display: support the position indicator also when --softwrap is used

A new member ('chunk_nr') is added to each 'linestruct', to store
the serial number of the first chunk of that line, so that, when
softwrap is on, the scroll-bar thing can be computed relative to
chunks instead of relative to actual lines.

To guarantee that 'chunk_nr' is correctly synced, the buffer is
renumbered whenever the number of chunks in a line changes, and
also when softwrap is toggled on, and when buffers are switched.

Signed-off-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>

src/cut.c

@@ -52,10 +52,12 @@ void do_deletion(undo_type action)
 					&openfile->current->data[openfile->current_x + charlen],
 					line_len - charlen + 1);
 #ifndef NANO_TINY
-		/* If the number of screen rows that a softwrapped line occupies
-		 * has changed, we need a full refresh. */
-		if (ISSET(SOFTWRAP) && extra_chunks_in(openfile->current) != old_amount)
+		/* When softwrapping and the number of chunks in the current line has
+		 * changed, the chunks must be renumbered and the screen refreshed. */
+		if (ISSET(SOFTWRAP) && extra_chunks_in(openfile->current) != old_amount) {
+			renumber_from(openfile->current);
 			refresh_needed = TRUE;
+		}
 
 		/* Adjust the mark if it is after the cursor on the current line. */
 		if (openfile->mark == openfile->current &&

src/nano.c

@@ -76,6 +76,9 @@ linestruct *make_new_node(linestruct *prevnode)
 #endif
 	newnode->lineno = (prevnode) ? prevnode->lineno + 1 : 1;
 #ifndef NANO_TINY
+	if (ISSET(SOFTWRAP))
+		newnode->chunk_nr = (prevnode) ?
+						prevnode->chunk_nr + extra_chunks_in(prevnode) + 1 : 1;
 	newnode->has_anchor = FALSE;
 #endif
 
@@ -151,6 +154,7 @@ linestruct *copy_node(const linestruct *src)
 #endif
 	dst->lineno = src->lineno;
 #ifndef NANO_TINY
+	dst->chunk_nr = src->chunk_nr;
 	dst->has_anchor = FALSE;
 #endif
 
@@ -186,8 +190,21 @@ void renumber_from(linestruct *line)
 {
 	ssize_t number = (line->prev == NULL) ? 0 : line->prev->lineno;
 
+#ifndef NANO_TINY
+	if (ISSET(SOFTWRAP) && line->prev == NULL) {
+		line->lineno = ++number;
+		line->chunk_nr = 1;
+		line = line->next;
+	}
+#endif
+
 	while (line != NULL) {
 		line->lineno = ++number;
+#ifndef NANO_TINY
+		if (ISSET(SOFTWRAP))
+			line->chunk_nr = line->prev->chunk_nr +
+									extra_chunks_in(line->prev) + 1;
+#endif
 		line = line->next;
 	}
 }
@@ -1085,7 +1102,9 @@ void do_toggle(int flag)
 			signal_init();
 			break;
 		case SOFTWRAP:
-			if (!ISSET(SOFTWRAP))
+			if (ISSET(SOFTWRAP))
+				renumber_from(openfile->filetop);
+			else
 				openfile->firstcolumn = 0;
 			refresh_needed = TRUE;
 			break;
@@ -1487,6 +1506,7 @@ void inject(char *burst, size_t count)
 	if (ISSET(SOFTWRAP) && ((openfile->current_y == editwinrows - 1 &&
 				chunk_for(xplustabs(), openfile->current) > original_row) ||
 				extra_chunks_in(openfile->current) != old_amount)) {
+		renumber_from(openfile->current);
 		refresh_needed = TRUE;
 		focusing = FALSE;
 	}

src/nano.h

@@ -284,6 +284,10 @@ typedef struct linestruct {
 		/* The text of this line. */
 	ssize_t lineno;
 		/* The number of this line. */
+#ifndef NANO_TINY
+	ssize_t chunk_nr;
+		/* The ordinal number of the first chunk in this line. */
+#endif
 	struct linestruct *next;
 		/* Next node. */
 	struct linestruct *prev;

src/winio.c

@@ -2954,7 +2954,16 @@ bool less_than_a_screenful(size_t was_lineno, size_t was_leftedge)
 void draw_scrollbar(void)
 {
 	int totalrows = openfile->filebot->lineno;
-	int lowest = ((openfile->edittop->lineno - 1) * editwinrows) / totalrows;
+	int first_row = openfile->edittop->lineno;
+
+	if (ISSET(SOFTWRAP)) {
+		totalrows = openfile->filebot->chunk_nr +
+							extra_chunks_in(openfile->filebot);
+		first_row = openfile->edittop->chunk_nr +
+							chunk_for(openfile->firstcolumn, openfile->edittop);
+	}
+
+	int lowest = ((first_row - 1) * editwinrows) / totalrows;
 	int highest = lowest + (editwinrows * editwinrows) / totalrows;
 
 	if (editwinrows > totalrows)
@@ -3133,10 +3142,11 @@ size_t leftedge_for(size_t column, linestruct *line)
  * has changed, because then the width of softwrapped chunks has changed. */
 void ensure_firstcolumn_is_aligned(void)
 {
-	if (ISSET(SOFTWRAP))
+	if (ISSET(SOFTWRAP)) {
 		openfile->firstcolumn = leftedge_for(openfile->firstcolumn,
 														openfile->edittop);
-	else
+		renumber_from(openfile->filetop);
+	} else
 		openfile->firstcolumn = 0;
 
 	/* If smooth scrolling is on, make sure the viewport doesn't center. */