delphi - Delphi:TOleControl将ActiveControl置于错误状态？

在Mike Lischke的Virtual Treeview中，有解决方法的代码
添加了修复在同一表单上使用TWebBrowser控件时的错误。

问题在于，如果用户尝试与TOleControl（TWebBrowser从其降级）进行交互，则会吃掉第一次鼠标单击。然后，他们必须再次单击以赋予控件焦点。然后，他们可以与控件进行交互。

他有评论要解释：


从TOleControl派生的每个控件都可能存在焦点问题。

为了避免包含允许测试TOleControl类的OleCtrls单元（其中包括Variants），将使用IOleClientSite接口进行测试，该接口受TOleControl和一个很好的指标。


从完整的代码段开始：

procedure TBaseVirtualTree.WMKillFocus(var Msg: TWMKillFocus);
var
  Form: TCustomForm;
  Control: TWinControl;
  Pos: TSmallPoint;
  Unknown: IUnknown;
begin
  inherited;

  [snip]

  {
    Workaround for wrapped non-VCL controls (like TWebBrowser),
    which do not use VCL mechanisms and
    leave the ActiveControl property in the wrong state,
    which causes trouble when the control is refocused.
  }
  Form := GetParentForm(Self);
  if Assigned(Form) and (Form.ActiveControl = Self) then
  begin
    Cardinal(Pos) := GetMessagePos;
    Control := FindVCLWindow(SmallPointToPoint(Pos));
    {
      Every control derived from TOleControl has potentially
      the focus problem. In order to avoid including
      the OleCtrls unit (which will, among others, include Variants),
      which would allow to test for the TOleControl
      class, the IOleClientSite interface is used for the test,
      which is supported by TOleControl and a good indicator.
    }
    if Assigned(Control) and Control.GetInterface(IOleClientSite, Unknown) then
      Form.ActiveControl := nil;

    // For other classes the active control should not be modified. Otherwise you need two clicks to select it.
  end;
end;

问题是该解决方法不再对我有用。老实说，我不知道问题出在哪里，他的解决方案如何解决。

是否有人知道他的评论理解他在说什么，可以解释问题所在，以及他应该怎么做才能解决该问题？


包装的非VCL的解决方法
控件（例如TWebBrowser），
不使用VCL机制，并留下
ActiveControl属性中的错误
状态，当
控制重新定位。每个控件
从TOleControl派生有
可能是焦点问题。


代码已达到预期的

Form.ActiveControl := nil;

声明，但事实并非如此。

我会修复它，但是我不知道他是怎么找到它的，或者它是怎么产生的，TOleControl不会“使用VCL机制并使ActiveControl属性处于错误状态”。



奖励阅读

我最初问这个问题onborland.public.delphi.nativeapi.win32 newsgroup in 2008

Question on Soft-Gems forum

凹凸20110515（12个月后）

凹凸20150401（7年后）：在XE6中仍然不起作用

最佳答案

我通过使用TEmbeddedWB（比标准的TWebBrowser更好）解决了这个问题，然后我不得不添加此OnShowUI事件：

function THtmlFrame.webBrowserShowUI(const dwID: Cardinal;
  const pActiveObject: IOleInPlaceActiveObject;
  const pCommandTarget: IOleCommandTarget; const pFrame: IOleInPlaceFrame;
  const pDoc: IOleInPlaceUIWindow): HRESULT;
begin
  try
    if WebBrowser.CanFocus then
      WebBrowser.SetFocus; // tell the VCL that the web-browser is focused
  except
    on E: EInvalidOperation do
      ; // ignore "Cannot focus inactive or invisible control"
  end;
  Result := S_FALSE;
end;

但是，如果必须使用TWebBrowser，则需要编写更多代码：

type
  IDocHostUIHandler = interface(IUnknown)
    ['{bd3f23c0-d43e-11cf-893b-00aa00bdce1a}']
    function ShowContextMenu(const dwID: DWORD; const ppt: PPOINT;
      const CommandTarget: IUnknown; const Context: IDispatch): HRESULT; stdcall;
    function GetHostInfo(var pInfo: TDOCHOSTUIINFO): HRESULT; stdcall;
    function ShowUI(const dwID: DWORD; const pActiveObject: IOleInPlaceActiveObject;
      const pCommandTarget: IOleCommandTarget; const pFrame: IOleInPlaceFrame;
      const pDoc: IOleInPlaceUIWindow): HRESULT; stdcall;
    function HideUI: HRESULT; stdcall;
    function UpdateUI: HRESULT; stdcall;
    function EnableModeless(const fEnable: BOOL): HRESULT; stdcall;
    function OnDocWindowActivate(const fActivate: BOOL): HRESULT; stdcall;
    function OnFrameWindowActivate(const fActivate: BOOL): HRESULT; stdcall;
    function ResizeBorder(const prcBorder: PRECT; const pUIWindow: IOleInPlaceUIWindow; const fRameWindow: BOOL): HRESULT; stdcall;
    function TranslateAccelerator(const lpMsg: PMSG; const pguidCmdGroup: PGUID; const nCmdID: DWORD): HRESULT; stdcall;
    function GetOptionKeyPath(out pchKey: POLESTR; const dw: DWORD): HRESULT; stdcall;
    function GetDropTarget(const pDropTarget: IDropTarget; out ppDropTarget: IDropTarget): HRESULT; stdcall;
    function GetExternal(out ppDispatch: IDispatch): HRESULT; stdcall;
    function TranslateUrl(const dwTranslate: DWORD; const pchURLIn: POLESTR; out ppchURLOut: POLESTR): HRESULT; stdcall;
    function FilterDataObject(const pDO: IDataObject; out ppDORet: IDataObject): HRESULT; stdcall;
  end; // IDocHostUIHandler

  ICustomDoc = interface(IUnknown)
    ['{3050f3f0-98b5-11cf-bb82-00aa00bdce0b}']
    function SetUIHandler(const pUIHandler: IDocHostUIHandler): HResult; stdcall;
  end;

  TDocHostUIHandler = class(TInterfacedObject, IDocHostUIHandler)
  private
    FWebBrowser: TWebBrowser;
  protected
    function EnableModeless(const fEnable: BOOL): HResult; stdcall;
    function FilterDataObject(const pDO: IDataObject; out ppDORet: IDataObject): HResult; stdcall;
    function GetDropTarget(const pDropTarget: IDropTarget; out ppDropTarget: IDropTarget): HResult; stdcall;
    function GetExternal(out ppDispatch: IDispatch): HResult; stdcall;
    function GetHostInfo(var pInfo: TDocHostUIInfo): HResult; stdcall;
    function GetOptionKeyPath(var pchKey: POLESTR; const dw: DWORD): HResult; stdcall;
    function HideUI: HResult; stdcall;
    function OnDocWindowActivate(const fActivate: BOOL): HResult; stdcall;
    function OnFrameWindowActivate(const fActivate: BOOL): HResult; stdcall;
    function ResizeBorder(const prcBorder: PRECT; const pUIWindow: IOleInPlaceUIWindow;
      const fFrameWindow: BOOL): HResult; stdcall;
    function ShowContextMenu(const dwID: DWORD; const ppt: PPOINT;
      const pcmdtReserved: IInterface; const pdispReserved: IDispatch): HResult; stdcall;
    function ShowUI(const dwID: DWORD; const pActiveObject: IOleInPlaceActiveObject;
      const pCommandTarget: IOleCommandTarget; const pFrame: IOleInPlaceFrame;
      const pDoc: IOleInPlaceUIWindow): HResult; stdcall;
    function TranslateAccelerator(const lpMsg: PMSG; const pguidCmdGroup: PGUID; const nCmdID: DWORD): HResult; stdcall;
    function TranslateUrl(const dwTranslate: DWORD; const pchURLIn: POLESTR; var ppchURLOut: POLESTR): HResult; stdcall;
    function UpdateUI: HResult; stdcall;
  public
    constructor Create(AWebBrowser: TWebBrowser);
    property WebBrowser: TWebBrowser read FWebBrowser;
  end;


{ TDocHostUIHandler }

function TDocHostUIHandler.EnableModeless(const fEnable: BOOL): HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.FilterDataObject(const pDO: IDataObject; out ppDORet: IDataObject): HResult;
begin
  ppDORet := nil;
  Result := S_FALSE;
end;

function TDocHostUIHandler.GetDropTarget(const pDropTarget: IDropTarget; out ppDropTarget: IDropTarget): HResult;
begin
  ppDropTarget := nil;
  Result := E_FAIL;
end;

function TDocHostUIHandler.GetExternal(out ppDispatch: IDispatch): HResult;
begin
  ppDispatch := nil;
  Result := E_FAIL;
end;

function TDocHostUIHandler.GetHostInfo(var pInfo: TDocHostUIInfo): HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.GetOptionKeyPath(var pchKey: POLESTR; const dw: DWORD): HResult;
begin
  Result := E_FAIL;
end;

function TDocHostUIHandler.HideUI: HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.OnDocWindowActivate(const fActivate: BOOL): HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.OnFrameWindowActivate(const fActivate: BOOL): HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.ResizeBorder(const prcBorder: PRECT; const pUIWindow: IOleInPlaceUIWindow; const fFrameWindow: BOOL): HResult;
begin
  Result := S_FALSE;
end;

function TDocHostUIHandler.ShowContextMenu(const dwID: DWORD; const ppt: PPOINT; const pcmdtReserved: IInterface; const pdispReserved: IDispatch): HResult;
begin
  Result := S_FALSE
end;

function TDocHostUIHandler.TranslateAccelerator(const lpMsg: PMSG; const pguidCmdGroup: PGUID; const nCmdID: DWORD): HResult;
begin
  Result := S_FALSE;
end;

function TDocHostUIHandler.TranslateUrl(const dwTranslate: DWORD; const pchURLIn: POLESTR; var ppchURLOut: POLESTR): HResult;
begin
  Result := E_FAIL;
end;

function TDocHostUIHandler.UpdateUI: HResult;
begin
  Result := S_OK;
end;

function TDocHostUIHandler.ShowUI(const dwID: DWORD; const pActiveObject: IOleInPlaceActiveObject; const pCommandTarget: IOleCommandTarget;
  const pFrame: IOleInPlaceFrame; const pDoc: IOleInPlaceUIWindow): HResult;
begin
  try
    if WebBrowser.CanFocus then
      WebBrowser.SetFocus; // tell the VCL that the web-browser is focused
  except
    on E: EInvalidOperation do
      ; // ignore "Cannot focus inactive or invisible control"
  end;
  Result := S_OK;
end;



// install the DocHostUIHandler into the WebBrowser
var
  CustomDoc: ICustomDoc;
begin
  if WebBrowser1.Document.QueryInterface(ICustomDoc, CustomDoc) = S_OK then
    CustomDoc.SetUIHandler(TDocHostUIHandler.Create(WebBrowser1));
end;