Hello again - we observed one other issue when trying to experimentally compile one of our larger library fonts with fontc at Dalton Maag.

A particular arrangement of deltas succeeds with fontmake but crashes fontc compilation with an IUP error:

[... ThreadId(1) fontc ERROR] IUP error for glyph: AchievedInvalidState("No best solution identified")
error: process didn't exit successfully: `...\fontc.exe .../Deltas.designspace` (exit code: 1)

Reproducing

As with the earlier issue (#1115), the original font is proprietary and so we've made an independent minimal reproducer to share and use here.

ZIP containing designspace and UFO

Original script used to construct them:


from fontTools.designspaceLib import (
AxisDescriptor,
DesignSpaceDocument,
InstanceDescriptor,
SourceDescriptor,
)
from ufoLib2 import Font
from ufoLib2.objects import Contour, Point

Deltas that trigger the IUP crash

(more minimal deltas are probably possible, but at this point I struggled to

use fewer while still triggering the crash)

DELTAS = [ Point(x=0, y=0, type="line"), Point(x=1, y=0, type="line"), Point(x=1, y=0, type="line"), Point(x=0, y=1, type="line"), Point(x=0, y=0, type="line"), Point(x=1, y=0, type="line"), Point(x=1, y=3, type="line"), Point(x=2, y=0, type="line"), Point(x=2, y=3, type="line"), Point(x=0, y=0, type="line"), Point(x=0, y=0, type="line"), Point(x=0, y=3, type="line"), ]

Create designspace with weight axis

doc = DesignSpaceDocument() doc.addAxis( AxisDescriptor(tag="wght", name="Weight", minimum=400, maximum=700, default=400) )

Create a glyph with all points at origin in one source, and all points at

particular offsets in another.

for style, weight, points in [ ("Regular", 400, DELTAS), ("Bold", 700, [Point(x=0, y=0, type="line") for _ in range(len(DELTAS))]), ]: ufo = Font()

inner = ufo.newGlyph("glyph")
inner.contours.append(Contour(points))

ufo.save(f"{style}.ufo", overwrite=True)

doc.addSource(SourceDescriptor(path=f"{style}.ufo", location={"Weight": weight}))
doc.addInstance(InstanceDescriptor(styleName=style, location={"Weight": weight}))

doc.write("Deltas.designspace")

googlefonts / fontc

Certain deltas crash IUP optimisation #1116