Docking: Added an assert to clarify that ImGuiDockNodeFlags_CentralNode flag does not need to be passed to DockSpace(). (#8145)

docs/CHANGELOG.txt

@@ -64,6 +64,9 @@ Other changes:
 
 Docking+Viewports Branch:
 
+- Docking: Added an assert to clarify that ImGuiDockNodeFlags_CentralNode flag
+  (from internals) does not need to be passed to DockSpace(), as it causes general
+  havoc. (#8145)
 - Backends: Win32: Fixed a crash/regression in 1.91.5 when running two processes
   with multi-viewports (was using GetProp() to query property which could have
   belonged to another process). (#8162, #8069) [@sammyfreg, @ocornut]

imgui.cpp

@@ -4957,7 +4957,7 @@ void ImGui::StartMouseMovingWindowOrNode(ImGuiWindow* window, ImGuiDockNode* nod
     {
         // Can undock if:
         // - part of a hierarchy with more than one visible node (if only one is visible, we'll just move the root window)
-        // - part of a dockspace node hierarchy: so we can undock the last single visible node too (trivia: undocking from a fixed/central node will create a new node and copy windows)
+        // - part of a dockspace node hierarchy: so we can undock the last single visible node too. Undocking from a fixed/central node will create a new node and copy windows.
         ImGuiDockNode* root_node = DockNodeGetRootNode(node);
         if (root_node->OnlyNodeWithWindows != node || root_node->CentralNode != NULL)   // -V1051 PVS-Studio thinks node should be root_node and is wrong about that.
             can_undock_node = true;
@@ -19320,7 +19320,9 @@ ImGuiID ImGui::DockSpace(ImGuiID dockspace_id, const ImVec2& size_arg, ImGuiDock
     if ((flags & ImGuiDockNodeFlags_KeepAliveOnly) == 0)
         window = GetCurrentWindow(); // call to set window->WriteAccessed = true;
 
-    IM_ASSERT((flags & ImGuiDockNodeFlags_DockSpace) == 0);
+    IM_ASSERT((flags & ImGuiDockNodeFlags_DockSpace) == 0); // Flag is automatically set by DockSpace() as LocalFlags, not SharedFlags!
+    IM_ASSERT((flags & ImGuiDockNodeFlags_CentralNode) == 0); // Flag is automatically set by DockSpace() as LocalFlags, not SharedFlags! (#8145)
+
     IM_ASSERT(dockspace_id != 0);
     ImGuiDockNode* node = DockContextFindNodeByID(&g, dockspace_id);
     if (node == NULL)

imgui_internal.h

@@ -1835,6 +1835,7 @@ enum ImGuiDockNodeFlagsPrivate_
     ImGuiDockNodeFlags_NoResizeX                = 1 << 16,  //       //
     ImGuiDockNodeFlags_NoResizeY                = 1 << 17,  //       //
     ImGuiDockNodeFlags_DockedWindowsInFocusRoute= 1 << 18,  //       // Any docked window will be automatically be focus-route chained (window->ParentWindowForFocusRoute set to this) so Shortcut() in this window can run when any docked window is focused.
+
     // Disable docking/undocking actions in this dockspace or individual node (existing docked nodes will be preserved)
     // Those are not exposed in public because the desirable sharing/inheriting/copy-flag-on-split behaviors are quite difficult to design and understand.
     // The two public flags ImGuiDockNodeFlags_NoDockingOverCentralNode/ImGuiDockNodeFlags_NoDockingSplit don't have those issues.
@@ -1843,6 +1844,7 @@ enum ImGuiDockNodeFlagsPrivate_
     ImGuiDockNodeFlags_NoDockingOverOther       = 1 << 21,  //       // Disable this node from being docked over another window or non-empty node.
     ImGuiDockNodeFlags_NoDockingOverEmpty       = 1 << 22,  //       // Disable this node from being docked over an empty node (e.g. DockSpace with no other windows)
     ImGuiDockNodeFlags_NoDocking                = ImGuiDockNodeFlags_NoDockingOverMe | ImGuiDockNodeFlags_NoDockingOverOther | ImGuiDockNodeFlags_NoDockingOverEmpty | ImGuiDockNodeFlags_NoDockingSplit | ImGuiDockNodeFlags_NoDockingSplitOther,
+
     // Masks
     ImGuiDockNodeFlags_SharedFlagsInheritMask_  = ~0,
     ImGuiDockNodeFlags_NoResizeFlagsMask_       = (int)ImGuiDockNodeFlags_NoResize | ImGuiDockNodeFlags_NoResizeX | ImGuiDockNodeFlags_NoResizeY,