WebKit的JavaScript对象扩展

必威体育网址 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。

必威体育网址 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. 必威体育网址 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>

[参考资料]

1. webkit的js对象扩展(一)——binding方式创建自定义对象(单实例)

2. android 上 webkit js 本地扩展之全局本地对象实现步骤

WebKit的JavaScript对象扩展》上有13条评论

    1. eric

      public:

      HelloObject* helloObject() const;

      HelloObject* optionalHelloObject() const { return m_helloObject.get(); }

      private:

      mutable RefPtr m_helloObject;

      请问这个加在Domwindows.h的哪里呢,前后要不要加上
      #if ENABLE(HelloOjbect)
      #endif
      呢?

      回复
    1. alex

      eric :
      public:
      HelloObject* helloObject() const;
      HelloObject* optionalHelloObject() const { return m_helloObject.get(); }
      private:
      mutable RefPtr m_helloObject;
      请问这个加在Domwindows.h的哪里呢,前后要不要加上
      #if ENABLE(HelloOjbect)
      #endif
      呢?

      只要是放在类定义里面,都可以,不需要加上ENABLE(HelloOjbect)

      回复
    1. callsoso

      4>C:WebKitWebKit-r114801WebKitBuildDebugobjWebCoreDerivedSourcesJSDOMWindow.cpp(179) : fatal error C1083: Cannot open include file: ‘JSHelloObject.h’: No such file or directory

      怎么解决呢?

      回复
    1. 匿名

      5>C:WebKit-r114801WebKitBuildDebugobjWebCoreDerivedSourcesJSDOMWindow.cpp(1300) : error C2665: ‘WebCore::toJS’ : none of the 137 overloads could convert all the argument types

      回复
    1. 匿名

      froyo/out/target/product/obj/STATIC_LIBRARIES/libwebcore_intermediates/WebCore/bindings/V8DOMWindow.cpp:148: undefined reference to `WebCore::toV8(WebCore::HelloObject*)’
      collect2: ld returned 1 exit status
      请问这个是什么问题呢, 头文件我看都是有的;

      回复
    1. miyuehu

      DOMWindow.h:446: error: ‘m_iSTB’ was not declared in this scope
      DOMWindow.h: At global scope:
      DOMWindow.h:531: error: non-member ‘m_iSTB’ cannot be declared ‘mutable’
      DOMWindow.h: At global scope:
      DOMWindow.h:531: error: non-member ‘m_iSTB’ cannot be declared ‘mutable’
      make: *** [out/libwebcore_intermediates/Source/WebCore/dom/CompositionEvent.o] Error 1
      make: *** Waiting for unfinished jobs….
      make: *** [out/Source/WebCore/dom/DeviceMotionController.o] Error 1
      In file included from external/webkit/Source/WebCore/bindings/generic/BindingSecurityBase.cpp:34:
      DOMWindow.h: In member function ‘WebCore::ISTB* WebCore::DOMWindow::optionalISTB() const’:
      DOMWindow.h:446: error: ‘m_iSTB’ was not declared in this scope
      DOMWindow.h: At global scope:
      DOMWindow.h:531: error: non-member ‘m_iSTB’ cannot be declared ‘mutable’
      make: *** [out/libwebcore_intermediates/Source/WebCore/bindings/generic/BindingSecurityBase.o] Error 1
      In file included from external/webkit/Source/WebCore/dom/Document.cpp:50:
      DOMWindow.h: In member function ‘WebCore::ISTB* WebCore::DOMWindow::optionalISTB() const’:
      page/DOMWindow.h:446: error: ‘m_iSTB’ was not declared in this scope
      page/DOMWindow.h: At global scope:
      WebCore/page/DOMWindow.h:531: error: non-member ‘m_iSTB’ cannot be declared ‘mutable’
      make: *** [out/libwebcore_intermediates/Source/WebCore/dom/Document.o] Error 1

      回复
    1. 匿名

      请教下高人,webkit里面可以扩展hml标签么? 看到有人扩展通过修改渲染引擎扩展了html标签,是怎么实现的?

      回复

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