Function estimateLabelUnionRect

libs/echarts/echarts.simple.js:37899–37941

* @param {module:echarts/coord/Axis} axis * @return {module:zrender/core/BoundingRect} Be null/undefined if no labels.

(axis)

 * @return {module:zrender/core/BoundingRect} Be null/undefined if no labels.
 */
function estimateLabelUnionRect(axis) {
    var axisModel = axis.model;
    var scale = axis.scale;

    if (!axisModel.get('axisLabel.show') || scale.isBlank()) {
        return;
    }

    var isCategory = axis.type === 'category';

    var realNumberScaleTicks;
    var tickCount;
    var categoryScaleExtent = scale.getExtent();

    // Optimize for large category data, avoid call `getTicks()`.
    if (isCategory) {
        tickCount = scale.count();
    }
    else {
        realNumberScaleTicks = scale.getTicks();
        tickCount = realNumberScaleTicks.length;
    }

    var axisLabelModel = axis.getLabelModel();
    var labelFormatter = makeLabelFormatter(axis);

    var rect;
    var step = 1;
    // Simple optimization for large amount of labels
    if (tickCount > 40) {
        step = Math.ceil(tickCount / 40);
    }
    for (var i = 0; i < tickCount; i += step) {
        var tickValue = realNumberScaleTicks ? realNumberScaleTicks[i] : categoryScaleExtent[0] + i;
        var label = labelFormatter(tickValue);
        var unrotatedSingleRect = axisLabelModel.getTextRect(label);
        var singleRect = rotateTextRect(unrotatedSingleRect, axisLabelModel.get('rotate') || 0);

        rect ? rect.union(singleRect) : (rect = singleRect);
    }

    return rect;
}

function rotateTextRect(textRect, rotate) {
    var rotateRadians = rotate * Math.PI / 180;