Docking without a central node?

[nikitablack]

Version/Branch of Dear ImGui:

Version v1.90.5, Branch: docking

Back-ends:

custom

Compiler, OS:

Ubuntu 20.04

Full config/build information:

No response

Details:

In my application I don't want to have the central node in a main docking area. I.e., when I start the application for the first time, the area should be empty. Next, I want to create multiple windows and arrange them whatever I want, but there should be no empty spaces in the main area as soon as I add at least one window. With the default implementation, I can drop a window to one of the 5 predefined sections, like this:

If I drop a window to a left side there's an empty space to the right:

I'd like to avoid that empty space and make the very first window to fill the complete docking area. For this, I created a dockspace with the ImGuiDockNodeFlags_NoDockingSplit flag:

    ImGuiWindowClass windowClass{};
    windowClass.DockNodeFlagsOverrideSet = ImGuiDockNodeFlags_NoUndocking | ImGuiDockNodeFlags_NoTabBar;
    ImGui::SetNextWindowClass(&windowClass);

    ImGui::Begin(viewerContainerName.c_str(), nullptr, ImGuiWindowFlags_None | ImGuiWindowFlags_NoBringToFrontOnFocus);

    auto viewerDockspace = ImGui::GetID("viewerDockspace");

    ImGui::DockSpace(viewerDockspace, ImVec2(0.0f, 0.0f), ImGuiDockNodeFlags_NoDockingSplit);
    ImGui::End();

Now I can drop a window only to the central node, which seems like what I want:

But now I can't split the newly added window, i.e. I can't arrange windows in rows and columns, only stacking works:

(if I move the mouse cursor exactly on border, the side dropping areas appear, but I can't use them - as soon as I move the mouse, they disappear again).

To be honest, I don't fully understand how the docking works - how it keeps the state, why there are multiple DockBuilderXXX functions. Is it possible at all to achieve what I want without modifying the source code?

[nikitablack]

For now, the solution from 3834 works for me (i.e. changing the dockspace's LocalFlags). It basically removes the central dropping area leaving only sides and any docked window takes the complete space.