How to combine a fixed docking layout with floating windows and different WindowClassIDs?

[magsell]

Version/Branch of Dear ImGui:

Version 1.91.3, Branch: docking

Back-ends:

imgui_impl_opengl3.cpp + imgui_impl_glfw.cpp

Compiler, OS:

Linux + GCC

Full config/build information:

Dear ImGui 1.91.4 WIP (19131)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201103
define: __linux__
define: __GNUC__=13
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000083
 NavEnableKeyboard
 NavEnableGamepad
 DockingEnable
io.ConfigViewportsNoDecoration
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00001C0E
 HasMouseCursors
 HasSetMousePos
 PlatformHasViewports
 HasMouseHoveredViewport
 RendererHasVtxOffset
 RendererHasViewports
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,64
io.DisplaySize: 1280.00,720.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Dear ImGui 1.91.4 WIP (19131)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201103
define: __linux__
define: __GNUC__=13
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK
--------------------------------
io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000083
 NavEnableKeyboard
 NavEnableGamepad
 DockingEnable
io.ConfigViewportsNoDecoration
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x00001C0E
 HasMouseCursors
 HasSetMousePos
 PlatformHasViewports
 HasMouseHoveredViewport
 RendererHasVtxOffset
 RendererHasViewports
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,64
io.DisplaySize: 1280.00,720.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00

Details:

My Issue/Question:

I created a fixed window layout using the dock builder API
with three docking nodes and each docking node contains a
non-movable and non-collapsible window.

I want to use the WindowClassID because I read in another
issue that only windows with the same ID can be docked.

Each window belongs to its own window class:

• ModelWindow: WindowClassID = 1
• LogWindow: WindowClassID = 2
• SceneWindow: WindowClassID = 3

I want docking to work only with windows that belong to the
same window class. For example, Window1 and Window2
have WindowClassID = 3 and docking should only work with
SceneWindow but I can only dock Window1 and Window2.

Thank you for your help!

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

    ImGuiViewport* viewport = ImGui::GetMainViewport();
    // ========================================================================
    // CREATE FIXED DOCKING LAYOUT
    // ========================================================================
    {
      constexpr ImGuiDockNodeFlags dock_space_flags = ImGuiDockNodeFlags_PassthruCentralNode;

      ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
      ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
      
      ImGuiWindowFlags dock_window_flags = ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking |
                                           ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse |
                                           ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove |
                                           ImGuiWindowFlags_NoBringToFrontOnFocus | ImGuiWindowFlags_NoNavFocus |
                                           ImGuiWindowFlags_NoBackground;

      ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));

      ImGui::SetNextWindowPos(viewport->Pos);
      ImGui::SetNextWindowSize(viewport->Size);
      ImGui::SetNextWindowViewport(viewport->ID);
      if (ImGui::Begin("DockSpace", nullptr, dock_window_flags))
      {
        const ImGuiID dock_space_id = ImGui::GetID("MyDockSpace");
        ImGui::DockSpace(dock_space_id, ImVec2(0.0f, 0.0f), dock_space_flags);

        static bool dockspace_initialized = false;
        if (!dockspace_initialized)
        {
          ImGui::DockBuilderRemoveNode(dock_space_id);
          ImGui::DockBuilderAddNode(dock_space_id, dock_space_flags | ImGuiDockNodeFlags_DockSpace);
          ImGui::DockBuilderSetNodeSize(dock_space_id, viewport->Size);

          ImGuiID dock_scene_id = dock_space_id;
          const ImGuiID dock_model_id = ImGui::DockBuilderSplitNode(dock_scene_id, ImGuiDir_Left, 0.2f, nullptr, &dock_scene_id);
          const ImGuiID dock_log_id = ImGui::DockBuilderSplitNode(dock_scene_id, ImGuiDir_Down, 0.2f, nullptr, &dock_scene_id);

          ImGui::DockBuilderDockWindow("ModelWindow", dock_model_id);
          ImGui::DockBuilderDockWindow("SceneWindow", dock_scene_id);
          ImGui::DockBuilderDockWindow("LogWindow", dock_log_id);

          ImGui::DockBuilderFinish(dock_space_id);
          dockspace_initialized = true;
        }
      }
      ImGui::End();
      ImGui::PopStyleVar(3);
    }
    // ========================================================================
    // DRAW MODEL-WINDOW
    // ========================================================================
    {
      ImGui::SetNextWindowClass(&models_window_class);  // models_window_class is defined with  WindowClassID = 1
      const ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoMove;
      if (ImGui::Begin("ModelWindow", nullptr, window_flags)) {
        ...
      }
      ImGui::End();
    }
    // ========================================================================
    // DRAW LOG-WINDOW
    // ========================================================================
    {
      ImGui::SetNextWindowClass(&log_window_class);  // log_window_class is defined with  WindowClassID = 2
      const ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize |
                                            ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoMove;
      if (ImGui::Begin("LogWindow", nullptr, window_flags)) {
        ...
      }
      ImGui::End();
    }
    // ========================================================================
    // DRAW SCENE-WINDOW
    // ========================================================================
    {
      const ImGuiWindowFlags window_flags = ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoCollapse |
                                            ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove;
      ImGui::SetNextWindowClass(&scenes_window_class);  // scenes_window_class is defined with  WindowClassID = 3
      if (ImGui::Begin("SceneWindow", nullptr, window_flags)) {
        ...
      }
      ImGui::End();
    }
    // ========================================================================
    // DRAW WINDOW1
    // ========================================================================
    {
      ImGui::SetNextWindowClass(&scene_window_class);  // scene_window_class is defined with  WindowClassID = 3
      const ImGuiWindowFlags window_flags = 0;
      if (ImGui::Begin("Window1", nullptr, window_flags)) {
        ...
      }
      ImGui::End();
    }
    // ========================================================================
    // DRAW WINDOW2
    // ========================================================================
    {
      ImGui::SetNextWindowClass(&scene_window_class);
      const ImGuiWindowFlags window_flags = 0;
      if (ImGui::Begin("Window2", nullptr, window_flags)){
        ...
      }
      ImGui::End();
    }