enumobjunit.pas

DelphiWin32核心API参考光盘内容.是学习书籍中的源码,便于学习.

unit EnumObjUnit;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
  TForm1 = class(TForm)
    ListBox: TListBox;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  {the callback function prototype}
  function EnumObjProc(ObjType: PLogPen; lData: lParam): Integer; stdcall;

var
  Form1: TForm1;

implementation

{$R *.DFM}

function EnumObjProc(ObjType: PLogPen; lData: lParam): Integer;
var
  LocalObjType: TLogPen;    // holds logical pen information
  PenDescription: String;   // holds a pen description
begin
  {get the pen information}
  LocalObjType := ObjType^;

  {determine the type of pen being enumerated}
  case LocalObjType.lopnStyle of
    PS_SOLID:       PenDescription := 'PS_SOLID';
    PS_DASH:        PenDescription := 'PS_DASH';
    PS_DOT:         PenDescription := 'PS_DOT';
    PS_DASHDOT:     PenDescription := 'PS_DASHDOT';
    PS_DASHDOTDOT:  PenDescription := 'PS_DASHDOTDOT';
    PS_NULL:        PenDescription := 'PS_NULL';
    PS_INSIDEFRAME: PenDescription := 'PS_INSIDEFRAME';
  end;

  {determine the color of the pen being enumerated}
  case LocalObjType.lopnColor of
    clBlack:   PenDescription := PenDescription+' Color: clBlack';
    clMaroon:  PenDescription := PenDescription+' Color: clMaroon';
    clGreen:   PenDescription := PenDescription+' Color: clGreen';
    clOlive:   PenDescription := PenDescription+' Color: clOlive';
    clNavy:    PenDescription := PenDescription+' Color: clNavy';
    clPurple:  PenDescription := PenDescription+' Color: clPurple';
    clTeal:    PenDescription := PenDescription+' Color: clTeal';
    clGray:    PenDescription := PenDescription+' Color: clGray';
    clSilver:  PenDescription := PenDescription+' Color: clSilver';
    clRed:     PenDescription := PenDescription+' Color: clRed';
    clLime:    PenDescription := PenDescription+' Color: clLime';
    clYellow:  PenDescription := PenDescription+' Color: clYellow';
    clBlue:    PenDescription := PenDescription+' Color: clBlue';
    clFuchsia: PenDescription := PenDescription+' Color: clFuchsia';
    clAqua:    PenDescription := PenDescription+' Color: clAqua';
    clWhite:   PenDescription := PenDescription+' Color: clWhite';
  end;

  {indicate the pen's width}
  PenDescription:=PenDescription+' Width: '+IntToStr(LocalObjType.lopnWidth.X);

  {add the description to the list box}
  Form1.ListBox.Items.Add(PenDescription);

  {indicate that enumeration should continue}
  Result := 1;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  {enumerate all pens in the form's device context}
  EnumObjects(Canvas.Handle, OBJ_PEN, @EnumObjProc, 0);
end;

end.