qt QCustomplot如何设计当鼠标处于Y轴区域时可以自由拖动Y轴

您可以通过以下步骤在QCustomPlot中实现该功能：

1. 检测鼠标是否在Y轴区域内，可以使用以下方法：

QList<QCPAxis*> axes = customPlot->selectedAxes(); // 获取选中的轴
foreach (QCPAxis *axis, axes) {
    if (axis->orientation() == Qt::Orientation::Vertical) {
        QRect axisRect = axis->axisRect()->rect();
        QPoint mousePos = customPlot->mapFromGlobal(QCursor::pos());
        if (axisRect.contains(mousePos)) {
            // 鼠标在Y轴区域内
            // TODO: 以下代码实现拖动Y轴的功能
            break;
        }
    }
}

2. 实现拖动Y轴的功能，可以使用以下方法：

// 鼠标按下时记录当前Y轴范围和鼠标位置
if (event->button() == Qt::LeftButton) {
    if (axisRect.contains(mousePos)) {
        QCPRange range = axis->range();
        startYRange = range;
        startYPos = mousePos.y();
    }
}

// 鼠标移动时根据鼠标位置计算新的Y轴范围
if (event->buttons() & Qt::LeftButton) {
    if (startYPos != -1) {
        double deltaY = (startYPos - mousePos.y()) / axisRect.height() * startYRange.size();
        QCPRange newRange(startYRange.lower + deltaY, startYRange.upper + deltaY);
        axis->setRange(newRange);
    }
}

// 鼠标释放时清除记录的状态
if (event->button() == Qt::LeftButton) {
    startYPos = -1;
}

完整示例代码如下：

QCPRange startYRange;
int startYPos = -1;

void MainWindow::mousePressEvent(QMouseEvent *event)
{
    QCustomPlot *customPlot = ui->customPlot;

    QList<QCPAxis*> axes = customPlot->selectedAxes(); // 获取选中的轴
    foreach (QCPAxis *axis, axes) {
        if (axis->orientation() == Qt::Orientation::Vertical) {
            QRect axisRect = axis->axisRect()->rect();
            QPoint mousePos = customPlot->mapFromGlobal(QCursor::pos());
            if (axisRect.contains(mousePos)) {
                // 鼠标在Y轴区域内
                // 记录当前Y轴范围和鼠标位置
                if (event->button() == Qt::LeftButton) {
                    QCPRange range = axis->range();
                    startYRange = range;
                    startYPos = mousePos.y();
                }
                break;
            }
        }
    }
}

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    QCustomPlot *customPlot = ui->customPlot;

    QList<QCPAxis*> axes = customPlot->selectedAxes(); // 获取选中的轴
    foreach (QCPAxis *axis, axes) {
        if (axis->orientation() == Qt::Orientation::Vertical) {
            QRect axisRect = axis->axisRect()->rect();
            QPoint mousePos = customPlot->mapFromGlobal(QCursor::pos());
            if (startYPos != -1 && axisRect.contains(mousePos)) {
                // 鼠标在Y轴区域内，根据鼠标位置计算新的Y轴范围
                double deltaY = (startYPos - mousePos.y()) / axisRect.height() * startYRange.size();
                QCPRange newRange(startYRange.lower + deltaY, startYRange.upper + deltaY);
                axis->setRange(newRange);
            }
        }
    }
}

void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    QCustomPlot *customPlot = ui->customPlot;

    QList<QCPAxis*> axes = customPlot->selectedAxes(); // 获取选中的轴
    foreach (QCPAxis *axis, axes) {
        if (axis->orientation() == Qt::Orientation::Vertical) {
            QRect axisRect = axis->axisRect()->rect();
            QPoint mousePos = customPlot->mapFromGlobal(QCursor::pos());
            if (startYPos != -1 && axisRect.contains(mousePos)) {
                // 鼠标在Y轴区域内，清除记录的状态
                startYPos = -1;
            }
        }
    }
}