// This may look like C code, but it's really -*- C++ -*-
/*
 * Copyright (C) 2008 Emweb bvba, Kessel-Lo, Belgium.
 *
 * See the LICENSE file for terms of use.
 */
#ifndef WLOADING_INDICATOR_H_
#define WLOADING_INDICATOR_H_

#include <Wt/WDllDefs.h>

namespace Wt {

class WString;
class WWidget;

/*! \class WLoadingIndicator Wt/WLoadingIndicator Wt/WLoadingIndicator
 *  \brief An abstract interface for a loading indicator.
 *
 * The loading indicator displays a message while a response from the
 * server is pending.
 *
 * By providing a custom implementation of this interface, you may use
 * a custom loading indicator using
 * WApplication::setLoadingIndicator(),instead of the default
 * implementation (WDefaultLoadingIndicator).
 *
 * \sa WApplication::setLoadingIndicator()
 */
class WT_API WLoadingIndicator
{
public:
  /*! \brief Destructor.
   *
   * The destructor must delete the widget().
   */
  virtual ~WLoadingIndicator();

  /*! \brief Returns the widget that visually represents the indicator.
   *
   * You should reimplement this method to return a widget that will
   * be shown to indicate that a response is pending. The widget
   * should be positioned using CSS.
   *
   * The widget will be shown and hidden using WWidget::show() and
   * WWidget::hide(). If you want to customize this behaviour, you
   * should reimplement the WWidget::setHidden() method. Note that
   * show() and hide() are stateless slots, and thus you need to make
   * sure that your implementation comforms to that contract, so that
   * it may be optimized to JavaScript (the server-side implementation
   * will only be called during stateless slot prelearning).
   *
   * \note The widget will not be added to the WApplication::root() container.
   */
  virtual WWidget *widget() = 0;

  /*! \brief Sets the message that you want to be displayed.
   *
   * If the indicator is capable of displaying a text message, then
   * you should reimplement this method to allow this message to be
   * modified.
   */
  virtual void setMessage(const WString& text) = 0;
};

}

#endif // WLOADING_INDICATOR_H_
