clutter/color-state: Add transfer function

Another enum, defining SRGB gamma transfer function, and the PQ transfer
function. As with color spaces, add a 'default' that for now is treated
as if it was sRGB.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3433>

clutter/clutter/clutter-actor.c

@@ -17838,7 +17838,8 @@ create_default_color_state (ClutterActor *self)
 {
   ClutterColorState *color_state;
 
-  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_DEFAULT);
+  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_DEFAULT,
+                                         CLUTTER_TRANSFER_FUNCTION_DEFAULT);
 
   return color_state;
 }

clutter/clutter/clutter-color-state.c

@@ -56,6 +56,7 @@ enum
   PROP_0,
 
   PROP_COLORSPACE,
+  PROP_TRANSFER_FUNCTION,
 
   N_PROPS
 };
@@ -72,6 +73,7 @@ struct _ClutterColorState
 struct _ClutterColorStatePrivate
 {
   ClutterColorspace colorspace;
+  ClutterTransferFunction transfer_function;
 };
 
 G_DEFINE_TYPE_WITH_PRIVATE (ClutterColorState,
@@ -91,6 +93,19 @@ clutter_color_state_get_colorspace (ClutterColorState *color_state)
   return priv->colorspace;
 }
 
+ClutterTransferFunction
+clutter_color_state_get_transfer_function (ClutterColorState *color_state)
+{
+  ClutterColorStatePrivate *priv;
+
+  g_return_val_if_fail (CLUTTER_IS_COLOR_STATE (color_state),
+                        CLUTTER_TRANSFER_FUNCTION_DEFAULT);
+
+  priv = clutter_color_state_get_instance_private (color_state);
+
+  return priv->transfer_function;
+}
+
 static void
 clutter_color_state_set_property (GObject      *object,
                                   guint         prop_id,
@@ -108,6 +123,10 @@ clutter_color_state_set_property (GObject      *object,
       priv->colorspace = g_value_get_enum (value);
       break;
 
+    case PROP_TRANSFER_FUNCTION:
+      priv->transfer_function = g_value_get_enum (value);
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -129,6 +148,11 @@ clutter_color_state_get_property (GObject    *object,
                         clutter_color_state_get_colorspace (color_state));
       break;
 
+    case PROP_TRANSFER_FUNCTION:
+      g_value_set_enum (value,
+                        clutter_color_state_get_transfer_function (color_state));
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -157,6 +181,19 @@ clutter_color_state_class_init (ClutterColorStateClass *klass)
                        G_PARAM_STATIC_STRINGS |
                        G_PARAM_CONSTRUCT_ONLY);
 
+  /**
+   * ClutterColorState:transfer-function:
+   *
+   * Transfer function.
+   */
+  obj_props[PROP_TRANSFER_FUNCTION] =
+    g_param_spec_enum ("transfer-function", NULL, NULL,
+                       CLUTTER_TYPE_TRANSFER_FUNCTION,
+                       CLUTTER_TRANSFER_FUNCTION_SRGB,
+                       G_PARAM_READWRITE |
+                       G_PARAM_STATIC_STRINGS |
+                       G_PARAM_CONSTRUCT_ONLY);
+
   g_object_class_install_properties (gobject_class, N_PROPS, obj_props);
 }
 
@@ -172,10 +209,12 @@ clutter_color_state_init (ClutterColorState *color_state)
  *
  * Return value: A new ClutterColorState object.
  **/
-ClutterColorState*
+ClutterColorState *
-clutter_color_state_new (ClutterColorspace colorspace)
+clutter_color_state_new (ClutterColorspace       colorspace,
+                         ClutterTransferFunction transfer_function)
 {
   return g_object_new (CLUTTER_TYPE_COLOR_STATE,
                        "colorspace", colorspace,
+                       "transfer-function", transfer_function,
                        NULL);
 }

clutter/clutter/clutter-color-state.h

@@ -39,9 +39,13 @@ G_DECLARE_FINAL_TYPE (ClutterColorState, clutter_color_state,
                       GObject)
 
 CLUTTER_EXPORT
-ClutterColorState * clutter_color_state_new (ClutterColorspace colorspace);
+ClutterColorState * clutter_color_state_new (ClutterColorspace       colorspace,
+                                             ClutterTransferFunction transfer_function);
 
 CLUTTER_EXPORT
 ClutterColorspace clutter_color_state_get_colorspace (ClutterColorState *color_state);
 
+CLUTTER_EXPORT
+ClutterTransferFunction clutter_color_state_get_transfer_function (ClutterColorState *color_state);
+
 G_END_DECLS

clutter/clutter/clutter-enums.h

@@ -1015,6 +1015,23 @@ typedef enum
   CLUTTER_COLORSPACE_BT2020,
 } ClutterColorspace;
 
+/**
+ * ClutterTransferFunction:
+ * @CLUTTER_TRANSFER_FUNCTION_DEFAULT: Unknown transfer function
+ * @CLUTTER_TRANSFER_FUNCTION_SRGB: The sRGB gamma transfer function
+ * @CLUTTER_TRANSFER_FUNCTION_PQ: Perceptual quantizer (PQ)
+ * @CLUTTER_TRANSFER_FUNCTION_LINEAR: Linear transfer function
+ *
+ * Colorspace information.
+ */
+typedef enum
+{
+  CLUTTER_TRANSFER_FUNCTION_DEFAULT,
+  CLUTTER_TRANSFER_FUNCTION_SRGB,
+  CLUTTER_TRANSFER_FUNCTION_PQ,
+  CLUTTER_TRANSFER_FUNCTION_LINEAR,
+} ClutterTransferFunction;
+
 /**
  * ClutterStepMode:
  * @CLUTTER_STEP_MODE_START: The change in the value of a

src/tests/clutter/conform/actor-color-state.c

@@ -49,8 +49,10 @@ actor_color_state_passed (void)
   ClutterActor *actor;
   ClutterColorState *color_state;
   ClutterColorspace colorspace;
+  ClutterTransferFunction transfer_function;
 
-  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_BT2020);
+  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_BT2020,
+                                         CLUTTER_TRANSFER_FUNCTION_PQ);
 
   if (!color_state)
     g_critical ("Failed to create color state with provided colorspace.");
@@ -67,8 +69,10 @@ actor_color_state_passed (void)
 
   color_state = clutter_actor_get_color_state (actor);
   colorspace = clutter_color_state_get_colorspace (color_state);
+  transfer_function = clutter_color_state_get_transfer_function (color_state);
 
   g_assert_cmpuint (colorspace, ==, CLUTTER_COLORSPACE_BT2020);
+  g_assert_cmpuint (transfer_function, ==, CLUTTER_TRANSFER_FUNCTION_PQ);
 
   clutter_actor_destroy (actor);
 }
@@ -80,10 +84,12 @@ actor_change_color_state (void)
   ClutterActor *actor;
   ClutterColorState *color_state;
   ClutterColorspace colorspace;
+  ClutterTransferFunction transfer_function;
 
   actor = clutter_actor_new ();
 
-  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_BT2020);
+  color_state = clutter_color_state_new (CLUTTER_COLORSPACE_BT2020,
+                                         CLUTTER_TRANSFER_FUNCTION_PQ);
 
   if (!color_state)
     g_critical ("Failed to create color state with provided colorspace.");
@@ -92,8 +98,10 @@ actor_change_color_state (void)
 
   color_state = clutter_actor_get_color_state (actor);
   colorspace = clutter_color_state_get_colorspace (color_state);
+  transfer_function = clutter_color_state_get_transfer_function (color_state);
 
   g_assert_cmpuint (colorspace, ==, CLUTTER_COLORSPACE_BT2020);
+  g_assert_cmpuint (transfer_function, ==, CLUTTER_TRANSFER_FUNCTION_PQ);
 
   clutter_actor_destroy (actor);
 }
@@ -106,6 +114,7 @@ actor_change_color_state_to_null (void)
   ClutterActor *actor;
   ClutterColorState *color_state;
   ClutterColorspace colorspace;
+  ClutterTransferFunction transfer_function;
 
   actor = clutter_actor_new ();
 
@@ -113,8 +122,10 @@ actor_change_color_state_to_null (void)
 
   color_state = clutter_actor_get_color_state (actor);
   colorspace = clutter_color_state_get_colorspace (color_state);
+  transfer_function = clutter_color_state_get_transfer_function (color_state);
 
   g_assert_cmpuint (colorspace, ==, CLUTTER_COLORSPACE_DEFAULT);
+  g_assert_cmpuint (transfer_function, ==, CLUTTER_TRANSFER_FUNCTION_DEFAULT);
 
   clutter_actor_destroy (actor);
 }