replace heuristic shift in TikZ alignment with depth of last row

lib/LaTeXML/Package/pgfsys-latexml.def.ltxml

@@ -929,7 +929,7 @@ sub tikzAlignmentBindings {
 
 # Note that pgf *seems* to have set the coordinate system to the center(?) (w/ \pgfsys@transformcm)
 # Additionally, there's a svg:g outside the alignment (w/ ltx_svg_fog)
-# The following tweaks (heuristically) the transform to position the alignment object
+# The following tweaks the transform to position the alignment object
 #
 # Coordinates are currently pgf: y moves UP
 # Coordinates of alignment are : y moves DOWN
@@ -939,14 +939,14 @@ sub openTikzAlignment {
   my $h          = ($props{cheight} && $props{cheight}->pxValue) || 0;
   my $d          = ($props{cdepth}  && $props{cdepth}->pxValue)  || 0;
   my @rowheights = ($props{rowheights}   ? @{ $props{rowheights} }   : (Dimension(0)));
+  my @rowdepths  = ($props{rowdepths}    ? @{ $props{rowdepths} }    : (Dimension(0)));
   my @colwidths  = ($props{columnwidths} ? @{ $props{columnwidths} } : (Dimension(0)));
   my $x          = 0;
-  # This SHOULD be just $h+$d, but the shift is necessary to align
-  # w/additional material outside the \halign ( arrows & such)
-  my $y = ($h + $d) - $rowheights[-1]->pxValue / 2;    # HEURISTIC adjustment! half of LAST row!?
+  my $y          = ($h + $d) - $rowdepths[-1]->pxValue;    # set baseline to baseline of last row
   Debug("TIKZ Alignment size $w x $h + $d"
-      . "  rows: " . join(',', map { $_->pxValue; } @rowheights)
-      . "  cols: " . join(',', map { $_->pxValue; } @colwidths)
+      . "    rows: " . join(',', map { $_->pxValue; } @rowheights)
+      . "    cols: " . join(',', map { $_->pxValue; } @colwidths)
+      . "  depths: " . join(',', map { $_->pxValue; } @rowdepths)
       . " => alignment adjustment = $x, $y") if $LaTeXML::DEBUG{pgf};
   my $array = $doc->openElement($tag, class => 'ltx_tikzmatrix',
     _scopebegin => 1,