta_monitor_set_for_lease (MetaMonitor *monitor,
 META_EXPORT_TEST
 gboolean meta_monitor_is_for_lease (MetaMonitor *monitor);
 
+GList * meta_monitor_get_supported_color_modes (MetaMonitor *monitor);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC (MetaMonitorSpec, meta_monitor_spec_free)

src/backends/meta-output.h

@@ -40,6 +40,12 @@ typedef enum
   META_OUTPUT_HDR_METADATA_EOTF_HLG,
 } MetaOutputHdrMetadataEOTF;
 
+typedef enum _MetaColorMode
+{
+  META_COLOR_MODE_DEFAULT = 0,
+  META_COLOR_MODE_BT2100 = 1,
+} MetaColorMode;
+
 typedef enum _MetaOutputRGBRange
 {
   META_OUTPUT_RGB_RANGE_UNKNOWN = 0,