DUring loading of a JPEG image i use the on progress to provide feedback
and application.processmessages to give the user some control over the
application.  However  i want that control to include cancelling the
loading of the current image, is that possible?

Thanks

William
The_White_Ho...@USA.Net

William,

interface

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

type
  ELoadCanceled = Class(Exception);
  TForm1 = class(TForm)
    Image1: TImage;
    ProgressBar1: TProgressBar;
    Button1: TButton;
    Button2: TButton;
    OpenDialog1: TOpenDialog;
    procedure Image1Progress(Sender: TObject; Stage: TProgressStage;
      PercentDone: Byte; RedrawNow: Boolean; const R: TRect;
      const Msg: String);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    bCancel : Boolean;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Image1Progress(Sender: TObject; Stage: TProgressStage;
  PercentDone: Byte; RedrawNow: Boolean; const R: TRect;
  const Msg: String);
begin
  Application.ProcessMessages;
  if bCancel then begin
    bCancel := False; //  This is important! You get an AV without it.
    Abort;  //  Raise silent exception
  end
  else
    ProgressBar1.Position := Integer(PercentDone);
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
  if OpenDialog1.Execute then begin
    try
      Image1.Picture.LoadFromFile(OpenDialog1.Filename);
    Except  //wrap up
      on E: ELoadCanceled do begin
        showmessage(E.Message);
        bCancel := False;
      end;
    end;    //try / finally    
  end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
  bCancel := True;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
  bCancel := False;
end;
end.
===================

Ummm... Ignore the try/except block in Button1Click - it is a hangover
from a previous attempt. :-)

Miles

Thanks this code was most excellent!

William

RICHM...@goodluck.prodigy.net wrote in article
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