Avoid row breaking at inconvenient places.

The test that was used to avoid breaking a string that was followed
by a too long element was not correct (especially the part that
compared with total row width).

Typical example here is:
- a word with a part that has a font change like /un/breakable;
- a longish sentence after it.

Use a new test that is good enough for this particular case, although
with sortcomings. I do not want to overcomplicate and prefer to wait
for other complaints (this code is already more complicated that I
would like).

Document known shortcoming.

Fix ticket #12660.
This commit is contained in:
Jean-Marc Lasgouttes 2023-02-20 15:04:31 +01:00
parent c90ea03884
commit f7de345f85

View File

@ -601,12 +601,31 @@ Row::Elements Row::shortenIfNeeded(int const w, int const next_width)
*/
if (brk.splitAt(min(w - wid_brk, brk.dim.wid - 2), next_width, false, tail)) {
/* if this element originally did not cause a row overflow
* in itself, and the remainder of the row would still be
* too large after breaking, then we will have issues in
* next row. Thus breaking does not help.
* in itself, and the next item is not breakable and would
* still be too large after breaking, then we will have
* issues in next row. Thus breaking does not help.
*
* FIXME: this is not perfect, since it is difficult to
* know whether next element in tail is too large:
*
* - next element could be a very long word, which is
* theoretically breakable, but not in practice
* (difficult to solve).
*
* - next element could be short enough, but linked to
* another one with a NoBreak bond.
*
* Basically, it is difficult to solve that in a purely
* left-to-right algorithm; implementing the TeX badness
* algorithm is more difficult and more costly, so we do
* our best in our restricted setting.
*/
auto const cit_next = cit_brk + 1;
int const tail_wid = !tail.empty() ? tail.front().dim.wid : 0;
if (wid_brk + cit_brk->dim.wid < w
&& dim_.wid - (wid_brk + brk.dim.wid) >= next_width) {
&& cit_next != elements_.end()
&& tail_wid + cit_next->dim.wid > next_width
&& !(cit_next->row_flags & CanBreakInside)) {
tail.clear();
break;
}