Do not break row at inset boundary if possible

The first change is to concentrate on the last ro elements that contain separators and try to break it a a width that is shorter than both
- its current width (we want to break it, after all)
- the amount of space available.

This simple heuristic seems to give good results.

diff --git a/src/Row.cpp b/src/Row.cpp
index 0974265328e9158df888f629bea47f7656218ab0..a619874b93fb714c748cd4d917fc171617b70687 100644 (file)
--- a/src/Row.cpp
+++ b/src/Row.cpp
@@ -382,13 +382,44 @@ void Row::shortenIfNeeded(pos_type const keep, int const w)
        Elements::iterator const end = elements_.end();
        int wid = left_margin;
 
+       // The last breakable element that has been found and its x position.
+       Elements::iterator last_brk = elements_.end();
+       int last_wid = 0;
+
        Elements::iterator cit = beg;
        for ( ; cit != end ; ++cit) {
-               if (cit->endpos >= keep && wid + cit->dim.wid > w)
+               if (cit->countSeparators() && cit->pos >= keep) {
+                       last_brk = cit;
+                       last_wid = wid;
+               }
+               if (wid + cit->dim.wid > w)
                        break;
                wid += cit->dim.wid;
        }
 
+       /* We have found a suitable separable element. This is the common case.
+        * Try to break it cleanly (at word boundary) at a length that is both
+        * - less than the available space on the row
+        * - shorter than the natural width of the element, in order to enforce
+        *   break-up.
+        */
+       if (last_brk != end
+               && last_brk->breakAt(min(w - last_wid, last_brk->dim.wid - 2), false)) {
+               end_ = last_brk->endpos;
+               /* after breakAt, there may be spaces at the end of the
+                * string, but they are not counted in the string length
+                * (QTextLayout feature, actually). We remove them, but do not
+                * change the endo of the row, since the spaces at row break
+                * are invisible.
+                */
+               last_brk->str = rtrim(last_brk->str);
+               last_brk->endpos = last_brk->pos + last_brk->str.length();
+               dim_.wid = last_wid + last_brk->dim.wid;
+               // If there are other elements, they should be removed.
+               elements_.erase(next(last_brk, 1), end);
+               return;
+       }
+
        if (cit == end) {
                // This should not happen since the row is too long.
                LYXERR0("Something is wrong cannot shorten row: " << *this);
@@ -402,22 +433,6 @@ void Row::shortenIfNeeded(pos_type const keep, int const w)
                wid -= cit->dim.wid;
        }
 
-       // Try to break this row cleanly (at word boundary)
-       if (cit->breakAt(w - wid, false)) {
-               end_ = cit->endpos;
-               // after breakAt, there may be spaces at the end of the
-               // string, but they are not counted in the string length
-               // (qtextlayout feature, actually). We remove them, but do not
-               // change the endo of the row, since the spaces at row break
-               // are invisible.
-               cit->str = rtrim(cit->str);
-               cit->endpos = cit->pos + cit->str.length();
-               dim_.wid = wid + cit->dim.wid;
-               // If there are other elements, they should be removed.
-               elements_.erase(next(cit, 1), end);
-               return;
-       }
-
        if (cit != beg) {
                // There is no separator, but several elements have been
                // added. We can cut right here.