[gjs] object: Support external construction of gjs-defined GObjects

[Florian Müllner <fmuellner src gnome org>]

commit a7296c180771de23040d630e3f63e65eed16dfe5
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Dec 1 13:30:54 2015 +0100

    object: Support external construction of gjs-defined GObjects
    
    Currently GObject subclasses defined in JS must be instantiated from JS
    constructors, as that's where the association of the newly created native
    object with the JS context and wrapper object happens. Allow this code to
    run as well for GObjects that are instantiated externally via g_object_new()
    (e.g. by GtkBuilder, gom, json-glib, ...) by creating the wrapper object
    from the ->constructor() vfunc in that case.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=681254

 gi/object.cpp |  103 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 93 insertions(+), 10 deletions(-)
---
diff --git a/gi/object.cpp b/gi/object.cpp
index ca31883..af79482 100644
--- a/gi/object.cpp
+++ b/gi/object.cpp
@@ -2416,6 +2416,94 @@ gjs_object_get_gproperty (GObject    *object,
 }
 
 static void
+jsobj_set_gproperty (JSContext    *context,
+                     JSObject     *object,
+                     const GValue *value,
+                     GParamSpec   *pspec)
+{
+    jsval jsvalue;
+    gchar *underscore_name;
+
+    if (!gjs_value_from_g_value(context, &jsvalue, value))
+        return;
+
+    underscore_name = hyphen_to_underscore((gchar *)pspec->name);
+    if (!JS_SetProperty(context, object, underscore_name, &jsvalue))
+        gjs_log_exception(context);
+    g_free (underscore_name);
+}
+
+static GObject *
+gjs_object_constructor (GType                  type,
+                        guint                  n_construct_properties,
+                        GObjectConstructParam *construct_properties)
+{
+    GObject *gobj = NULL;
+
+    if (object_init_list) {
+        GType parent_type = g_type_parent(type);
+
+        /* The object is being constructed from JS:
+         * Simply chain up to the first non-gjs constructor
+         */
+        while (G_OBJECT_CLASS(g_type_class_peek(parent_type))->constructor == gjs_object_constructor)
+            parent_type = g_type_parent(parent_type);
+
+        gobj = G_OBJECT_CLASS(g_type_class_peek(parent_type))->constructor(type, n_construct_properties, 
construct_properties);
+    } else {
+        GjsContext *gjs_context;
+        JSContext *context;
+        JSObject *object, *constructor;
+        ObjectInstance *priv;
+
+        /* The object is being constructed from native code (e.g. GtkBuilder):
+         * Construct the JS object from the constructor, then use the GObject
+         * that was associated in gjs_object_custom_init()
+         */
+        gjs_context = gjs_context_get_current();
+        context = (JSContext*) gjs_context_get_native_context(gjs_context);
+
+        JS_BeginRequest(context);
+
+        constructor = gjs_lookup_object_constructor_from_info(context, NULL, type);
+        if (!constructor)
+          goto out;
+
+        if (n_construct_properties) {
+            JSObject *args;
+            jsval argv;
+            guint i;
+
+            args = JS_NewObject(context, NULL, NULL, NULL);
+
+            for (i = 0; i < n_construct_properties; i++)
+                jsobj_set_gproperty(context, args,
+                                    construct_properties[i].value,
+                                    construct_properties[i].pspec);
+
+            argv = OBJECT_TO_JSVAL(args);
+            object = JS_New(context, constructor, 1, &argv);
+        } else {
+            object = JS_New(context, constructor, 0, NULL);
+        }
+
+        if (!object)
+          goto out;
+
+        priv = (ObjectInstance*) JS_GetPrivate(object);
+        /* We only hold a toggle ref at this point, add back a ref that the
+         * native code can own.
+         */
+        gobj = G_OBJECT(g_object_ref(priv->gobj));
+
+out:
+        JS_EndRequest(context);
+    }
+
+    return gobj;
+}
+
+static void
 gjs_object_set_gproperty (GObject      *object,
                           guint         property_id,
                           const GValue *value,
@@ -2424,21 +2512,12 @@ gjs_object_set_gproperty (GObject      *object,
     GjsContext *gjs_context;
     JSContext *context;
     JSObject *js_obj;
-    jsval jsvalue;
-    gchar *underscore_name;
 
     gjs_context = gjs_context_get_current();
     context = (JSContext*) gjs_context_get_native_context(gjs_context);
 
     js_obj = peek_js_obj(object);
-
-    if (!gjs_value_from_g_value(context, &jsvalue, value))
-        return;
-
-    underscore_name = hyphen_to_underscore((gchar *)pspec->name);
-    if (!JS_SetProperty(context, js_obj, underscore_name, &jsvalue))
-        gjs_log_exception(context);
-    g_free (underscore_name);
+    jsobj_set_gproperty(context, js_obj, value, pspec);
 }
 
 static JSBool
@@ -2527,6 +2606,7 @@ gjs_object_class_init(GObjectClass *klass,
 
     gtype = G_OBJECT_CLASS_TYPE (klass);
 
+    klass->constructor = gjs_object_constructor;
     klass->set_property = gjs_object_set_gproperty;
     klass->get_property = gjs_object_get_gproperty;
 
@@ -2554,6 +2634,9 @@ gjs_object_custom_init(GTypeInstance *instance,
     ObjectInstance *priv;
     jsval v, r;
 
+    if (!object_init_list)
+      return;
+
     object = (JSObject*) object_init_list->data;
     priv = (ObjectInstance*) JS_GetPrivate(object);