keripix/fabric.js-squareBrush — pull request #1 by raitisg (2014-03-05 18:54:16+00:00)
Title: Group objects before adding to canvas

Grouping objects before adding to canvas greatly improves performance and only fires object:added event once, instead once for each rectange.

If object:added is needed to fire for each rectangle, you could introduce setting which switches between grouping and one-by-one adding.