Method DockContextProcessUndockNode

imgui_tiny_app/imgui/imgui.cpp:18457–18496

}

void ImGui::DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
{
    ImGuiContext& g = *ctx;
    IMGUI_DEBUG_LOG_DOCKING("[docking] DockContextProcessUndockNode node %08X\n", node->ID);
    IM_ASSERT(node->IsLeafNode());
    IM_ASSERT(node->Windows.Size >= 1);

    if (node->IsRootNode() || node->IsCentralNode())
    {
        // In the case of a root node or central node, the node will have to stay in place. Create a new node to receive the payload.
        ImGuiDockNode* new_node = DockContextAddNode(ctx, 0);
        new_node->Pos = node->Pos;
        new_node->Size = node->Size;
        new_node->SizeRef = node->SizeRef;
        DockNodeMoveWindows(new_node, node);
        DockSettingsRenameNodeReferences(node->ID, new_node->ID);
        node = new_node;
    }
    else
    {
        // Otherwise extract our node and merge our sibling back into the parent node.
        IM_ASSERT(node->ParentNode->ChildNodes[0] == node || node->ParentNode->ChildNodes[1] == node);
        int index_in_parent = (node->ParentNode->ChildNodes[0] == node) ? 0 : 1;
        node->ParentNode->ChildNodes[index_in_parent] = NULL;
        DockNodeTreeMerge(ctx, node->ParentNode, node->ParentNode->ChildNodes[index_in_parent ^ 1]);
        node->ParentNode->AuthorityForViewport = ImGuiDataAuthority_Window; // The node that stays in place keeps the viewport, so our newly dragged out node will create a new viewport
        node->ParentNode = NULL;
    }
    for (ImGuiWindow* window : node->Windows)
    {
        window->Flags &= ~ImGuiWindowFlags_ChildWindow;
        if (window->ParentWindow)
            window->ParentWindow->DC.ChildWindows.find_erase(window);
        UpdateWindowParentAndRootLinks(window, window->Flags, NULL);
    }
    node->AuthorityForPos = node->AuthorityForSize = ImGuiDataAuthority_DockNode;
    node->Size = FixLargeWindowsWhenUndocking(node->Size, node->Windows[0]->Viewport);
    node->WantMouseMove = true;
    MarkIniSettingsDirty();
}

// This is mostly used for automation.
bool ImGui::DockContextCalcDropPosForDocking(ImGuiWindow* target, ImGuiDockNode* target_node, ImGuiWindow* payload_window, ImGuiDockNode* payload_node, ImGuiDir split_dir, bool split_outer, ImVec2* out_pos)