[royale-docs] branch master updated: Create externs.md

[an...@apache.org]

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The following commit(s) were added to refs/heads/master by this push:
     new 20e3798  Create externs.md
20e3798 is described below

commit 20e3798ac8b945dc81a55617607baa14e678ad11
Author: Andrew Wetmore <an...@cottage14.com>
AuthorDate: Wed Aug 21 14:15:09 2019 -0300

    Create externs.md
    
    Adding an explanation of @externs for using existing JavaScript libraries.
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 user-interface/externs.md | 29 +++++++++++++++++++++++++++++
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+---
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+# 
+# http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+layout: docpage
+title: externs
+---
+
+# Externs
+
+Some Apache Royale elements, like HTML dialog, at the moment have limited cross-browser support. To get reliable display and performance in those cases, Royale makes use of existing external JavaScript libraries.
+
+Google Closure Compiler (GCC) provides a mechanism called @externs that is used in Apache Royale for declaring that a name is defined in external code and so should not be renamed.
+
+The compiler assumes that externs will exist in the environment in which the compiled JavaScript will be interpreted.
+
+So dialogPolyfill is an AS3 class with a line in the comments with @externs. That informs Apache Royale that this class is an extern for GCC. So that code already exists as a JS library and Apache Royale knows the methods a properties so you can get those in IDEs using code intelligence :)