annotate data/model/PowerOfTwoZoomConstraint.cpp @ 1324:d4a28d1479a8 zoom

Some hackery toward having a zoomlevel type

/* -*- 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.
*/

#include "PowerOfTwoZoomConstraint.h"

ZoomLevel
PowerOfTwoZoomConstraint::getNearestZoomLevel(ZoomLevel requested,
                                              RoundingDirection dir) const
{
    int blockSize;

    if (requested.zone == ZoomLevel::FramesPerPixel) {
        blockSize = getNearestBlockSize(requested.level, dir);
        if (blockSize > getMaxZoomLevel().level) {
            blockSize = getMaxZoomLevel().level;
        }
        return { requested.zone, blockSize };
    } else {
        RoundingDirection opposite = dir;
        if (dir == RoundUp) opposite = RoundDown;
        else if (dir == RoundDown) opposite = RoundUp;
        blockSize = getNearestBlockSize(requested.level, opposite);
        if (blockSize > getMinZoomLevel().level) {
            blockSize = getMinZoomLevel().level;
        }
        if (blockSize == 1) {
            return { ZoomLevel::FramesPerPixel, 1 };
        } else {
            return { requested.zone, blockSize };
        }
    }
}

int
PowerOfTwoZoomConstraint::getNearestBlockSize(int req,
					      RoundingDirection dir) const
{
    int result = 0;

    for (int bs = 1; ; bs *= 2) {
	if (bs >= req) {
	    if (dir == RoundNearest) {
		if (bs - req < req - bs/2) {
		    result = bs;
		    break;
		} else {
		    result = bs/2;
		    break;
		}
	    } else if (dir == RoundDown) {
		result = bs/2;
		break;
	    } else {
		result = bs;
		break;
	    }
	}
    }

    if (result > getMaxZoomLevel().level) result = getMaxZoomLevel().level;
    return result;
}