From 48aa43748df011ae8476a241f1d6d4297a1408f4 Mon Sep 17 00:00:00 2001
From: Rod S <rsheeter@google.com>
Date: Wed, 29 Dec 2021 19:08:03 -0800
Subject: [PATCH] Exploratory mapping of things to space to match observed
 shaping in CBDT

---
 colrv1_postproc.py            |  40 ++++++++++++++++++++++++++++++++++
 fonts/Noto-COLRv1-noflags.ttf | Bin 2846160 -> 2846592 bytes
 2 files changed, 40 insertions(+)

diff --git a/colrv1_postproc.py b/colrv1_postproc.py
index 4ae28e6dd..833568f92 100644
--- a/colrv1_postproc.py
+++ b/colrv1_postproc.py
@@ -58,6 +58,44 @@ def _add_vs_cmap(colr_font):
   add_vs_cmap.modify_font("COLRv1 Emoji", colr_font, "emoji", emoji_variants)
 
 
+def _is_variation_selector_cmap_table(table):
+  assert table.format in {4, 12, 14}
+  return table.format == 14
+
+
+def _lookup_in_cmap(colr_font, codepoint):
+  result = set()
+  for table in colr_font["cmap"].tables:
+    if _is_variation_selector_cmap_table(table):
+      continue
+    assert codepoint in table.cmap
+    result.add(table.cmap[codepoint])
+  assert len(result) == 1, f"Ambiguous mapping for {codepoint}: {result}"
+  return next(iter(result))
+
+
+def _map_flag_tag_chars_to_space(colr_font):
+  gn_space = _lookup_in_cmap(colr_font, ord(" "))
+
+  # Add all tag characters used in flags
+  tag_cps = set(range(0xE0030, 0xE0039 + 1)) | set(range(0xE0061, 0xE007A + 1))
+
+  # CBDT maps these things to space based on hb-shape testing
+  # Android fontchain_lint is unhappy if no such mapping exists
+  for table in colr_font["cmap"].tables:
+    if _is_variation_selector_cmap_table(table):
+      continue
+    for cp in tag_cps:
+      if not _is_bmp(cp) and table.format == 4:
+        continue
+      table.cmap[cp] = gn_space
+      print(f"Map 0x{cp:04x} to space, format {table.format}")
+
+
+def _is_bmp(cp):
+  return cp in range(0x0000, 0xFFFF + 1)
+
+
 def main(argv):
     if len(argv) != 3:
       raise ValueError("Must have two args, a COLRv1 font and a CBDT emojicompat font")
@@ -78,6 +116,8 @@ def main(argv):
 
     _add_vs_cmap(colr_font)
 
+    _map_flag_tag_chars_to_space(colr_font)
+
     colr_font.save('fonts/Noto-COLRv1-noflags.ttf')
 
 
diff --git a/fonts/Noto-COLRv1-noflags.ttf b/fonts/Noto-COLRv1-noflags.ttf
index 95995dcc9540878c8ff513aa074fadb7f0b23cde..c20bb749cdfcc862f66b6c7152df9edc55566d4e 100644
GIT binary patch
delta 826
zcmXZYJ7`l;7{KxGCXLow(`ajL8~aeBMi({dD<GonP$;58b<m12&8xO~wY_~hq~PEr
zw40-Y!d((HDT)r(L2wZ%t}4>af|MdS3F`kQ--Z9ZzjL_vaPHaoQZSak7mStWJDaA|
ze||oA?b78^?VHEqU-O9!Ee(y_7%074-WLC#CnDi1S4YkS2LJxJFJg>~$lYi<l6xKU
zwTTojiZnk;rWO+)N<Tk|qkT<U-`*ULM`E2jsg_kU;CR2WYIO|X+7U<7N+yzyo2}0*
z@qYD)xCV0B8S~#u35s{~I_q|c!JRh3+rDta`QPHKVM65F*64iY`Rn6W*<%bB9F11_
zcJYF<&SQVaWsH`ezHqtoZaFJ<_A+icSE=d%4(NOk2i4uUTit_u)V;V@-G}?s{kUHp
z!Xb48NAfxtV=$(U;;1@?W9m4Ls}ne(PU56`9NQ;u|IEEgRZrjvou9;$>U@epN(X72
zR%dWVoyA#o4(HTUcuGBur`0ofMr~qKJ&R}6b9hcTV0)+Ym8v^kzzh1)B3@K4;U(J-
zto4W1x<L+dQVqFi7wx86+Cz1;m+EOBxv7CXw4V-8BQ?=MYNkWfLao$BUOG(e)Ipup
ZMMvl;9U~tdrxSFN{B-J-wSL-P{14ufzuo`<

delta 391
zcmW;EJxfAy6bA6~zrJK<S1q%AN$pi@32bPIFdZa`5~Sf$q*9hcme7T$7NMb4w?2S@
z4Oi+)1r3oDv_(XL6yj<T(Gt{BJ$2ys960ctOig09PZG<T=WAD_yE_bo$0udY*&cah
zktnzojLi7ui_9B&zTSzVQ`3<lZ{WMWO~jH!6kABe)5jBPD^bx$WU4N&Y%X2PuQ$Zm
zm1H>=l8N}Dvo2P0qL;gL<qD3F;3LkIU5%#_qGi88w#OKe%Aa0a7k^G@m~6E?{<?@E
zp%QlANA;s0q)_5ORDGV^_}?!N2PFdwNu2SsG*=u`X!*Y$hK-c+M=E|tDDMho1{^3r
z2`W%S18ATTw9o`PXa*kiU;rbuKr5J_4b0FE9bf?~*uV~*-~cDMpbNU82YR6o`oRqz
L7&sNmgYM!l6pE8w