From 2188c2d237eab62054ad0e746fa624cb1c85a795 Mon Sep 17 00:00:00 2001
From: Cosimo Lupo <clupo@google.com>
Date: Mon, 24 Jan 2022 18:06:46 +0000
Subject: [PATCH] also add soft-light to flags from emoji_aliases.txt

---
 colrv1_add_soft_light_to_flags.py | 91 ++++++++++++++++++++++++-------
 1 file changed, 71 insertions(+), 20 deletions(-)

diff --git a/colrv1_add_soft_light_to_flags.py b/colrv1_add_soft_light_to_flags.py
index c23a751db..0acd767b7 100644
--- a/colrv1_add_soft_light_to_flags.py
+++ b/colrv1_add_soft_light_to_flags.py
@@ -5,10 +5,35 @@ from fontTools import ttLib
 from fontTools.ttLib.tables import otTables as ot
 from fontTools.ttLib.tables.C_P_A_L_ import Color
 from fontTools.colorLib.builder import LayerListBuilder
+from add_aliases import read_default_emoji_aliases
 from flag_glyph_name import flag_code_to_glyph_name
 from map_pua_emoji import get_glyph_name_from_gsub
 
 
+REGIONAL_INDICATOR_RANGE = range(0x1F1E6, 0x1F1FF + 1)
+BLACK_FLAG = 0x1F3F4
+CANCEL_TAG = 0xE007F
+TAG_RANGE = range(0xE0000, CANCEL_TAG + 1)
+
+
+def is_flag(sequence):
+    # regular region flags are comprised of regional indicators
+    if all(cp in REGIONAL_INDICATOR_RANGE for cp in sequence):
+        return True
+
+    # subdivision flags start with  black flag, contain some tag characters and end with
+    # a cancel tag
+    if (
+        len(sequence) > 2
+        and sequence[0] == BLACK_FLAG
+        and sequence[-1] == CANCEL_TAG
+        and all(cp in TAG_RANGE for cp in sequence[1:-1])
+    ):
+        return True
+
+    return False
+
+
 def read_makefile_variable(var_name):
     # see `print-%` command in Makefile
     value = subprocess.run(
@@ -26,6 +51,19 @@ def flag_code_to_sequence(flag_code):
     return tuple(int(v, 16) for v in name[1:].split("_"))
 
 
+def all_flag_sequences():
+    """Return the set of all noto-emoji's region and subdivision flag sequences.
+    These include those in SELECTED_FLAGS Makefile variable plus those listed
+    in the 'emoji_aliases.txt' file.
+    """
+    result = {
+        flag_code_to_sequence(flag_code)
+        for flag_code in read_makefile_variable("SELECTED_FLAGS").split()
+    }
+    result.update(seq for seq in read_default_emoji_aliases() if is_flag(seq))
+    return result
+
+
 _builder = LayerListBuilder()
 
 
@@ -96,6 +134,38 @@ def _soft_light_gradient(cpal):
     )
 
 
+def flag_ligature_glyphs(font):
+    """Yield ligature glyph names for all the region/subdivision flags in the font."""
+    for flag_sequence in all_flag_sequences():
+        flag_name = get_glyph_name_from_gsub(flag_sequence, font)
+        if flag_name is not None:
+            yield flag_name
+
+
+def add_soft_light_to_flags(font, flag_glyph_names=None):
+    """Add soft-light effect to region and subdivision flags in CORLv1 font."""
+    if flag_glyph_names is None:
+        flag_glyph_names = flag_ligature_glyphs(font)
+
+    colr_glyphs = {
+        rec.BaseGlyph: rec
+        for rec in font["COLR"].table.BaseGlyphList.BaseGlyphPaintRecord
+    }
+    cpal = font["CPAL"]
+
+    for flag_name in flag_glyph_names:
+        flag = colr_glyphs[flag_name]
+        flag.Paint = _paint_composite(
+            source=_paint_composite(
+                source=_soft_light_gradient(cpal),
+                mode=ot.CompositeMode.SRC_IN,
+                backdrop=flag.Paint,
+            ),
+            mode=ot.CompositeMode.SOFT_LIGHT,
+            backdrop=flag.Paint,
+        )
+
+
 def main():
     try:
         input_file, output_file = sys.argv[1:]
@@ -109,26 +179,7 @@ def main():
         print("error: missing required COLRv1 table")
         return 1
 
-    colr_glyphs = {
-        rec.BaseGlyph: rec
-        for rec in font["COLR"].table.BaseGlyphList.BaseGlyphPaintRecord
-    }
-    cpal = font["CPAL"]
-
-    for flag_code in read_makefile_variable("SELECTED_FLAGS").split():
-        flag_sequence = flag_code_to_sequence(flag_code)
-        flag_name = get_glyph_name_from_gsub(flag_sequence, font)
-        if flag_name is not None:
-            flag = colr_glyphs[flag_name]
-            flag.Paint = _paint_composite(
-                source=_paint_composite(
-                    source=_soft_light_gradient(cpal),
-                    mode=ot.CompositeMode.SRC_IN,
-                    backdrop=flag.Paint,
-                ),
-                mode=ot.CompositeMode.SOFT_LIGHT,
-                backdrop=flag.Paint,
-            )
+    add_soft_light_to_flags(font)
 
     font.save(output_file)