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Fix texture-based anti-aliasing with RGBA textures #5132

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Fix texture-based anti-aliasing with RGBA textures #5132

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cfillion
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@cfillion cfillion commented Mar 23, 2022 •
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Texture-based anti-aliasing is broken after loading a font using imgui_freetype.cpp with ImGuiFreeTypeBuilderFlags_LoadColor set in ImFontConfig::FontBuilderFlags. Using the OpenGL3 backend (haven't tested others).

Screenshot of the bug

#define IMGUI_ENABLE_FREETYPE
// ...
ImFontConfig cfg;
cfg.FontBuilderFlags |= ImGuiFreeTypeBuilderFlags_LoadColor;
io.Fonts->AddFontFromFileTTF("/usr/share/fonts/TTF/DejaVuSans.ttf", 14, &cfg);

This appears to be because ImFontAtlasBuildRenderLinesTexData uses transparent black when writing to TexPixelsRGBA32. Transparent white is produced (via GetTexDataAsRGBA32) when it writes to TexPixelsAlpha8.

This PR removes that difference by having ImFontAtlasBuildRenderLinesTexData write transparent white to TexPixelsRGBA32. It restores anti-aliasing (although I don't fully understand why, so I'm not 100% certain whether this is the correct fix):

Patched to write transparent white

@cfillion
fix texture-based anti-aliasing with RGBA textures
00f43be 
When using an Alpha8 font texture, GetTexDataAsRGBA32 converts 0x00 to transparent white.

When using a RGBA32 font texture, ImFontAtlasBuildRenderLinesTexData was writing transparent black.
ocornut pushed a commit that referenced this pull request Mar 23, 2022
@cfillion @ocornut
ImDrawList: Fix texture-based anti-aliasing with RGBA textures (#5132, …
7d7bf99 
…#3245)

When using an Alpha8 font texture, GetTexDataAsRGBA32 converts 0x00 to transparent white.
When using a RGBA32 font texture, ImFontAtlasBuildRenderLinesTexData was writing transparent black.
@ocornut
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ocornut commented Mar 23, 2022

Nice catch, thank you!
Merged as 7d7bf99

@ocornut ocornut closed this Mar 23, 2022
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@cfillion @ocornut