private void calculateCircleOval() {
        Rect contentRect = computator.getContentRectMinusAllMargins();
        final float circleRadius = Math.min(contentRect.width() / 2f, contentRect.height() / 2f);
        final float centerX = contentRect.centerX();
        final float centerY = contentRect.centerY();
        final float left = centerX - circleRadius + touchAdditional;
        final float top = centerY - circleRadius + touchAdditional;
        final float right = centerX + circleRadius - touchAdditional;
        final float bottom = centerY + circleRadius - touchAdditional;
        originCircleOval.set(left, top, right, bottom);
        final float inest = 0.5f * originCircleOval.width() * (1.0f - circleFillRatio);
        originCircleOval.inset(inest, inest);
    }
Calculates rectangle(square) that will constraint chart circle.
hellocharts-library/src/lecho/lib/hellocharts/renderer/PieChartRenderer.java