a hack to add italic constraint to the fontparts' base object

moveBy_italicAngle.py

import math
import mojo.roboFont as rf
from fontParts.fontshell import RBPoint
from fontParts.base import normalizers


IntFloatType = int | float
Coordinate = tuple[IntFloatType, IntFloatType]
CoordinateLike = list[IntFloatType] | Coordinate

### thanks tal for the x and y idea!
def moveBy_(
    self,
    value: CoordinateLike | IntFloatType,
    xConstraintAngle: IntFloatType | None = None,
    yConstraintAngle: IntFloatType | None = None,
) -> None:

    assert not (xConstraintAngle and yConstraintAngle)

    if xConstraintAngle:
        if isinstance(value, tuple):
            deltaX = value[0]
        elif isinstance(value, (int, float)):
            deltaX = value
        deltaY = deltaX * math.tan(math.radians(xConstraintAngle))
        value = deltaX, deltaY
        #self.moveBy((deltaX, deltaY))

    if yConstraintAngle:
        if isinstance(value, tuple):
            deltaY = value[1]
        elif isinstance(value, (int, float)):
            deltaY = value
        deltaX = -deltaY * math.tan(math.radians(yConstraintAngle))
        value = deltaX, deltaY
        #self.moveBy((deltaX, deltaY))

    value = normalizers.normalizeTransformationOffset(value)
    self.moveBy(value)


for obj in (dir(rf)):
    if obj.startswith("R") and obj[1].isupper():
        attr = getattr(rf, obj)
        if hasattr(attr, "moveBy"):
            setattr(attr, "moveBy_", moveBy_)
RBPoint.moveBy_ = moveBy_