new feature: a position-plus-portion indicator on the righthand side

This displays a scrollbar-like thing on the right edge of the screen,
giving a rough indication where in the buffer the text that is being
shown in the viewport is located, and how large/small a portion of
the buffer this text is.

(Support for softwrapping, and an option to turn the indicator on,
will arrive in subsequent commits.)

This fulfills https://savannah.gnu.org/bugs/?57956.

Original-patch-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>

src/global.c

@@ -134,7 +134,11 @@ int editwincols = -1;
 		/* The number of usable columns in the edit window: COLS - margin. */
 int margin = 0;
 		/* The amount of space reserved at the left for line numbers. */
+int thebar = 0;
+		/* Becomes 1 when a scrollbar is shown. */
 #ifndef NANO_TINY
+int *bardata = NULL;
+		/* An array of characters that together depict the scrollbar. */
 ssize_t stripe_column = 0;
 		/* The column at which a vertical bar will be drawn. */
 #endif

src/help.c

@@ -44,7 +44,7 @@ void wrap_help_text_into_buffer(void)
 {
 	size_t sum = 0;
 	/* Avoid overtight and overwide paragraphs in the introductory text. */
-	size_t wrapping_point = (COLS < 40) ? 40 : (COLS > 74) ? 74 : COLS;
+	size_t wrapping_point = ((COLS < 40) ? 40 : (COLS > 74) ? 74 : COLS) - thebar;
 	const char *ptr = start_of_body;
 
 	make_new_buffer();
@@ -55,7 +55,7 @@ void wrap_help_text_into_buffer(void)
 		char *oneline;
 
 		if (ptr == end_of_intro)
-			wrapping_point = (COLS < 40) ? 40 : COLS;
+			wrapping_point = ((COLS < 40) ? 40 : COLS) - thebar;
 
 		if (ptr < end_of_intro || *(ptr - 1) == '\n') {
 			length = break_line(ptr, wrapping_point, TRUE);
@@ -63,7 +63,7 @@ void wrap_help_text_into_buffer(void)
 			shim = (*(ptr + length - 1) == ' ') ? 0 : 1;
 			snprintf(oneline, length + shim, "%s", ptr);
 		} else {
-			length = break_line(ptr, (COLS < 40) ? 22 : COLS - 18, TRUE);
+			length = break_line(ptr, ((COLS < 40) ? 22 : COLS - 18) - thebar, TRUE);
 			oneline = nmalloc(length + 5);
 			snprintf(oneline, length + 5, "\t\t  %s", ptr);
 		}
@@ -145,7 +145,7 @@ void show_help(void)
 
 #ifdef ENABLE_LINENUMBERS
 	UNSET(LINE_NUMBERS);
-	editwincols = COLS;
+	editwincols = COLS - thebar;
 	margin = 0;
 #endif
 	tabsize = 8;
@@ -250,7 +250,7 @@ void show_help(void)
 
 #ifdef ENABLE_LINENUMBERS
 	margin = was_margin;
-	editwincols = COLS - margin;
+	editwincols = COLS - margin - thebar;
 #endif
 	tabsize = was_tabsize;
 #ifdef ENABLE_COLOR

src/nano.c

@@ -1039,7 +1039,10 @@ void regenerate_screen(void)
 	COLS = win.ws_col;
 	LINES = win.ws_row;
 #endif
-	editwincols = COLS - margin;
+	thebar = (LINES > 5 && COLS > 9) ? 1 : 0;
+	bardata = nrealloc(bardata, LINES * sizeof(int));
+
+	editwincols = COLS - margin - thebar;
 
 	/* Do as the website suggests: leave and immediately reenter curses mode. */
 	endwin();
@@ -1246,7 +1249,7 @@ void confirm_margin(void)
 
 	if (needed_margin != margin) {
 		margin = needed_margin;
-		editwincols = COLS - margin;
+		editwincols = COLS - margin - thebar;
 
 #ifndef NANO_TINY
 		/* Ensure that firstcolumn is the starting column of its chunk. */
@@ -2283,7 +2286,11 @@ int main(int argc, char **argv)
 	window_init();
 	curs_set(0);
 
-	editwincols = COLS;
+#ifndef NANO_TINY
+	thebar = (LINES > 5 && COLS > 9) ? 1 : 0;
+	bardata = nrealloc(bardata, LINES * sizeof(int));
+#endif
+	editwincols = COLS - thebar;
 
 	/* Set up the signal handlers. */
 	signal_init();

src/proto.h

@@ -95,7 +95,9 @@ extern WINDOW *bottomwin;
 extern int editwinrows;
 extern int editwincols;
 extern int margin;
+extern int thebar;
 #ifndef NANO_TINY
+extern int *bardata;
 extern ssize_t stripe_column;
 #endif
 

src/winio.c

@@ -2398,6 +2398,9 @@ void draw_row(int row, const char *converted, linestruct *line, size_t from_col)
 	if (is_shorter || ISSET(SOFTWRAP))
 		wclrtoeol(edit);
 
+	if (thebar)
+		mvwaddch(edit, row, COLS - 1, bardata[row]);
+
 #ifdef USING_OLD_NCURSES
 	/* Tell ncurses to really redraw the line without trying to optimize
 	 * for what it thinks is already there, because it gets it wrong in
@@ -2766,7 +2769,7 @@ int update_line(linestruct *line, size_t index)
 	}
 	if (has_more) {
 		wattron(edit, hilite_attribute);
-		mvwaddch(edit, row, COLS - 1, '>');
+		mvwaddch(edit, row, COLS - 1 - thebar, '>');
 		wattroff(edit, hilite_attribute);
 	}
 
@@ -2946,6 +2949,24 @@ bool less_than_a_screenful(size_t was_lineno, size_t was_leftedge)
 		return (openfile->current->lineno - was_lineno < editwinrows);
 }
 
+#ifndef NANO_TINY
+/* Draw a scroll bar on the righthand side of the screen. */
+void draw_scrollbar(void)
+{
+	int totalrows = openfile->filebot->lineno;
+	int lowest = ((openfile->edittop->lineno - 1) * editwinrows) / totalrows;
+	int highest = lowest + (editwinrows * editwinrows) / totalrows;
+
+	if (editwinrows > totalrows)
+		highest = editwinrows;
+
+	for (int row = 0; row < editwinrows; row++) {
+		bardata[row] = ' '|((row >= lowest && row <= highest) ? A_REVERSE : 0);
+		mvwaddch(edit, row, COLS - 1, bardata[row]);
+	}
+}
+#endif
+
 /* Scroll the edit window one row in the given direction, and
  * draw the relevant content on the resultant blank row. */
 void edit_scroll(bool direction)
@@ -2979,6 +3000,9 @@ void edit_scroll(bool direction)
 		go_forward_chunks(editwinrows - nrows, &line, &leftedge);
 
 #ifndef NANO_TINY
+	if (thebar)
+		draw_scrollbar();
+
 	if (ISSET(SOFTWRAP)) {
 		/* Compensate for the earlier chunks of a softwrapped line. */
 		nrows += chunk_for(leftedge, line);
@@ -3249,6 +3273,11 @@ void edit_refresh(void)
 	if (current_is_offscreen())
 		adjust_viewport((focusing || ISSET(JUMPY_SCROLLING)) ? CENTERING : FLOWING);
 
+#ifndef NANO_TINY
+	if (thebar)
+		draw_scrollbar();
+#endif
+
 	line = openfile->edittop;
 
 	while (row < editwinrows && line != NULL) {
@@ -3259,8 +3288,14 @@ void edit_refresh(void)
 		line = line->next;
 	}
 
-	while (row < editwinrows)
-		blank_row(edit, row++);
+	while (row < editwinrows) {
+		blank_row(edit, row);
+#ifndef NANO_TINY
+		if (thebar)
+			mvwaddch(edit, row, COLS - 1, bardata[row]);
+#endif
+		row++;
+	}
 
 	place_the_cursor();
 	wnoutrefresh(edit);
@@ -3407,7 +3442,7 @@ void spotlight(size_t from_col, size_t to_col)
 	wattron(edit, interface_color_pair[SELECTED_TEXT]);
 	waddnstr(edit, word, actual_x(word, to_col));
 	if (overshoots)
-		mvwaddch(edit, openfile->current_y, COLS - 1, '>');
+		mvwaddch(edit, openfile->current_y, COLS - 1 - thebar, '>');
 	wattroff(edit, interface_color_pair[SELECTED_TEXT]);
 
 	free(word);