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feat(chat): render emoji in messages and user text (Q12)

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Merge a monochrome Noto Emoji subset into the text fonts so chat messages, the
composer, contact names, and memos render emoji (😀 🎉 ❤ 🔥 👍 …) instead of
tofu.

- Enable IMGUI_USE_WCHAR32 (imconfig.h): emoji live above the BMP (U+1F300+), so
  16-bit ImWchar literally can't address them. This widens ImWchar build-wide;
  the only ImWchar uses in-tree are glyph-range arrays and one BMP private-use
  codepoint, so nothing else is affected. Tests + full build pass.
- Bundle res/fonts/NotoEmoji-Subset.ttf — the OFL monochrome Noto Emoji (color
  CBDT/COLR fonts can't be rasterized by ImGui's stb_truetype) pinned to wght=400
  and subset to the emoji planes (1411 glyphs, 747 KB). Reproducible via
  scripts/build_emoji_subset.py. Embedded via INCBIN like the CJK subset.
- Typography::loadFont merges it (MergeMode) only into the small text fonts
  (Body/Subtitle/Caption/Button) — not headers, which don't need 1400 emoji.
  The base font keeps precedence for U+2600–26FF, so text-style symbols stay.

Limits: ImGui does no shaping, so single-codepoint emoji render but ZWJ sequences
(family/profession) and regional-indicator flags won't compose; emoji are
monochrome (the OS emoji picker still inputs them fine, and the composer byte
counter already counts their 4-byte UTF-8 cost against the on-chain cap).

Verified headless: sizeof(ImWchar)==4 and every probed emoji is in-font and bakes
into the atlas.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
DanS
2026-07-16 17:28:50 -05:00
parent fac0245297
commit 11de117331
6 changed files with 133 additions and 2 deletions
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41
src/ui/material/typography.cpp
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@@ -325,11 +325,50 @@ ImFont* Typography::loadFont(ImGuiIO& io, int weight, float size, const char* na
name, g_noto_cjk_subset_size);
}
}
// Merge monochrome emoji for chat + user text (Q12). Only into the small text fonts — baking
// ~1400 emoji at heading sizes would bloat the atlas for glyphs no heading needs. ImGui does no
// shaping, so single-codepoint emoji render but ZWJ sequences / flags won't compose. The
// >0xFFFF ranges require IMGUI_USE_WCHAR32 (imconfig.h).
static const char* const kEmojiFonts[] = {
"Body1", "Body2", "Subtitle1", "Subtitle2", "Caption", "Overline", "Button", "ButtonSm"
};
bool wantEmoji = false;
for (const char* n : kEmojiFonts) if (strcmp(name, n) == 0) { wantEmoji = true; break; }
if (wantEmoji && g_noto_emoji_subset_size > 0) {
void* emojiCopy = IM_ALLOC(g_noto_emoji_subset_size);
memcpy(emojiCopy, g_noto_emoji_subset_data, g_noto_emoji_subset_size);
ImFontConfig emojiCfg;
emojiCfg.FontDataOwnedByAtlas = true;
emojiCfg.MergeMode = true; // merge into the text font just loaded
emojiCfg.OversampleH = 1;
emojiCfg.OversampleV = 1;
emojiCfg.PixelSnapH = true;
emojiCfg.GlyphMinAdvanceX = 0;
// The base Ubuntu font already owns U+2600–26FF etc.; MergeMode keeps the first-loaded glyph,
// so its text-style symbols win and only the codepoints it lacks fall through to emoji.
static const ImWchar emojiRanges[] = {
0x2600, 0x27BF, // Misc Symbols + Dingbats
0x2B00, 0x2BFF, // stars (⭐) + arrows
0x1F000, 0x1FAFF, // emoji planes (emoticons, pictographs, transport, supplement, extended)
0,
};
emojiCfg.GlyphRanges = emojiRanges;
snprintf(emojiCfg.Name, sizeof(emojiCfg.Name), "NotoEmoji %.0fpx (merge)", size);
ImFont* emojiMerge = io.Fonts->AddFontFromMemoryTTF(emojiCopy, g_noto_emoji_subset_size, size, &emojiCfg);
if (emojiMerge) {
DEBUG_LOGF("Typography: Merged emoji (%u bytes) into %s OK\n", g_noto_emoji_subset_size, name);
} else {
DEBUG_LOGF("Typography: WARNING — emoji merge FAILED for %s (size=%u)\n", name, size);
}
}
} else {
DEBUG_LOGF("Typography: Failed to load %s\n", name);
IM_FREE(fontDataCopy);
}
return font;
}