Change Base.isObject() to also check for instances of plain Base objects, and rename it to Base.isPlainObject().

lib/bootstrap.js

@@ -315,9 +315,15 @@ var Base = new function() { // Bootstrap scope
 				return create(ctor.prototype);
 			},
 
-			isObject: function(obj) {
-				return obj !== null && typeof obj === 'object'
-					&& Object.getPrototypeOf(obj) === Object.prototype;
+			/**
+			 * Returns true if obj is a plain JavaScript object literal, or a 
+			 * plain Base object, as produced by Base.merge().
+			 */
+			isPlainObject: function(obj) {
+				var proto = obj !== null && typeof obj === 'object'
+					&& Object.getPrototypeOf(obj);
+				return proto && (proto === Object.prototype
+						|| proto === Base.prototype);
 			},
 
 			check: function(obj) {

src/browser/DomElement.js

@@ -38,7 +38,7 @@ var DomElement = new function() {
 				continue;
 			}
 			// Do we have attributes?
-			if (Base.isObject(nodes[i]))
+			if (Base.isPlainObject(nodes[i]))
 				DomElement.set(el, nodes[i++]);
 			// Do we have children?
 			if (Array.isArray(nodes[i]))

src/core/Base.js

@@ -200,7 +200,7 @@ this.Base = Base.inject(/** @lends Base# */{
 				res = [];
 				for (var i = 0, l = obj.length; i < l; i++)
 					res[i] = Base.serialize(obj[i], true);
-			} else if (Base.isObject(obj)) {
+			} else if (Base.isPlainObject(obj)) {
 				res = {};
 				for (var i in obj)
 					if (obj.hasOwnProperty(i))
@@ -235,7 +235,7 @@ this.Base = Base.inject(/** @lends Base# */{
 					res = Base.create(type);
 					res.initialize.apply(res, args);
 				}
-			} else if (Base.isObject(obj)) {
+			} else if (Base.isPlainObject(obj)) {
 				res = {};
 				for (var key in obj)
 					res[key] = Base.deserialize(obj[key]);

src/core/PaperScript.js

@@ -146,7 +146,7 @@ var PaperScript = this.PaperScript = new function() {
 				if (Array.isArray(value)) {
 					for (var i = 0, l = value.length; i < l; i++)
 						walkAst(value[i]);
-				} else if (Base.isObject(value)) {
+				} else if (Base.isPlainObject(value)) {
 					walkAst(value);
 				}
 			}

src/item/Item.js

@@ -123,7 +123,7 @@ var Item = this.Item = Base.extend(Callback, /** @lends Item# */{
 	// one object literal describing all the properties to be set on the created
 	// instance.
 	_setProperties: function(props) {
-		if (Base.isObject(props))
+		if (Base.isPlainObject(props))
 			return this.set(props);
 	},