delphi - 选项卡的关闭按钮不支持 vcl 样式

Question

我使用了本例中提供的代码How to implement a close button for a TTabsheet of a TPageControl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;

Answer 1

如果您使用的是vcl样式，则必须编写一个vcl样式钩子(Hook)来在选项卡控件中绘制关闭按钮，请查看Vcl.Styles.ColorTabs单元(在这些文章 Creating colorful tabsheets with the VCL Styles 、 Added border to TTabColorControlStyleHook 中介绍)来了解编写这样的样式钩子(Hook)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 Hook 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 Hook 时遇到问题，请告诉我在这里发布完整的解决方案。

更新

我刚刚编写了这个简单的样式 Hook 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