Unity-Technologies/UnityCsReference · error · LayoutException

Error while reading window layout: no root view on main wind

Error message

Error while reading window layout: no root view on main window.

What it means

After loading a layout, the editor requires the main window to have a valid rootView; if it is null the layout is considered missing a main window and is unrecoverable. The code destroys the broken main window and throws LayoutException so the caller can fall back to the previous/default layout. Without this, every subsequent load attempt would also fail.

Source

Thrown at Editor/Mono/GUI/WindowLayout.cs:1433

                    if (w is SceneHierarchyWindow || (w?.GetType() == HierarchyPreferences.HierarchyV2WindowType))
                        HierarchyPreferences.EnsureCorrectHierarchyIsInUse(w);
                }

                if (mainWindowToSetSize)
                {
                    mainWindowToSetSize.position = mainWindowPosition;
                }
                // Always show main window before other windows. So that other windows can
                // get their parent/owner.
                if (mainWindow)
                {
                    // If at this point the mainWindow still doesn't have a rootView, it probably means we loaded a layout without a main window.
                    // Delete the current mainWindow so that we can load back the previous layout otherwise every attemp at loading a layout will fail.
                    if (mainWindow.rootView == null || !mainWindow.rootView)
                    {
                        mainWindow.Close();
                        UnityObject.DestroyImmediate(mainWindow, true);
                        throw new LayoutException("Error while reading window layout: no root view on main window.");
                    }

                    mainWindow.Show(mainWindow.showMode, loadPosition: true, displayImmediately: true, setFocus: true);
                    if (mainWindowToSetSize && mainWindow.maximized != mainWindowMaximized)
                        mainWindow.ToggleMaximize();

                    // Make sure to restore the save to layout flag when loading a layout from a file.
                    if (flags.HasFlag(LoadWindowLayoutFlags.KeepMainWindow))
                        mainWindow.m_DontSaveToLayout = false;
                }
                else if (!flags.HasFlag(LoadWindowLayoutFlags.NoMainWindowSupport))
                {
                    throw new LayoutException("Error while reading window layout: no main window found");
                }

                // Show other windows
                for (int i = 0; i < newWindows.Count; i++)
                {

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Let Unity fall back to the previous/default layout (the throw is designed to trigger that recovery).
2. Replace the offending layout file with a known-good one.
3. Avoid manually editing the main window entry in layout files.
4. On persistent failures, delete the user's current layout settings (e.g. CurrentLayout.dwlt) to force regeneration.

try { LoadWindowLayout(path, flags); }
catch (LayoutException ex) when (ex.Message.Contains("no root view on main window"))
{ LoadDefaultWindowLayout(); }

When it happens

Trigger: A layout file that serializes auxiliary windows but omits/not-wires the main window's rootView; a layout from a platform/build where the main window failed to serialize its root; corrupted main-window entry.

Common situations: Loading a layout saved on a different display setup or Unity version; a half-written layout file; editor startup with a stale default layout.

Related errors

• Invalid split view data
• No parent view
• No windows found in layout.
• Error while reading window layout: no main window found
• Parameter asset is null

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/30604658be280ab6. Report an issue: GitHub.