使用轻标记和点选择

注意：这是Charts with Widgets Gallery示例的一部分。

我们开始创建一个序列，用数据填充它，并设置选择功能。不要设置点可见性为true非常重要，因为轻标记功能是一个独立的特征，同时设置两者会导致不良行为。

constexpr qreal marker_size = 20.;

auto series = new QSplineSeries;
series->append({QPointF(0., 0.),
                QPointF(0.5, 2.27),
                QPointF(1.5, 2.2),
                QPointF(3.3, 1.7),
                QPointF(4.23, 3.1),
                QPointF(5.3, 2.3),
                QPointF(6.47, 4.1)
});
series->setMarkerSize(marker_size);
series->setLightMarker(rectangle(marker_size, Qt::red));
series->setSelectedLightMarker(blueTriangle(marker_size));

QObject::connect(series, &QXYSeries::clicked, series, [=](const QPointF &point) {
    int index = series->points().indexOf(point);
    if (index != -1)
        series->toggleSelection({index});
});

然后我们创建QChart、QChartview以及带有其布局的控制小部件来排列自定义元素。

auto chart = new QChart;
chart->addSeries(series);
chart->createDefaultAxes();
chart->legend()->setVisible(false);
chart->layout()->setContentsMargins(0, 0, 0, 0);
chart->setTitle("Select points with mouse click");

auto chartView = new QChartView(chart, this);
chartView->setRenderHint(QPainter::Antialiasing);

auto controlWidget = new QWidget(this);
auto controlLayout = new QGridLayout(controlWidget);

下一步是创建自定义元素。

auto charPointCombobox = new QComboBox(controlWidget);
auto charPointSelectedCombobox = new QComboBox(controlWidget);
auto lineColorCombobox = new QComboBox(controlWidget);
auto showUnselectedPointsCheckbox = new QCheckBox(controlWidget);

我们创建标记选择组合框的标签并添加项目填充组合框。我们还为组合框提供了功能。考虑到轻标记功能的实现，我们需要确保已检查显示未选择点。通过将可见性设置为"empty" QImage来关闭轻标记的可见性。如果用户取消勾选显示未选择点并更改轻标记图像，则未选择点必须保持不可见。如果没有进行检查，新QImage将用于轻标记，即使已关闭，未选择点也会可见。

auto charPoint = new QLabel(tr("Char point: "), controlWidget);
charPointCombobox->addItems({tr("Red rectangle"),
                             tr("Green triangle"),
                             tr("Orange circle")
});
QObject::connect(charPointCombobox, &QComboBox::currentIndexChanged, series, [=](const int index) {
    if (showUnselectedPointsCheckbox->isChecked())
        series->setLightMarker(getPointRepresentation(PointType(index), marker_size));
});

几乎相同的程序也适用于选定点轻标记和线条颜色。唯一的不同之处在于，不需要检查未选择点的可见性，因为它不会影响功能。

auto charPointSelected = new QLabel(tr("Char point selected: "), controlWidget);
charPointSelectedCombobox->addItems({tr("Blue triangle"),
                                     tr("Yellow rectangle"),
                                     tr("Lavender circle")
});
QObject::connect(charPointSelectedCombobox, &QComboBox::currentIndexChanged, series, [=](const int index) {
    series->setSelectedLightMarker(getSelectedPointRepresentation(SelectedPointType(index), marker_size));
});

auto lineColorLabel = new QLabel(tr("Line color: "), controlWidget);
lineColorCombobox->addItems({tr("Blue"),
                             tr("Black"),
                             tr("Mint")
});
QObject::connect(lineColorCombobox, &QComboBox::currentIndexChanged, series, [=](const int index) {
    series->setColor(makeLineColor(LineColor(index)));
});

改变未选择点可见性有一个小差异。如前所述，使轻标记不可见是通过将它们设置为"empty" QImage来实现的。这就是为什么，根据复选框的状态，选择点轻标记被设置为"empty" QImage或从相应组合框的当前索引提取的轻标记。

auto showUnselectedPointsLabel = new QLabel(tr("Display unselected points: "), controlWidget);
showUnselectedPointsCheckbox->setChecked(true);
QObject::connect(showUnselectedPointsCheckbox, &QCheckBox::stateChanged, series, [=](const int state) {
    if (state)
        series->setLightMarker(getPointRepresentation(PointType(charPointCombobox->currentIndex()), marker_size));
    else
        series->setLightMarker(QImage());
});

最后一部分是排列元素，将所有小部件添加到主小部件，并设置主窗口的大小。

controlLayout->addWidget(charPoint, 0, 0);
controlLayout->addWidget(charPointCombobox, 0, 1);

controlLayout->addWidget(charPointSelected, 1, 0);
controlLayout->addWidget(charPointSelectedCombobox, 1, 1);

controlLayout->addWidget(lineColorLabel, 2, 0);
controlLayout->addWidget(lineColorCombobox, 2, 1);

controlLayout->addWidget(showUnselectedPointsLabel, 3, 0);
controlLayout->addWidget(showUnselectedPointsCheckbox, 3, 1, 1, 2);

m_mainWidget = new QWidget(this);
auto mainLayout = new QHBoxLayout(m_mainWidget);
mainLayout->addWidget(chartView);
mainLayout->addWidget(controlWidget);