view layer/ScrollableImageCache.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 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 SCROLLABLE_IMAGE_CACHE_H
#define SCROLLABLE_IMAGE_CACHE_H

#include "base/BaseTypes.h"

#include "LayerGeometryProvider.h"

#include <QImage>
#include <QRect>
#include <QPainter>

/**
 * A cached image for a view that scrolls horizontally, such as a
 * spectrogram. The cache object holds an image, reports the size of
 * the image (likely the same as the underlying view, but it's the
 * caller's responsibility to set the size appropriately), can scroll
 * the image, and can report and update which contiguous horizontal
 * range of the image is valid.
 *
 * The only way to *update* the valid area in a cache is to draw to it
 * using the drawImage call.
 */
class ScrollableImageCache
{
public:
    ScrollableImageCache() :
	m_validLeft(0),
	m_validWidth(0),
	m_startFrame(0),
	m_zoomLevel(0)
    {}

    void invalidate() {
	m_validWidth = 0;
    }
    
    bool isValid() const {
	return m_validWidth > 0;
    }

    QSize getSize() const {
	return m_image.size();
    }

    /**
     * Set the size of the cache. If the new size differs from the
     * current size, the cache is invalidated.
     */
    void resize(QSize newSize) {
        if (getSize() != newSize) {
            m_image = QImage(newSize, QImage::Format_ARGB32_Premultiplied);
            invalidate();
        }
    }
	
    int getValidLeft() const {
	return m_validLeft;
    }
    
    int getValidWidth() const {
	return m_validWidth;
    }

    int getValidRight() const {
	return m_validLeft + m_validWidth;
    }

    QRect getValidArea() const {
	return QRect(m_validLeft, 0, m_validWidth, m_image.height());
    }
    
    int getZoomLevel() const {
	return m_zoomLevel;
    }

    /**
     * Set the zoom level. If the new zoom level differs from the
     * current one, the cache is invalidated. (Determining whether to
     * invalidate the cache here is the only thing the zoom level is
     * used for.)
     */
    void setZoomLevel(int zoom) {
        if (m_zoomLevel != zoom) {
            m_zoomLevel = zoom;
            invalidate();
        }
    }

    sv_frame_t getStartFrame() const {
	return m_startFrame;
    }

    /**
     * Set the start frame. If the new start frame differs from the
     * current one, the cache is invalidated. To scroll, i.e. to set
     * the start frame while retaining cache validity where possible,
     * use scrollTo() instead.
     */
    void setStartFrame(sv_frame_t frame) {
        if (m_startFrame != frame) {
            m_startFrame = frame;
            invalidate();
        }
    }
    
    const QImage &getImage() const {
	return m_image;
    }

    /**
     * Set the new start frame for the cache, according to the
     * geometry of the supplied LayerGeometryProvider, if possible
     * also moving along any existing valid data within the cache so
     * that it continues to be valid for the new start frame.
     */
    void scrollTo(const LayerGeometryProvider *v, sv_frame_t newStartFrame);

    /**
     * Take a left coordinate and width describing a region, and
     * adjust them so that they are contiguous with the cache valid
     * region and so that the union of the adjusted region with the
     * cache valid region contains the supplied region.  Does not
     * modify anything about the cache, only about the arguments.
     */
    void adjustToTouchValidArea(int &left, int &width,
				bool &isLeftOfValidArea) const;
    
    /**
     * Draw from an image onto the cache. The supplied image must have
     * the same height as the cache and the full height is always
     * drawn. The left and width parameters determine the target
     * region of the cache, the imageLeft and imageWidth parameters
     * the source region of the image.
     */
    void drawImage(int left,
		   int width,
		   QImage image,
		   int imageLeft,
		   int imageWidth);
    
private:
    QImage m_image;
    int m_validLeft;
    int m_validWidth;
    sv_frame_t m_startFrame;
    int m_zoomLevel;
};

#endif