There is no need to clear every line entirely before drawing to it, this

means moving the cursor and messes up wrapping. Better to just clear the
sections that aren't written over. GitHub issue 2537.

1 files changed, 25 insertions, 7 deletions

diff --git a/screen-write.c b/screen-write.c
index 92f1aa39..7df5cd92 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -259,7 +259,6 @@ screen_write_start_callback(struct screen_write_ctx *ctx, struct screen *s,
 	}
 }
 
-
 /* Initialize writing. */
 void
 screen_write_start(struct screen_write_ctx *ctx, struct screen *s)
@@ -1517,6 +1516,7 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 	struct screen_write_collect_item	*ci, *tmp;
 	struct screen_write_collect_line	*cl;
 	u_int					 y, cx, cy, items = 0;
+	int					 clear = 0;
 	struct tty_ctx				 ttyctx;
 	size_t					 written = 0;
 
@@ -1540,22 +1540,29 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 	cx = s->cx; cy = s->cy;
 	for (y = 0; y < screen_size_y(s); y++) {
 		cl = &ctx->s->write_list[y];
-		if (cl->bg != 0) {
-			screen_write_set_cursor(ctx, 0, y);
-			screen_write_initctx(ctx, &ttyctx, 1);
-			ttyctx.bg = cl->bg - 1;
-			tty_write(tty_cmd_clearline, &ttyctx);
-		}
 		TAILQ_FOREACH_SAFE(ci, &cl->items, entry, tmp) {
+			if (clear != -1 &&
+			    (u_int)clear != ci->x &&
+			    cl->bg != 0) {
+				screen_write_set_cursor(ctx, clear, y);
+				screen_write_initctx(ctx, &ttyctx, 1);
+				ttyctx.bg = cl->bg - 1;
+				ttyctx.num = ci->x - clear;
+				log_debug("clear %u at %u", ttyctx.num, clear);
+				tty_write(tty_cmd_clearcharacter, &ttyctx);
+			}
+
 			screen_write_set_cursor(ctx, ci->x, y);
 			if (ci->type == CLEAR_END) {
 				screen_write_initctx(ctx, &ttyctx, 1);
 				ttyctx.bg = ci->bg;
 				tty_write(tty_cmd_clearendofline, &ttyctx);
+				clear = -1;
 			} else if (ci->type == CLEAR_START) {
 				screen_write_initctx(ctx, &ttyctx, 1);
 				ttyctx.bg = ci->bg;
 				tty_write(tty_cmd_clearstartofline, &ttyctx);
+				clear = ci->x + 1;
 			} else {
 				screen_write_initctx(ctx, &ttyctx, 0);
 				ttyctx.cell = &ci->gc;
@@ -1563,6 +1570,7 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 				ttyctx.ptr = cl->data + ci->x;
 				ttyctx.num = ci->used;
 				tty_write(tty_cmd_cells, &ttyctx);
+				clear = ci->x + ci->used;
 			}
 
 			items++;
@@ -1571,6 +1579,16 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 			TAILQ_REMOVE(&cl->items, ci, entry);
 			free(ci);
 		}
+		if (clear != -1 &&
+		    (u_int)clear != screen_size_x(s) - 1 &&
+		    cl->bg != 0) {
+			screen_write_set_cursor(ctx, clear, y);
+			screen_write_initctx(ctx, &ttyctx, 1);
+			ttyctx.bg = cl->bg - 1;
+			log_debug("clear to end at %u", clear);
+			tty_write(tty_cmd_clearendofline, &ttyctx);
+		}
+		clear = 0;
 		cl->bg = 0;
 	}
 	s->cx = cx; s->cy = cy;