view widgets/WidgetScale.h @ 1386:fc3d89f88690 spectrogramparam

Use log-frequency rather than log-bin for calculating x coord in spectrum. This has the advantage that frequency positions don't move when we change the window size or oversampling ratio, but it does give us an unhelpfully large amount of space for very low frequencies - to be considered

/* -*- 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 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 SV_WIDGET_SCALE_H
#define SV_WIDGET_SCALE_H

#include <QFont>
#include <QFontMetrics>

#include "base/Debug.h"

class WidgetScale
{
public:   
    /**
     * Take a "design pixel" size and scale it for the actual
     * display. This is relevant to hi-dpi systems that do not do
     * pixel doubling (i.e. Windows and Linux rather than OS/X).
     */
    static int scalePixelSize(int pixels) {

        static double ratio = 0.0;
        if (ratio == 0.0) {
            double baseEm;
#ifdef Q_OS_MAC
            baseEm = 17.0;
#else
            baseEm = 15.0;
#endif
            double em = QFontMetrics(QFont()).height();
            ratio = em / baseEm;
            SVDEBUG << "WidgetScale::scalePixelSize: baseEm = " << baseEm
                    << ", platform default font height = " << em
                    << ", resulting scale factor = " << ratio << endl;
            if (ratio < 1.0) {
                SVDEBUG << "WidgetScale::scalePixelSize: rounding up to 1.0"
                        << endl;
                ratio = 1.0;
            }
        }

        int scaled = int(pixels * ratio + 0.5);
        if (pixels != 0 && scaled == 0) scaled = 1;
        return scaled;
    }

    static QSize scaleQSize(QSize size) {
        return QSize(scalePixelSize(size.width()),
                     scalePixelSize(size.height()));
    }
};

#endif