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qglcolormap.cpp

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** This file is part of the QtOpenGL module of the Qt Toolkit.
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/*!
    \class QGLColormap
    \brief The QGLColormap class is used for installing custom colormaps into
    QGLWidgets.

    \module OpenGL
    \ingroup multimedia
    \ingroup shared

    QGLColormap provides a platform independent way of specifying and
    installing indexed colormaps into QGLWidgets. QGLColormap is
    especially useful when using the OpenGL color-index mode.

    Under X11 you must use an X server that supports either a \c
    PseudoColor or \c DirectColor visual class. If your X server
    currently only provides a \c GrayScale, \c TrueColor, \c
    StaticColor or \c StaticGray visual, you will not be able to
    allocate colorcells for writing. If this is the case, try setting
    your X server to 8 bit mode. It should then provide you with at
    least a \c PseudoColor visual. Note that you may experience
    colormap flashing if your X server is running in 8 bit mode.

    Under Windows the size of the colormap is always set to 256
    colors. Note that under Windows you can also install colormaps
    in child widgets.

    This class uses \l{implicit sharing} as a memory and speed
    optimization.

    Example of use:
    \code
    #include <QApplication>
    #include <QGLColormap>

    int main()
    {
        QApplication app(argc, argv);

        MySuperGLWidget widget;     // a QGLWidget in color-index mode
        QGLColormap colormap;

        // This will fill the colormap with colors ranging from
        // black to white.
        for (int i = 0; i < colormap.size(); i++)
            colormap.setEntry(i, qRgb(i, i, i));

        widget.setColormap(colormap);
        widget.show();
        return app.exec();
    }
    \endcode

    \sa QGLWidget::setColormap(), QGLWidget::colormap()
*/

/*!
    \fn Qt::HANDLE QGLColormap::handle()

    \internal

    Returns the handle for this color map.
*/

/*!
    \fn void QGLColormap::setHandle(Qt::HANDLE handle)

    \internal

    Sets the handle for this color map to \a handle.
*/

#include "qglcolormap.h"

QGLColormap::QGLColormapData QGLColormap::shared_null = { Q_ATOMIC_INIT(1), 0, 0 };

/*!
    Construct a QGLColormap.
*/
00102 QGLColormap::QGLColormap()
    : d(&shared_null)
{
    d->ref.ref();
}


/*!
    Construct a shallow copy of \a map.
*/
00112 QGLColormap::QGLColormap(const QGLColormap &map)
    : d(map.d)
{
    d->ref.ref();
}

/*!
    Dereferences the QGLColormap and deletes it if this was the last
    reference to it.
*/
00122 QGLColormap::~QGLColormap()
{
    if (!d->ref.deref())
        cleanup(d);
}

void QGLColormap::cleanup(QGLColormap::QGLColormapData *x)
{
    delete x->cells;
    x->cells = 0;
    delete x;
}

/*!
    Assign a shallow copy of \a map to this QGLColormap.
*/
00138 QGLColormap & QGLColormap::operator=(const QGLColormap &map)
{
    QGLColormapData *x = map.d;
    x->ref.ref();
    x = qAtomicSetPtr(&d, x);
    if (!x->ref.deref())
        cleanup(x);
    return *this;
}

/*!
    \fn void QGLColormap::detach()
    \internal

    Detaches this QGLColormap from the shared block.
*/

void QGLColormap::detach_helper()
{
    QGLColormapData *x = new QGLColormapData;
    x->ref.init(1);
    x->cmapHandle = 0;
    x->cells = 0;
    if (d->cells) {
        x->cells = new QVector<QRgb>(256);
        *x->cells = *d->cells;
    }
    x = qAtomicSetPtr(&d, x);
    if (!x->ref.deref())
        cleanup(x);
}

/*!
    Set cell at index \a idx in the colormap to color \a color.
*/
00173 void QGLColormap::setEntry(int idx, QRgb color)
{
    detach();
    if (!d->cells)
        d->cells = new QVector<QRgb>(256);
    d->cells->insert(idx, color);
}

/*!
    Set an array of cells in this colormap. \a count is the number of
    colors that should be set, \a colors is the array of colors, and
    \a base is the starting index.
*/
00186 void QGLColormap::setEntries(int count, const QRgb *colors, int base)
{
    detach();
    if (!d->cells)
        d->cells = new QVector<QRgb>(256);

    Q_ASSERT_X(!colors || base >= 0 || base + count < d->cells->size(), "QGLColormap::setEntries",
               "preconditions not met");
    for (int i = base; i < base + count; ++i)
        setEntry(i, colors[i]);
}

/*!
    Returns the QRgb value in the colorcell with index \a idx.
*/
00201 QRgb QGLColormap::entryRgb(int idx) const
{
    if (d == &shared_null || !d->cells)
        return 0;
    else
        return d->cells->at(idx);
}

/*!
    \overload

    Set the cell with index \a idx in the colormap to color \a color.
*/
00214 void QGLColormap::setEntry(int idx, const QColor &color)
{
    setEntry(idx, color.rgb());
}

/*!
    Returns the QRgb value in the colorcell with index \a idx.
*/
00222 QColor QGLColormap::entryColor(int idx) const
{
    if (d == &shared_null || !d->cells)
        return QColor();
    else
        return QColor(d->cells->at(idx));
}

/*!
    Returns true if the colormap is empty; otherwise returns false. A
    colormap with no color values set is considered to be empty.
*/
00234 bool QGLColormap::isEmpty() const
{
    return d == &shared_null || d->cells == 0 || d->cells->size() == 0 || d->cmapHandle == 0;
}


/*!
    Returns the number of colorcells in the colormap.
*/
00243 int QGLColormap::size() const
{
    return d->cells ? d->cells->size() : 0;
}

/*!
    Returns the index of the color \a color. If \a color is not in the
    map, -1 is returned.
*/
00252 int QGLColormap::find(QRgb color) const
{
    if (d->cells)
        return d->cells->indexOf(color);
    return -1;
}

/*!
    Returns the index of the color that is the closest match to color
    \a color.
*/
00263 int QGLColormap::findNearest(QRgb color) const
{
    int idx = find(color);
    if (idx >= 0)
        return idx;
    int mapSize = size();
    int mindist = 200000;
    int r = qRed(color);
    int g = qGreen(color);
    int b = qBlue(color);
    int rx, gx, bx, dist;
    for (int i = 0; i < mapSize; ++i) {
        QRgb ci = d->cells->at(i);
        rx = r - qRed(ci);
        gx = g - qGreen(ci);
        bx = b - qBlue(ci);
        dist = rx * rx + gx * gx + bx * bx;        // calculate distance
        if (dist < mindist) {                // minimal?
            mindist = dist;
            idx = i;
        }
    }
    return idx;
}

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