libgimpwidgets: add a "value" property to GimpIntComboBox…

… and have gimp_prop_int_combo_box_new() bind to "value" instead of
"active".

The "active" property is defined by GtkComboBox and is the index of the
combo box, not its values, whereas with gimp_prop_int_combo_box_new(),
we want to bind an int property to the combobox value. Therefore the
commit 0828a371c2 was only properly working when we were creating a
combo box with values starting at 0 and incremented by 1.

By adding a "value" property to GimpIntComboBox, I allow binding any
property to the int value rather than the index.

See also !265 where the issue was raised as it affected our HEIF
plug-in.

libgimpwidgets/gimpintcombobox.c

@@ -48,7 +48,8 @@ enum
   PROP_0,
   PROP_ELLIPSIZE,
   PROP_LABEL,
-  PROP_LAYOUT
+  PROP_LAYOUT,
+  PROP_VALUE
 };
 
 
@@ -148,6 +149,21 @@ gimp_int_combo_box_class_init (GimpIntComboBoxClass *klass)
                                                       GIMP_TYPE_INT_COMBO_BOX_LAYOUT,
                                                       GIMP_INT_COMBO_BOX_LAYOUT_ABBREVIATED,
                                                       GIMP_PARAM_READWRITE));
+
+  /**
+   * GimpIntComboBox:value:
+   *
+   * The active value (different from the "active" property of
+   * GtkComboBox which is the active index).
+   *
+   * Since: 3.0
+   */
+  g_object_class_install_property (object_class, PROP_VALUE,
+                                   g_param_spec_int ("value",
+                                                     "Value",
+                                                     "Value of active item",
+                                                     G_MININT, G_MAXINT, 0,
+                                                     GIMP_PARAM_READWRITE));
 }
 
 static void
@@ -217,6 +233,10 @@ gimp_int_combo_box_set_property (GObject      *object,
       gimp_int_combo_box_set_layout (GIMP_INT_COMBO_BOX (object),
                                      g_value_get_enum (value));
       break;
+    case PROP_VALUE:
+      gimp_int_combo_box_set_active (GIMP_INT_COMBO_BOX (object),
+                                     g_value_get_int (value));
+      break;
 
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
@@ -243,6 +263,14 @@ gimp_int_combo_box_get_property (GObject    *object,
     case PROP_LAYOUT:
       g_value_set_enum (value, priv->layout);
       break;
+    case PROP_VALUE:
+      {
+        gint v;
+
+        gimp_int_combo_box_get_active (GIMP_INT_COMBO_BOX (object), &v);
+        g_value_set_int (value, v);
+      }
+    break;
 
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);

libgimpwidgets/gimppropwidgets.c

@@ -411,7 +411,7 @@ gimp_prop_int_combo_box_new (GObject      *config,
     gimp_help_set_help_data (combo_box, blurb, NULL);
 
   g_object_bind_property (config, property_name,
-                          combo_box, "active",
+                          combo_box, "value",
                           G_BINDING_BIDIRECTIONAL | G_BINDING_SYNC_CREATE);
 
   return combo_box;