Chris@147: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@147: 
Chris@147: /*
Chris@147:     Sonic Visualiser
Chris@147:     An audio file viewer and annotation editor.
Chris@147:     Centre for Digital Music, Queen Mary, University of London.
Chris@147:     This file copyright 2006 Chris Cannam.
Chris@147:     
Chris@147:     This program is free software; you can redistribute it and/or
Chris@147:     modify it under the terms of the GNU General Public License as
Chris@147:     published by the Free Software Foundation; either version 2 of the
Chris@147:     License, or (at your option) any later version.  See the file
Chris@147:     COPYING included with this distribution for more information.
Chris@147: */
Chris@147: 
Chris@147: #include "PowerOfTwoZoomConstraint.h"
Chris@147: 
Chris@1324: ZoomLevel
Chris@1324: PowerOfTwoZoomConstraint::getNearestZoomLevel(ZoomLevel requested,
Chris@1324:                                               RoundingDirection dir) const
Chris@1324: {
Chris@1324:     int blockSize;
Chris@1324: 
Chris@1324:     if (requested.zone == ZoomLevel::FramesPerPixel) {
Chris@1324:         blockSize = getNearestBlockSize(requested.level, dir);
Chris@1324:         if (blockSize > getMaxZoomLevel().level) {
Chris@1324:             blockSize = getMaxZoomLevel().level;
Chris@1324:         }
Chris@1324:         return { requested.zone, blockSize };
Chris@1324:     } else {
Chris@1324:         RoundingDirection opposite = dir;
Chris@1324:         if (dir == RoundUp) opposite = RoundDown;
Chris@1324:         else if (dir == RoundDown) opposite = RoundUp;
Chris@1324:         blockSize = getNearestBlockSize(requested.level, opposite);
Chris@1324:         if (blockSize > getMinZoomLevel().level) {
Chris@1324:             blockSize = getMinZoomLevel().level;
Chris@1324:         }
Chris@1324:         if (blockSize == 1) {
Chris@1324:             return { ZoomLevel::FramesPerPixel, 1 };
Chris@1324:         } else {
Chris@1324:             return { requested.zone, blockSize };
Chris@1324:         }
Chris@1324:     }
Chris@1324: }
Chris@1324: 
Chris@929: int
Chris@929: PowerOfTwoZoomConstraint::getNearestBlockSize(int req,
Chris@1429:                                               RoundingDirection dir) const
Chris@147: {
Chris@929:     int result = 0;
Chris@147: 
Chris@929:     for (int bs = 1; ; bs *= 2) {
Chris@1429:         if (bs >= req) {
Chris@1429:             if (dir == RoundNearest) {
Chris@1429:                 if (bs - req < req - bs/2) {
Chris@1429:                     result = bs;
Chris@1429:                     break;
Chris@1429:                 } else {
Chris@1429:                     result = bs/2;
Chris@1429:                     break;
Chris@1429:                 }
Chris@1429:             } else if (dir == RoundDown) {
Chris@1429:                 result = bs/2;
Chris@1429:                 break;
Chris@1429:             } else {
Chris@1429:                 result = bs;
Chris@1429:                 break;
Chris@1429:             }
Chris@1429:         }
Chris@147:     }
Chris@147: 
Chris@1324:     if (result > getMaxZoomLevel().level) result = getMaxZoomLevel().level;
Chris@147:     return result;
Chris@147: }
Chris@147: