annotate layer/ScrollableImageCache.cpp @ 1248:fc40742bb911

Explanatory comment

/* -*- 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.
*/

#include "ScrollableImageCache.h"

#include "base/HitCount.h"

#include <iostream>
using namespace std;

//#define DEBUG_SCROLLABLE_IMAGE_CACHE 1

void
ScrollableImageCache::scrollTo(const LayerGeometryProvider *v,
                               sv_frame_t newStartFrame)
{
    static HitCount count("ScrollableImageCache: scrolling");
    
    int dx = (v->getXForFrame(m_startFrame) -
	      v->getXForFrame(newStartFrame));
    
#ifdef DEBUG_SCROLLABLE_IMAGE_CACHE
    cerr << "ScrollableImageCache::scrollTo: start frame " << m_startFrame
	 << " -> " << newStartFrame << ", dx = " << dx << endl;
#endif

    if (m_startFrame == newStartFrame) {
	// haven't moved
        count.hit();
        return;
    }
	
    m_startFrame = newStartFrame;
	
    if (!isValid()) {
        count.miss();
	return;
    }

    int w = m_image.width();

    if (dx == 0) {
	// haven't moved visibly (even though start frame may have changed)
        count.hit();
	return;
    }

    if (dx <= -w || dx >= w) {
	// scrolled entirely off
	invalidate();
        count.miss();
	return;
    }

    count.partial();
	
    // dx is in range, cache is scrollable

    int dxp = dx;
    if (dxp < 0) dxp = -dxp;

    int copylen = (w - dxp) * int(sizeof(QRgb));
    for (int y = 0; y < m_image.height(); ++y) {
	QRgb *line = (QRgb *)m_image.scanLine(y);
	if (dx < 0) {
	    memmove(line, line + dxp, copylen);
	} else {
	    memmove(line + dxp, line, copylen);
	}
    }
	
    // update valid area
        
    int px = m_validLeft;
    int pw = m_validWidth;
	
    px += dx;
	
    if (dx < 0) {
	// we scrolled left
	if (px < 0) {
	    pw += px;
	    px = 0;
	    if (pw < 0) {
		pw = 0;
	    }
	}
    } else {
	// we scrolled right
	if (px + pw > w) {
	    pw = w - px;
	    if (pw < 0) {
		pw = 0;
	    }
	}
    }

    m_validLeft = px;
    m_validWidth = pw;
}

void
ScrollableImageCache::adjustToTouchValidArea(int &left, int &width,
					     bool &isLeftOfValidArea) const
{
#ifdef DEBUG_SCROLLABLE_IMAGE_CACHE
    cerr << "ScrollableImageCache::adjustToTouchValidArea: left " << left
         << ", width " << width << endl;
    cerr << "ScrollableImageCache: my left " << m_validLeft
         << ", width " << m_validWidth << " so right " << (m_validLeft + m_validWidth) << endl;
#endif
    if (left < m_validLeft) {
	isLeftOfValidArea = true;
	if (left + width <= m_validLeft + m_validWidth) {
	    width = m_validLeft - left;
	}
#ifdef DEBUG_SCROLLABLE_IMAGE_CACHE
        cerr << "ScrollableImageCache: we're left of valid area, adjusted width to " << width << endl;
#endif
    } else {
	isLeftOfValidArea = false;
	width = left + width - (m_validLeft + m_validWidth);
	left = m_validLeft + m_validWidth;
	if (width < 0) width = 0;
#ifdef DEBUG_SCROLLABLE_IMAGE_CACHE
        cerr << "ScrollableImageCache: we're right of valid area, adjusted left to " << left << ", width to " << width << endl;
#endif
    }
}
    
void
ScrollableImageCache::drawImage(int left,
				int width,
				QImage image,
				int imageLeft,
				int imageWidth)
{
    if (image.height() != m_image.height()) {
	cerr << "ScrollableImageCache::drawImage: ERROR: Supplied image height "
	     << image.height() << " does not match cache height "
	     << m_image.height() << endl;
	throw std::logic_error("Image height must match cache height in ScrollableImageCache::drawImage");
    }
    if (left < 0 || width < 0 || left + width > m_image.width()) {
	cerr << "ScrollableImageCache::drawImage: ERROR: Target area (left = "
	     << left << ", width = " << width << ", so right = " << left + width
             << ") out of bounds for cache of width " << m_image.width() << endl;
	throw std::logic_error("Target area out of bounds in ScrollableImageCache::drawImage");
    }
    if (imageLeft < 0 || imageWidth < 0 ||
	imageLeft + imageWidth > image.width()) {
	cerr << "ScrollableImageCache::drawImage: ERROR: Source area (left = "
	     << imageLeft << ", width = " << imageWidth << ", so right = "
             << imageLeft + imageWidth << ") out of bounds for image of "
	     << "width " << image.width() << endl;
	throw std::logic_error("Source area out of bounds in ScrollableImageCache::drawImage");
    }
	
    QPainter painter(&m_image);
    painter.drawImage(QRect(left, 0, width, m_image.height()),
		      image,
		      QRect(imageLeft, 0, imageWidth, image.height()));
    painter.end();

    if (!isValid()) {
	m_validLeft = left;
	m_validWidth = width;
	return;
    }
	
    if (left < m_validLeft) {
	if (left + width > m_validLeft + m_validWidth) {
	    // new image completely contains the old valid area --
	    // use the new area as is
	    m_validLeft = left;
	    m_validWidth = width;
	} else if (left + width < m_validLeft) {
	    // new image completely off left of old valid area --
	    // we can't extend the valid area because the bit in
	    // between is not valid, so must use the new area only
	    m_validLeft = left;
	    m_validWidth = width;
	} else {
	    // new image overlaps old valid area on left side --
	    // use new left edge, and extend width to existing
	    // right edge
	    m_validWidth = (m_validLeft + m_validWidth) - left;
	    m_validLeft = left;
	}
    } else {
	if (left > m_validLeft + m_validWidth) {
	    // new image completely off right of old valid area --
	    // we can't extend the valid area because the bit in
	    // between is not valid, so must use the new area only
	    m_validLeft = left;
	    m_validWidth = width;
	} else if (left + width > m_validLeft + m_validWidth) {
	    // new image overlaps old valid area on right side --
	    // use existing left edge, and extend width to new
	    // right edge
	    m_validWidth = (left + width) - m_validLeft;
	    // (m_validLeft unchanged)
	} else {
	    // new image completely contained within old valid
	    // area -- leave the old area unchanged
	}
    }
}