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Delphi 如何删除MDI客户端窗口的凹陷内边缘？

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Delphi 如何删除MDI客户端窗口的凹陷内边缘？,delphi,mdi,delphi-xe3,Delphi,Mdi,Delphi Xe3,前几天，我开始开发我的新项目。应该有一个MDI表单，上面有一些子表单。但当我开始开发时，我遇到了以下问题：当主窗体变成MDI窗体时，它会在里面绘制一个可怕的边框（斜面）。我不能把它拿走。您可以在屏幕截图中看到这种情况： 相反，MDI子窗体绘制时没有相同的倒角 该项目包含两个表格，表格1和表格2。Form1是一个主要的MDI表单 Form1源代码： object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeig

前几天，我开始开发我的新项目。应该有一个MDI表单，上面有一些子表单。但当我开始开发时，我遇到了以下问题：当主窗体变成MDI窗体时，它会在里面绘制一个可怕的边框（斜面）。我不能把它拿走。您可以在屏幕截图中看到这种情况：

相反，MDI子窗体绘制时没有相同的倒角

该项目包含两个表格，表格1和表格2。Form1是一个主要的MDI表单

Form1源代码：

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 346
  ClientWidth = 439
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  FormStyle = fsMDIForm
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
end

object Form2: TForm2
  Left = 0
  Top = 0
  Caption = 'Form2'
  ClientHeight = 202
  ClientWidth = 331
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  FormStyle = fsMDIChild
  OldCreateOrder = False
  Visible = True
  PixelsPerInch = 96
  TextHeight = 13
end
Form2源代码：

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 346
  ClientWidth = 439
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  FormStyle = fsMDIForm
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
end

object Form2: TForm2
  Left = 0
  Top = 0
  Caption = 'Form2'
  ClientHeight = 202
  ClientWidth = 331
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  FormStyle = fsMDIChild
  OldCreateOrder = False
  Visible = True
  PixelsPerInch = 96
  TextHeight = 13
end
请告诉我如何将此斜面从主窗体移除。

由于MDI客户端窗口具有扩展窗口样式，因此绘制边框。这种风格是这样描述的：

这扇窗户有一个凹陷的边缘

然而，我第一次尝试删除这种风格的尝试失败了。例如，您可以尝试以下代码：

procedure TMyMDIForm.CreateWnd;
var
  ExStyle: DWORD;
begin
  inherited;
  ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
  SetWindowLongPtr(ClientHandle, GWL_EXSTYLE,
    ExStyle and not WS_EX_CLIENTEDGE);
  SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
    SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
end;
此代码确实删除了
WS_EX_CLIENTEDGE
。但是您看不到任何视觉变化，如果使用Spy++之类的工具检查窗口，您将看到MDI客户端窗口保留了
WS_EX_CLIENTEDGE

那么，有什么好处呢？事实证明，MDI客户端窗口的窗口过程（在VCL代码中实现）正在强制显示客户端边缘。这将覆盖您删除样式的任何尝试

所讨论的代码如下所示：

procedure ShowMDIClientEdge(ClientHandle: THandle; ShowEdge: Boolean);
var
  Style: Longint;
begin
  if ClientHandle <> 0 then
  begin
    Style := GetWindowLong(ClientHandle, GWL_EXSTYLE);
    if ShowEdge then
      if Style and WS_EX_CLIENTEDGE = 0 then
        Style := Style or WS_EX_CLIENTEDGE
      else
        Exit
    else if Style and WS_EX_CLIENTEDGE <> 0 then
      Style := Style and not WS_EX_CLIENTEDGE
    else
      Exit;
    SetWindowLong(ClientHandle, GWL_EXSTYLE, Style);
    SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
      SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
  end;
end;
....
procedure TCustomForm.ClientWndProc(var Message: TMessage);
....
begin
  with Message do
    case Msg of
      ....
      $3F://!
        begin
          Default;
          if FFormStyle = fsMDIForm then
            ShowMDIClientEdge(ClientHandle, (MDIChildCount = 0) or
              not MaximizedChildren);
        end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure CreateWnd; override;
  end;

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

type
  PInstruction = ^TInstruction;
  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;//jump relative
  NewCode.Offset := NativeInt(NewAddress)-NativeInt(OldAddress)-SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode));
end;

function SetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall; external user32 name 'SetWindowLongW';

function MySetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall;
var
  ClassName: array [0..63] of Char;
begin
  if GetClassName(hWnd, ClassName, Length(ClassName))>0 then
    if (ClassName='MDIClient') and (nIndex=GWL_EXSTYLE) then
      dwNewLong := dwNewLong and not WS_EX_CLIENTEDGE;
  Result := SetWindowLongPtr(hWnd, nIndex, dwNewLong);
end;

procedure TMyMDIForm.CreateWnd;
var
  ExStyle: DWORD;
begin
  inherited;
  // unless we remove WS_EX_CLIENTEDGE here, ShowMDIClientEdge never calls SetWindowLong
  ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
  SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle and not WS_EX_CLIENTEDGE);
end;

initialization
  RedirectProcedure(@Winapi.Windows.SetWindowLongPtr, @MySetWindowLongPtr);

type
  TFormHelper = class helper for TCustomForm
    function DefClientProc: TFarProc;
  end;

function TFormHelper.DefClientProc: TFarProc;
begin
  Result := Self.FDefClientProc;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      Message.Result := CallWindowProc(DefClientProc, ClientHandle, Message.Msg, Message.wParam, Message.lParam);
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;
最终结果如下所示：

procedure ShowMDIClientEdge(ClientHandle: THandle; ShowEdge: Boolean);
var
  Style: Longint;
begin
  if ClientHandle <> 0 then
  begin
    Style := GetWindowLong(ClientHandle, GWL_EXSTYLE);
    if ShowEdge then
      if Style and WS_EX_CLIENTEDGE = 0 then
        Style := Style or WS_EX_CLIENTEDGE
      else
        Exit
    else if Style and WS_EX_CLIENTEDGE <> 0 then
      Style := Style and not WS_EX_CLIENTEDGE
    else
      Exit;
    SetWindowLong(ClientHandle, GWL_EXSTYLE, Style);
    SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
      SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
  end;
end;
....
procedure TCustomForm.ClientWndProc(var Message: TMessage);
....
begin
  with Message do
    case Msg of
      ....
      $3F://!
        begin
          Default;
          if FFormStyle = fsMDIForm then
            ShowMDIClientEdge(ClientHandle, (MDIChildCount = 0) or
              not MaximizedChildren);
        end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure CreateWnd; override;
  end;

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

type
  PInstruction = ^TInstruction;
  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;//jump relative
  NewCode.Offset := NativeInt(NewAddress)-NativeInt(OldAddress)-SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode));
end;

function SetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall; external user32 name 'SetWindowLongW';

function MySetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall;
var
  ClassName: array [0..63] of Char;
begin
  if GetClassName(hWnd, ClassName, Length(ClassName))>0 then
    if (ClassName='MDIClient') and (nIndex=GWL_EXSTYLE) then
      dwNewLong := dwNewLong and not WS_EX_CLIENTEDGE;
  Result := SetWindowLongPtr(hWnd, nIndex, dwNewLong);
end;

procedure TMyMDIForm.CreateWnd;
var
  ExStyle: DWORD;
begin
  inherited;
  // unless we remove WS_EX_CLIENTEDGE here, ShowMDIClientEdge never calls SetWindowLong
  ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
  SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle and not WS_EX_CLIENTEDGE);
end;

initialization
  RedirectProcedure(@Winapi.Windows.SetWindowLongPtr, @MySetWindowLongPtr);

type
  TFormHelper = class helper for TCustomForm
    function DefClientProc: TFarProc;
  end;

function TFormHelper.DefClientProc: TFarProc;
begin
  Result := Self.FDefClientProc;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      Message.Result := CallWindowProc(DefClientProc, ClientHandle, Message.Msg, Message.wParam, Message.lParam);
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;

请注意，上面的代码不调用默认窗口过程。我不确定这是否会导致其他问题，但其他MDI行为可能会受到影响。因此，您可能需要实现一个功能更强大的行为补丁。希望这个答案能为您提供所需的知识，使您的应用程序按您所希望的方式运行

我在考虑如何实现一个全面的解决方案，确保为
$3F
消息调用默认窗口过程，不管该消息是什么。由于默认窗口过程存储在一个私有字段
FDefClientProc
中，因此实现它并不简单。这使得它很难到达

我想你可以用一个类助手来破解私有成员。但我更喜欢另一种方法。我的方法是让窗口过程保持原样，并将VCL代码的调用挂接到
SetWindowLong
。每当VCL尝试为MDI客户端窗口添加
WS_EX_CLIENTEDGE
，挂接的代码都会阻止该样式

实现如下所示：

procedure ShowMDIClientEdge(ClientHandle: THandle; ShowEdge: Boolean);
var
  Style: Longint;
begin
  if ClientHandle <> 0 then
  begin
    Style := GetWindowLong(ClientHandle, GWL_EXSTYLE);
    if ShowEdge then
      if Style and WS_EX_CLIENTEDGE = 0 then
        Style := Style or WS_EX_CLIENTEDGE
      else
        Exit
    else if Style and WS_EX_CLIENTEDGE <> 0 then
      Style := Style and not WS_EX_CLIENTEDGE
    else
      Exit;
    SetWindowLong(ClientHandle, GWL_EXSTYLE, Style);
    SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
      SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
  end;
end;
....
procedure TCustomForm.ClientWndProc(var Message: TMessage);
....
begin
  with Message do
    case Msg of
      ....
      $3F://!
        begin
          Default;
          if FFormStyle = fsMDIForm then
            ShowMDIClientEdge(ClientHandle, (MDIChildCount = 0) or
              not MaximizedChildren);
        end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure CreateWnd; override;
  end;

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

type
  PInstruction = ^TInstruction;
  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;//jump relative
  NewCode.Offset := NativeInt(NewAddress)-NativeInt(OldAddress)-SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode));
end;

function SetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall; external user32 name 'SetWindowLongW';

function MySetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall;
var
  ClassName: array [0..63] of Char;
begin
  if GetClassName(hWnd, ClassName, Length(ClassName))>0 then
    if (ClassName='MDIClient') and (nIndex=GWL_EXSTYLE) then
      dwNewLong := dwNewLong and not WS_EX_CLIENTEDGE;
  Result := SetWindowLongPtr(hWnd, nIndex, dwNewLong);
end;

procedure TMyMDIForm.CreateWnd;
var
  ExStyle: DWORD;
begin
  inherited;
  // unless we remove WS_EX_CLIENTEDGE here, ShowMDIClientEdge never calls SetWindowLong
  ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
  SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle and not WS_EX_CLIENTEDGE);
end;

initialization
  RedirectProcedure(@Winapi.Windows.SetWindowLongPtr, @MySetWindowLongPtr);

type
  TFormHelper = class helper for TCustomForm
    function DefClientProc: TFarProc;
  end;

function TFormHelper.DefClientProc: TFarProc;
begin
  Result := Self.FDefClientProc;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      Message.Result := CallWindowProc(DefClientProc, ClientHandle, Message.Msg, Message.wParam, Message.lParam);
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;
或者，如果您更喜欢使用私有成员类助手破解的版本，则如下所示：

procedure ShowMDIClientEdge(ClientHandle: THandle; ShowEdge: Boolean);
var
  Style: Longint;
begin
  if ClientHandle <> 0 then
  begin
    Style := GetWindowLong(ClientHandle, GWL_EXSTYLE);
    if ShowEdge then
      if Style and WS_EX_CLIENTEDGE = 0 then
        Style := Style or WS_EX_CLIENTEDGE
      else
        Exit
    else if Style and WS_EX_CLIENTEDGE <> 0 then
      Style := Style and not WS_EX_CLIENTEDGE
    else
      Exit;
    SetWindowLong(ClientHandle, GWL_EXSTYLE, Style);
    SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
      SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
  end;
end;
....
procedure TCustomForm.ClientWndProc(var Message: TMessage);
....
begin
  with Message do
    case Msg of
      ....
      $3F://!
        begin
          Default;
          if FFormStyle = fsMDIForm then
            ShowMDIClientEdge(ClientHandle, (MDIChildCount = 0) or
              not MaximizedChildren);
        end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or 
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure CreateWnd; override;
  end;

procedure PatchCode(Address: Pointer; const NewCode; Size: Integer);
var
  OldProtect: DWORD;
begin
  if VirtualProtect(Address, Size, PAGE_EXECUTE_READWRITE, OldProtect) then
  begin
    Move(NewCode, Address^, Size);
    FlushInstructionCache(GetCurrentProcess, Address, Size);
    VirtualProtect(Address, Size, OldProtect, @OldProtect);
  end;
end;

type
  PInstruction = ^TInstruction;
  TInstruction = packed record
    Opcode: Byte;
    Offset: Integer;
  end;

procedure RedirectProcedure(OldAddress, NewAddress: Pointer);
var
  NewCode: TInstruction;
begin
  NewCode.Opcode := $E9;//jump relative
  NewCode.Offset := NativeInt(NewAddress)-NativeInt(OldAddress)-SizeOf(NewCode);
  PatchCode(OldAddress, NewCode, SizeOf(NewCode));
end;

function SetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall; external user32 name 'SetWindowLongW';

function MySetWindowLongPtr(hWnd: HWND; nIndex: Integer; dwNewLong: LONG_PTR): LONG_PTR; stdcall;
var
  ClassName: array [0..63] of Char;
begin
  if GetClassName(hWnd, ClassName, Length(ClassName))>0 then
    if (ClassName='MDIClient') and (nIndex=GWL_EXSTYLE) then
      dwNewLong := dwNewLong and not WS_EX_CLIENTEDGE;
  Result := SetWindowLongPtr(hWnd, nIndex, dwNewLong);
end;

procedure TMyMDIForm.CreateWnd;
var
  ExStyle: DWORD;
begin
  inherited;
  // unless we remove WS_EX_CLIENTEDGE here, ShowMDIClientEdge never calls SetWindowLong
  ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
  SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle and not WS_EX_CLIENTEDGE);
end;

initialization
  RedirectProcedure(@Winapi.Windows.SetWindowLongPtr, @MySetWindowLongPtr);

type
  TFormHelper = class helper for TCustomForm
    function DefClientProc: TFarProc;
  end;

function TFormHelper.DefClientProc: TFarProc;
begin
  Result := Self.FDefClientProc;
end;

type
  TMyMDIForm = class(TForm)
  protected
    procedure ClientWndProc(var Message: TMessage); override;
  end;

procedure TMyMDIForm.ClientWndProc(var Message: TMessage);
var
  ExStyle: DWORD;
begin
  case Message.Msg of
  $3F:
    begin
      Message.Result := CallWindowProc(DefClientProc, ClientHandle, Message.Msg, Message.wParam, Message.lParam);
      ExStyle := GetWindowLongPtr(ClientHandle, GWL_EXSTYLE);
      ExStyle := ExStyle and not WS_EX_CLIENTEDGE;
      SetWindowLongPtr(ClientHandle, GWL_EXSTYLE, ExStyle);
      SetWindowPos(ClientHandle, 0, 0,0,0,0, SWP_FRAMECHANGED or
        SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
    end;
  else
    inherited;
  end;
end;
最后，我感谢你提出了一个非常有趣的问题。探索这个问题当然很有趣

您可以使用我的开源组件（可从下载），它有一个
ShowClientEdge
属性。（代码与的类似，尽管我是拦截
WM\u NCCALCSIZE
，而不是
$3F
）

除此之外，该组件还具有以下方便的MDI属性：

  • BackgroundPicture
    ：来自磁盘、资源或DFM的图像将绘制在客户端窗口的中心
  • CleverMaximizing
    ：双击多个MDI客户端的标题栏，从而将其最大化为MDI表单中的最大可用空间，从而重新排列多个MDI客户端
  • ShowScrollBars
    ：将客户端拖动到MDI表单扩展之外时，打开或关闭MDI表单的滚动条
在我看来，您确实需要调用默认窗口过程。@kobik好的，我现在已经搞定了。酷。不过听起来不要惊讶！；-）或者（对于最后一部分），您可以在修改帧之前调用
inherited
，并使用
PeekMessage
删除无关的
$3F
（显然是
SetWindowPos
调用导致再次发布的）。这将保存重定向代码+1不管怎样。@Sertac谢谢。额外的3F美元导致了闪烁。我没有追问。