Setting MinWidth and using Auto columns breaks layout when scrolling

[wieslawsoltes]

Repro

• resize window so horizontal scrollbar is visible
• scroll to right
• scroll up/down
• some rows are shifted (see screenshot)
  

       public CountriesPageViewModel()
        {
            _data = new ObservableCollection<Country>(Countries.All);

            Source = new FlatTreeDataGridSource<Country>(_data)
            {
                Columns =
                {
                    new TextColumn<Country, string>("Country", x => x.Name, (r, v) => r.Name = v, new GridLength(1, GridUnitType.Star), new()
                    {
                        IsTextSearchEnabled = true,
                    }),
                    new TemplateColumn<Country>("Region", "RegionCell", "RegionEditCell"),
                    new TextColumn<Country, int>("Population", x => x.Population, new GridLength(200, GridUnitType.Auto), new TextColumnOptions<Country>() { MinWidth = new GridLength(300)}),
                    new TextColumn<Country, int>("Area", x => x.Area, new GridLength(200, GridUnitType.Auto), new TextColumnOptions<Country>() { MinWidth = new GridLength(200)}),
                    new TextColumn<Country, int>("GDP", x => x.GDP, new GridLength(200, GridUnitType.Auto), new()
                    {
                        TextAlignment = Avalonia.Media.TextAlignment.Right,
                        MaxWidth = new GridLength(150)
                    }),
                }
            };
            Source.RowSelection!.SingleSelect = false;
        }

[wieslawsoltes]

Repro video:

TreeDataGridDemo_Dop2Rhbv73.mp4

[artizzq]

Same issue

[wieslawsoltes]

Tested it can reproed also in 11.0.0 and 11.0.1

[wieslawsoltes]

Tested 11.0.0-preview1 and seems to be working properly

[wieslawsoltes]

Repro branch: https://github.com/AvaloniaUI/Avalonia.Controls.TreeDataGrid/tree/issues-256-repro

[wieslawsoltes]

Seems to be related to this:

Avalonia.Controls.TreeDataGrid/src/Avalonia.Controls.TreeDataGrid/Primitives/TreeDataGridPresenterBase.cs

Lines 424 to 427 in 95632c9

	// We sometimes get sent a viewport of 0,0 because the EffectiveViewportChanged event
	// is being raised when the parent control hasn't yet been arranged. This is a bug in
	// Avalonia, but we can work around it by forcing MeasureOverride to estimate the
	// viewport.

[wieslawsoltes]

Actually even without min/max width the layout breaks when scrolling.

repro:

                Columns =
                {
                    new TextColumn<Country, string>("Country", x => x.Name, (r, v) => r.Name = v, new GridLength(1, GridUnitType.Star), new()
                    {
                        IsTextSearchEnabled = true,
                    }),
                    new TemplateColumn<Country>("Region", "RegionCell", "RegionEditCell"),
                    new TextColumn<Country, int>("Population", x => x.Population, new GridLength(200, GridUnitType.Auto), new TextColumnOptions<Country>() ),
                    new TextColumn<Country, int>("Area", x => x.Area, new GridLength(200, GridUnitType.Auto), new TextColumnOptions<Country>() ),
                    new TextColumn<Country, int>("GDP", x => x.GDP, new GridLength(200, GridUnitType.Auto), new()
                    {
                        TextAlignment = Avalonia.Media.TextAlignment.Right,
                    }),
                }

screenshots:

[artizzq]

@wieslawsoltes, Isn't it something with the RealizeElements function inside TreeDataGridPresenterBase? Is it really related to viewport?

Seems to be related to this:

Avalonia.Controls.TreeDataGrid/src/Avalonia.Controls.TreeDataGrid/Primitives/TreeDataGridPresenterBase.cs

Lines 424 to 427 in 95632c9

	// We sometimes get sent a viewport of 0,0 because the EffectiveViewportChanged event
	// is being raised when the parent control hasn't yet been arranged. This is a bug in
	// Avalonia, but we can work around it by forcing MeasureOverride to estimate the
	// viewport.

At least, I've tried to catch those problematic rows, but dont know what to do with them exactly and how to update them properly... Does it make sense?

private void RealizeElements(
    IReadOnlyList<TItem> items,
    Size availableSize,
    ref MeasureViewport viewport)
{
    Debug.Assert(_measureElements is not null);
    Debug.Assert(_realizedElements is not null);
    Debug.Assert(items.Count > 0);

    var index = viewport.anchorIndex;
    var horizontal = Orientation == Orientation.Horizontal;
    var u = viewport.anchorU;

    // If the anchor element is at the beginning of, or before, the start of the viewport
    // then we can recycle all elements before it.
    if (u <= viewport.anchorU)
        _realizedElements.RecycleElementsBefore(viewport.anchorIndex, _recycleElement);

    // Start at the anchor element and move forwards, realizing elements.
    do
    {
        var e = GetOrCreateElement(items, index);
        var constraint = GetInitialConstraint(e, index, availableSize);
        var slot = MeasureElement(index, e, constraint);

        var sizeU = horizontal ? slot.Width : slot.Height;
        var sizeV = horizontal ? slot.Height : slot.Width;

        _measureElements!.Add(index, e, u, sizeU);

        //viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
        if (horizontal == false && items.GetType() == typeof(AnonymousSortableRows<DataRowView>))
        {
            if (sizeV - viewport.measuredV == sizeV)
                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
            else
            {
                if (viewport.measuredV != sizeV)
                    if (Math.Abs(sizeV - viewport.measuredV) <= 200 || Math.Abs(sizeV - viewport.measuredV) > 200)
                    {
                        if (sizeV > viewport.measuredV)
                        {
                            sizeV = viewport.measuredV;
                            e.Arrange(new Rect(e.Bounds.Left, e.Bounds.Top, viewport.measuredV, sizeU));
                            e.Measure(e.Bounds.Size);
                        } else
                        {
                            viewport.measuredV = sizeV;
                            e.Arrange(new Rect(e.Bounds.Left, e.Bounds.Top, viewport.measuredV, sizeU));
                            e.Measure(e.Bounds.Size);
                        }
                    }
                    else if (viewport.measuredV == sizeV)
                    {

                    }
            }

        }
        else 
            viewport.measuredV = Math.Max(viewport.measuredV, sizeV);

        u += sizeU;
        ++index;
    } while (u < viewport.viewportUEnd && index < items.Count);

    // Store the last index and end U position for the desired size calculation.
    viewport.lastIndex = index - 1;
    viewport.realizedEndU = u;

    // We can now recycle elements after the last element.
    _realizedElements.RecycleElementsAfter(viewport.lastIndex, _recycleElement);

    // Next move backwards from the anchor element, realizing elements.
    index = viewport.anchorIndex - 1;
    u = viewport.anchorU;

    while (u > viewport.viewportUStart && index >= 0)
    {
        var e = GetOrCreateElement(items, index);
        var constraint = GetInitialConstraint(e, index, availableSize);
        var slot = MeasureElement(index, e, constraint);

        var sizeU = horizontal ? slot.Width : slot.Height;
        var sizeV = horizontal ? slot.Height : slot.Width;
        u -= sizeU;

        _measureElements.Add(index, e, u, sizeU);

        //viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
        if (horizontal == false && items.GetType() == typeof(AnonymousSortableRows<DataRowView>))
        {
            if (sizeV - viewport.measuredV == sizeV)
                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
            else
            {
                if (viewport.measuredV != sizeV)
                    if (Math.Abs(sizeV - viewport.measuredV) <= 200 || Math.Abs(sizeV - viewport.measuredV) > 200)
                    {
                        if (sizeV > viewport.measuredV)
                        {
                            sizeV = viewport.measuredV;
                            e.Arrange(new Rect(e.Bounds.Left, e.Bounds.Top, viewport.measuredV, sizeU));
                            e.Measure(e.Bounds.Size);
                        }
                        else
                        {
                            viewport.measuredV = sizeV;
                            e.Arrange(new Rect(e.Bounds.Left, e.Bounds.Top, viewport.measuredV, sizeU));
                            e.Measure(e.Bounds.Size);
                        }
                    }
                    else if (viewport.measuredV == sizeV)
                    {

                    }
            }

        }
        else
            viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
        --index;
    }

    // We can now recycle elements before the first element.
    _realizedElements.RecycleElementsBefore(index + 1, _recycleElement);
}

Also, I've noticed when columns have equal widths there's no bug at all, and when I change width manually it happens.

[Hover233]

The sorting operation also triggers this bug, hopefully it will be fixed sooner!