Tweak computation of io.Framerate so it is less biased toward high-values in the first 120 frames. (#4138)

docs/CHANGELOG.txt

@@ -62,6 +62,7 @@ Other Changes:
 - LabelText: Fixed clipping of multi-line value text when label is single-line. (#4004)
 - LabelText: Fixed vertical alignment of single-line value text when label is multi-line. (#4004)
 - Popups: Added 'OpenPopup(ImGuiID id)' overload to facilitate calling from nested stacks. (#3993, #331) [@zlash]
+- Tweak computation of io.Framerate so it is less biased toward high-values in the first 120 frames. (#4138)
 - Optimization: Disabling some of MSVC most aggressive Debug runtime checks for some simple/low-level functions
   (e.g. ImVec2, ImVector) leading to a 10-20% increase of performances with MSVC "default" Debug settings.
 - ImDrawList: Add and use SSE-enabled ImRsqrt() in place of 1.0f / ImSqrt(). (#4091) [@wolfpld]

imgui.cpp

@@ -3923,7 +3923,8 @@ void ImGui::NewFrame()
     g.FramerateSecPerFrameAccum += g.IO.DeltaTime - g.FramerateSecPerFrame[g.FramerateSecPerFrameIdx];
     g.FramerateSecPerFrame[g.FramerateSecPerFrameIdx] = g.IO.DeltaTime;
     g.FramerateSecPerFrameIdx = (g.FramerateSecPerFrameIdx + 1) % IM_ARRAYSIZE(g.FramerateSecPerFrame);
-    g.IO.Framerate = (g.FramerateSecPerFrameAccum > 0.0f) ? (1.0f / (g.FramerateSecPerFrameAccum / (float)IM_ARRAYSIZE(g.FramerateSecPerFrame))) : FLT_MAX;
+    g.FramerateSecPerFrameCount = ImMin(g.FramerateSecPerFrameCount + 1, IM_ARRAYSIZE(g.FramerateSecPerFrame));
+    g.IO.Framerate = (g.FramerateSecPerFrameAccum > 0.0f) ? (1.0f / (g.FramerateSecPerFrameAccum / (float)g.FramerateSecPerFrameCount)) : FLT_MAX;
 
     UpdateViewportsNewFrame();
 

imgui.h

@@ -1864,7 +1864,7 @@ struct ImGuiIO
     bool        WantSaveIniSettings;            // When manual .ini load/save is active (io.IniFilename == NULL), this will be set to notify your application that you can call SaveIniSettingsToMemory() and save yourself. Important: clear io.WantSaveIniSettings yourself after saving!
     bool        NavActive;                      // Keyboard/Gamepad navigation is currently allowed (will handle ImGuiKey_NavXXX events) = a window is focused and it doesn't use the ImGuiWindowFlags_NoNavInputs flag.
     bool        NavVisible;                     // Keyboard/Gamepad navigation is visible and allowed (will handle ImGuiKey_NavXXX events).
-    float       Framerate;                      // Application framerate estimate, in frame per second. Solely for convenience. Rolling average estimation based on io.DeltaTime over 120 frames.
+    float       Framerate;                      // Rough estimate of application framerate, in frame per second. Solely for convenience. Rolling average estimation based on io.DeltaTime over 120 frames.
     int         MetricsRenderVertices;          // Vertices output during last call to Render()
     int         MetricsRenderIndices;           // Indices output during last call to Render() = number of triangles * 3
     int         MetricsRenderWindows;           // Number of visible windows

imgui_internal.h

@@ -1586,6 +1586,7 @@ struct ImGuiContext
     // Misc
     float                   FramerateSecPerFrame[120];          // Calculate estimate of framerate for user over the last 2 seconds.
     int                     FramerateSecPerFrameIdx;
+    int                     FramerateSecPerFrameCount;
     float                   FramerateSecPerFrameAccum;
     int                     WantCaptureMouseNextFrame;          // Explicit capture via CaptureKeyboardFromApp()/CaptureMouseFromApp() sets those flags
     int                     WantCaptureKeyboardNextFrame;
@@ -1733,7 +1734,7 @@ struct ImGuiContext
         DebugItemPickerBreakId = 0;
 
         memset(FramerateSecPerFrame, 0, sizeof(FramerateSecPerFrame));
-        FramerateSecPerFrameIdx = 0;
+        FramerateSecPerFrameIdx = FramerateSecPerFrameCount = 0;
         FramerateSecPerFrameAccum = 0.0f;
         WantCaptureMouseNextFrame = WantCaptureKeyboardNextFrame = WantTextInputNextFrame = -1;
         memset(TempBuffer, 0, sizeof(TempBuffer));