Hook DHTML Commands

Hook DHTML Commands

浏览器在执行很多命令之前都会允许容器来替换默认的处理。在执行一些默认的命令之前，系统会查询用户对IDocHostUIHandler的实现对象的IOleCommandTarget接口，调用默认(NULL)或者CGID_DocHostCommandHandler命令组的命令。如果容器的对应命令处理返回S_OK。那么默认的处理就不会被调用。

下面列出一些可以在容器中自定义的操作：（这些常量的定义位于docobj.h中）

• OLECMDID_PRINT，默认命令组
  
• OLECMDID_SHOWSCRIPTERROR, CGID_DocHostCommandHandler命令组
  
• OLECMDID_FOCUSVIEWCONTROLSQUERY, CGID_DocHostCommandHandler命令组
  
• OLECMDID_SHOWPAGEACTIONMENU, CGID_DocHostCommandHandler命令组

MFC提供了一些比较容易扩展的类和宏，这样可以很容易地在扩展容器来实现新的接口。这里使用CCmdTarget类提供的GetInterfaceHook虚函数来进行扩展。

//This sample is based on MFC sample DHTMLExplore.<br />//a button is inserted into explore.htm:<br />//<BUTTON class=hotElement id=print accesskey="P"><U>P</U>rint</BUTTON><br />//to invoke the print command<br /><br />#include <afxole.h><br />#include <mshtmcid.h><br />/////////////////////////////////////////////////////////////////////////////<br />// CDHtmlExploreDlg dialog<br />class CDHtmlExploreDlg;<br />//customize the CBrowserControlSite class to implement IOleCommandTarget.<br />//the IDocHostUIHandler interface is implemented in CBrowserControlSite, <br />//an internal control site class declared within afxdhtml.h<br />class CDHtmlExploreControlSite: public CBrowserControlSite<br /> , public IOleCommandTarget<br /> CDHtmlExploreControlSite(<br /> COleControlContainer* pCtrlCont,<br /> CDHtmlExploreDlg *pHandler) <br /> : CBrowserControlSite(pCtrlCont,pHandler){};<br />protected:<br />// Implementation<br /> LPUNKNOWN GetInterfaceHook(const void *iid);<br />// IUnknown methods<br />...//omitted<br />// IOleCommandTargetmethods <br />...//omitted<br /> friend class CDHtmlExploreDlg;<br />};<br />class CDHtmlExploreDlg : public CDHtmlDialog<br />{<br />......<br /> virtual BOOL CreateControlSite(COleControlContainer* pContainer, <br />COleControlSite** ppSite, UINT /* nID */, REFCLSID /* clsid */);<br /> HRESULT OnPrint(IHTMLElement *phtmlElement);<br />// IOleCommandTargetmethods <br />...//omitted<br />......<br /> afx_msg void OnContextPrint();<br />......<br /> friend class CDHtmlExploreControlSite ;<br />};<br />LPUNKNOWN CDHtmlExploreControlSite::GetInterfaceHook(const void *iid)<br />{<br /> if (IsEqualIID((REFIID) (*(IID*)iid), IID_IOleCommandTarget))<br /> return (IOleCommandTarget*) this;<br /> //important ,base class implementation <br /> //customized GetInterfaceHook to support IDocHostUIHandler<br /> return CBrowserControlSite::GetInterfaceHook(iid); <br />}<br />// IUnknown methods<br />STDMETHODIMP CDHtmlExploreControlSite::QueryInterface(REFIID riid, void **ppvObject)<br />{<br /> return COleControlSite::ExternalQueryInterface(&riid, ppvObject);<br />}<br />STDMETHODIMP_(ULONG) CDHtmlExploreControlSite::AddRef()<br />{<br /> return ExternalAddRef();<br />}<br /><br />STDMETHODIMP_(ULONG) CDHtmlExploreControlSite::Release()<br />{<br /> return ExternalRelease();<br />}<br />// redirect IOleCommandTarget calls<br />STDMETHODIMP CDHtmlExploreControlSite::QueryStatus(const GUID *pguidCmdGroup,<br /> ULONG cCmds,<br /> OLECMD prgCmds[ ],<br /> OLECMDTEXT *pCmdText)<br />{<br /> return reinterpret_cast<CDHtmlExploreDlg*>(m_pHandler)->QueryStatus(<br /> pguidCmdGroup,<br /> cCmds,<br /> prgCmds,<br /> pCmdText);<br />}<br />STDMETHODIMP CDHtmlExploreControlSite::Exec(const GUID *pguidCmdGroup,<br /> DWORD nCmdID,<br /> DWORD nCmdexecopt,<br /> VARIANT *pvaIn,<br /> VARIANT *pvaOut)<br />{<br /> return reinterpret_cast<CDHtmlExploreDlg*>(m_pHandler)->Exec(<br /> pguidCmdGroup,<br /> nCmdID,<br /> nCmdexecopt,<br /> pvaIn,<br /> pvaOut);<br />}<br />//replace the control site to support IOleCommandTarget<br />BOOL CDHtmlExploreDlg::CreateControlSite(COleControlContainer* pContainer, <br />COleControlSite** ppSite, UINT /* nID */, REFCLSID /* clsid */)<br />{<br /> if(ppSite == NULL)<br /> {<br /> ASSERT(FALSE);<br /> return FALSE;<br /> }<br /><br /> CDHtmlExploreControlSite *pBrowserSite = <br /> new CDHtmlExploreControlSite(pContainer, this);<br /> if (!pBrowserSite)<br /> return FALSE;<br /> *ppSite = pBrowserSite;<br /> return TRUE;<br />}<br />.....<br />ON_COMMAND(ID_CONTEXT_PRINT, OnContextPrint) //message map<br />.....<br />DHTML_EVENT_ONCLICK(_T("print"), OnPrint)//DHTML event map<br />void CDHtmlExploreDlg::OnContextPrintPreview() <br />{<br /> // TODO: Add your command handler code here<br /> OnPrintPreview(NULL);<br />}<br />//for more information about <br />HRESULT CDHtmlExploreDlg::OnPrint(IHTMLElement* /*phtmlElement*/)<br />{<br /> CComQIPtr<IOleCommandTarget> poctBrowserApp(m_pBrowserApp);<br /> if(poctBrowserApp==NULL)return E_FAIL;<br /> return poctBrowserApp->Exec<br /> (&CGID_MSHTML,IDM_PRINT,OLECMDEXECOPT_PROMPTUSER,NULL,NULL);<br />}<br />//dump information about commands <br />//and ignore the print command<br />STDMETHODIMP CDHtmlExploreDlg::QueryStatus(const GUID *pguidCmdGroup,<br /> ULONG cCmds,<br /> OLECMD prgCmds[ ],<br /> OLECMDTEXT *pCmdText)<br />{<br /> CString strTrace(_T("QueryStatus:Command Group:"));<br /> CStringW strCommandGroup(_T("NULL"));<br /> CString strCommand;<br /> CString strCommands;<br /> if(pguidCmdGroup)<br /> {<br /> LPOLESTR pwstrCommandGroup=NULL;<br /> ::StringFromCLSID (*pguidCmdGroup,&pwstrCommandGroup);<br /> if(pwstrCommandGroup)<br /> {<br /> strCommandGroup=pwstrCommandGroup;<br /> CoTaskMemFree(pwstrCommandGroup);<br /> } <br /> }<br /> strTrace+=strCommandGroup;<br /><br /> for(UINT i=0;i<cCmds;i++)<br /> {<br /> strCommand.Format(_T("%x"),prgCmds[i].cmdID);<br /> strCommands+=",";<br /> strCommands+=strCommand;<br /> }<br /> strTrace+=strCommands;<br /> strTrace+=_T("\r\n");<br /> TRACE(strTrace);<br /> return E_NOTIMPL;<br />}<br />STDMETHODIMP CDHtmlExploreDlg::Exec(const GUID *pguidCmdGroup,<br /> DWORD nCmdID,<br /> DWORD nCmdexecopt,<br /> VARIANT *pvaIn,<br /> VARIANT *pvaOut)<br />{<br /> CString strTrace(_T("Exec:Command Group:"));<br /> CStringW strCommandGroup(_T("NULL"));<br /> CString strCommand;<br /> if(pguidCmdGroup)<br /> {<br /> LPOLESTR pwstrCommandGroup=NULL;<br /> ::StringFromCLSID (*pguidCmdGroup,&pwstrCommandGroup);<br /> if(pwstrCommandGroup)<br /> {<br /> strCommandGroup=pwstrCommandGroup;<br /> CoTaskMemFree(pwstrCommandGroup);<br /> } <br /> }<br /> strTrace+=strCommandGroup;<br /> strCommand.Format(_T("%x"),nCmdID);<br /> strTrace+=",";<br /> strTrace+=strCommand;<br /> strTrace+=_T("\r\n");<br /> TRACE(strTrace);<br /> if (pguidCmdGroup&&IsEqualIID((REFIID) (*(IID*)pguidCmdGroup)<br /> ,CGID_DocHostCommandHandler))<br /> {<br /> switch(nCmdID)<br /> {<br /> case OLECMDID_PRINT:<br /> return S_OK; //ignore it<br /> }<br /> }<br /> return E_NOTIMPL;<br />}<br />

浏览器控件访问容器的方式是查询容器的IDocHostUIHandler接口，而对于浏览器辅助对象(Browser Helper Object/ BHO)，不能修改容器来增加一个新的接口。这时候可以通过HTML文档的ICustomDoc接口来设置自己的IDocHostUIHandler接口。

class ATL_NO_VTABLE CBHO : <br /> public IObjectWithSiteImpl<CBHO>,<br /> public IDispatchImpl<IBHOb, &__uuidof(IBHO)>,<br /> public IDocHostUIHandler,<br /> public IOleCommandTarget<br /> case DISPID_DOCUMENTCOMPLETE:<br /> ATLTRACE(_T("(%ld) DISPID_DOCUMENTCOMPLETE\n"), ::GetCurrentThreadId());<br /> //if the page is done downloading<br /> if (m_pWBDisp && <br /> m_pWBDisp == pDispParams->rgvarg[1].pdispVal)<br /> {<br /> ......<br /> CComPtr<IDispatch> spDisp;<br /> HRESULT hr = m_spWebBrowser2->get_Document(&spDisp);<br /> ......<br /> // replace the IDocHostUIHandler<br /> CComQIPtr<ICustomDoc, &IID_ICustomDoc> spCustomDoc(spDisp);<br /> if (spCustomDoc)<br /> spCustomDoc->SetUIHandler(this);<br /> .....<br /> }<br />

在捕获容器的命令的过程中发现一些其他命令也被发送到容器（按时间顺序）：

行为	命令组	命令
加载	NULL	OLECMDID_SETDOWNLOADSTATE
	000214D0-0000-0000-C000-000000000046	OLECMDID_PASTESPECIAL/ OLECMDID_HIDETOOLBARS / OLECMDID_PREREFRESH/ OLECMDID_ONUNLOAD
	NULL	OLECMDID_SETPROGRESSMAX/ OLECMDID_SETPROGRESSPOS/ OLECMDID_SETDOWNLOADSTATE
打印	CGID_DocHostCommandHandler	OLECMDID_PRINT
刷新	CGID_DocHostCommandHandler	0x1799
	NULL	OLECMDID_PREREFRESH/ OLECMDID_SETPROGRESSMAX/ OLECMDID_SETPROGRESSPOS/ OLECMDID_SETDOWNLOADSTATE
	000214D0-0000-0000-C000-000000000046	OLECMDID_ONUNLOAD/ OLECMDID_PREREFRESH

不是所有常用操作都会转发到容器。OLECMDID_PRINTPREVIEW、OLECMDID_SAVEAS、OLECMDID_REFRESH看起来就没有被转发。

参考文档：

• MSDN文章 MFC技术文档TN038 MFC/OLE IUnknown Implementation (http://msdn.microsoft.com/library/en-us/vclib/html/_mfcnotes_tn038.asp)
  
• 微软知识库文章 Q261003 How to handle script errors as a WebBrowser control host (http://support.microsoft.com/kb/261003)
  
• 微软知识库文章 Q317024 Script error notification is not sent to Exec method of WebBrowser Host(http://support.microsoft.com/kb/317024)
  
• MSDN文章 WebBrowser Customization (http://msdn.microsoft.com/workshop/browser/hosting/wbcustomization.asp)
  
• 微软知识库文章 Q267240 How to print custom headers and footers for a WebBrowser control in Internet Explorer (http://support.microsoft.com/kb/267240)

Visual Studio 2005 June CTP的资源编辑器似乎有点问题，改过资源就保存不到原文件了，只能保存到另一个文件，关闭Visual Stuio之后替换(关闭solution都不行)。