browser: add the option showcursor, to place the cursor on the highlight

This lets users of braille displays find the selected item immediately.

This fulfills a request by Enrico Mioso.
See https://lists.gnu.org/archive/html/nano-devel/2016-09/msg00025.html.

doc/man/nanorc.5

@@ -200,6 +200,10 @@ won't work properly with this option enabled.
 .B set regexp
 Do extended regular expression searches by default.
 .TP
+.B set showcursor
+Put the cursor on the highlighted item in the file browser, to aid
+braille users.
+.TP
 .B set smarthome
 Make the Home key smarter.  When Home is pressed anywhere but at the
 very beginning of non-whitespace characters on a line, the cursor will

doc/nanorc.sample.in

@@ -138,6 +138,10 @@
 ## Do extended regular expression searches by default.
 # set regexp
 
+## Put the cursor on the highlighted item in the file browser;
+## useful for people who use a braille display.
+# set showcursor
+
 ## Make the Home key smarter.  When Home is pressed anywhere but at the
 ## very beginning of non-whitespace characters on a line, the cursor
 ## will jump to that beginning (either forwards or backwards).  If the

doc/syntax/nanorc.nanorc

@@ -7,7 +7,7 @@ comment "#"
 icolor brightred "^[[:space:]]*((un)?(bind|set)|include|syntax|header|comment|magic|linter|i?color|extendsyntax).*$"
 
 # Keywords
-icolor brightgreen "^[[:space:]]*(set|unset)[[:space:]]+(allow_insecure_backup|autoindent|backup|backwards|boldtext|casesensitive|const(antshow)?|cut|fill|historylog|justifytrim|locking|morespace|mouse|multibuffer|noconvert|nohelp|nonewlines|nowrap|pos(ition)?log|preserve|quickblank|quiet|rebinddelete|rebindkeypad|regexp|smarthome|smooth|softwrap|suspend|tabsize|tabstospaces|tempfile|unix|view|wordbounds)\>"
+icolor brightgreen "^[[:space:]]*(set|unset)[[:space:]]+(allow_insecure_backup|autoindent|backup|backwards|boldtext|casesensitive|const(antshow)?|cut|fill|historylog|justifytrim|locking|morespace|mouse|multibuffer|noconvert|nohelp|nonewlines|nowrap|pos(ition)?log|preserve|quickblank|quiet|rebinddelete|rebindkeypad|regexp|showcursor|smarthome|smooth|softwrap|suspend|tabsize|tabstospaces|tempfile|unix|view|wordbounds)\>"
 icolor yellow "^[[:space:]]*set[[:space:]]+(functioncolor|keycolor|statuscolor|titlecolor)[[:space:]]+(bright)?(white|black|red|blue|green|yellow|magenta|cyan)?(,(white|black|red|blue|green|yellow|magenta|cyan))?\>"
 icolor brightgreen "^[[:space:]]*set[[:space:]]+(backupdir|brackets|functioncolor|keycolor|matchbrackets|operatingdir|punct|quotestr|speller|statuscolor|titlecolor|whitespace)[[:space:]]+"
 icolor brightgreen "^[[:space:]]*bind[[:space:]]+((\^|M-)([[:alpha:]]|space|[]]|[0-9^_=+{}|;:'\",./<>\?-])|F([1-9]|1[0-6])|Ins|Del)[[:space:]]+[[:alpha:]]+[[:space:]]+(all|main|search|replace(2|with)?|gotoline|writeout|insert|ext(ernal)?cmd|help|spell|linter|browser|whereisfile|gotodir)([[:space:]]+#|[[:space:]]*$)"

doc/texinfo/nano.texi

@@ -782,6 +782,10 @@ won't work properly with this option enabled.
 @item set regexp
 Do extended regular expression searches by default.
 
+@item set showcursor
+Put the cursor on the highlighted item in the file browser, to aid
+braille users.
+
 @item set smarthome
 Make the Home key smarter.  When Home is pressed anywhere but at the
 very beginning of non-whitespace characters on a line, the cursor will

src/browser.c

@@ -502,6 +502,8 @@ void browser_refresh(void)
     size_t i;
     int line = 0, col = 0;
 	/* The current line and column while the list is getting displayed. */
+    int the_line = 0, the_column = 0;
+	/* The line and column of the selected item. */
     char *info;
 	/* The additional information that we'll display about a file. */
 
@@ -536,9 +538,13 @@ void browser_refresh(void)
 		 * "(dir)", or the file size, plus three columns for the
 		 * ellipsis. */
 
-	/* Start highlighting the currently selected file or directory. */
+	/* If this is the selected item, start its highlighting, and
-	if (i == selected)
+	 * remember its location to be able to place the cursor on it. */
+	if (i == selected) {
 	    wattron(edit, hilite_attribute);
+	    the_line = line;
+	    the_column = col;
+	}
 
 	blank_line(edit, line, col, longest);
 
@@ -610,7 +616,7 @@ void browser_refresh(void)
 
 	mvwaddstr(edit, line, col - infolen, info);
 
-	/* Finish highlighting the currently selected file or directory. */
+	/* If this is the selected item, finish its highlighting. */
 	if (i == selected)
 	    wattroff(edit, hilite_attribute);
 
@@ -629,6 +635,12 @@ void browser_refresh(void)
 	wmove(edit, line, col);
     }
 
+    /* If requested, put the cursor on the selected item and switch it on. */
+    if (ISSET(SHOW_CURSOR)) {
+	wmove(edit, the_line, the_column);
+	curs_set(1);
+    }
+
     wnoutrefresh(edit);
 }
 

src/nano.h

@@ -535,7 +535,8 @@ enum
     LOCKING,
     NOREAD_MODE,
     MAKE_IT_UNIX,
-    JUSTIFY_TRIM
+    JUSTIFY_TRIM,
+    SHOW_CURSOR
 };
 
 /* Flags for the menus in which a given function should be present. */

src/rcfile.c

@@ -96,6 +96,7 @@ static const rcoption rcopts[] = {
     {"noconvert", NO_CONVERT},
     {"quickblank", QUICK_BLANK},
     {"quiet", QUIET},
+    {"showcursor", SHOW_CURSOR},
     {"smarthome", SMART_HOME},
     {"smooth", SMOOTH_SCROLL},
     {"softwrap", SOFTWRAP},