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LibGfx: Always lookup emojis without emoji presentation specifiers

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This allows us to treat unqualified, minimally-qualified, and
fully-qualified emojis the same as long as emoji filenames are in their
least qualified form (with respect to emoji presentation).

For example, the transgender flag emoji has 4 possible forms:

    1F3F3 FE0F 200D 26A7 FE0F ; fully-qualified  # 🏳️‍⚧️
    1F3F3 200D 26A7 FE0F      ; unqualified      # 🏳‍⚧️
    1F3F3 FE0F 200D 26A7      ; unqualified      # 🏳️‍⚧
    1F3F3 200D 26A7           ; unqualified      # 🏳‍⚧

In order to treat them all as the same, we now drop all forms down
to 1F3F3 200D 26A7 (skipping any FE0F codepoints) and then do the
lookup for that form.
This commit is contained in:
Ryan Liptak 2022-08-18 17:49:49 -07:00 committed by Linus Groh
parent f64f5e79a8
commit 379baa984d
Notes: sideshowbarker 2024-07-17 08:06:50 +09:00 
Author: https://github.com/squeek502
Commit: https://github.com/SerenityOS/serenity/commit/379baa984d
Pull-request: https://github.com/SerenityOS/serenity/pull/14917
Reviewed-by: https://github.com/Xexxa ✅
Reviewed-by: https://github.com/kleinesfilmroellchen
Reviewed-by: https://github.com/linusg
1 changed files with 49 additions and 7 deletions
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56
Userland/Libraries/LibGfx/Font/Emoji.cpp
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@ -58,18 +58,60 @@ Bitmap const* Emoji::emoji_for_code_point_iterator(Utf8CodePointIterator& it)
struct EmojiAndCodePoints {
Bitmap const* emoji;
Span<u32> code_points;
u8 real_codepoint_length;
};
Vector<EmojiAndCodePoints, max_emoji_code_point_sequence_length> possible_emojis;
// Determine all existing emojis for the longest possible ZWJ emoji sequence,
// or until we run out of code points in the iterator.
for (size_t i = 0; i < max_emoji_code_point_sequence_length; ++i) {
bool last_codepoint_sequence_found = false;
for (u8 i = 0; i < max_emoji_code_point_sequence_length; ++i) {
auto code_point = it.peek(i);
if (!code_point.has_value())
break;
code_points.append(*code_point);
if (auto const* emoji = emoji_for_code_points(code_points))
possible_emojis.empend(emoji, code_points);
// NOTE: The following only applies to emoji presentation, not to other
// emoji modifiers.
//
// For a single emoji core sequence, we assume that emoji presentation
// is implied, since this function will only be called for characters
// with default text presentation when either (1) the character is not
// found in the font, or (2) the character is followed by an explicit
// emoji presentation selector.
//
// For emoji zwj sequences, Serenity chooses to treat minimally-qualified
// and unqualified emojis the same as fully-qualified emojis (with regards
// to emoji presentation).
//
// From https://unicode.org/reports/tr51/#Emoji_Implementation_Notes:
// > minimally-qualified or unqualified emoji zwj sequences may be handled
// > in the same way as their fully-qualified forms; the choice is up to
// > the implementation.
//
// In both cases, whenever an emoji presentation selector (U+FE0F) is found, we
// just skip it in order to drop fully-qualified emojis down to their
// minimally-qualified or unqualified forms (with respect to emoji presentation)
// for doing emoji lookups. This ensures that all forms are treated the same
// assuming the emoji filenames are named accordingly (with all emoji presentation
// selector codepoints removed).
if (code_point.value() == 0xFE0F) {
// If the last sequence was found, then we can just update
// its real length.
if (last_codepoint_sequence_found) {
possible_emojis.last().real_codepoint_length++;
}
// And we can always skip the lookup since the code point sequence
// will be unchanged since last time.
continue;
} else {
code_points.append(*code_point);
}
if (auto const* emoji = emoji_for_code_points(code_points)) {
u8 real_codepoint_length = i + 1;
possible_emojis.empend(emoji, code_points, real_codepoint_length);
last_codepoint_sequence_found = true;
} else {
last_codepoint_sequence_found = false;
}
}
if (possible_emojis.is_empty())
@ -77,12 +119,12 @@ Bitmap const* Emoji::emoji_for_code_point_iterator(Utf8CodePointIterator& it)
// If we found one or more matches, return the longest, i.e. last. For example:
// U+1F3F3 - white flag
// U+1F3F3 U+FE0F U+200D U+1F308 - rainbow flag
auto& [emoji, emoji_code_points] = possible_emojis.last();
// U+1F3F3 U+200D U+1F308 - rainbow flag (unqualified form)
auto& [emoji, emoji_code_points, codepoint_length] = possible_emojis.last();
// Advance the iterator, so it's on the last code point of our found emoji and
// whoever is iterating will advance to the next new code point.
for (size_t i = 0; i < emoji_code_points.size() - 1; ++i)
for (u8 i = 0; i < codepoint_length - 1; ++i)
++it;
return emoji;