使用 WM_NCHITTEST 訊息判斷滑鼠所在視窗的部位

本例:

WM_NCHITTEST 訊息返回後, 訊息的 Result 參數表示了滑鼠所在視窗的部位.

表單設計步驟: 建立工程後, 隨便添加一個菜單; 設定表單的 AutoScroll 屬性為 True, 並添加一個 Panel 放在合適的位置, 以讓視窗出現捲軸.

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, ExtCtrls, StdCtrls, Menus;type  TForm1 = class(TForm)    Panel1: TPanel;    MainMenu1: TMainMenu;    mnuFile: TMenuItem;  private    procedure MyMsg(var msg: TWMNCHitTest); message WM_NCHITTEST;  end;var  Form1: TForm1;implementation{$R *.dfm}const  arr: array[-2..21] of string = (    'HTERROR',    'HTTRANSPARENT',    'HTNOWHERE',    'HTCLIENT - 客戶區',    'HTCAPTION - 標題',    'HTSYSMENU - 系統功能表',    'HTGROWBOX',    'HTMENU - 菜單',    'HTHSCROLL - 水平捲軸',    'HTVSCROLL - 垂直捲軸',    'HTMINBUTTON - 最小化按鈕',    'HTMAXBUTTON - 最大化按鈕',    'HTLEFT - 左邊界',    'HTRIG - 右邊界',    'HTTOP - 上邊界',    'HTTOPLEFT - 左上方',    'HTTOPRIG - 右上方',    'HTBOTTOM - 下邊界',    'HTBOTTOMLEFT - 左下角',    'HTBOTTOMRIG - 右下角',    'HTBORDER',    'HTOBJECT',    'HTCLOSE - 關閉按鈕',    'HTHELP');procedure TForm1.MyMsg(var msg: TWMNCHitTest);var  i: Integer;begin  Inherited;  i := msg.Result;  Text := Format('%d: %s', [i, arr[i]]);end;end.//另附 WM_NCHITTEST 訊息中 Result 參數的所有可能值的列表:HTERROR       = -2;HTTRANSPARENT = -1;HTNOWHERE     = 0;HTCLIENT      = 1;HTCAPTION     = 2;HTSYSMENU     = 3;HTGROWBOX     = 4;HTSIZE        = HTGROWBOX;HTMENU        = 5;HTHSCROLL     = 6;HTVSCROLL     = 7;HTMINBUTTON   = 8;HTMAXBUTTON   = 9;HTLEFT        = 10;HTRIGHT       = 11;HTTOP         = 12;HTTOPLEFT     = 13;HTTOPRIGHT    = 14;HTBOTTOM      = 15;HTBOTTOMLEFT  = $10;HTBOTTOMRIGHT = 17;HTBORDER      = 18;HTREDUCE      = HTMINBUTTON;HTZOOM        = HTMAXBUTTON;HTSIZEFIRST   = HTLEFT;HTSIZELAST    = HTBOTTOMRIGHT;HTOBJECT      = 19;HTCLOSE       = 20;HTHELP        = 21;