Docking: floating node with a central node hides properly when nothing is docked + rename.

docs/CHANGELOG.txt

@@ -145,7 +145,8 @@ Docking+Viewports Branch:
   docking hierarchy. Added ImGuiFocusedFlags_DockHierarchy flag to consider docking hierarchy in the test.
 - IsWindowHovered: Fixed using ImGuiHoveredFlags_ChildWindows (without _RootWindow) from leaking the
   docking hierarchy. Added ImGuiHoveredFlags_DockHierarchy flag to consider docking hierarchy in the test.
-- Docking: fixed settings load issue when mouse wheeling. (#4310)
+- Docking: Fixed settings load issue when mouse wheeling. (#4310)
+- Docking: Fixed manually created floating node with a central node from not hiding when windows are gone.
 - Docking + Drag and Drop: Fixed using BeginDragDropSource() or BeginDragDropTarget() inside a Begin()
   that returned false because the window is docked. (#4515)
 - Viewports: Fixed a crash while a window owning its viewport disappear while being dragged.

imgui.cpp

@@ -13330,6 +13330,7 @@ ImGuiDockNode::ImGuiDockNode(ImGuiID id)
     State = ImGuiDockNodeState_Unknown;
     HostWindow = VisibleWindow = NULL;
     CentralNode = OnlyNodeWithWindows = NULL;
+    CountNodeWithWindows = 0;
     LastFrameAlive = LastFrameActive = LastFrameFocused = -1;
     LastFocusedNodeId = 0;
     SelectedTabId = 0;
@@ -13715,6 +13716,7 @@ static void ImGui::DockNodeUpdateForRootNode(ImGuiDockNode* node)
     DockNodeFindInfo(node, &info);
     node->CentralNode = info.CentralNode;
     node->OnlyNodeWithWindows = (info.CountNodesWithWindows == 1) ? info.FirstNodeWithWindows : NULL;
+    node->CountNodeWithWindows = info.CountNodesWithWindows;
     if (node->LastFocusedNodeId == 0 && info.FirstNodeWithWindows != NULL)
         node->LastFocusedNodeId = info.FirstNodeWithWindows->ID;
 
@@ -13764,9 +13766,14 @@ static void ImGui::DockNodeUpdate(ImGuiDockNode* node)
 
     // Early out for hidden root dock nodes (when all DockId references are in inactive windows, or there is only 1 floating window holding on the DockId)
     bool want_to_hide_host_window = false;
-    if (node->Windows.Size <= 1 && node->IsFloatingNode() && node->IsLeafNode())
+    if (node->IsFloatingNode())
-        if (!g.IO.ConfigDockingAlwaysTabBar && (node->Windows.Size == 0 || !node->Windows[0]->WindowClass.DockingAlwaysTabBar))
+    {
+        if (node->Windows.Size <= 1 && node->IsLeafNode())
+            if (!g.IO.ConfigDockingAlwaysTabBar && (node->Windows.Size == 0 || !node->Windows[0]->WindowClass.DockingAlwaysTabBar))
+                want_to_hide_host_window = true;
+        if (node->CountNodeWithWindows == 0)
             want_to_hide_host_window = true;
+    }
     if (want_to_hide_host_window)
     {
         if (node->Windows.Size == 1)

imgui_internal.h

@@ -1363,6 +1363,7 @@ struct IMGUI_API ImGuiDockNode
     ImGuiWindow*            VisibleWindow;              // Generally point to window which is ID is == SelectedTabID, but when CTRL+Tabbing this can be a different window.
     ImGuiDockNode*          CentralNode;                // [Root node only] Pointer to central node.
     ImGuiDockNode*          OnlyNodeWithWindows;        // [Root node only] Set when there is a single visible node within the hierarchy.
+    int                     CountNodeWithWindows;       // [Root node only]
     int                     LastFrameAlive;             // Last frame number the node was updated or kept alive explicitly with DockSpace() + ImGuiDockNodeFlags_KeepAliveOnly
     int                     LastFrameActive;            // Last frame number the node was updated.
     int                     LastFrameFocused;           // Last frame number the node was focused.
@@ -1617,7 +1618,7 @@ struct ImGuiContext
     ImGuiWindow*            CurrentWindow;                      // Window being drawn into
     ImGuiWindow*            HoveredWindow;                      // Window the mouse is hovering. Will typically catch mouse inputs.
     ImGuiWindow*            HoveredWindowUnderMovingWindow;     // Hovered window ignoring MovingWindow. Only set if MovingWindow is set.
-    ImGuiDockNode*          HoveredDockNode;                    // Hovered dock node.
+    ImGuiDockNode*          HoveredDockNode;                    // [Debug] Hovered dock node.
     ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actual window that is moved is generally MovingWindow->RootWindowDockTree.
     ImGuiWindow*            WheelingWindow;                     // Track the window we started mouse-wheeling on. Until a timer elapse or mouse has moved, generally keep scrolling the same window even if during the course of scrolling the mouse ends up hovering a child window.
     ImVec2                  WheelingWindowRefMousePos;