tui-cs/Terminal.Gui · error · InvalidOperationException

WordWrap settings was changed after the {_currentCaller} cal

Error message

WordWrap settings was changed after the {_currentCaller} call.

What it means

Thrown by TextView's word-wrap machinery (InvalidOperationException, interpolated message) when _currentCaller is non-null at a point where the wrap routine expected it to be cleared — i.e. word-wrap settings were changed in the middle of an operation tracked by _currentCaller. The wrap pass sets _currentCaller to detect exactly this: if a callee mutates WordWrap while a dependent operation is in flight, the invariants the operation relied on are broken, so it aborts.

Source

Thrown at Terminal.Gui/Views/TextInput/TextView/TextView.WordWrap.cs:387

                                       out int nStartCol,
                                       CurrentRow,
                                       CurrentColumn,
                                       _selectionStartRow,
                                       _selectionStartColumn,
                                       _tabWidth,
                                       true);
            CurrentRow = nRow;
            CurrentColumn = nCol;
            _selectionStartRow = nStartRow;
            _selectionStartColumn = nStartCol;
            _wrapNeeded = true;

            SetNeedsDraw ();
        }

        if (_currentCaller is { })
        {
            throw new InvalidOperationException ($"WordWrap settings was changed after the {_currentCaller} call.");
        }
    }

    /// <summary>
    ///     INTERNAL: Wraps or rewraps the text model to fit the current Viewport width.
    /// </summary>
    /// <remarks>
    ///     <para>
    ///         This method regenerates the wrapped model whenever the viewport width changes or when
    ///         word wrap is first enabled. It is typically called during layout operations.
    ///     </para>
    ///     <para>
    ///         The wrapping process:
    ///         <list type="bullet">
    ///             <item>Takes each line from the original model</item>
    ///             <item>Breaks it into multiple lines to fit within the viewport width</item>
    ///             <item>Preserves tab expansion based on <see cref="TabWidth"/></item>
    ///             <item>Maintains word boundaries (doesn't break words mid-character)</item>

View on GitHub (pinned to 2e47b11478)

Solutions

Do not mutate WordWrap from within TextView event handlers or commands; defer the change to after the operation completes (e.g. via Application.Invoke/Post).
Gate wrap toggles on user input only, outside the model's own change notifications.
If a programmatic wrap change is required mid-session, queue it and apply it once _currentCaller has cleared.

Example fix

// before
textView.TextChanged += (_, _) => { textView.WordWrap = !textView.WordWrap; }; // throws 177

// after
bool pending = false;
textView.TextChanged += (_, _) => pending = true;
// apply later, outside the operation:
app.Invoke(() => { if (pending) { textView.WordWrap = !textView.WordWrap; pending = false; } });

Defensive patterns

Strategy: validation

Validate before calling

// Do not change WordWrap inside TextView handlers; defer
textView.TextChanged += (_, _) => { _pendingWrapToggle = true; };
app.Invoke(() => { if (_pendingWrapToggle) { textView.WordWrap = !textView.WordWrap; _pendingWrapToggle = false; } });

Prevention

Never mutate WordWrap from within TextView event handlers or commands.
Defer wrap changes to after the current operation completes.
Gate programmatic wrap toggles on user input, not on internal change notifications.

When it happens

Trigger: Toggling WordWrap (or a setting that forces a rewrap) from within a callback/handler invoked during a TextView operation that set _currentCaller — e.g. changing wrap inside a TextChanged, selection, or layout handler that runs mid-operation.

Common situations: A reactive handler that re-enables/disables word wrap in response to content events; programmatic wrap toggles triggered from within command handling; recursive layout driven by a wrap change.

Related errors

AI-assisted analysis of tui-cs/Terminal.Gui@2e47b11478 (2026-08-13). Data as JSON: /api/errors/57ea51e7c170e2fc. Report an issue: GitHub.