Seshat 1.9.4 respects the folding standard and finds white hidden by blend modes
Seshat keeps text clear of folds by at least the ISO 16763 folding tolerance, reports white that vanishes in Multiply, reads colours inside patterns, and fixes that change nothing when run twice.
Folds: never closer than the standard allows
No standard says how far text should stay from a fold, so each shop sets its own distance in Seshat. A standard does say how precisely a sheet must be folded. ISO 16763, the international standard for post-press, allows a fold to lie up to 0.6 mm from its intended place with one fold, and up to 1.0 mm with four.
A safe distance smaller than that would let text land on the fold even when the folding is done to standard. From 1.9.4, Seshat never uses a distance below the folding tolerance for the number of folds on the page. A shop that sets less gets a note saying which distance was used, and the fold findings always give the distance applied. Nothing changes for shops using the common 3 mm or more.
White that vanishes without overprint
White painted in blend mode Multiply or Darken leaves whatever is below it unchanged, so on press it prints as nothing, even with overprint switched off. Seshat now reports this as white_vanishes_in_blend, with the places on the page. It is not fixed automatically, because a designer may have meant it.
Colours wherever they are drawn
Seshat already followed forms nested inside forms. It now also reads the colours inside tiling patterns and shadings, so an RGB colour hidden in a pattern is found like any other.
Fixes that hold
Running the fixes on a file Seshat has already fixed now changes nothing: the bleed is not added a second time, and a file that was only rewritten is not counted as changed. A new set of tests covers what breaks preflight engines: rotated pages, boxes that do not start at zero, grey and near-white, truncated and protected files, drawings with a quarter of a million paths, and colour differences (ΔE 2000) on pages a fix should leave alone.