tui-cs/Terminal.Gui · error · ArgumentException

ContentSize cannot be negative.

Error message

ContentSize cannot be negative.

What it means

SetContentSize sets both width and height of the content area as a Size. Either dimension being negative is rejected — content space is always non-negative. Pass null to clear both and revert to Viewport tracking.

Source

Thrown at Terminal.Gui/ViewBase/View.Content.cs:121

    ///         currently visible to the user. This enables
    ///         virtual scrolling and the behavior of <see cref="DimAutoStyle.Content"/> will be to use
    ///         <see cref="GetContentSize ()"/> to determine the size
    ///         of the view.
    ///     </para>
    ///     <para>
    ///         This method follows the Cancellable Work Pattern (CWP). The <see cref="ContentSizeChanging"/> event
    ///         is raised before the change, and <see cref="ContentSizeChanged"/> is raised after.
    ///     </para>
    /// </remarks>
    /// <seealso cref="ContentSizeChanging"/>
    /// <seealso cref="ContentSizeChanged"/>
    /// <seealso cref="SetContentWidth"/>
    /// <seealso cref="SetContentHeight"/>
    public void SetContentSize (Size? contentSize)
    {
        if (contentSize is { } s && (s.Width < 0 || s.Height < 0))
        {
            throw new ArgumentException (@"ContentSize cannot be negative.", nameof (contentSize));
        }

        ApplyContentDimensionChange (contentSize?.Width, contentSize?.Height);
    }

    /// <summary>
    ///     Internal helper that applies a content dimension change using the CWP pattern.
    ///     Both dimensions are passed so the composite <see cref="Size"/>? events fire correctly.
    /// </summary>
    private void ApplyContentDimensionChange (int? newWidth, int? newHeight)
    {
        // Compute old and new composite sizes for CWP events.
        Size? oldComposite = _contentWidth is null && _contentHeight is null
                                 ? null
                                 : new Size (_contentWidth ?? Viewport.Size.Width, _contentHeight ?? Viewport.Size.Height);

        Size? newComposite = newWidth is null && newHeight is null ? null : new Size (newWidth ?? Viewport.Size.Width, newHeight ?? Viewport.Size.Height);

View on GitHub (pinned to 2e47b11478)

Solutions

1. Clamp both Width and Height to >= 0 before constructing the Size.
2. Pass null when you want the content to track the Viewport.
3. Use SetContentWidth/SetContentHeight individually if only one dimension is dynamic.

Example fix

// before
view.SetContentSize(new Size(offset - 5, height));
// after
view.SetContentSize(new Size(Math.Max(0, offset - 5), height));

if (size is { } sz && (sz.Width < 0 || sz.Height < 0)) size = null;
view.SetContentSize (size);

static bool IsValidContentSize (Size? s) => s is null || (s.Value.Width >= 0 && s.Value.Height >= 0);

When it happens

Trigger: Calling SetContentSize(new Size(-1, 10)), SetContentSize(new Size(w, h)) where w or h computed negative, or passing a Size built from scroll offsets that underflow.

Common situations: Scrolling logic that subtracts offsets from content bounds producing a negative remainder, deserializing a Size from config with invalid values, pre-layout computation when dimensions are unknown.

Related errors

• Content width cannot be negative.
• Content height cannot be negative.
• The size of an item cannot be negative.
• X cannot be null
• Y cannot be null

AI-assisted analysis of tui-cs/Terminal.Gui@2e47b11478 (2026-08-13). Data as JSON: /api/errors/ab319c6230317bcd. Report an issue: GitHub.