Delphi 讓無標題列表單任意拖曳移動 (WM_NCHITTEST)

技巧

攔截 WM_NCHITTEST 訊息，當滑鼠在工作區 (htClient) 按下時，回傳 htCaption 欺騙系統以為點在標題列，即可拖曳移動無框/無標題視窗。

完整程式碼

unit DragMain;

interface
uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms,
     Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    procedure WMNCHitTest(var Msg: TWMNCHitTest); message WM_NCHITTEST;
  end;

var Form1: TForm1;

implementation
{$R *.DFM}

procedure TForm1.WMNCHitTest(var Msg: TWMNCHitTest);
begin
  inherited;
  if Msg.Result = htClient then
    Msg.Result := htCaption;  // 讓系統以為點在標題列
end;

procedure TForm1.Button1Click(Sender: TObject);
begin Close; end;

end.

表單屬性設定 (DFM)

object Form1: TForm1
  BorderIcons = []      // 無系統按鈕
  BorderStyle = bsNone  // 無邊框/標題列
  ClientHeight = 273
  ClientWidth = 427
  object Button1: TButton
    Left = 160; Top = 104; Width = 89; Height = 33
    Caption = 'Close'; OnClick = Button1Click
  end
end

應用場景

• 自訂外觀視窗 (Skins、非矩形視窗)。
• 啟動畫面、工具箱、浮動面板。