view data/model/PowerOfSqrtTwoZoomConstraint.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 "PowerOfSqrtTwoZoomConstraint.h"

#include <iostream>
#include <cmath>


ZoomLevel
PowerOfSqrtTwoZoomConstraint::getNearestZoomLevel(ZoomLevel requested,
						  RoundingDirection dir) const
{
    int type, power;
    int blockSize;

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

int
PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(int blockSize,
						  int &type, 
						  int &power,
						  RoundingDirection dir) const
{
//    cerr << "given " << blockSize << endl;

    int minCachePower = getMinCachePower();

    if (blockSize < (1 << minCachePower)) {
	type = -1;
	power = 0;
	float val = 1.0, prevVal = 1.0;
	while (val + 0.01 < blockSize) {
	    prevVal = val;
	    val *= sqrtf(2.f);
	}
	int rval;
	if (dir == RoundUp) rval = int(val + 0.01f);
	else if (dir == RoundDown) rval = int(prevVal + 0.01f);
	else if (val - float(blockSize) <
                 float(blockSize) - prevVal) rval = int(val + 0.01f);
	else rval = int(prevVal + 0.01);
//	SVDEBUG << "returning " << rval << endl;
	return rval;
    }

    int prevBase = (1 << minCachePower);
    int prevPower = minCachePower;
    int prevType = 0;

    int result = 0;

    for (unsigned int i = 0; ; ++i) {

	power = minCachePower + i/2;
	type = i % 2;

	int base;
	if (type == 0) {
	    base = (1 << power);
	} else {
	    base = (((unsigned int)((1 << minCachePower) * sqrt(2.) + 0.01))
		    << (power - minCachePower));
	}

//	SVDEBUG << "Testing base " << base << endl;

        if (base == blockSize) {
            result = base;
            break;
        }

	if (base > blockSize) {
	    if (dir == RoundNearest) {
		if (base - blockSize < blockSize - prevBase) {
		    dir = RoundUp;
		} else {
		    dir = RoundDown;
		}
	    }
	    if (dir == RoundUp) {
		result = base;
		break;
	    } else {
		type = prevType;
		power = prevPower;
		result = prevBase;
		break;
	    }
	}

	prevType = type;
	prevPower = power;
	prevBase = base;
    }

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

    return result;
}