Function DockNodeIsDropAllowedOne

imgui_tiny_app/imgui/imgui.cpp:19714–19744

}

static bool DockNodeIsDropAllowedOne(ImGuiWindow* payload, ImGuiWindow* host_window)
{
    if (host_window->DockNodeAsHost && host_window->DockNodeAsHost->IsDockSpace() && payload->BeginOrderWithinContext < host_window->BeginOrderWithinContext)
        return false;

    ImGuiWindowClass* host_class = host_window->DockNodeAsHost ? &host_window->DockNodeAsHost->WindowClass : &host_window->WindowClass;
    ImGuiWindowClass* payload_class = &payload->WindowClass;
    if (host_class->ClassId != payload_class->ClassId)
    {
        bool pass = false;
        if (host_class->ClassId != 0 && host_class->DockingAllowUnclassed && payload_class->ClassId == 0)
            pass = true;
        if (payload_class->ClassId != 0 && payload_class->DockingAllowUnclassed && host_class->ClassId == 0)
            pass = true;
        if (!pass)
            return false;
    }

    // Prevent docking any window created above a popup
    // Technically we should support it (e.g. in the case of a long-lived modal window that had fancy docking features),
    // by e.g. adding a 'if (!ImGui::IsWindowWithinBeginStackOf(host_window, popup_window))' test.
    // But it would requires more work on our end because the dock host windows is technically created in NewFrame()
    // and our ->ParentXXX and ->RootXXX pointers inside windows are currently mislading or lacking.
    ImGuiContext& g = *GImGui;
    for (int i = g.OpenPopupStack.Size - 1; i >= 0; i--)
        if (ImGuiWindow* popup_window = g.OpenPopupStack[i].Window)
            if (ImGui::IsWindowWithinBeginStackOf(payload, popup_window))   // Payload is created from within a popup begin stack.
                return false;

    return true;
}

static bool ImGui::DockNodeIsDropAllowed(ImGuiWindow* host_window, ImGuiWindow* root_payload)
{