Change folding behavior when no lines are selected as suggested by the nano dev

src/folding.c

@@ -21,6 +21,9 @@
 #include "prototypes.h"
 
 #include <string.h>
+	/* strlen */
+#include <ctype.h>
+	/* isspace */
 
 #ifdef ENABLE_FOLDING
 
@@ -80,18 +83,10 @@ bool do_unfold_segments(linestruct *top, linestruct *bot)
 	if (top != bot)
 		return FALSE;
 
-	linestruct *match_line = openfile->current;
-	size_t match_x = openfile->current_x;
-
-	if (!top->folded && !find_matching_bracket_pos(&match_line, &match_x)){
-		if (openfile->current->lineno > match_line->lineno) {
-			top = match_line->next;
-			bot = openfile->current->prev;
-		} else {
-			top = openfile->current->next;
-			bot = match_line->prev;
-		}
-	}
+	/* Attempt to find a bracketed region first.
+	 * If not, top is unmodified. */
+	if (!top->folded)
+		find_bracketed_region(openfile->current, &top, &bot);
 
 	if (top->folded) {
 		unfold_folded_segment(top);
@@ -112,35 +107,26 @@ void do_fold_segment(void)
 	if (do_unfold_segments(top, bot)) {
 		return;
 	}
-	if (top == bot) {
-		linestruct *match_line = openfile->current;
-		size_t match_x = openfile->current_x;
 
-		if (!find_matching_bracket_pos(&match_line, &match_x)){
-			int linedist = openfile->current->lineno - match_line->lineno;
-			linedist = linedist < 0 ? -linedist : linedist;
+	/* When not selecting multiple lines, try to find bounding
+	 * brackets to act as top and bot. */
+	if (top == bot)
+		if (!find_bracketed_region(openfile->current, &top, &bot)) {
+			statusline(AHEM, _("No valid region found for automatic fold"));
+			return;
+		}
 
-			if (linedist >= 2) {
-				if (openfile->current->lineno > match_line->lineno) {
-					top = match_line->next;
-					bot = openfile->current->prev;
-				} else {
-					top = openfile->current->next;
-					bot = match_line->prev;
-				}
-			}
-		}
-	}
 	for (linestruct* line = top;line != bot->next;line = line->next)
 		line->folded = TRUE;
 
 	if (top->lineno < openfile->edittop->lineno &&
 	    bot->lineno > openfile->edittop->lineno)
-		openfile->edittop = top->next;
+		openfile->edittop = top;
 
 	/* Place the cursor at the start of the fold segment.
 	 * Anywhere else within the segment is invalid. */
 	openfile->current = get_start_of_folded_segment(openfile->current);
+	openfile->mark = NULL;
 
 	refresh_needed = TRUE;
 }

src/prototypes.h

@@ -472,6 +472,8 @@ void goto_line_and_column(ssize_t line, ssize_t column, bool retain_answer,
 void do_gotolinecolumn(void);
 #ifndef NANO_TINY
 int find_matching_bracket_pos(linestruct **line, size_t *xpos);
+bool find_bracketed_region(linestruct *in_region,
+                           linestruct **top, linestruct **bot);
 void do_find_bracket(void);
 void put_or_lift_anchor(void);
 void to_prev_anchor(void);

src/search.c

@@ -880,6 +880,92 @@ void do_gotolinecolumn(void)
 }
 
 #ifndef NANO_TINY
+/* Search backwards for a line ending with a bracket, including the current line.
+ * top is an in/out parameter. The passed value is the start line for searching.
+ * xpos is an out parameter. It is the position in the line where the bracket is
+ * found. bracket_half is the halfway mark in the matchbrackets array. This way in
+ * a loop the halfway value isn't recomputed. */
+bool find_start_of_bracketed_region(linestruct **top, size_t *xpos, size_t bracket_half)
+{
+	/* Search backwards for a line ending with a bracket, including the current line */
+	for (;(*top) != NULL;*top = (*top)->prev) {
+		char *found;
+		const char *bracket;
+		int len = strlen((*top)->data);
+
+		/* Find the last bracket on the search line */
+		found = mbrevstrpbrk((*top)->data, matchbrackets, (*top)->data + len);
+		if (found == NULL)
+			continue;
+
+		*xpos = found - (*top)->data;
+		bracket = mbstrchr(matchbrackets, found);
+
+		/* We're looking for opening braces, not closing */
+		if (bracket >= matchbrackets + bracket_half)
+			continue;
+
+		/* Check if this is the last character in the line */
+		char *next = (*top)->data + step_right((*top)->data, *xpos);
+		if (*next == '\0')
+			return TRUE;
+	}
+	*xpos = 0;
+	return FALSE;
+}
+
+/* Get the halfway point in matchbrackets, where open and close
+ * brackets meet. */
+size_t get_matchbrackets_halfway(void)
+{
+	size_t charcount = mbstrlen(matchbrackets) / 2;
+	size_t halfway = 0;
+
+	for (size_t i = 0;i < charcount;++i)
+		halfway += char_length(matchbrackets + halfway);
+	return halfway;
+}
+/* Get a region surrounding the line in_region. A region here is defined
+ * as a block of text starting with an opening bracket at the end of a line,
+ * and ending with a matching closing bracket.
+ * top and bot are out parameters. Returns the top/bottom line of the region.
+ * top_pos and bot_pos are out parameters. Returns the position within the
+ * top and bottom lines where the brackets are found. */
+bool find_bracketed_region(linestruct *in_region,
+                           linestruct **top, linestruct **bot)
+{
+	size_t bracket_half = get_matchbrackets_halfway();
+	size_t top_pos;
+	size_t bot_pos;
+	linestruct *was_top = *top;
+	linestruct *was_bot = *bot;
+	*top = in_region;
+
+	for (;find_start_of_bracketed_region(top, &top_pos, bracket_half)
+	     ;*top = (*top)->prev)
+	{
+		*bot = *top;
+		bot_pos = top_pos;
+
+		if (!find_matching_bracket_pos(bot, &bot_pos)) {
+			if ((*bot)->lineno < in_region->lineno)
+				continue;
+
+			int linedist = (*bot)->lineno - (*top)->lineno;
+
+			if (linedist >= 2) {
+				*top = (*top)->next;
+				*bot = (*bot)->prev;
+				return TRUE;
+			}
+		}
+	}
+	*top = was_top;
+	*bot = was_bot;
+	return FALSE;
+}
+
+
 /* Search, starting from the current position, for any of the two characters
  * in bracket_pair.  If reverse is TRUE, search backwards, otherwise forwards.
  * Return TRUE when one of the brackets was found, and FALSE otherwise. */
@@ -997,8 +1083,7 @@ int find_matching_bracket_pos(linestruct **line, size_t *xpos)
 	bool reversed;
 		/* The direction we search. */
 
-	br_ch  = mbstrchr(matchbrackets,
-	                  openfile->current->data + openfile->current_x);
+	br_ch  = mbstrchr(matchbrackets, (*line)->data + (*xpos));
 
 	if (br_ch == NULL)
 		return NOT_A_BRACKET;