delphi - 如何从主窗体中拉出MDI子窗口？

Question

我想创建一个带有自己的任务栏的 MDI 应用程序，以便用户可以快速访问他/她想要显示在前面的子窗口。然后我想到，使用两个或更多显示器的用户可以将子窗口从应用程序的主窗体内部拖动到应用程序的外部，例如另一个显示器。

如何做到这一点？

Answer 1

也许这个示例 MDI 客户端表单代码可以提供启发:

unit Unit3;

interface

uses
  Windows, Messages, Controls, Forms;

type
  TForm3 = class(TForm)
  private
    FSizing: Boolean;
    procedure WMNCMouseLeave(var Message: TMessage);
      message WM_NCMOUSELEAVE;
    procedure WMWindowPosChanged(var Message: TWMWindowPosChanged);
      message WM_WINDOWPOSCHANGED;
  protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure Resize; override;
  end;

implementation

{$R *.dfm}

{ TForm3 }

var
  FDragging: Boolean = False;

procedure TForm3.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  if FormStyle = fsNormal then
    Params.ExStyle := Params.ExStyle or WS_EX_APPWINDOW
  else
    Params.ExStyle := Params.ExStyle and not WS_EX_APPWINDOW;
end;

procedure TForm3.Resize;
begin
  inherited Resize;
  FSizing := True;
end;

procedure TForm3.WMNCMouseLeave(var Message: TMessage);
begin
  inherited;
  FDragging := False;
end;

procedure TForm3.WMWindowPosChanged(var Message: TWMWindowPosChanged);
var
  P: TPoint;
  F: TCustomForm;
  R: TRect;
begin
  inherited;
  if not FDragging and not FSizing and not (fsShowing in FormState) and
    (WindowState = wsNormal) then
  begin
    F := Application.MainForm;
    P := F.ScreenToClient(Mouse.CursorPos);
    R := F.ClientRect;
    InflateRect(R, -5, -5);
    if not PtInRect(R, P) and (FormStyle = fsMDIChild) then
    begin
      FDragging := True;
      FormStyle := fsNormal;
      Top := Top + F.Top;
      Left := Left + F.Left;
    end
    else if PtInRect(R, P) and (FormStyle = fsNormal) then
    begin
      FDragging := True;
      FormStyle := fsMDIChild;
    end;
  end;
  FSizing := False;
end;

end.