Alignment issue in matrix with an empty cell.

[Orace]

There is an alignment problem in the matrix rendering when there is an empty cell.

Ex: \matrix{A & B \\ A & B \\ & B}

It seems that the issue is located in GetTopBottomPadding:

xaml-math/src/XamlMath.Shared/Atoms/MatrixAtom.cs

Lines 139 to 145 in 77d0bce

	Tuple<Box, Box> GetTopBottomPadding(int i, int j)
	{
	var value = matrixCellGaps[i][j].Vertical;
	var topBox = new StrutBox(0.0, VerticalPadding / 2 + value, 0.0, VerticalPadding);
	var bottomBox = new StrutBox(0.0, VerticalPadding / 2 + value, 0.0, VerticalPadding);
	return new Tuple<Box, Box>(topBox, bottomBox);
	}

If one replace the shift argument by 0:

Tuple<Box, Box> GetTopBottomPadding(int i, int j)
{
    var value = matrixCellGaps[i][j].Vertical;
    var topBox = new StrutBox(0.0, VerticalPadding / 2 + value, 0.0, 0.0);
    var bottomBox = new StrutBox(0.0, VerticalPadding / 2 + value, 0.0, 0.0);
    return new Tuple<Box, Box>(topBox, bottomBox);
}

The issue disappears:

I don't have enough hindsight to know if there are side effects.

[ForNeVeR]

I believe that your fix is correct. I can't remember the purpose of non-zero Shift in this place either.