imgui: Menu's and window dragging doesn't respond well to empty update

In our engine, we process all input messages which were sent during the last frame including a paint message which pumps ImGui every frame regardless of the number of additional input messages.

The goal here is to respond to input as early as possible and to capture all user input and not discard anything.

A frame with a mouse click would look something like this

Game_BeginFrame();

    UpdateGui_LMB_Click();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    UpdateGui_Paint();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    DrawImGui()

Game_EndFrame()

A frame with a mouse move and a mouse click would look something like this

Game_BeginFrame();

    UpdateGui_Mouse_Move();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    UpdateGui_LMB_Click();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    UpdateGui_Paint();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    DrawImGui()

Game_EndFrame()

A frame without a mouse click would be

Game_BeginFrame();

    UpdateGui_Paint();
        Update_ImGuiIO();
        ImGui::NewFrame();
        UpdateImGuiWindows(); // Do the actual gui work

    DrawImGui()

Game_EndFrame()

In this setup, I’m able to click on widgets in an open window, scroll the scroll bar both with the wheel or by dragging it and I can also resize the window by dragging the resize grip.

I cannot however click in the empty space of the window to bring it into focus, or click out of the window to move it out of focus. I also cannot click and drag the window.

In a MenuBar I’m able to click on and open a Menu, I can click MenuItems and they’ll do whatever they’re supposed to do. But I cannot click off the menu (say into another window or just empty space) to close the menu or cause it to lose focus.

What’s most odd to me (and what I’m hoping makes the sense to you) is that if I put the Paint update first instead of last, everything seems to behave correctly?

I’m not sure if this is a bug, something I’m doing wrong or both?

Thanks for keeping this project going!