alias: atConnectionRatio

Move and auto-orient the subelement to the point at a given ratio of the connection total length. It accepts a number in the [0,1] range. It is valid only within the LinkView context.

link.attr('rectSelector', { atConnectionRatio: .5, width: 10, height: 10, fill: 'red' });
link.attr('rectSelector', { atConnectionRatioKeepGradient: .5, width: 10, height: 10, fill: 'red' });