我应该如何提供一个非可视VCL组件的内部私有非可视窗口(句柄)？

Question

这是一个后续问题.

我之前的问题:

• 如何将自定义格式剪贴板数据粘贴到TMemo中？
• 加入剪贴板链最佳实践？

我的问题:

TComponent没有像TWinControl这样的窗口句柄.我不想依赖外部的.

这是我的自定义组件的片段

type
  TMyClipBoardListener = class(TComponent)
  private
    FInnerWindowHandle: HWnd;
    FNextHWnd:  HWnd;
    //...
  protected
    procedure Loaded; override;
    procedure WndProc(var Msg: TMessage); // <<< This is my wouldbe Window to handle messages
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    // ...
  published
    // ...
  end;

我的自定义组件的实现摘录

constructor TMyClipBoardListener .Create(AOwner: TComponent);
begin
  inherited;
  //
  FInnerWindowHandle := ...; // <<< What to do here ? Should I pass it to a function/procedure I missed?
end;

destructor TMyClipBoardListener .Destroy;
begin
  if not(csDesigning in ComponentState) then
  begin
    ChangeClipboardChain(FInnerWindowHandle, FNextHWnd);
  end;
  //
  // <<< Are there some cleaning code related to FInnerWindowHandle to implement here or elsewhereCreates a window that implements a specified window procedure. ?
  //
  inherited;
end;

procedure TMyClipBoardListener.Loaded;
begin
  inherited;
  //
  if not(csDesigning in ComponentState) then
  begin
    FNextHWnd:= SetClipboardViewer(FInnerWindowHandle);
  end;
end;

procedure TMyClipBoardListener.WndProc(var Msg: TMessage);
begin
  with Msg do
  begin
    // Message to handle : WM_CHANGECBCHAIN and WM_DRAWCLIPBOARD
    // ... 
    else
      Result := DefWindowProc(FInnerWindowHandle, Msg, WParam, LParam); // <<< Is this the right way to do default handling properly?
  end;
end;

我的问题:

如何为我的自定义组件获取实现嵌入式窗口过程的内部窗口？

Answer 1

AllocateHwnd从Classes单元调用(不是表单).

FInnerWindowHandle := AllocateHwnd(WndProc);

完成后,请致电DeallocateHwnd.