AccessViolationException in ImGuiImplOpenGL3.RenderDrawDataNative with Bonsai.ImGui 0.1.0

[bruno-f-cruz]

Environment

Bonsai 2.9.0
Bonsai.ImGui / Bonsai.ImPlot / Bonsai.ImGui.Visualizers / Bonsai.ImGui.Visualizers.Design: 0.1.0
Hexa.NET.ImGui / Hexa.NET.ImPlot: 2.2.9
Hexa.NET.ImGui.Backends: 1.0.18
HexaGen.Runtime: 1.1.24
Target framework: .NET Framework 4.8 (net480), Windows
OpenGL backend (the default)
Symptoms
Repeated crashes with:

Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory.
   at Hexa.NET.ImGui.Backends.OpenGL3.ImGuiImplOpenGL3.RenderDrawDataNative(ImDrawData* drawData)
   at Bonsai.ImGui.Design.ImGuiControl.OnPaint(PaintEventArgs e)
   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
   at System.Windows.Forms.Control.WmPaint(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.UserControl.WndProc(Message& m)
   at Bonsai.ImGui.Design.ImGuiControl.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
  ...

The crash occurs frequently (10% rate) at workflow startup, and very rarely during a running session.

What I tried

I initially suspected my own custom Combinator-based ImGui operators in this workflow. After working through several iterations (snapshot pattern for thread safety, removing nested ImGui.Begin/End in favor of BeginChild, disabling recoverable native asserts via io.ConfigErrorRecoveryEnableAssert = false per #29, removing stale package references, etc.), the crash rate decreased somewhat, but did not stop.

I then disabled all custom visualizers — leaving only operators from the Bonsai.ImGui / Bonsai.ImPlot / Bonsai.ImGui.Visualizers packages (ImPlotVisualizerBuilder, ImGuiVisualizerBuilder, PlotBuilder, line/scatter series operators, etc.). The AV in RenderDrawDataNative still occurs, on the same startup-frequent / (never during session).

The workflow I used for test is here:

https://github.com/AllenNeuralDynamics/Aind.Behavior.VrForaging/tree/5950d06888ae41d19a3781357c3c864dc8960186

[bruno-f-cruz]

After some testing I think we narrowed down the issue to programmatically resizing the control containing imgui visualizers at the start of the workflow. The solution was the allow the visualizer to spawn with default dimensions and maximizing manually. I will report back if we see any other issues. I should note that this affects ANY visualizer from the new package as well as custom visualizers.