in src/visual.ts [903:915]
private getTextRect(properties: TextProperties, x: number, y: number): ITextRect {
let textHeight: number = textMeasurementService.estimateSvgTextHeight(properties);
let textWidth: number = textMeasurementService.measureSvgTextWidth(properties);
let curTextUpperPointX: number = x + textWidth;
let curTextUpperPointY: number = y - textHeight;
return <ITextRect>{
x1: x,
y1: y,
x2: curTextUpperPointX,
y2: curTextUpperPointY
};
}