From 42c272c059a7f44daa8bcb94d3eb9517084f773a Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Tue, 28 Feb 2023 08:02:02 -0500
Subject: [PATCH] LibUnicode: Allow ignoring text presentation emoji in
 sequence detection

This adds an option to only detect emoji that should always present as
emoji. For example, the copyright symbol (unless followed by an emoji
presentation selector) should render as text.
---
 Userland/Libraries/LibUnicode/Emoji.cpp | 26 ++++++++++++++++---------
 Userland/Libraries/LibUnicode/Emoji.h   |  9 +++++++--
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/Userland/Libraries/LibUnicode/Emoji.cpp b/Userland/Libraries/LibUnicode/Emoji.cpp
index 32e45d9351..c6bbad1f36 100644
--- a/Userland/Libraries/LibUnicode/Emoji.cpp
+++ b/Userland/Libraries/LibUnicode/Emoji.cpp
@@ -21,7 +21,7 @@ Optional<Emoji> __attribute__((weak)) find_emoji_for_code_points(ReadonlySpan<u3
 #if ENABLE_UNICODE_DATA
 
 // https://unicode.org/reports/tr51/#def_emoji_core_sequence
-static bool could_be_start_of_emoji_core_sequence(u32 code_point, Optional<u32> const& next_code_point)
+static bool could_be_start_of_emoji_core_sequence(u32 code_point, Optional<u32> const& next_code_point, SequenceType type)
 {
     // emoji_core_sequence := emoji_character | emoji_presentation_sequence | emoji_keycap_sequence | emoji_modifier_sequence | emoji_flag_sequence
 
@@ -38,8 +38,16 @@ static bool could_be_start_of_emoji_core_sequence(u32 code_point, Optional<u32>
         return false;
 
     // https://unicode.org/reports/tr51/#def_emoji_character
-    if (code_point_has_property(code_point, Property::Emoji))
-        return true;
+    switch (type) {
+    case SequenceType::Any:
+        if (code_point_has_property(code_point, Property::Emoji))
+            return true;
+        break;
+    case SequenceType::EmojiPresentation:
+        if (code_point_has_property(code_point, Property::Emoji_Presentation))
+            return true;
+        break;
+    }
 
     // https://unicode.org/reports/tr51/#def_emoji_presentation_sequence
     // emoji_presentation_sequence := emoji_character emoji_presentation_selector
@@ -71,7 +79,7 @@ static bool could_be_start_of_serenity_emoji(u32 code_point)
 
 // https://unicode.org/reports/tr51/#def_emoji_sequence
 template<typename CodePointIterator>
-static bool could_be_start_of_emoji_sequence_impl(CodePointIterator const& it)
+static bool could_be_start_of_emoji_sequence_impl(CodePointIterator const& it, [[maybe_unused]] SequenceType type)
 {
     // emoji_sequence := emoji_core_sequence | emoji_zwj_sequence | emoji_tag_sequence
 
@@ -92,7 +100,7 @@ static bool could_be_start_of_emoji_sequence_impl(CodePointIterator const& it)
     auto code_point = *it;
     auto next_code_point = it.peek(1);
 
-    if (could_be_start_of_emoji_core_sequence(code_point, next_code_point))
+    if (could_be_start_of_emoji_core_sequence(code_point, next_code_point, type))
         return true;
     if (could_be_start_of_serenity_emoji(code_point))
         return true;
@@ -102,14 +110,14 @@ static bool could_be_start_of_emoji_sequence_impl(CodePointIterator const& it)
 #endif
 }
 
-bool could_be_start_of_emoji_sequence(Utf8CodePointIterator const& it)
+bool could_be_start_of_emoji_sequence(Utf8CodePointIterator const& it, SequenceType type)
 {
-    return could_be_start_of_emoji_sequence_impl(it);
+    return could_be_start_of_emoji_sequence_impl(it, type);
 }
 
-bool could_be_start_of_emoji_sequence(Utf32CodePointIterator const& it)
+bool could_be_start_of_emoji_sequence(Utf32CodePointIterator const& it, SequenceType type)
 {
-    return could_be_start_of_emoji_sequence_impl(it);
+    return could_be_start_of_emoji_sequence_impl(it, type);
 }
 
 }
diff --git a/Userland/Libraries/LibUnicode/Emoji.h b/Userland/Libraries/LibUnicode/Emoji.h
index 7e772e9c3e..0104cee693 100644
--- a/Userland/Libraries/LibUnicode/Emoji.h
+++ b/Userland/Libraries/LibUnicode/Emoji.h
@@ -47,8 +47,13 @@ Optional<Emoji> find_emoji_for_code_points(u32 const (&code_points)[Size])
     return find_emoji_for_code_points(ReadonlySpan<u32> { code_points });
 }
 
-bool could_be_start_of_emoji_sequence(Utf8CodePointIterator const&);
-bool could_be_start_of_emoji_sequence(Utf32CodePointIterator const&);
+enum class SequenceType {
+    Any,
+    EmojiPresentation,
+};
+
+bool could_be_start_of_emoji_sequence(Utf8CodePointIterator const&, SequenceType = SequenceType::Any);
+bool could_be_start_of_emoji_sequence(Utf32CodePointIterator const&, SequenceType = SequenceType::Any);
 
 constexpr StringView emoji_group_to_string(EmojiGroup group)
 {