MessageDialog.this

Creates a new adw.message_dialog.MessageDialog.

heading and body can be set to NULL. This can be useful if they need to be formatted or use markup. In that case, set them to NULL and call adw.message_dialog.MessageDialog.formatBody or similar methods afterwards:

GtkWidget *dialog;

dialog = adw_message_dialog_new (parent, _("Replace File?"), NULL);
adw_message_dialog_format_body (ADW_MESSAGE_DIALOG (dialog),
                                _("A file named “%s” already exists.  Do you want to replace it?"),
                                filename);