Method DrawLabel

core/graphics/axis/AxisController.cpp:660–803

}

void xg::axis::AxisController::DrawLabel(XChart &chart, std::unique_ptr<xg::axis::Axis> &axis, canvas::CanvasContext &context) {
    // xg::util::Point start = GetOffsetPoint(axis, label.value);
    // GetSidePoint(start, 5 * chart.GetRatio(), axis.dimType);
    // 修改x,y 这里计算的真实值
    // std::unique_ptr<xg::shape::Text> text = xg::make_unique<xg::shape::Text>(label.text.c_str(), xg::util::Point(start.x,
    // start.y), label.fontSize, "", label.fill);

    auto &coord = chart.GetCoord();
    size_t size = axis->labels.size();
    
    //textAlign 默认center textBaseline 默认bottom
    //pt默认对应的是字体中下方的锚点
    int index = 0;
    axis->labelBBoxes.clear();
    while(axis->labels.size() > 0) {
        auto text = std::move(axis->labels[0]);
        axis->labels.erase(axis->labels.begin());
        index++;

        bool isFirst = axis->labels.size() == (size - 1);
        bool isLast = axis->labels.size() == 0;
        
        const nlohmann::json &labelCfg = axis->GetLabelCfgForIndex(index);
        float labelMargin = 0.f;
        // 是否每个label都可设置labelMargin，默认只有首位两个label,true的化每个label都可使用
        bool labelMarginUseAll = false;
        if (labelCfg.is_object()) {
            labelMargin = labelCfg["labelMargin"];
            labelMarginUseAll = json::GetBool(labelCfg, "labelMarginUseAll", false);
        }
        labelMargin *= context.GetDevicePixelRatio();

        float labelOffset = 0.f;
        if (labelCfg.is_object()) {
            labelOffset = labelCfg["labelOffset"];
        }
        labelOffset *= context.GetDevicePixelRatio();

        double tickValue = text->ext["tickValue"];
        xg::util::Point pt = axis->GetOffsetPoint(tickValue, labelOffset);
        string dimType = axis->dimType;
        if(chart.GetCoord().IsTransposed()) {
            dimType = axis->dimType == "x" ? "y" : "x";
        }
        
        bool inner = json::GetBool(labelCfg, "inner");
        
        //等于把pt.y轴下移了5个dp，textbaseline变成了middle
        //这时候textAlign是center textBaseline是middle，等于pt对应了字体中心的锚点
        GetSidePoint(pt, inner ? 0 : 5 * chart.GetCanvasContext().GetDevicePixelRatio(), dimType);
        auto txtPoint = text->GetPoint();
        pt.x += txtPoint.x;
        pt.y += txtPoint.y;

        xg::util::BBox bbox = text->GetBBox(context);

        if(axis->position == "bottom") {
             if (labelMarginUseAll){