[mattiasgeniar]

SquareModule adds every point of every edge to one big Path with move() and line(). Path is immutable, so each call copies all operations added so far, and the cost grows with the square of the number of points. This builds each edge as its own short path and appends it once, so the big path is copied once per edge instead of once per point. It also flips cells inline in EdgeIterator, instead of through two method calls per cell. The SVG output is byte-identical for 264 inputs, and the test suite has the same result as main (the two GD tests error on both here, without the extension).

Benchmark (an otpauth:// URL, the usual 2FA QR code)	Before	After	% change
Writer::writeString(), 400 px SVG	7.16 ms	5.70 ms	−20.4%
Writer::writeString(), first call	8.21 ms	6.74 ms	−18.0%

Median of 15 fresh PHP 8.5 processes per side, run interleaved, opcache on. "First call" is the first run in a new process.