Steps to reproduce

const doc = new jsPDF({ unit: 'mm', format: [200, 200], orientation: 'p' }) // with unit: 'pt' it works as expected

doc.advancedAPI()

doc.beginFormObject(-50, -50, 100, 100, doc.unitMatrix)
doc.rect(-50, -50, 100, 100).fill()
doc.endFormObject('0')

doc.doFormObject('0', new doc.Matrix(1, 0, 0, 1, 100, 100))

doc.setDrawColor(255, 0, 0)
doc.rect(50, 50, 100, 100).stroke()

doc.compatAPI()

Expected output

Actual output

actual.pdf
Form object:

24 0 obj
<<
/Type /XObject
/Subtype /Form
/BBox [-50. -50. -14.7222222222222285 -14.7222222222222285]
/Matrix [1. 0. 0. 1. 0. 0.]
/Length 24
>>
stream
-50. -50. 100. 100. re
f
endstream
endobj

Issue

The width and height of the bbox are scaled with the inverse scaling factor:

called by

called by

x and y are not scaled.

The expected behavior is that x, y, with, height are all scaled by the normal (not inverse) scaling factor. This way the values passed to beginFormObject are actually interpreted with the correct unit.

This issue came up in yWorks/svg2pdf.js#244.