view base/ZoomConstraint.h @ 492:23945cdd7161

* Update RDF query stuff again so as to set up a temporary datastore
  each time we want to query over an rdf file, instead of using rasqal
  against the file.  Seems the only way to avoid threading and storage
  management issues when trying to load from a single-source file and
  perform queries against our main datastore at the same time.  Maybe.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _ZOOM_CONSTRAINT_H_
#define _ZOOM_CONSTRAINT_H_

#include <stdlib.h>

/**
 * ZoomConstraint is a simple interface that describes a limitation on
 * the available zoom sizes for a view, for example based on cache
 * strategy or a (processing) window-size limitation.
 *
 * The default ZoomConstraint imposes no actual constraint except for
 * a nominal maximum.
 */

class ZoomConstraint
{
public:
    virtual ~ZoomConstraint() { }

    enum RoundingDirection {
	RoundDown,
	RoundUp,
	RoundNearest
    };

    /**
     * Given the "ideal" block size (frames per pixel) for a given
     * zoom level, return the nearest viable block size for this
     * constraint.
     *
     * For example, if a block size of 1523 frames per pixel is
     * requested but the underlying model only supports value
     * summaries at powers-of-two block sizes, return 1024 or 2048
     * depending on the rounding direction supplied.
     */
    virtual size_t getNearestBlockSize(size_t requestedBlockSize,
				       RoundingDirection = RoundNearest)
	const
    {
	if (requestedBlockSize > getMaxZoomLevel()) return getMaxZoomLevel();
	else return requestedBlockSize;
    }

    /**
     * Return the maximum zoom level within range for this constraint.
     */
    virtual size_t getMaxZoomLevel() const { return 262144; }
};

#endif