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1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
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2
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3 /*
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4 Sonic Visualiser
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5 An audio file viewer and annotation editor.
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6 Centre for Digital Music, Queen Mary, University of London.
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7 This file copyright 2006 Chris Cannam.
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8
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9 This program is free software; you can redistribute it and/or
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10 modify it under the terms of the GNU General Public License as
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11 published by the Free Software Foundation; either version 2 of the
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12 License, or (at your option) any later version. See the file
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13 COPYING included with this distribution for more information.
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14 */
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15
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16 #ifndef SV_ZOOM_CONSTRAINT_H
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17 #define SV_ZOOM_CONSTRAINT_H
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18
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19 #include <stdlib.h>
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20
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21 #include "BaseTypes.h"
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22
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23 /**
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24 * ZoomConstraint is a simple interface that describes a limitation on
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25 * the available zoom sizes for a view, for example based on cache
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26 * strategy or a (processing) window-size limitation.
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27 *
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28 * The default ZoomConstraint imposes no actual constraint except for
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29 * a nominal maximum.
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30 */
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31
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32 class ZoomConstraint
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33 {
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34 public:
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35 virtual ~ZoomConstraint() { }
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36
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37 enum RoundingDirection {
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38 RoundDown,
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39 RoundUp,
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40 RoundNearest
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41 };
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42
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43 /**
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44 * Given an "ideal" zoom level (frames per pixel or pixels per
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45 * frame) for a given zoom level, return the nearest viable block
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46 * size for this constraint.
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47 *
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48 * For example, if a block size of 1523 frames per pixel is
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49 * requested but the underlying model only supports value
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50 * summaries at powers-of-two block sizes, return 1024 or 2048
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51 * depending on the rounding direction supplied.
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52 */
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53 virtual ZoomLevel getNearestZoomLevel(ZoomLevel requestedZoomLevel,
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54 RoundingDirection = RoundNearest)
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55 const
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56 {
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57 if (getMaxZoomLevel() < requestedZoomLevel) return getMaxZoomLevel();
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58 else return requestedZoomLevel;
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59 }
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60
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61 /**
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62 * Return the minimum zoom level within range for this constraint.
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63 * Individual views will probably want to limit this, for example
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64 * in order to ensure that at least one or two samples fit in the
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65 * current window size, or in order to save on interpolation cost.
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66 */
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67 virtual ZoomLevel getMinZoomLevel() const {
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68 return { ZoomLevel::PixelsPerFrame, 16384 };
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69 }
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70
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71 /**
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72 * Return the maximum zoom level within range for this constraint.
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73 * This is quite large -- individual views will probably want to
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74 * limit how far a user might reasonably zoom out based on other
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75 * factors such as the duration of the file.
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76 */
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77 virtual ZoomLevel getMaxZoomLevel() const {
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78 return { ZoomLevel::FramesPerPixel, 4194304 }; // 2^22, arbitrarily
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79 }
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80 };
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81
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82 #endif
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83
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