tui-cs/Terminal.Gui · critical · LayoutException

ComputedLayout for "{superView}": "{from}" linked with "{to}

Error message

ComputedLayout for "{superView}": "{from}" linked with "{to}" was not found. Did you forget to add it to {superView}?

What it means

During the layout topological sort, a Pos/Dim referenced another view (e.g. Pos.Left(someView)) that is not present in the same SuperView hierarchy. The layout engine cannot position a view relative to one it does not know about, so it throws with a 'did you forget to add it' hint.

Source

Thrown at Terminal.Gui/ViewBase/View.Layout.cs:1256

                }

                // if 'to' is not yet added to the result, add it
                if (result.Find (v => v == to) is null)
                {
                    result.Add (to);
                }

                // remove from edge
                edges.Remove ((from, to));
            }
            else if (from != superView?.GetTopSuperView (to, from) && !ReferenceEquals (from, to))
            {
                if (ReferenceEquals (from.SuperView, to))
                {
                    throw new LayoutException ($"ComputedLayout for \"{superView}\": \"{to}\" " + $"references a SubView (\"{from}\").");
                }

                throw new LayoutException ($"ComputedLayout for \"{superView}\": \"{from}\" "
                                           + $"linked with \"{to}\" was not found. Did you forget to add it to {superView}?");
            }
        }

        // return L (a topologically sorted order)
        return result;
    } // TopologicalSort

    #endregion Topological Sort

    #region Utilities

    /// <summary>
    ///     Gets the size of the SuperView's content (nominally the same as
    ///     the SuperView's <see cref="GetContentSize ()"/>) or the screen size if there's no SuperView.
    /// </summary>
    /// <remarks>
    ///     This method provides fallback logic to ensure that a size is always returned, even if the SuperView is not set or

View on GitHub (pinned to 2e47b11478)

Solutions

1. Add both views to the same SuperView before relying on relative Pos/Dim.
2. If a referenced view was removed, update the Pos to an Absolute or to the correct sibling.
3. Check the from/to names in the message to identify the missing view.

Example fix

// before
var a = new View(); var b = new View();
a.X = Pos.Right(b); // b not in hierarchy
// after
container.Add(a, b);
a.X = Pos.Right(b);

if (other.SuperView is null || !InternalSubViews.Contains(other))
    Add(other); // or fix the reference
view.X = Pos.Right(other);

static bool AreInSameHierarchy (View a, View b) =>
    a.SuperView is not null && a.SuperView == b.SuperView;

When it happens

Trigger: view.X = Pos.Right(otherView) where otherView was never Add()ed to the same SuperView (or any SuperView); otherView was removed before layout; otherView belongs to a different container.

Common situations: Creating a view and setting relative positions before adding either view to a container; moving a view between containers but leaving stale Pos references; referencing a view from a different dialog/window.

Related errors

• ComputedLayout for "{superView}": "{to}" references a SubVie
• Target
• X cannot be null
• Y cannot be null
• The Viewport of an AdornmentView cannot be modified.

AI-assisted analysis of tui-cs/Terminal.Gui@2e47b11478 (2026-08-13). Data as JSON: /api/errors/db9772349662f21a. Report an issue: GitHub.