From c9c0359b1d0711c0dceeef7c853c6377c6a2af08 Mon Sep 17 00:00:00 2001
From: Roozbeh Pournader <roozbeh@google.com>
Date: Wed, 30 Mar 2016 17:48:34 -0700
Subject: [PATCH] Try putting combining marks in the same font run
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Indic combining marks, when combined with a common character such as
a hyphen or a dotted circle, used to get rendered in a different font
due to the greedy algorithm used in determining runs, which resulted
in the base character and the combining mark getting rendered in
separate font runs, resulting in a dotted circle appearing in phrases
such as "100-ാം" (0031 0030 0030 002D 0D3E 0D02).

This change makes combining marks change the font run of the base
character if the base character is supported in the same font as the
combining mark, similar to the support for emoji modifiers and the
combining keycap.

Bug: 25036888
Bug: 24535344
Change-Id: I8e2798e8ecb8efaf723a0fd02c05c6fbdef8b365
---
 .../src/flutter/libs/minikin/FontCollection.cpp   | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/engine/src/flutter/libs/minikin/FontCollection.cpp b/engine/src/flutter/libs/minikin/FontCollection.cpp
index e2582508ef..5f669a176a 100644
--- a/engine/src/flutter/libs/minikin/FontCollection.cpp
+++ b/engine/src/flutter/libs/minikin/FontCollection.cpp
@@ -293,14 +293,13 @@ 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 KEYCAP = 0x20e3;
 const uint32_t HYPHEN = 0x2010;
 const uint32_t NB_HYPHEN = 0x2011;
 
 // 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,
-        KEYCAP, HYPHEN, NB_HYPHEN };
+        HYPHEN, NB_HYPHEN };
 
 static bool isStickyWhitelisted(uint32_t c) {
     for (size_t i = 0; i < sizeof(stickyWhitelist) / sizeof(stickyWhitelist[0]); i++) {
@@ -380,12 +379,14 @@ void FontCollection::itemize(const uint16_t *string, size_t string_size, FontSty
                     langListId, variant);
             if (utf16Pos == 0 || family != lastFamily) {
                 size_t start = utf16Pos;
-                // Workaround for Emoji keycap and emoji modifier until we implement per-cluster
-                // font selection: if a keycap or an emoji modifier is found in a different font
-                // that also supports previous char, attach previous char to the new run.
-                // Bug 7557244.
+                // Workaround for combining marks and emoji modifiers until we implement
+                // per-cluster font selection: if a combining mark or an emoji modifier is found in
+                // a different font that also supports the previous character, attach previous
+                // character to the new run. U+20E3 COMBINING ENCLOSING KEYCAP, used in emoji, is
+                // handled properly by this since it's a combining mark too.
                 if (utf16Pos != 0 &&
-                        (ch == KEYCAP || (isEmojiModifier(ch) && isEmojiBase(prevCh))) &&
+                        ((U_GET_GC_MASK(ch) & U_GC_M_MASK) != 0 ||
+                         (isEmojiModifier(ch) && isEmojiBase(prevCh))) &&
                         family && family->getCoverage()->get(prevCh)) {
                     const size_t prevChLength = U16_LENGTH(prevCh);
                     run->end -= prevChLength;