WebKit的JavaScript对象扩展
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本文的内容主要参考网上收集的资料，不过在Android 4.0 webkit上做扩展时，碰到一些问题，觉得有必要记录下来。
所谓扩展JavaScript对象，就是增加一个JS对象，但它并没有定义在标准的JS对象集合中。如果网页中包含了扩展的JS对象，使用普通的浏览器就会报JS错误。
下面以添加HelloObject对象为例说明具体步骤，该对象具有description属性：
1. 添加HelloObject.h, HelloObject.cpp, HelloObject.idl文件，简单起见，将这三个文件放到Source/WebCore/page目录下。
#ifndef HelloObject_h
#define HelloObject_h#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>#include "PlatformString.h"
namespace WebCore {
class HelloObject : public RefCounted<HelloObject> {
public:
static PassRefPtr<HelloObject> create() { return adoptRef(new HelloObject()); }String description() const;
private:
HelloObject();
};} // namespace WebCore
#endif // HelloObject_h
HelloObject.h
#include "config.h"
#include "HelloObject.h"namespace WebCore {
HelloObject::HelloObject()
{
}String HelloObject::description() const
{
return "Hello Object";
}} // namespace WebCore
HelloObject.cpp
module window {
interface [OmitConstructor] HelloObject {
readonly attribute DOMString description;
};}
HelloObject.idl
2. 修改Source/WebCore/page/下的DOMWindow.h文件，添加如下声明：
class HelloObject;
…
public:
HelloObject* helloObject() const;
HelloObject* optionalHelloObject() const { return m_helloObject.get(); }
private:
mutable RefPtr<HelloObject> m_helloObject;
3. 修改Source/WebCore/page/下的DOMWindow.cpp文件，添加接口实现:
HelloObject* DOMWindow::helloObject() const
{
if (!m_helloObject)
m_helloObject = HelloObject::create();
return m_helloObject.get();
}
在DOMWindow::clear()函数中添加一行语句：
m_helloObject = 0;
4. 修改DOMWindow.idl文件，添加:
attribute [Replaceable] HelloObject helloObject;
5. 接下来需要修改编译系统，让android编译系统编译新增的文件：
首先修改Source/WebCore/Android.mk，增加page/HelloObject.cpp到LOCAL_SRC_FILES变量，其次需要修改Source/WebCore/Android.derived.v8bindings.mk，增加$(intermediates)/bindings/V8HelloObject.h到GEN变量。（注：这个是必须的，否则就不会根据HelloObject.idl生成V8HelloObject.h文件，在编译时会出错，这也是折腾了半天得出的成果）
至此，工作基本上完成，待webkit重新编译后，可以用如下的网页进行验证：
<html>
<body>
<script type="text/javascript">
document.write("<p> This is from HelloObject: ");
document.write(helloObject.description + "</p>");
</script>
</body>
</html>
#ifndef HelloObject_h
#define HelloObject_h
#include <wtf/PassRefPtr.h>
#include <wtf/RefCounted.h>
#include "PlatformString.h"
namespace WebCore {
class HelloObject : public RefCounted<HelloObject> {
public:
static PassRefPtr<HelloObject> create() { return adoptRef(new HelloObject()); }
String description() const;
private:
HelloObject();
};
} // namespace WebCore
#endif // HelloObject_h
#include "config.h"
#include "HelloObject.h"
namespace WebCore {
HelloObject::HelloObject()
{
}
String HelloObject::description() const
{
return "Hello Object";
}
} // namespace WebCore
module window {
interface [OmitConstructor] HelloObject {
readonly attribute DOMString description;
};
}
class HelloObject;
…
public:
HelloObject* helloObject() const;
HelloObject* optionalHelloObject() const { return m_helloObject.get(); }
private:
mutable RefPtr<HelloObject> m_helloObject;
HelloObject* DOMWindow::helloObject() const
{
if (!m_helloObject)
m_helloObject = HelloObject::create();
return m_helloObject.get();
}
m_helloObject = 0;
attribute [Replaceable] HelloObject helloObject;
<html>
<body>
<script type="text/javascript">
document.write("<p> This is from HelloObject: ");
document.write(helloObject.description + "</p>");
</script>
</body>
</html>
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