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/*!
    \class QGLColormap
    \brief The QGLColormap class is used for installing custom colormaps into
    a QGLWidget.

    \module OpenGL
    \ingroup painting-3D
    \ingroup shared

    QGLColormap provides a platform independent way of specifying and
    installing indexed colormaps for a QGLWidget. 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.

    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:
    \snippet doc/src/snippets/code/src_opengl_qglcolormap.cpp 0

    \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"

QT_BEGIN_NAMESPACE

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

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


/*!
    Construct a shallow copy of \a map.
*/
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.
*/
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.
*/
QGLColormap & QGLColormap::operator=(const QGLColormap &map)
{
    map.d->ref.ref();
    if (!d->ref.deref())
        cleanup(d);
    d = map.d;
    return *this;
}

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

    Detaches this QGLColormap from the shared block.
*/

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

/*!
    Set cell at index \a idx in the colormap to color \a color.
*/
void QGLColormap::setEntry(int idx, QRgb color)
{
    detach();
    if (!d->cells)
        d->cells = new QVector<QRgb>(256);
    d->cells->replace(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.  The first element in \a colors
    is set at \a base in the colormap.
*/
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 = 0; i < count; ++i)
        setEntry(base + i, colors[i]);
}

/*!
    Returns the QRgb value in the colorcell with index \a idx.
*/
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.
*/
void QGLColormap::setEntry(int idx, const QColor &color)
{
    setEntry(idx, color.rgb());
}

/*!
    Returns the QRgb value in the colorcell with index \a idx.
*/
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 or it is not in use
    by a QGLWidget; otherwise returns false.

    A colormap with no color values set is considered to be empty.
    For historical reasons, a colormap that has color values set
    but which is not in use by a QGLWidget is also considered empty.

    Compare size() with zero to determine if the colormap is empty
    regardless of whether it is in use by a QGLWidget or not.

    \sa size()
*/
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.
*/
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.
*/
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.
*/
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;
}

QT_END_NAMESPACE
