"Устранение ошибки "Невозможно сделать видимое окно модальным" при перемещении приложения Delphi 2009 из окружения Windows 2003 / Citrix в 64-битную среду Windows 2008 R2"

Delphi , Программа и Интерфейс , Модальные формы

Title: Resolving "Cannot make a visible Window modal" Error in Delphi 2009 Application on Windows 2008 R2

Introduction: After migrating a Delphi 2009 application from a Windows 2003/Citrix environment to a 64-bit Windows 2008 R2 environment, users started experiencing runtime errors saying "Cannot make a visible Window modal". This issue occurs when a user opens a modal form, and an event handler assigned to a menu item in the main form is triggered, seemingly by pressing its shortcut key. This article provides a solution to this problem.

Problem Description: The user opens a modal form, and somehow an event handler assigned to a menu item in the main form is triggered. The call stack suggests that the user is able to invoke the menu item by pressing its shortcut key. The error message is: "Cannot make a visible Window modal".

Solution:

1. Update Windows Server: Ensure that Windows Server 2008 R2 Service Pack 1 (SP1) is installed. If not, install it, as it contains various bug fixes and improvements.

2. Check for Event Bouncing: The issue might be due to event bouncing, where an event is triggered multiple times, leading to unexpected behavior. To diagnose this:

a. Add logging or breakpoint in the event handler that is being triggered unexpectedly.

b. Try to reproduce the issue by pressing the shortcut key combination quickly or repeatedly.

c. Check if the event handler is being triggered multiple times.

1. Avoid Using Application.ProcessMessages: Be cautious when using Application.ProcessMessages in your code. It can lead to re-entrancy issues if not used properly. In this context, avoid using it, as the message loop in ShowModal should provide the necessary message pumping.

2. Check for Shortcut Key Conflicts: Ensure that the shortcut key combinations assigned to menu items do not conflict with any system-wide or other application shortcuts.

3. Update Delphi: If the issue persists, consider updating your Delphi version to a newer one, as it might contain bug fixes related to this problem.

Alternative Solution: If the issue is related to the usage of an Acrobat ActiveX control in the application, investigate and address that specific issue. The errors mentioned in the update section seem to be related to Acrobat, so ensure that the ActiveX control is used correctly and that there are no known bugs or compatibility issues with the specific Acrobat version.

Conclusion: By following the steps above, you should be able to resolve the "Cannot make a visible Window modal" error in your Delphi 2009 application on Windows 2008 R2. If the issue persists, consider seeking further assistance or providing additional information about your application and environment.

Example Code: To demonstrate the proper use of modal forms and event handling, here's an example of how to show a modal form and handle a menu item click event without using Application.ProcessMessages:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    btnShowModal: TButton;
    mnuFile: TMenuItem;
    popFile: TPopupMenu;
    procedure btnShowModalClick(Sender: TObject);
    procedure mnuFileClick(Sender: TObject);
  private
    { Private declarations }
    FModalForm: TForm;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.btnShowModalClick(Sender: TObject);
begin
  FModalForm := TForm1.Create(nil);
  try
    FModalForm.ShowModal;
  finally
    FModalForm.Free;
  end;
end;

procedure TForm1.mnuFileClick(Sender: TObject);
begin
  // Handle menu item click event here
  ShowMessage('Menu item clicked!');
end;

end.

In this example, when the user clicks the "Show Modal" button, a new instance of TForm1 is created and shown modally. When the user clicks the "File" menu item, the mnuFileClick event handler is triggered, displaying a message box. The ShowModal method provides the necessary message pumping, so there's no need to call Application.ProcessMessages.

Создано по материалам из источника по ссылке.

В контексте: Пользователи сталкиваются с ошибкой "Не удалось сделать видимое окно модальным" в приложении Delphi 2009 на Windows 2008 R2 после миграции из среды Windows 2003/Citrix.

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