Misc: Tolerate zero delta-time under Emscripten. (#6114, #3644)
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 6c19b78..df9f554 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -51,6 +51,9 @@
- PlotHistogram, PlotLines: Passing negative sizes honor alignment like other widgets.
- ImDrawList: Added missing early-out in AddPolyline() and AddConvexPolyFilled() when
color alpha is zero.
+- Misc: Tolerate zero delta-time under Emscripten as backends are imprecise in their
+ values for io.DeltaTime, and browser features such as "privacy.resistFingerprinting=true"
+ can exacerbate that. (#6114, #3644)
- Examples: Win32: Fixed examples using RegisterClassW() since 1.89 to also call
DefWindowProcW() instead of DefWindowProc() so that title text are correctly converted
when application is compiled without /DUNICODE. (#5725, #5961, #5975) [@markreidvfx]
diff --git a/imgui.cpp b/imgui.cpp
index df8b1dc..da04669 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -8852,6 +8852,13 @@
// #define IM_ASSERT(EXPR) do { if (SomeCode(EXPR)) SomeMoreCode(); } while (0) // Correct!
if (true) IM_ASSERT(1); else IM_ASSERT(0);
+ // Emscripten backends are often imprecise in their submission of DeltaTime. (#6114, #3644)
+ // Ideally the Emscripten app/backend should aim to fix or smooth this value and avoid feeding zero, but we tolerate it.
+#ifdef __EMSCRIPTEN__
+ if (g.IO.DeltaTime <= 0.0f && g.FrameCount > 0)
+ g.IO.DeltaTime = 0.00001f;
+#endif
+
// Check user data
// (We pass an error message in the assert expression to make it visible to programmers who are not using a debugger, as most assert handlers display their argument)
IM_ASSERT(g.Initialized);
