选项卡的关闭按钮不支持 vcl 样式

我已经使用了本示例中提供的代码如何为 TPageControl 的 Ttabsheet 实现关闭按钮在页面控件的每个选项卡上绘制一个关闭按钮，我在代码中用样式服务替换了 ThemeServices，并且在应用样式时，关闭按钮不会显示，也不会做出任何反应。谁能指出我解决这个问题的不同路径。谢谢你！这是 OnDrawTab 事件的代码：

  procedure TFormMain.PageControlCloseButtonDrawTab(Control: TCustomTabControl;
  TabIndex: Integer; const Rect: TRect; Active: Boolean);
var
  CloseBtnSize: Integer;
  PageControl: TPageControl;
  TabCaption: TPoint;
  CloseBtnRect: TRect;
  CloseBtnDrawState: Cardinal;
  CloseBtnDrawDetails: TThemedElementDetails;
begin
  PageControl := Control as TPageControl;

  if InRange(TabIndex, 0, Length(FCloseButtonsRect) - 1) then
  begin
    CloseBtnSize := 14;
    TabCaption.Y := Rect.Top + 3;

    if Active then
    begin
      CloseBtnRect.Top := Rect.Top + 4;
      CloseBtnRect.Right := Rect.Right - 5;
      TabCaption.X := Rect.Left + 6;
    end
    else
    begin
      CloseBtnRect.Top := Rect.Top + 3;
      CloseBtnRect.Right := Rect.Right - 5;
      TabCaption.X := Rect.Left + 3;
    end;

    CloseBtnRect.Bottom := CloseBtnRect.Top + CloseBtnSize;
    CloseBtnRect.Left := CloseBtnRect.Right - CloseBtnSize;
    FCloseButtonsRect[TabIndex] := CloseBtnRect;

    PageControl.Canvas.FillRect(Rect);
    PageControl.Canvas.TextOut(TabCaption.X, TabCaption.Y, PageControl.Pages[TabIndex].Caption);

    if not UseThemes then
    begin
      if (FCloseButtonMouseDownIndex = TabIndex) and FCloseButtonShowPushed then
        CloseBtnDrawState := DFCS_CAPTIONCLOSE + DFCS_PUSHED
      else
        CloseBtnDrawState := DFCS_CAPTIONCLOSE;

      Winapi.Windows.DrawFrameControl(PageControl.Canvas.Handle,
        FCloseButtonsRect[TabIndex], DFC_CAPTION, CloseBtnDrawState);
    end
    else
    begin
      Dec(FCloseButtonsRect[TabIndex].Left);

      if (FCloseButtonMouseDownIndex = TabIndex) and FCloseButtonShowPushed then
        CloseBtnDrawDetails := StyleServices.GetElementDetails(twCloseButtonPushed)
      else
        CloseBtnDrawDetails := StyleServices.GetElementDetails(twCloseButtonNormal);

      StyleServices.DrawElement(PageControl.Canvas.Handle, CloseBtnDrawDetails,
        FCloseButtonsRect[TabIndex]);
    end;
  end;
end;

如果您使用的是vcl样式，则必须编写一个vcl样式钩子来在选项卡控件中绘制关闭按钮，请查看Vcl.Styles.ColorTabs单位（在这些文章中介绍使用 VCL 样式创建彩色选项卡, 为 TTabColorControlStyleHook 添加边框）以了解编写这样的样式钩子需要什么。除了在选项卡中绘制按钮的代码之外，您还必须处理 WM_MOUSEMOVE 和 WM_LBUTTONUP 消息（在样式挂钩中）以更改按钮的状态（正常、热）并检测关闭按钮中的单击。

如果您在实现样式挂钩时遇到问题，请告诉我在这里发布完整的解决方案。

UPDATE

我刚刚编写了这个简单的样式挂钩来添加对选项卡中关闭按钮的支持。

uses
  Vcl.Styles,
  Vcl.Themes;

type
  TTabControlStyleHookBtnClose = class(TTabControlStyleHook)
  private
    FHotIndex       : Integer;
    FWidthModified  : Boolean;
    procedure WMMouseMove(var Message: TMessage); message WM_MOUSEMOVE;
    procedure WMLButtonUp(var Message: TWMMouse); message WM_LBUTTONUP;
    function GetButtonCloseRect(Index: Integer):TRect;
  strict protected
    procedure DrawTab(Canvas: TCanvas; Index: Integer); override;
    procedure MouseEnter; override;
    procedure MouseLeave; override;
  public
    constructor Create(AControl: TWinControl); override;
  end;

constructor TTabControlStyleHookBtnClose.Create(AControl: TWinControl);
begin
  inherited;
  FHotIndex:=-1;
  FWidthModified:=False;
end;

procedure TTabControlStyleHookBtnClose.DrawTab(Canvas: TCanvas; Index: Integer);
var
  Details : TThemedElementDetails;
  ButtonR : TRect;
  FButtonState: TThemedWindow;
begin
  inherited;

  if (FHotIndex>=0) and (Index=FHotIndex) then
   FButtonState := twSmallCloseButtonHot
  else
  if Index = TabIndex then
   FButtonState := twSmallCloseButtonNormal
  else
   FButtonState := twSmallCloseButtonDisabled;

  Details := StyleServices.GetElementDetails(FButtonState);

  ButtonR:= GetButtonCloseRect(Index);
  if ButtonR.Bottom - ButtonR.Top > 0 then
   StyleServices.DrawElement(Canvas.Handle, Details, ButtonR);
end;

procedure TTabControlStyleHookBtnClose.WMLButtonUp(var Message: TWMMouse);
Var
  LPoint : TPoint;
  LIndex : Integer;
begin
  LPoint:=Message.Pos;
  for LIndex := 0 to TabCount-1 do
   if PtInRect(GetButtonCloseRect(LIndex), LPoint) then
   begin
      if Control is TPageControl then
      begin
        TPageControl(Control).Pages[LIndex].Parent:=nil;
        TPageControl(Control).Pages[LIndex].Free;
      end;
      break;
   end;
end;

procedure TTabControlStyleHookBtnClose.WMMouseMove(var Message: TMessage);
Var
  LPoint : TPoint;
  LIndex : Integer;
  LHotIndex : Integer;
begin
  inherited;
  LHotIndex:=-1;
  LPoint:=TWMMouseMove(Message).Pos;
  for LIndex := 0 to TabCount-1 do
   if PtInRect(GetButtonCloseRect(LIndex), LPoint) then
   begin
      LHotIndex:=LIndex;
      break;
   end;

   if (FHotIndex<>LHotIndex) then
   begin
     FHotIndex:=LHotIndex;
     Invalidate;
   end;
end;

function TTabControlStyleHookBtnClose.GetButtonCloseRect(Index: Integer): TRect;
var
  FButtonState: TThemedWindow;
  Details : TThemedElementDetails;
  R, ButtonR : TRect;
begin
  R := TabRect[Index];
  if R.Left < 0 then Exit;

  if TabPosition in [tpTop, tpBottom] then
  begin
    if Index = TabIndex then
      InflateRect(R, 0, 2);
  end
  else
  if Index = TabIndex then
    Dec(R.Left, 2)
  else
    Dec(R.Right, 2);

  Result := R;
  FButtonState := twSmallCloseButtonNormal;

  Details := StyleServices.GetElementDetails(FButtonState);
  if not StyleServices.GetElementContentRect(0, Details, Result, ButtonR) then
    ButtonR := Rect(0, 0, 0, 0);

  Result.Left :=Result.Right - (ButtonR.Width) - 5;
  Result.Width:=ButtonR.Width;
end;

procedure TTabControlStyleHookBtnClose.MouseEnter;
begin
  inherited;
  FHotIndex := -1;
end;

procedure TTabControlStyleHookBtnClose.MouseLeave;
begin
  inherited;
  if FHotIndex >= 0 then
  begin
    FHotIndex := -1;
    Invalidate;
  end;
end;

通过这种方式注册

  TStyleManager.Engine.RegisterStyleHook(TCustomTabControl, TTabControlStyleHookBtnClose);
  TStyleManager.Engine.RegisterStyleHook(TTabControl, TTabControlStyleHookBtnClose);

这是一个演示