function isRectVisible(rect, frameDimensions, isVwm) {
        if (isVwm) {
            return rect.top >= 0 && rect.top < frameDimensions.height;
        }
        return rect.left >= 0 && rect.left < frameDimensions.width;
    }
@private
Checks whether or not a (fully adjusted) rectangle is at least partly visible

@param {Object} rect
@param {Object} frameDimensions
@param {boolean} [isVwm]           isVerticalWritingMode
@returns {boolean}