I'm using CodeTyphon 4.10 on ubuntu mint 14 desktop (x86-64)
- CodeTyphon 4.10 = FPC 2.7.1, Lazarus 2013-03-25 SVN 40461CT x86_64-linux-gtk2

Barcode reader is MOTOROLA DS3578 with FIPS model (configed HID Keyboard Emulation, USB Type)

I make reader code using TForm.KeyPreview property.

1. There is main form. (Keypreview := True)
2. Make OnKeyPress event handler
3. Read a sample QRCode ( http://localhost/qrcode/Test_2012/A001 )
4. OnKeyPress missing some characters.
-> Readed -> http://localhost/qrcode/est2012/001
-> Missed capital character(T, A) and under bar character(_) -> Lower case character is no problem.

When I read barcode(qrcode) focus to text editor like pluma, qrcode data is inserted correctly without missing characters.

Here is test project main form unit source code:

//----------------------------------- SAMPLE CODE
unit Unit1;
{$mode objfpc}{$H+}
interface

uses
Classes, SysUtils, FileUtil, ubarcodes, Forms, Controls, Graphics, Dialogs,

  StdCtrls, LCLType;

type
  { TForm1 }
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormKeyPress(Sender: TObject; var Key: char);
  private
    FBuffer: string;
  public
    { public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.lfm}

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
begin
  KeyPreview := True;
end;
procedure TForm1.FormKeyPress(Sender: TObject; var Key: char);
begin
  FBuffer += Key;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(FBuffer);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
  FBuffer := '';
end;

end.
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I can confirm this behavior with Lazarus 1.6 (gtk2) / FPC 3.0 on Xubuntu 16.04.

Typing keys rapidly (even by hand with a normal keyboard) will make it lose keypress events occasionally, using a barcode reader (it emulates an USB-Keyboard) through the KeyPress event is virtually impossible with Gtk2-LCL. No problems on Windows.

Bypassing the LCL and binding a handler directly to the gtk signal proves that gtk will fire events for *all* keys, no matter how rapidly the keyboard will send them, its just LCL that is missing some of them :-(

2013-03-25 14:17 GMT+01:00 byungho jeon :