From ecc22c521d83f8ce480c0e2866fdf3ed14bd6131 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicm@openbsd.org>
Date: Tue, 25 Jan 2011 23:40:26 +0000
Subject: [PATCH] When clearing the entire screen, clear lines that are used
 into the history like xterm does. Requested ages ago by someone I've
 forgotten.

---
 grid-view.c    | 24 ++++++++++++++++++++++++
 screen-write.c | 19 +++++++++++++++----
 tmux.h         |  1 +
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/grid-view.c b/grid-view.c
index ba142a1c..075feb6b 100644
--- a/grid-view.c
+++ b/grid-view.c
@@ -74,6 +74,30 @@ grid_view_set_utf8(
 	grid_set_utf8(gd, grid_view_x(gd, px), grid_view_y(gd, py), gu);
 }
 
+/* Clear into history. */
+void
+grid_view_clear_history(struct grid *gd)
+{
+	struct grid_line	*gl;
+	u_int			 yy, last;
+
+	GRID_DEBUG(gd, "");
+
+	/* Find the last used line. */
+	last = 0;
+	for (yy = 0; yy < gd->sy; yy++) {
+		gl = &gd->linedata[grid_view_y(gd, yy)];
+		if (gl->cellsize != 0 || gl->utf8size != 0)
+			last = yy + 1;
+	}
+	if (last == 0)
+		return;
+
+	/* Scroll the lines into the history. */
+	for (yy = 0; yy < last; yy++)
+		grid_scroll_history(gd);
+}
+
 /* Clear area. */
 void
 grid_view_clear(struct grid *gd, u_int px, u_int py, u_int nx, u_int ny)
diff --git a/screen-write.c b/screen-write.c
index 88c183ae..4c8382de 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -931,9 +931,14 @@ screen_write_clearendofscreen(struct screen_write_ctx *ctx)
 	sx = screen_size_x(s);
 	sy = screen_size_y(s);
 
-	if (s->cx <= sx - 1)
-		grid_view_clear(s->grid, s->cx, s->cy, sx - s->cx, 1);
-	grid_view_clear(s->grid, 0, s->cy + 1, sx, sy - (s->cy + 1));
+	/* Scroll into history if it is enabled and clearing entire screen. */
+	if (s->cy == 0 && s->grid->flags & GRID_HISTORY)
+		grid_view_clear_history(s->grid);
+	else {
+		if (s->cx <= sx - 1)
+			grid_view_clear(s->grid, s->cx, s->cy, sx - s->cx, 1);
+		grid_view_clear(s->grid, 0, s->cy + 1, sx, sy - (s->cy + 1));
+	}
 
 	tty_write(tty_cmd_clearendofscreen, &ttyctx);
 }
@@ -969,7 +974,13 @@ screen_write_clearscreen(struct screen_write_ctx *ctx)
 
 	screen_write_initctx(ctx, &ttyctx, 0);
 
-	grid_view_clear(s->grid, 0, 0, screen_size_x(s), screen_size_y(s));
+	/* Scroll into history if it is enabled. */
+	if (s->grid->flags & GRID_HISTORY)
+		grid_view_clear_history(s->grid);
+	else {
+		grid_view_clear(
+		    s->grid, 0, 0, screen_size_x(s), screen_size_y(s));
+	}
 
 	tty_write(tty_cmd_clearscreen, &ttyctx);
 }
diff --git a/tmux.h b/tmux.h
index a1e31e32..89cf2b99 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1741,6 +1741,7 @@ const struct grid_utf8 *grid_view_peek_utf8(struct grid *, u_int, u_int);
 struct grid_utf8 *grid_view_get_utf8(struct grid *, u_int, u_int);
 void	 grid_view_set_utf8(
 	     struct grid *, u_int, u_int, const struct grid_utf8 *);
+void	 grid_view_clear_history(struct grid *);
 void	 grid_view_clear(struct grid *, u_int, u_int, u_int, u_int);
 void	 grid_view_scroll_region_up(struct grid *, u_int, u_int);
 void	 grid_view_scroll_region_down(struct grid *, u_int, u_int);