Merge pull request #424 from googlefonts/zero-width-colr-to-svg

fix maximum_color'ing 0-width glyphs

src/nanoemoji/colr_to_svg.py

@@ -312,8 +312,6 @@ def glyph_region(ttfont: ttLib.TTFont, glyph_name: str) -> Rect:
 
     map_font_space_to_viewbox handles font +y goes up => svg +y goes down."""
     width = ttfont["hmtx"][glyph_name][0]
-    if width == 0:
-        width = ttfont["glyf"][glyph_name].xMax
     return Rect(
         0,
         -ttfont["OS/2"].sTypoAscender,
@@ -325,15 +323,9 @@ def glyph_region(ttfont: ttLib.TTFont, glyph_name: str) -> Rect:
 def _view_box_and_transform(
     ttfont: ttLib.TTFont, view_box_callback: ViewboxCallback, glyph_name: str
 ) -> Tuple[Rect, Affine2D]:
-
     view_box = view_box_callback(glyph_name)
-    assert view_box.w > 0, f"0-width viewBox for {glyph_name}?!"
-
     region = glyph_region(ttfont, glyph_name)
-    assert region.w > 0, f"0-width region for {glyph_name}?!"
-
     font_to_vbox = map_font_space_to_viewbox(view_box, region)
-
     return (view_box, font_to_vbox)
 
 

src/nanoemoji/generate_svgs_from_colr.py

@@ -37,9 +37,7 @@
 
 def _view_box(font: ttLib.TTFont, glyph_name: str) -> Rect:
     # we want a viewbox that results in no scaling when translating from font-space
-    region = glyph_region(font, glyph_name)
-    assert region.w > 0, f"0-width region for {glyph_name}"
-    return region
+    return glyph_region(font, glyph_name)
 
 
 def main(argv):

tests/maximum_color_test.py

@@ -17,6 +17,7 @@
 import copy
 from fontTools import ttLib
 from nanoemoji.keep_glyph_names import keep_glyph_names
+from picosvg.svg import SVG
 from pathlib import Path
 import pytest
 import sys
@@ -109,3 +110,55 @@ def test_keep_glyph_names(keep_names):
         assert all(
             not gn.startswith("duck_") for gn in maximum_font.getGlyphOrder()
         ), maximum_font.getGlyphOrder()
+
+
+def test_zero_advance_width_colrv1_to_svg():
+    tmp_dir = run_nanoemoji(
+        (
+            "--color_format",
+            "glyf_colr_1",
+            # use proportional widths, based on viewBox.w
+            "--width=0",
+            # don't clip to viewBox else zero-width glyph disappears
+            "--noclip_to_viewbox",
+            locate_test_file("emoji_u42.svg"),
+            # this one has viewBox="0 0 0 1200", i.e. zero width, like
+            # combining marks usually are (e.g. 'acutecomb')
+            locate_test_file("u0301.svg"),
+        )
+    )
+
+    initial_font_file = tmp_dir / "Font.ttf"
+    assert initial_font_file.is_file()
+
+    initial_font = ttLib.TTFont(initial_font_file)
+    # sanity check widths are proportional and we have 2 colr glyphs
+    assert initial_font["hmtx"]["B"] == (1200, 0)
+    assert initial_font["hmtx"]["acutecomb"] == (0, 0)
+    assert initial_font["COLR"].table.BaseGlyphList.BaseGlyphCount == 2
+
+    maxmium_font_file = _maximize_color(initial_font_file, ())
+    maximum_font = ttLib.TTFont(maxmium_font_file)
+
+    assert "COLR" in maximum_font
+    assert maximum_font["COLR"].table.BaseGlyphList.BaseGlyphCount == 2
+    assert "SVG " in maximum_font
+    assert len(maximum_font["SVG "].docList) == 2
+
+    # check that 'acutecomb' still has 0 advance width
+    assert initial_font["hmtx"]["acutecomb"] == (0, 0)
+    # it has not been cropped away (has a non-empty bounding box)
+    doc = maximum_font["SVG "].docList[1]
+    assert doc.startGlyphID == doc.endGlyphID == maximum_font.getGlyphID("acutecomb")
+    svg = SVG.fromstring(doc.data)
+    shapes = list(svg.shapes())
+    assert len(shapes) == 1
+    bbox = shapes[0].bounding_box()
+    assert bbox.w > 0
+    assert bbox.h > 0
+    # its bbox matches the respective COLR ClipBox dimensions (quantized to 10)
+    clipBox = maximum_font["COLR"].table.ClipList.clips["acutecomb"]
+    assert abs(bbox.w - (clipBox.xMax - clipBox.xMin)) <= 10
+    assert abs(bbox.h - (clipBox.yMax - clipBox.yMin)) <= 10
+    # the SVG shape's horizontal positioning also matches the respective COLR glyph
+    assert abs(bbox.x - clipBox.xMin) <= 10

tests/nanoemoji_test.py

@@ -408,7 +408,7 @@ def test_glyph_with_zero_advance_width(color_format, tmp_path):
         svg = font["SVG "]
         assert len(svg.docList) == 1
         gid = font.getGlyphID(gname)
-        assert svg.docList[0][1:] == [gid, gid]  # [start, end]
+        assert svg.docList[0][1:] == (gid, gid)  # (start, end)
     if "CBDT" in font:
         cbdt = font["CBDT"]
         assert len(cbdt.strikeData) == 1