Close open corners in UFO

Lib/glyphsLib/builder/font.py

@@ -16,7 +16,7 @@
 import logging
 
 from .common import to_ufo_time, from_ufo_time
-from .constants import GLYPHS_PREFIX
+from .constants import GLYPHS_PREFIX, UFO2FT_FILTERS_KEY
 
 logger = logging.getLogger(__name__)
 
@@ -82,11 +82,17 @@ def to_ufo_font_attributes(self, family_name):
 
         self.to_ufo_names(ufo, master, family_name)
         self.to_ufo_family_user_data(ufo)
+
+        ufo.lib[UFO2FT_FILTERS_KEY] = [
+            {"namespace": "glyphsLib.filters", "name": "eraseOpenCorners", "pre": True}
+        ]
+
         self.to_ufo_custom_params(ufo, font)
 
         self.to_ufo_master_attributes(source, master)
 
         ufo.lib[MASTER_ORDER_LIB_KEY] = index
+
         # FIXME: (jany) in the future, yield this UFO (for memory, lazy iter)
         self._designspace.addSource(source)
         self._sources[master.id] = source

Lib/glyphsLib/filters/eraseOpenCorners.py

@@ -0,0 +1,118 @@
+import logging
+
+from fontTools.pens.basePen import BasePen
+from fontTools.misc.bezierTools import (
+    segmentSegmentIntersections,
+    _split_segment_at_t,
+)
+from ufo2ft.filters import BaseFilter
+
+logger = logging.getLogger(__name__)
+
+
+def _pointIsLeftOfLine(line, aPoint):
+    a, b = line
+    return (
+        (b[0] - a[0]) * (aPoint[1] - a[1]) - (b[1] - a[1]) * (aPoint[0] - a[0])
+    ) >= 0
+
+
+class EraseOpenCornersPen(BasePen):
+    def __init__(self, outpen):
+        self.segments = []
+        self.is_closed = False
+        self.affected = False
+        self.outpen = outpen
+
+    def _moveTo(self, p1):
+        if self.segments or self.is_closed:
+            raise ValueError(
+                "EraseOpenCornersPen should only be used on single contours"
+            )
+
+    def _operate(self, *points):
+        self.segments.append((self._getCurrentPoint(), *points))
+
+    _qCurveTo = _curveTo = _lineTo = _qCurveToOne = _curveToOne = _operate
+
+    def closePath(self):
+        self.segments.append((self._getCurrentPoint(), self.segments[0][0]))
+        self.is_closed = True
+        self.endPath()
+
+    def endPath(self):
+        segs = self.segments
+        if not segs:
+            return
+
+        ix = 0
+        while ix < len(segs):
+            next_ix = (ix + 1) % len(segs)
+
+            # Am I a line segment?
+            if not len(segs[ix]) == 2:
+                ix = ix + 1
+                continue
+
+            # Are the first point of the previous segment and the last point
+            # of the next segment both on the right side of the line?
+            # (see discussion at https://github.com/googlefonts/glyphsLib/pull/663)
+            pt1 = segs[ix - 1][0]
+            pt2 = segs[next_ix][-1]
+            intersection = [
+                i
+                for i in segmentSegmentIntersections(segs[ix - 1], segs[next_ix])
+                if 0 <= i.t1 <= 1 and 0 <= i.t2 <= 1
+            ]
+            if (
+                not intersection
+                or _pointIsLeftOfLine(segs[ix], pt1)
+                or _pointIsLeftOfLine(segs[ix], pt2)
+            ):
+                ix = ix + 1
+                continue
+
+            if intersection and (intersection[0].t1 > 0.5 and intersection[0].t2 < 0.5):
+                (segs[ix - 1], _) = _split_segment_at_t(
+                    segs[ix - 1], intersection[0].t1
+                )
+                (_, segs[next_ix]) = _split_segment_at_t(
+                    segs[next_ix], intersection[0].t2
+                )
+                # Ensure the ends match up
+                segs[next_ix] = (segs[ix - 1][-1],) + segs[next_ix][1:]
+                segs[ix : ix + 1] = []
+                self.affected = True
+            ix = ix + 1
+
+        self.outpen.moveTo(segs[0][0])
+
+        for seg in segs:
+            if len(seg) == 2:
+                self.outpen.lineTo(*seg[1:])
+            elif len(seg) == 3:
+                self.outpen.qCurveTo(*seg[1:])
+            elif len(seg) == 4:
+                self.outpen.curveTo(*seg[1:])
+
+        if self.is_closed:
+            self.outpen.closePath()
+        else:
+            self.outpen.endPath()
+
+
+class EraseOpenCornersFilter(BaseFilter):
+    def filter(self, glyph):
+        if not len(glyph):
+            return False
+
+        affected = False
+        contours = list(glyph)
+        glyph.clearContours()
+        outpen = glyph.getPen()
+        for contour in contours:
+            p = EraseOpenCornersPen(outpen)
+            contour.draw(p)
+            if p.affected:
+                affected = True
+        return affected

requirements-dev.in

@@ -5,3 +5,4 @@ xmldiff>=2.2
 # extras
 ufoNormalizer>=0.3.2
 defcon>=0.6.0
+ufo2ft

requirements-dev.txt

@@ -4,33 +4,41 @@
 #
 #    pip-compile requirements-dev.in
 #
-
 appdirs==1.4.4
     # via fs
-atomicwrites==1.4.0
-    # via pytest
 attrs==20.3.0
     # via pytest
-colorama==0.4.4
-    # via pytest
-coverage==5.4
+booleanoperations==0.9.0
+    # via ufo2ft
+compreffor==0.5.1
+    # via ufo2ft
+coverage==5.5
     # via -r requirements-dev.in
+cu2qu==1.6.7
+    # via ufo2ft
 defcon==0.7.2
     # via -r requirements-dev.in
-fonttools[ufo,unicode]==4.19.0
-    # via defcon
+fonttools[ufo,unicode]==4.21.1
+    # via
+    #   booleanoperations
+    #   compreffor
+    #   cu2qu
+    #   defcon
+    #   ufo2ft
 fs==2.4.12
     # via fonttools
 iniconfig==1.1.1
     # via pytest
 lxml==4.6.2
     # via xmldiff
-packaging==20.8
+packaging==20.9
     # via pytest
 pluggy==0.13.1
     # via pytest
 py==1.10.0
     # via pytest
+pyclipper==1.2.1
+    # via booleanoperations
 pyparsing==2.4.7
     # via packaging
 pytest-randomly==3.5.0
@@ -39,14 +47,16 @@ pytest==6.2.2
     # via
     #   -r requirements-dev.in
     #   pytest-randomly
-pytz==2020.5
+pytz==2021.1
     # via fs
 six==1.15.0
     # via
     #   fs
     #   xmldiff
 toml==0.10.2
     # via pytest
+ufo2ft==2.19.2
+    # via -r requirements-dev.in
 ufonormalizer==0.5.3
     # via -r requirements-dev.in
 unicodedata2==13.0.0.post2

requirements.txt

@@ -4,18 +4,17 @@
 #
 #    pip-compile setup.py
 #
-
 appdirs==1.4.4
     # via fs
 attrs==20.3.0
     # via ufolib2
-fonttools[ufo,unicode]==4.19.0
+fonttools[ufo,unicode]==4.21.1
     # via
     #   glyphsLib (setup.py)
     #   ufolib2
 fs==2.4.12
     # via fonttools
-pytz==2020.5
+pytz==2021.1
     # via fs
 six==1.15.0
     # via fs