Docking+Viewports: Fix undocking window node causing parent viewport …

…to become unresponsive. (#5503)

Amend 67be485, Somehow ties to 58f5092 + 0eb45a0 (#4310)
Unsure of exact chain of event but this caused a parent link msimatch between the time of the MouseMoving test in AddUpdateViewport() setting _NoInputs on the wrong parent., and the release clearing _NoInputs on the rght one.

docs/CHANGELOG.txt

@@ -146,6 +146,8 @@ Docking+Viewports Branch:
 - Docking: Fixed regression introduced in v1.87 when docked window content not rendered
   while switching between with CTRL+Tab. [@rokups]
 - Docking: Fixed amending into an existing tab bar from rendering invisible items. (#5515)
+- Docking+Viewports: Fixed undocking window node causing parent viewports to become unresponsive
+  in certain situation (e.g. hidden tab bar). (#5503) [@rokups]
 - Backends: GLFW: Fixed leftover static variable preventing from changing or
   reinitializing backend while application is running. (#4616, #5434) [@rtoumazet]
 

imgui.cpp

@@ -14460,14 +14460,6 @@ void ImGui::DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
         new_node->SizeRef = node->SizeRef;
         DockNodeMoveWindows(new_node, node);
         DockSettingsRenameNodeReferences(node->ID, new_node->ID);
-        for (int n = 0; n < new_node->Windows.Size; n++)
-        {
-            ImGuiWindow* window = new_node->Windows[n];
-            window->Flags &= ~ImGuiWindowFlags_ChildWindow;
-            if (window->ParentWindow)
-                window->ParentWindow->DC.ChildWindows.find_erase(window);
-            UpdateWindowParentAndRootLinks(window, window->Flags, NULL);
-        }
         node = new_node;
     }
     else
@@ -14480,6 +14472,14 @@ void ImGui::DockContextProcessUndockNode(ImGuiContext* ctx, ImGuiDockNode* node)
         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 (int n = 0; n < node->Windows.Size; n++)
+    {
+        ImGuiWindow* window = node->Windows[n];
+        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;