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

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

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）：

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)。

打印 | 张贴于 2005-07-09 16:32:00 | Tag:用户界面  语言(Language)  平台SDK(Platform SDK)  类库(Library)  HTML编程(IE Programming)  集成开发环境(IDE)  脚本(Scripting)