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FreeType: bake color glyphs (COLR/COLRv1/sbix) as BGRA instead of an empty bitmap

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When ImGuiFreeTypeLoaderFlags_LoadColor is set, add FT_LOAD_RENDER to the
FreeType LoadFlags so color glyphs (COLR/COLRv1/sbix/CBDT) produce a BGRA
bitmap immediately during FT_Load_Glyph. In FontBakedLoadGlyph, skip the
subsequent FT_Render_Glyph(slot, FT_RENDER_MODE_NORMAL) when the glyph is
already a bitmap (slot->format == FT_GLYPH_FORMAT_BITMAP), because
re-rendering with FT_RENDER_MODE_NORMAL discards the color layers and, for
pure-COLR glyphs (no traditional outline), yields an empty bitmap -- so
color emoji never bakes and AddText renders nothing.

Monochrome fonts are unaffected: they have no color layers, so
FT_LOAD_COLOR is a no-op for them and the existing FT_RENDER_MODE_NORMAL
path runs as before (slot->format stays FT_GLYPH_FORMAT_OUTLINE until the
explicit FT_Render_Glyph call).
This commit is contained in:
s-celles 2026-08-17 14:46:57 +02:00
parent 46d39d56fe
commit 0aed89e880
1 changed files with 22 additions and 2 deletions
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24
misc/freetype/imgui_freetype.cpp
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@ -206,7 +206,18 @@ bool ImGui_ImplFreeType_FontSrcData::InitFont(FT_Library ft_library, const ImFon
LoadFlags |= FT_LOAD_TARGET_NORMAL;
if (UserFlags & ImGuiFreeTypeLoaderFlags_LoadColor)
{
LoadFlags |= FT_LOAD_COLOR;
// Auto-render during FT_Load_Glyph so color glyphs (COLR/COLRv1/
// sbix/CBDT) produce a BGRA bitmap immediately. Without
// FT_LOAD_RENDER, FT_Load_Glyph leaves the glyph unrendered and
// the later FT_Render_Glyph(slot, FT_RENDER_MODE_NORMAL) call in
// FontBakedLoadGlyph would render only the base outline (monochrome)
// -- for pure-COLR glyphs that yields an empty bitmap and the emoji
// never bakes. FontBakedLoadGlyph skips re-rendering when
// slot->format == FT_GLYPH_FORMAT_BITMAP.
LoadFlags |= FT_LOAD_RENDER;
}
return true;
}
@ -515,9 +526,18 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
return true;
}
// Render glyph into a bitmap (currently held by FreeType)
// Render glyph into a bitmap (currently held by FreeType).
// When FT_LOAD_COLOR was requested and FreeType already rendered a
// color bitmap (slot->format == FT_GLYPH_FORMAT_BITMAP, pixel_mode
// BGRA) during FT_Load_Glyph -- because we add FT_LOAD_RENDER to
// LoadFlags when LoadColor is set -- do NOT re-render with
// FT_RENDER_MODE_NORMAL, which would discard the color layers and
// for pure-COLR glyphs yield an empty bitmap. Only call
// FT_Render_Glyph when the glyph is not yet rendered (outline form).
FT_Render_Mode render_mode = (bd_font_data->UserFlags & ImGuiFreeTypeLoaderFlags_Monochrome) ? FT_RENDER_MODE_MONO : FT_RENDER_MODE_NORMAL;
FT_Error error = FT_Render_Glyph(slot, render_mode);
FT_Error error = 0;
if (slot->format != FT_GLYPH_FORMAT_BITMAP)
error = FT_Render_Glyph(slot, render_mode);
const FT_Bitmap* ft_bitmap = &slot->bitmap;
if (error != 0 || ft_bitmap == nullptr)
return false;