/*
  LAYOUT-MANAGER.hpp  -  global timeline layout management and display control

  Copyright (C)         Lumiera.org
    2016,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/


/** @file layout-manager.hpp
 ** A core service of the timeline UI to ensure consistent display and layout
 ** of all components within the timeline. The content of the timeline is organised
 ** into several nested collections, possibly holding several thousand individual elements.
 ** Together with the requirement to show media elements within a precisely defined, regular
 ** time grid, this forces us to control various aspects of the layout and display style
 ** manually, instead of letting the UI toolkit work out the details automatically. Note
 ** especially that the typical UI toolkit is not prepared to handle such a high number of
 ** individual elements smoothly. Even more so, when most of those elements are not even
 ** visible most of the time. Unfortunately, doing a manual display forces us to perform
 ** the task usually serviced by a table grid widget, that is, to keep flexible elements
 ** aligned in columns or (as is the case here) in rows. Basically we split our display
 ** horizontally, where the right part is just a custom drawing canvas. Consequently we
 ** have to ensure all tracks are perfectly aligned between the track header pane and
 ** the scrollable working space in the timeline body display.
 ** 
 ** # Architecture
 ** 
 ** A naive approach would have a global layout manager drill down into some model storage
 ** and reach into the components to manipulate and adjust the layout to fit. Doing so can
 ** be considered, since this links together details scattered all over the model into a
 ** huge global process carried out at a single code location. Any further extension or
 ** evolution of details of the UI presentation are bound to be worked into this core
 ** global piece of code, which soon becomes brittle, hard to understand and generally
 ** a liability and maintenance burden. We have seen this happen in numerous existing
 ** code bases (and in fact even our own initial approach started to go down that route).
 ** Thus we strive to break up the whole process of controlling the layout into several
 ** local concerns, each of which can be made self contained. The backbone is formed by
 ** a recursive collaboration between two abstractions (interfaces)
 ** - the building blocks of the timeline expose the interface timeline::Element
 ** - the global timeline widget implements a timeline::LayoutManager interface
 ** 
 ** ## Display evaluation pass
 ** 
 ** Whenever the layout of timeline contents has to be (re)established, we trigger a recursive
 ** evaluation pass, which in fact is a tree walk. The layout manager creates a DisplayEvaluation
 ** record, which is passed to the [Element's allocate function](Element::allocate). The element
 ** in turn has the liability to walks its children and recursively initiate a nested evaluation
 ** by invoking DisplayEvaluation::evaluateChild(Element), which in turn calls back to
 ** LayoutManager::evaluate() to initiate a recursive evaluation pass. Within the recursively
 ** created DisplayEvaluation elements, we are able to transport and aggregate information
 ** necessary to give each element it' screen allocation. And this in turn allows us to
 ** decide upon a suitable display strategy for each individual element.
 ** 
 ** For this to work, the _element_ can not be the actual widget, since the result of this whole
 ** process might be to create or retract an actual GTK widget. For this reason, the timeline
 ** layout management relies on a _Presenter_ entity, which in turn controls a mostly passive
 ** view -- our solution in fact relies on some flavour of the
 ** [MVP pattern](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93presenter) here.
 ** 
 ** @todo WIP-WIP-WIP as of 12/2016
 ** 
 */


#ifndef GUI_TIMELINE_LAYOUT_MANAGER_H
#define GUI_TIMELINE_LAYOUT_MANAGER_H

#include "gui/gtk-base.hpp"

//#include "lib/util.hpp"

//#include <memory>
//#include <vector>



namespace gui  {
namespace timeline {
  
  
  /**
   * @todo WIP-WIP as of 12/2016
   */
  class LayoutManager
    {
    public:
      LayoutManager ();
     ~LayoutManager();
     
    private:/* ===== Internals ===== */
     
    };
  
  
}}// namespace gui::timeline
#endif /*GUI_TIMELINE_LAYOUT_MANAGER_H*/