libgimp, libgimpwidgets: support of GimpRGB properties in…

… GimpProcedureDialog.

Technically I added:
- New gimp_prop_color_select_new() property widget to create a
  GimpColorButton for a given GimpRGB property.
- gimp_procedure_dialog_get_widget() now supports a GimpRGB property and
  will create a GimpColorArea by default.
- When the default doesn't suit you, a new function
  gimp_procedure_dialog_get_color_widget() allows to create either a
  GimpColorArea or a GimpColorButton (editable = TRUE), as well as
  choose the area type (small or large checks, as well as flat area,
  i.e. no alpha support).

libgimpwidgets/gimppropwidgets.c

@@ -3750,6 +3750,53 @@ gimp_prop_color_area_notify (GObject    *config,
                                      config);
 }
 
+/**
+ * gimp_prop_color_select_new:
+ * @config:        Object to which property is attached.
+ * @property_name: Name of RGB property.
+ * @width:         Width of the colorpreview in pixels.
+ * @height:        Height of the colorpreview in pixels.
+ * @type:          How transparency is represented.
+ *
+ * Creates a #GimpColorButton to set and display the value of an RGB
+ * property.
+ *
+ * Returns: (transfer full): A new #GimpColorButton widget.
+ *
+ * Since: 3.0
+ */
+GtkWidget *
+gimp_prop_color_select_new (GObject           *config,
+                            const gchar       *property_name,
+                            gint               width,
+                            gint               height,
+                            GimpColorAreaType  type)
+{
+  GParamSpec *param_spec;
+  GtkWidget  *button;
+  GimpRGB    *value;
+
+  param_spec = check_param_spec_w (config, property_name,
+                                   GIMP_TYPE_PARAM_RGB, G_STRFUNC);
+  if (! param_spec)
+    return NULL;
+
+  g_object_get (config,
+                property_name, &value,
+                NULL);
+
+  button = gimp_color_button_new (g_param_spec_get_nick (param_spec),
+                                  width, height, value, type);
+
+  g_free (value);
+
+  g_object_bind_property (config, property_name,
+                          button, "color",
+                          G_BINDING_BIDIRECTIONAL);
+  gtk_widget_show (button);
+
+  return button;
+}
 
 /********************/
 /*  unit combo box  */

libgimpwidgets/gimppropwidgets.h

@@ -213,6 +213,12 @@ GtkWidget     * gimp_prop_color_area_new          (GObject       *config,
                                                    gint           height,
                                                    GimpColorAreaType  type);
 
+GtkWidget     * gimp_prop_color_select_new        (GObject       *config,
+                                                   const gchar   *property_name,
+                                                   gint           width,
+                                                   gint           height,
+                                                   GimpColorAreaType  type);
+
 /*  GimpParamUnit  */
 
 GtkWidget     * gimp_prop_unit_combo_box_new      (GObject       *config,