作者：南京 邹莉

ReadBook是一款优秀的软件，我相信读者中也有不少人在使用它。关于它的病毒自我监测功能的实现，《电脑爱好者》已经讨论过了。今天，我想给大家谈谈它是如何在窗口的标题区添加按钮的。有可能我的实现方法和ReadBook的不一样，没关系，大家互相学习吧！

程序主要用到了几个消息，除了程序中消息函数定义的方法外，大家还要注意每一个消息函数中都调用了inherited，原因不用我饶舌了吧？程序中还调用了GetSystemMetrics、DrawButtonFace等几个函数。我本来在程序中详细地加了注释，不过我后来都删除了，因为Delphi的帮助文件可以说是最好的注释了。如果你有什么不懂之处，别忘了按“F1”键，怎么样，一切都写得清清楚楚的吧？

把下边的程序输进计算机，自己用帮助文件研究吧。记住，学习编程可不能偷懒哦。

unit Unit1;

interface

uses

Windows, Buttons, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;

type

TForm1 = class(TForm)

procedure FormResize(Sender: TObject);


private
{ Private declarations }

CaptionBtn:TRect;

procedure DrawCaptButton;

rocedure WMNCPaint(var Msg:TWMNCPaint);message WM_NCPaint;

procedure WMNCActivate(var Msg:TWMNCActivate);message WM_NCActivate;

procedure WMSetText(var Msg:TWMSetText);message WM_SetText;

procedure WMNCHitTest(var Msg:TWMNCHitTest);message WM_NCHittest;

procedure WMNCLButtonDown(var Msg:TWMNCLButtonDown);message WM_NCLButtonDown;

public

{ Public declarations }

end;


var

Form1: TForm1;

implementation

const

htCaptionBtn=htSizeLast+1;

{$R *.DFM}

procedure TForm1.DrawCaptButton;

var

xFrame,yFrame,xSize,ySize:Integer;

R:TRect;

begin

xFrame:=GetSystemMetrics(SM_CXFRAME);

yFrame:=GetSystemMetrics(SM_CYFRAME);

xSize:=GetSystemMetrics(SM_CXSIZE);

ySize:=GetSystemMetrics(SM_CYSIZE);

CaptionBtn:=Bounds(Width-xFrame-4*xSize+2,yFrame+2,xSize+1,ySize-4);

Canvas.Handle:=GetWindowDC(Self.Handle);

Canvas.Font.Name:='宋体';

Canvas.Font.Color:=clBlack;


Canvas.Pen.Color:=clYellow;
Canvas.Brush.Color:=clBtnFace;

try

DrawButtonFace(Canvas,CaptionBtn,1,bsAutoDetect,False,False,False);

R:=Bounds(Width-xFrame-4*xSize+3,yFrame+3,xSize-2,ySize-7);

with CaptionBtn do

Canvas.TextRect(R,R.Left+2,R.Top+2,'↘');

finally

ReleaseDC(Self.Handle,Canvas.Handle);

Canvas.Handle:=0;

end;

end;

procedure TForm1.WMNCActivate(var Msg: TWMNCActivate);

begin

inherited;

DrawCaptButton;

end;

procedure TForm1.WMNCHitTest(var Msg: TWMNCHitTest);

begin

inherited;

with Msg do

if PtInRect(CaptionBtn,Point(xPos-Left,yPos-Top)) then

Result:=htCaptionBtn;

end;

procedure TForm1.WMNCLButtonDown(var Msg: TWMNCLButtonDown);

begin

inherited;

if(Msg.HitTest=htCaptionBtn)then

showmessage('成功了!');

end;

procedure TForm1.WMNCPaint(var Msg: TWMNCPaint);

begin

inherited;

DrawCaptButton;

end;

procedure TForm1.WMSetText(var Msg: TWMSetText);

begin

inherited;

DrawCaptButton;

end;

procedure TForm1.FormResize(Sender: TObject);

begin

Perform(WM_NCACTIVATE,Word(Active),0);

end;

end.

仔细研究一下程序中有关计算的几个句子，试着改变某个数字看一看，这将有助于你理解程序。

本文中的程序在Windows98/WindowsMe环境下使用Delphi5/ Delphi6调试通过。