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Tweak CalcTextSize() awkward width rounding/ceiling code to reduce floating-point imprecisions altering the result by 1 even at relatively small width. (#791) + apply same fudge factor to less important roundings.

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ceilf() is still measurable e.g. ballpark +0.5 for 200k calls.
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ocornut
2026-05-28 19:19:11 +02:00
parent 33bb693b4c
commit 12b7977555
4 changed files with 10 additions and 9 deletions
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9
imgui.cpp
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@@ -6199,11 +6199,10 @@ ImVec2 ImGui::CalcTextSize(const char* text, const char* text_end, bool hide_tex
ImVec2 text_size = font->CalcTextSizeA(font_size, FLT_MAX, wrap_width, text, text_display_end, NULL);
// Round
// FIXME: This has been here since Dec 2015 (7b0bf230) but down the line we want this out.
// FIXME: Investigate using ceilf or e.g.
// - https://git.musl-libc.org/cgit/musl/tree/src/math/ceilf.c
// - https://embarkstudios.github.io/rust-gpu/api/src/libm/math/ceilf.rs.html
text_size.x = IM_TRUNC(text_size.x + 0.99999f);
// FIXME: This has been here since Dec 2015 (7b0bf230 then 4622fa4b6) but down the line we want this out. See #791.
// Investigate using ceilf or e.g. https://git.musl-libc.org/cgit/musl/tree/src/math/ceilf.c, https://embarkstudios.github.io/rust-gpu/api/src/libm/math/ceilf.rs.html
// The problem is that ceilf() has a measurable cost. Not high, but measurable!
text_size.x = IM_TRUNC(text_size.x + 0.999f);
return text_size;
}