- Slice prev = extents[d][i - 1];
- prev.intersect (extents[d][i]);
- if (prev.length () > 0
- || (extents[-d].size () && d * (extents[d][i][-d] - extents[-d][0][d]) < 0))
- for (vsize j = i; j < clash_groups[d].size (); j++)
- offsets[d][j] += d * 0.5;
+ Grob *col = clash_groups[d][i];
+ SCM sh = col->get_property ("horizontal-shift");
+ shifts.push_back (robust_scm2int (sh, 0));
+
+ if (i == 0)
+ offset = inner_offset;
+ else
+ {
+ bool explicit_shift = scm_is_number (sh);
+ if (!explicit_shift)
+ col->warning (_ ("this Voice needs a \\voiceXx or \\shiftXx setting"));
+
+ if (explicit_shift && shifts[i] == shifts[i - 1])
+ ; // Match the previous notecolumn offset
+ else if (extents[d][i][UP] > extents[d][i - 1][DOWN]
+ && extents[d][i][DOWN] < extents[d][i - 1][UP])
+ offset += 1.0; // fully clear the previous-notecolumn heads
+ else if (d * extents[d][i][-d] >= d * extents[d][i - 1][d])
+ offset += Stem::is_valid_stem (stems[d][i - 1])
+ ? 1.0 : 0.5; // we cross the previous notecolumn
+ else if (Stem::is_valid_stem (stems[d][i]))
+ offset += 0.5;
+
+ // check if we cross the opposite-stemmed voices
+ if (d * extents[d][i][-d] < d * extent_union[-d][d])
+ offset = max (offset, 0.5);
+ if (extents[-d].size ()
+ && extents[d][i][UP] > extents[-d][0][DOWN]
+ && extents[d][i][DOWN] < extents[-d][0][UP])
+ offset = max (offset, 1.0);
+ }
+ offsets[d].push_back (d * offset);