annotate layer/VerticalBinLayer.h @ 1127:9fb8dfd7ce4c spectrogram-minor-refactor

Fix threshold in spectrogram -- it wasn't working in the last release.
There is a new protocol for this. Formerly the threshold parameter had a
range from -50dB to 0 with the default at -50, and -50 treated internally
as "no threshold". However, there was a hardcoded, hidden internal threshold
for spectrogram colour mapping at -80dB with anything below this being rounded
to zero. Now the threshold parameter has range -81 to -1 with the default
at -80, -81 is treated internally as "no threshold", and there is no hidden
internal threshold. So the default behaviour is the same as before, an
effective -80dB threshold, but it is now possible to change this in both
directions. Sessions reloaded from prior versions may look slightly different
because, if the session says there should be no threshold, there will now
actually be no threshold instead of having the hidden internal one.

Still need to do something in the UI to make it apparent that the -81dB
setting removes the threshold entirely. This is at least no worse than the
previous, also obscured, magic -50dB setting.

/* -*- 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 2006-2016 Chris Cannam and QMUL.
    
    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 VERTICAL_BIN_LAYER_H
#define VERTICAL_BIN_LAYER_H

#include "SliceableLayer.h"

/**
 * Interface for layers in which the Y axis corresponds to bin number
 * rather than scale value. Colour3DPlotLayer is the obvious example.
 * Conceptually these are always SliceableLayers as well, and this
 * subclasses from SliceableLayer to avoid a big inheritance mess.
 */
class VerticalBinLayer : public SliceableLayer
{
public:
    /**
     * Return the y coordinate at which the given bin "starts"
     * (i.e. at the bottom of the bin, if the given bin is an integer
     * and the vertical scale is the usual way up). Bin number may be
     * fractional, to obtain a position part-way through a bin.
     */
    virtual double getYForBin(const LayerGeometryProvider *, double bin) const = 0;

    /**
     * As getYForBin, but rounding to integer values.
     */
    virtual int getIYForBin(const LayerGeometryProvider *v, int bin) const {
        return int(round(getYForBin(v, bin)));
    }
    
    /**
     * Return the bin number, possibly fractional, at the given y
     * coordinate. Note that the whole numbers occur at the positions
     * at which the bins "start" (i.e. the bottom of the visible bin,
     * if the vertical scale is the usual way up).
     */
    virtual double getBinForY(const LayerGeometryProvider *, double y) const = 0;

    /**
     * As getBinForY, but rounding to integer values.
     */
    virtual int getIBinForY(const LayerGeometryProvider *v, int y) const {
        return int(floor(getBinForY(v, y)));
    }
};

#endif