From 56bda7e82a59b3fcaa828960deeb2a766f8afdfe Mon Sep 17 00:00:00 2001
From: Seigo Nonaka <nona@google.com>
Date: Mon, 11 Jul 2016 17:28:44 +0900
Subject: [PATCH] Lookup glyph from color emoji font before and after ZWJ.

Unicode recommends that the zwj sequences should be emoji presentation
even if they don't have the proper U+FE0F. Thus always lookup the glyph
for the code point before and after zwj as if they have a U+FE0F
variation selector.

Bug: 30056627
Change-Id: I03958a92337eaba4a8dd9c5be824b2665aa4a103
---
 .../flutter/libs/minikin/FontCollection.cpp    | 18 +++++++++++-------
 .../tests/FontCollectionItemizeTest.cpp        | 12 +++++++++---
 2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/engine/src/flutter/libs/minikin/FontCollection.cpp b/engine/src/flutter/libs/minikin/FontCollection.cpp
index 33418ab1b5..e665615d93 100644
--- a/engine/src/flutter/libs/minikin/FontCollection.cpp
+++ b/engine/src/flutter/libs/minikin/FontCollection.cpp
@@ -335,18 +335,15 @@ FontFamily* FontCollection::getFamilyForChar(uint32_t ch, uint32_t vs,
 }
 
 const uint32_t NBSP = 0xa0;
-const uint32_t ZWJ = 0x200c;
-const uint32_t ZWNJ = 0x200d;
+const uint32_t ZWJ = 0x200d;
+const uint32_t ZWNJ = 0x200c;
 const uint32_t HYPHEN = 0x2010;
 const uint32_t NB_HYPHEN = 0x2011;
-const uint32_t FEMALE_SIGN = 0x2640;
-const uint32_t MALE_SIGN = 0x2642;
-const uint32_t STAFF_OF_AESCULAPIUS = 0x2695;
 
 // Characters where we want to continue using existing font run instead of
 // recomputing the best match in the fallback list.
 static const uint32_t stickyWhitelist[] = { '!', ',', '-', '.', ':', ';', '?', NBSP, ZWJ, ZWNJ,
-        HYPHEN, NB_HYPHEN, FEMALE_SIGN, MALE_SIGN, STAFF_OF_AESCULAPIUS };
+        HYPHEN, NB_HYPHEN };
 
 static bool isStickyWhitelisted(uint32_t c) {
     for (size_t i = 0; i < sizeof(stickyWhitelist) / sizeof(stickyWhitelist[0]); i++) {
@@ -432,8 +429,15 @@ void FontCollection::itemize(const uint16_t *string, size_t string_size, FontSty
         }
 
         if (!shouldContinueRun) {
-            FontFamily* family = getFamilyForChar(ch, isVariationSelector(nextCh) ? nextCh : 0,
+            FontFamily* family;
+            if ((prevCh == ZWJ || nextCh == ZWJ) && isEmoji(ch)) {
+                // Treat emoji before and after ZWJ as emoji presentation.
+                family = getFamilyForChar(ch, EMOJI_STYLE_VS, langListId, variant);
+            } else {
+                family = getFamilyForChar(ch, isVariationSelector(nextCh) ? nextCh : 0,
                     langListId, variant);
+            }
+
             if (utf16Pos == 0 || family != lastFamily) {
                 size_t start = utf16Pos;
                 // Workaround for combining marks and emoji modifiers until we implement
diff --git a/engine/src/flutter/tests/FontCollectionItemizeTest.cpp b/engine/src/flutter/tests/FontCollectionItemizeTest.cpp
index 468b4a28fa..85d223ceaf 100644
--- a/engine/src/flutter/tests/FontCollectionItemizeTest.cpp
+++ b/engine/src/flutter/tests/FontCollectionItemizeTest.cpp
@@ -1223,7 +1223,7 @@ TEST_F(FontCollectionItemizeTest, itemize_emojiSelection_withFE0E) {
     EXPECT_EQ(2, runs[0].end);
     EXPECT_EQ(kNoGlyphFont, getFontPath(runs[0]));
 
-    // U+26FA U+FE0E is specified but ColorTextMixedEmojiFont has a variation sequence U+26F9 U+FE0F
+    // U+26FA U+FE0E is specified but ColorTextMixedEmojiFont has a variation sequence U+26FA U+FE0F
     // in its cmap, so ColorTextMixedEmojiFont should be selected instaed of ColorEmojiFont.
     itemize(collection.get(), "U+26FA U+FE0E", kDefaultFontStyle, &runs);
     ASSERT_EQ(1U, runs.size());
@@ -1305,9 +1305,9 @@ TEST_F(FontCollectionItemizeTest, itemize_emojiSelection_withFE0F) {
     EXPECT_EQ(2, runs[0].end);
     EXPECT_EQ(kNoGlyphFont, getFontPath(runs[0]));
 
-    // U+26F9 U+FE0F is specified but ColorTextMixedEmojiFont has a variation sequence U+26F9 U+FE0F
+    // U+26F8 U+FE0F is specified but ColorTextMixedEmojiFont has a variation sequence U+26F8 U+FE0F
     // in its cmap, so ColorTextMixedEmojiFont should be selected instaed of ColorEmojiFont.
-    itemize(collection.get(), "U+26F9 U+FE0F", kDefaultFontStyle, &runs);
+    itemize(collection.get(), "U+26F8 U+FE0F", kDefaultFontStyle, &runs);
     ASSERT_EQ(1U, runs.size());
     EXPECT_EQ(0, runs[0].start);
     EXPECT_EQ(2, runs[0].end);
@@ -1396,4 +1396,10 @@ TEST_F(FontCollectionItemizeTest, itemize_genderBalancedEmoji) {
     EXPECT_EQ(0, runs[0].start);
     EXPECT_EQ(4, runs[0].end);
     EXPECT_EQ(kColorEmojiFont, getFontPath(runs[0]));
+
+    itemize(collection.get(), "U+26F9 U+200D U+2695", kDefaultFontStyle, &runs);
+    ASSERT_EQ(1U, runs.size());
+    EXPECT_EQ(0, runs[0].start);
+    EXPECT_EQ(3, runs[0].end);
+    EXPECT_EQ(kColorEmojiFont, getFontPath(runs[0]));
 }