[PATCH 3/3] knots: make current line knotted when deleting a knotted line or region

[Benno Schulenberg]

Whenever two lines are joined, a line is deleted, or a region is deleted,
and any of the affected lines was knotted, then the line where the cursor
ends up after the operation becomes knotted.  Thus a knot, once placed,
stays around until it is explicitly removed (or the buffer is closed).

Also, a knot does not travel into the cutbuffer, and will thus not be
pasted and duplicated elsewhere.
---
 src/cut.c  | 13 +++++++++++++
 src/text.c |  1 +
 2 files changed, 14 insertions(+)

diff --git a/src/cut.c b/src/cut.c
index 6c80e081..94cb61b4 100644
--- a/src/cut.c
+++ b/src/cut.c
@@ -87,6 +87,8 @@ void do_deletion(undo_type action)
                        openfile->mark = openfile->current;
                        openfile->mark_x += openfile->current_x;
                }
+
+               openfile->current->knotted |= joining->knotted;
 #endif
                unlink_node(joining);
                renumber_from(openfile->current);
@@ -249,9 +251,15 @@ void extract_segment(linestruct *top, size_t top_x, 
linestruct *bot, size_t bot_
                                                (openfile->mark != top || 
openfile->mark_x >= top_x) &&
                                                (openfile->mark != bot || 
openfile->mark_x <= bot_x));
        bool same_line = (openfile->mark == top);
+       bool was_knotted = top->knotted;
 
        if (top == bot && top_x == bot_x)
                return;
+
+       if (top != bot) {
+               for (linestruct *line = top->next; line != bot->next; line = 
line->next)
+                       was_knotted |= line->knotted;
+       }
 #endif
 
        /* Reduce the buffer to cover just the text that needs to be extracted. 
*/
@@ -302,6 +310,8 @@ void extract_segment(linestruct *top, size_t top_x, 
linestruct *bot, size_t bot_
        } else if (same_line)
                /* Update the pointer to this partially cut line. */
                openfile->mark = openfile->current;
+
+       openfile->current->knotted = was_knotted;
 #endif
 
        /* Glue the texts before and after the extraction together. */
@@ -331,6 +341,7 @@ void ingraft_buffer(linestruct *topline)
        /* Remember whether mark and cursor are on the same line, and their 
order. */
        bool right_side_up = (openfile->mark && mark_is_before_cursor());
        bool same_line = (openfile->mark == openfile->current);
+       bool was_knotted = openfile->current->knotted;
 #endif
        size_t was_x = openfile->current_x;
 
@@ -364,6 +375,8 @@ void ingraft_buffer(linestruct *topline)
                } else
                        openfile->mark = openfile->filetop;
        }
+
+       openfile->filetop->knotted = was_knotted;
 #endif
 
        /* Add the number of characters in the copied text to the file size. */
diff --git a/src/text.c b/src/text.c
index 33013146..c334bbee 100644
--- a/src/text.c
+++ b/src/text.c
@@ -576,6 +576,7 @@ void do_undo(void)
                line->data = charealloc(line->data, strlen(line->data) +
                                                                
strlen(&u->strdata[u->tail_x]) + 1);
                strcat(line->data, &u->strdata[u->tail_x]);
+               line->knotted |= line->next->knotted;
                unlink_node(line->next);
                renumber_from(line);
                goto_line_posx(u->head_lineno, u->head_x);
-- 
2.25.2