基类窗体要实现的需求包括：控件窗体的字体，权限控制，控制子窗体的显示范围，以及其它一些通用方法的声明。。。。。。
通用方法可声明为VIRTUAL方法，以允许从它继承的子窗体
可以OVERRIDE这些方法，达到多态的效果。
unit uBaseForm;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TBaseForm = class(TForm)
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
FRights: string;
procedure WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo ); message WM_GETMINMAXINFO;//控制子窗体的显示范围
public
property Rights: string read FRights write FRights;//权限控制
end;
var
BaseForm: TBaseForm;
implementation
{$R *.dfm}
procedure TBaseForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Action := caFree;
end;
procedure TBaseForm.WMGetMinMaxInfo(var Message: TWMGetMinMaxInfo);
begin
with Message.MinMaxInfo^ do
begin
ptMaxPosition.X := Screen.WorkAreaLeft; {Left position when maximized}
ptMaxPosition.Y := Application.MainForm.Height; {Top position when maximized}
ptMaxTrackSize.X := Screen.Width; {Maximum width}
ptMaxTrackSize.Y := screen.WorkAreaHeight - Application.MainForm.Height; {Maximum height}
end;
Message.Result := 0; {Tell windows you have changed minmaxinfo}
inherited;
end;
end.
)
