commit f9560742eabf2ce27a6204047984be113db92642
from: Omar Polo <op@omarpolo.com>
date: Sun Jun 20 14:22:58 2021 UTC

disentangle cmd_scroll_line_up/down and ncurses

cmd_scroll_line_up and down are the fundamental functions called every
time there's a need to scroll the window.  cmd_scroll_up/down calls
them in a loop, cmd_next_line and cmd_previous_line calls them too.
And so on.

These two functions, historically predates some of the abstractions of
the `struct buffer', and handle ncurses directly using wscrl and
print_line.

However, since dispatch_stdio calls redraw_tab anyway, there's no need
to update the window content here.  (Well, wscrl + one print_vline *may*
be a bit faster than the loop over print_vline in redraw_window, but
we can optimise the latter later.)

This also (should) dis-entangle the cmd_* functions and ncurses
completely \o/

commit - 676794769a5aafd21ed8d1136dc98c42a538ae96
commit + f9560742eabf2ce27a6204047984be113db92642
blob - d374bf181856428c29126bd1ae89cb9dc7e699dd
blob + dd9149bc39d552f9f124461aee85788c9ef010ad
--- ui.c
+++ ui.c
@@ -449,15 +449,14 @@ cmd_scroll_line_up(struct buffer *buffer)
 {
 	struct vline	*vl;
 
-	if (buffer->line_off == 0)
+	if (buffer->current_line == NULL)
 		return;
 
-	vl = nth_line(buffer, --buffer->line_off);
-	wscrl(body, -1);
-	wmove(body, 0, 0);
-	print_vline(body, vl);
+	if ((vl = TAILQ_PREV(buffer->current_line, vhead, vlines)) == NULL)
+		return;
 
-	buffer->current_line = TAILQ_PREV(buffer->current_line, vhead, vlines);
+	buffer->current_line = vl;
+	buffer->line_off--;
 	restore_cursor(buffer);
 }
 
@@ -466,21 +465,14 @@ cmd_scroll_line_down(struct buffer *buffer)
 {
 	struct vline	*vl;
 
-	vl = buffer->current_line;
-	if ((vl = TAILQ_NEXT(vl, vlines)) == NULL)
-		return;
-	buffer->current_line = vl;
+	if (buffer->current_line == NULL)
+		return;
 
-	buffer->line_off++;
-	wscrl(body, 1);
-
-	if (buffer->line_max - buffer->line_off < (size_t)body_lines)
+	if ((vl = TAILQ_NEXT(buffer->current_line, vlines)) == NULL)
 		return;
 
-	vl = nth_line(buffer, buffer->line_off + body_lines-1);
-	wmove(body, body_lines-1, 0);
-	print_vline(body, vl);
-
+	buffer->current_line = vl;
+	buffer->line_off++;
 	restore_cursor(buffer);
 }