使用 WM_NCHITTEST 消息判断鼠标所在窗口的部位

本例效果图:

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WM_NCHITTEST 消息返回后, 消息的 Result 参数表示了鼠标所在窗口的部位.

窗体设计步骤: 新建工程后, 随便添加一个菜单; 设置窗体的 AutoScroll 属性为 True, 并添加一个 Panel 放在合适的位置, 以让窗口出现滚动条.

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unit Unit1;



interface



uses

  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 - 客户区',

    'HTCAPTION - 标题',

    'HTSYSMENU - 系统菜单',

    'HTGROWBOX',

    'HTMENU - 菜单',

    'HTHSCROLL - 水平滚动条',

    'HTVSCROLL - 垂直滚动条',

    'HTMINBUTTON - 最小化按钮',

    'HTMAXBUTTON - 最大化按钮',

    'HTLEFT - 左边界',

    'HTRIG - 右边界',

    'HTTOP - 上边界',

    'HTTOPLEFT - 左上角',

    'HTTOPRIG - 右上角',

    'HTBOTTOM - 下边界',

    'HTBOTTOMLEFT - 左下角',

    'HTBOTTOMRIG - 右下角',

    'HTBORDER',

    'HTOBJECT',

    'HTCLOSE - 关闭按钮',

    '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 消息中 Result 参数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;