If the current screen was complex enough, it was possible to make redraw

itself hit the "terminal can't keep up" check. To avoid this, record how
much data we send during redraw (we know we will be starting with 0) and
skip the check until it has been flushed. GitHub issue 912.

3 files changed, 20 insertions, 2 deletions

diff --git a/server-client.c b/server-client.c
index 72b5d312..ae8e0d6e 100644
--- a/server-client.c
+++ b/server-client.c
@@ -1314,6 +1314,16 @@ server_client_check_redraw(struct client *c)
 
 	c->flags &= ~(CLIENT_REDRAW|CLIENT_BORDERS|CLIENT_STATUS|
 	    CLIENT_STATUSFORCE);
+
+	if (needed) {
+		/*
+		 * We would have deferred the redraw unless the output buffer
+		 * was empty, so we can record how many bytes the redraw
+		 * generated.
+		 */
+		c->redraw = EVBUFFER_LENGTH(tty->out);
+		log_debug("%s: redraw added %zu bytes", c->name, c->redraw);
+	}
 }
 
 /* Set client title. */
diff --git a/tmux.h b/tmux.h
index 1b1343b7..ea02cebf 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1306,6 +1306,7 @@ struct client {
 
 	size_t		 written;
 	size_t		 discarded;
+	size_t		 redraw;
 
 	void		(*stdin_callback)(struct client *, int, void *);
 	void		*stdin_callback_data;
diff --git a/tty.c b/tty.c
index e951f25c..ba7a5158 100644
--- a/tty.c
+++ b/tty.c
@@ -233,7 +233,14 @@ tty_write_callback(__unused int fd, __unused short events, void *data)
 		return;
 	log_debug("%s: wrote %d bytes (of %zu)", c->name, nwrite, size);
 
-	if (tty_block_maybe(tty))
+	if (c->redraw > 0) {
+		if ((size_t)nwrite >= c->redraw)
+			c->redraw = 0;
+		else
+			c->redraw -= nwrite;
+		log_debug("%s: waiting for redraw, %zu bytes left", c->name,
+		    c->redraw);
+	} else if (tty_block_maybe(tty))
 		return;
 
 	if (EVBUFFER_LENGTH(tty->out) != 0)
@@ -488,7 +495,7 @@ tty_add(struct tty *tty, const char *buf, size_t len)
 	}
 
 	evbuffer_add(tty->out, buf, len);
-	log_debug("%s: %.*s", c->name, (int)len, (const char *)buf);
+	log_debug("%s: %.*s", c->name, (int)len, buf);
 	c->written += len;
 
 	if (tty_log_fd != -1)