Macro window script for the current glyph, checks for point pairs getting twisted

twister.py

# brings macro window to front and clears its log:
Glyphs.clearLog()
Glyphs.showMacroWindow()

from math import sqrt, acos, degrees

def dot_product(v1, v2):
	return v1[0] * v2[0] + v1[1] * v2[1]

def magnitude(v):
	return sqrt(v[0] ** 2 + v[1] ** 2)

def angle_between_vectors(vector1, vector2):
	if vector1 == (0, 0) or vector2 == (0, 0):
		return False

	dot = dot_product(vector1, vector2)
	mag1 = magnitude(vector1)
	mag2 = magnitude(vector2)

	cos_theta = dot / (mag1 * mag2)
	theta = acos(max(-1, min(1, cos_theta)))  # Ensure acos input is within [-1, 1] range

	return degrees(theta)

def vectorForNodePair(n1, n2):
	p1, p2 = n1.position, n2.position
	return subtractPoints(p1, p2)

def distanceForNodePair(n1, n2):
	p1, p2 = n1.position, n2.position
	return distance(p1, p2)

def addToCurrentTab(layer):
	font = layer.parent.parent
	tab = font.currentTab
	if not tab:
		tab = font.newTab()
	if not layer in tab.layers:
		tab.layers.append(layer)

def checkGlyph(g):
	print(f"{g.name}:")
	print("PATH,  NODES:    ANGLE            VECTOR     LAYER")
	for layerGroup in g.layerGroups():
		layerGroup = tuple(layerGroup)
		groupLayer = g.layerForId_(layerGroup[0])
		groupLayer.clearSelection()
		for pi, path in enumerate(groupLayer.paths):
			for ni, node in enumerate(path.nodes):
				nextNode = node.nextNode
				nni = nextNode.nodeIndex()
				vectorDict = {}
				largestDist, largestID = 0, None
				for layerID in layerGroup:
					l = g.layerForId_(layerID)
					nodes = (
						l.paths[pi].nodes[ni],
						l.paths[pi].nodes[nni],
						)
					vectorDict[layerID] = vectorForNodePair(*nodes)
					if distanceForNodePair(*nodes) > largestDist:
						largestDist = distanceForNodePair(*nodes)
						largestID = layerID
				largestVector = vectorDict[largestID]
				largestLayer = g.layerForId_(largestID)
#				addToCurrentTab(largestLayer)
#				print("largestVector", *largestVector, largestLayer.name)
				for layerID in vectorDict.keys():
					if layerID == largestID:
						continue
					layerVector = vectorDict[layerID]
					layer = g.layerForId_(layerID)
					rotation = angle_between_vectors(largestVector, layerVector)
					if rotation != False and abs(rotation) > 90:
						print(f"{pi:3.0f}, {ni:3.0f}>{nni:3.0f}: {rotation:8.1f}° {layerVector.x:10.0f} {layerVector.y:6.0f}    {l.name}")
						layer.paths[pi].nodes[ni].selected = True
						layer.paths[pi].nodes[nni].selected = True
						addToCurrentTab(layer)

checkGlyph(Layer.parent)
print("✅ Done.")

Installation

1. Open Window > Macro Panel and open a new tab if necessary (with the plus button)
2. Paste the code from above

Usage

1. Select a glyph (in edit view or font view)
2. Run the script (press the Run button in the Macro window or Cmd-Enter)

To run on multiple glyphs, change the last two lines to:

for layer in Glyphs.font.selectedLayers:
	glyph = layer.parent
	checkGlyph(glyph)
	print()
print("✅ Done.")