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Fonts: amend/comment on FontDataOwnedByAtlas=false fix being a breaking change. (#9086, #8465)

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ocornut 2025-12-10 21:42:07 +01:00
parent a07b2828ce
commit 9971251574
4 changed files with 20 additions and 6 deletions
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17
docs/CHANGELOG.txt
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@ -41,14 +41,21 @@ HOW TO UPDATE?
Breaking Changes:
- Fonts: Fixed handling of `ImFontConfig::FontDataOwnedByAtlas = false` which
did erroneously make a copy of the font data, essentially defeating the purpose
of this flag and wasting memory (undetected since July 2015 and now spotted
by @TellowKrinkle, this is perhaps the oldest bug in Dear ImGui history,
albeit for a rarely used feature!) (#9086, #8465)
HOWEVER, fixing this bug is likely to surface bugs in user/app code:
- Prior to 1.92, font data only needs to be available during the atlas->AddFontXXX() call.
- Since 1.92, font data needs to available until atlas->RemoveFont(), or more typically
until a shutdown of the owning context or font atlas.
- The fact that handling of `FontDataOwnedByAtlas = false` was broken
bypassed the issue altogether.
Other Changes:
- Fonts:
- Fixed handling of `ImFontConfig::FontDataOwnedByAtlas = false` which
did erroneously make a copy of the font data, essentially defeating the purpose
of this flag and wasting memory.
Undetected since July 2015 and now spotted by @TellowKrinkle, this is perhaps
the oldest bug in Dear ImGui history (albeit for a rarely used feature)! (#9086)
- Fixed an issue related to EllipsisChar handling, while changing
font loader or font loader flags dynamically in Style->Fonts menus.
- Textures:

1
docs/FONTS.md
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@ -228,6 +228,7 @@ ImFontConfig font_cfg;
font_cfg.FontDataOwnedByAtlas = false;
ImFont* font = io.Fonts->AddFontFromMemoryTTF(data, data_size, size_pixels, &font_cfg);
```
IMPORTANT: Since 1.92, when using `FontDataOwnedByAtlas = false`, font data needs to available until `atlas->RemoveFont()`, or more typically until a shutdown of the owning context or font atlas. It was not immediately noticeable in 1.92.0 due to a bug in handling `FontDataOwnedByAtlas = false`, which was fixed in 1.92.6.
##### [Return to Index](#index)

6
imgui.cpp
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@ -394,6 +394,12 @@ IMPLEMENTING SUPPORT for ImGuiBackendFlags_RendererHasTextures:
When you are not sure about an old symbol or function name, try using the Search/Find function of your IDE to look for comments or references in all imgui files.
You can read releases logs https://github.com/ocornut/imgui/releases for more details.
- 2025/11/24 (1.92.6) - Fonts: Fixed handling of `ImFontConfig::FontDataOwnedByAtlas = false` which did erroneously make a copy of the font data, essentially defeating the purpose of this flag and wasting memory.
(trivia: undetected since July 2015, this is perhaps the oldest bug in Dear ImGui history, albeit for a rarely used feature, see #9086)
HOWEVER, fixing this bug is likely to surface bugs in user code using `FontDataOwnedByAtlas = false`.
- Prior to 1.92, font data only needed to be available during the atlas->AddFontXXX() call.
- Since 1.92, font data needs to available until atlas->RemoveFont(), or more typically until a shutdown of the owning context or font atlas.
- The fact that handling of `FontDataOwnedByAtlas = false` was broken bypassed the issue altogether.
- 2025/11/06 (1.92.5) - BeginChild: commented out some legacy names which were obsoleted in 1.90.0 (Nov 2023), 1.90.9 (July 2024), 1.91.1 (August 2024):
- ImGuiChildFlags_Border --> ImGuiChildFlags_Borders
- ImGuiWindowFlags_NavFlattened --> ImGuiChildFlags_NavFlattened (moved to ImGuiChildFlags). BeginChild(name, size, 0, ImGuiWindowFlags_NavFlattened) --> BeginChild(name, size, ImGuiChildFlags_NavFlattened, 0)

2
imgui.h
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@ -3521,7 +3521,7 @@ struct ImFontConfig
char Name[40]; // <auto> // Name (strictly to ease debugging, hence limited size buffer)
void* FontData; // // TTF/OTF data
int FontDataSize; // // TTF/OTF data size
bool FontDataOwnedByAtlas; // true // TTF/OTF data ownership taken by the owner ImFontAtlas (will delete memory itself).
bool FontDataOwnedByAtlas; // true // TTF/OTF data ownership taken by the owner ImFontAtlas (will delete memory itself). SINCE 1.92, THE DATA NEEDS TO PERSIST FOR WHOLE DURATION OF ATLAS.
// Options
bool MergeMode; // false // Merge into previous ImFont, so you can combine multiple inputs font into one ImFont (e.g. ASCII font + icons + Japanese glyphs). You may want to use GlyphOffset.y when merge font of different heights.