Delphi:TOleControl 将 ActiveControl 置于错误状态？

Question

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

问题是，如果用户尝试与 TOleControl(TWebBrowser 的下降)进行交互，第一次鼠标点击就会被吃掉。然后他们必须再次单击才能获得控制焦点。 然后他们可以与控件交互。

他有意见需要解释:

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.

摘自完整片段:

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适合我。老实说，我不知道问题到底是什么，以及他的解决方案如何解决它。

有谁知道他的评论是什么，理解他在说什么，可以解释问题是什么，以及他正在做的事情应该如何解决它？

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. Every control derived from TOleControl has potentially the focus problem.

代码已达到预期

Form.ActiveControl := nil; 

声明，但它只是没有起到作用。

我会修复它，但我不知道他是如何找到它的，或者如何导致 TOleControl 不“使用 VCL 机制并将 ActiveControl 属性保留在错误的状态。”

---

奖励阅读

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

Question on Soft-Gems forum

碰撞 20110515(12 个月后)

Bump 20150401(7年后):在XE6中仍然不起作用

碰撞 20210309(11 年后)

Answer 1

我通过使用 TEmbeddedWB(比标准 TWebBrowser 好得多)克服了这个问题，然后我必须添加此 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;

但如果您必须使用 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;