Message Dialog Boxes

• Nov 23, 2021
• 4 minutes to read

A message box is a modal dialog designed to display important information and optionally allow a user to make a choice or confirm an operation. All DevExpress products use the TdxMessageDialogForm class to display message dialog boxes that support skins and BBCode-inspired markup tags:

Create a Skinnable Message Box

Skinnable message dialog boxes allow you to keep the appearance of your application consistent. They import all look & feel settings from the TdxSkinController component if it is in an application project. To create such a message box, call one of the global DevExpress methods that have the same API as the corresponding standard VCL library methods:

DevExpress Method	Standard VCL Method	Description
dxCreateMessageDialog	CreateMessageDialog	Creates a message dialog box form with the specified settings.
dxMessageBox	TApplication.MessageBox	Invokes a modal message box dialog.
dxMessageDlg	MessageDlg	Invokes a modal message box dialog.
dxMessageDlgPos	MessageDlgPos	Invokes a modal message box dialog at the specified position on the screen.
dxMessageDlgPosHelp	MessageDlgPosHelp	Invokes a message box dialog whose help topic is supplied in a specified help file.
dxShowMessage	ShowMessage	Invokes a generic message dialog box with an OK button.
dxShowMessageFmt	ShowMessageFmt	Displays a message dialog box with a formatted message.
dxShowMessagePos	ShowMessagePos	Invokes the message dialog box at the specified position on the screen.

All DevExpress controls and components call these global methods to display message boxes. If you use DevExpress methods to invoke message boxes, you can use the global dxUseStandardMessageDialogs global variable to switch between standard and skinnable message boxes.

Customize Dialog Buttons

The TdxMessageDialogForm uses the TcxButton components to display message box buttons. You can use the TdxMessageDialogForm.Buttons property or the TdxMessageDialogForm.FindButton function to change predefined button captions before the form is displayed. The following code example changes captions of the Yes, No, and Cancel buttons:

Delphi

var
  ADialog: TdxMessageDialogForm;
  AMessage: string;
begin
  AMessage := 'One or more margins are set outside the printable area of the page.' + #13#10 +
    'Choose the [B]Fix[/B] button to increase the appropriate margins.';
  ADialog := dxCreateMessageDialog(AMessage, mtWarning, mbYesNoCancel);
try
  ADialog.FindButton(mbYes).Caption := 'Fix';
  ADialog.FindButton(mbNo).Caption := 'Restore Original';
  ADialog.FindButton(mbCancel).Caption := 'Close';

  ADialog.AlignButtons;   // Recalculates the button layout
  ADialog.ShowModal;      // Invokes the form as a modal dialog
finally
  ADialog.Free;
end;

C++

  TdxMessageDialogForm *ADialog;
  UnicodeString AMessage = "One or more margins are set outside the printable area of the page.\n" +
    "Choose the [B]Fix[/B] button to increase the appropriate margins.";
  ADialog = dxCreateMessageDialog(AMessage, wtWarning, mbYesNoCancel);
  try
  {
    ADialog->FindButton(mbYes)->Caption = "Fix";
    ADialog->FindButton(mbNo)->Caption = "Restore Original";
    ADialog->FindButton(mbCancel)->Caption = "Close";

    ADialog->AlignButtons();  // Recalculates the button layout
    ADialog->ShowModal();     // Invokes the form as a modal dialog
  }
  __finally
  {
    delete ADialog;
  }

Customize the Message Box Layout

The message dialog box form has multiple layout customization options:

Change the UseLatestCommonDialogs Global Variable

Set this variable to False or True to switch between two predefined layouts also available for standard message boxes:

Value	Description	Example
True (Default)	The modern message box style available on Microsoft Windows® Vista and later operating systems. The message box has a fixed width; the buttons are right-aligned.
False	The message box style found in Microsoft Windows® XP and older operating systems. The width of the message box depends on its content size; the buttons are centered.

Use the TdxMessageDialogForm.Style Property

This layout customization option is available only before you manually display a skinnable message dialog box form after you call the dxCreateMessageDialog function or the form constructor.

Set the form’s Style property to mdsMessageBox or mdsMessageDlg to switch between two layout styles that imitate the message boxes that different VCL library methods can invoke:

Value	Description	Example
mdsMessageDlg (default)	This message dialog style imitates the dialogs that the standard MessageDlg function invokes. The message box layout has increased paddings between borders and the message icon.
mdsMessageBox	This message box style imitates the dialog boxes that the standard MessageBox function invokes. The message box layout is smaller compared to the message dialog style (mdsMessageDlg).

Create a Custom Message Dialog Box Form

You can replace the message dialog box form with a custom implementation:

1. Derive a custom form from the TdxMessageDialogForm class.
2. Assign a reference to your form class to the dxMessageDialogFormClass global variable.