code: private Thumb evalPressedThumb(float touchX) {
          Thumb result = null;
          boolean minThumbPressed = isInThumbRange(touchX, normalizedMinValue);
          boolean maxThumbPressed = isInThumbRange(touchX, normalizedMaxValue);
          if (minThumbPressed && maxThumbPressed) {
              // if both thumbs are pressed (they lie on top of each other), choose the one with more room to drag. this avoids "stalling" the thumbs in a corner, not being able to drag them apart anymore.
              result = (touchX / getWidth() > 0.5f) ? Thumb.MIN : Thumb.MAX;
          } else if (minThumbPressed) {
              result = Thumb.MIN;
          } else if (maxThumbPressed) {
              result = Thumb.MAX;
          }
          return result;
      }
docs: Decides which (if any) thumb is touched by the given x-coordinate.
  
  @param touchX The x-coordinate of a touch event in screen space.
  @return The pressed thumb or null if none has been touched.