使用 WM_NCHITTEST 消息判断鼠标所在窗口的部位

本例效果图:



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.

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;