canvaspicker.cpp

QWT5.01用于Qt开发的二维图形库程序

#include <qapplication.h>
#include <qevent.h>
#include <qwhatsthis.h>
#include <qpainter.h>
#include <qwt_plot.h>
#include <qwt_symbol.h>
#include <qwt_scale_map.h>
#include <qwt_plot_canvas.h>
#include <qwt_plot_curve.h>
#include "canvaspicker.h"

CanvasPicker::CanvasPicker(QwtPlot *plot):
    QObject(plot),
    d_selectedCurve(NULL),
    d_selectedPoint(-1)
{
    QwtPlotCanvas *canvas = plot->canvas();

    canvas->installEventFilter(this);

    // We want the focus, but no focus rect. The
    // selected point will be highlighted instead.

#if QT_VERSION >= 0x040000
    canvas->setFocusPolicy(Qt::StrongFocus);
#ifndef QT_NO_CURSOR
    canvas->setCursor(Qt::PointingHandCursor);
#endif
#else
    canvas->setFocusPolicy(QWidget::StrongFocus);
#ifndef QT_NO_CURSOR
    canvas->setCursor(Qt::pointingHandCursor);
#endif
#endif
    canvas->setFocusIndicator(QwtPlotCanvas::ItemFocusIndicator);
    canvas->setFocus();

    const char *text =
        "All points can be moved using the left mouse button "
        "or with these keys:\n\n"
        "- Up:\t\tSelect next curve\n"
        "- Down:\t\tSelect previous curve\n"
        "- Left,