From b2443aa2f98c1a1fa5d53d4e79a3e7fd221cc365 Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Thu, 16 Apr 2020 13:35:24 +0000
Subject: [PATCH 1/3] Add support for the iTerm2 sychronized updates escape
 sequence which drastically reduces flickering.

---
 screen-redraw.c |  6 ++++++
 screen-write.c  | 11 ++++++++++-
 tmux.1          |  2 ++
 tmux.h          |  6 ++++++
 tty-keys.c      |  2 +-
 tty-term.c      |  5 +++++
 tty.c           | 26 ++++++++++++++++++++++++++
 7 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/screen-redraw.c b/screen-redraw.c
index 211f7f79..c510fb68 100644
--- a/screen-redraw.c
+++ b/screen-redraw.c
@@ -435,6 +435,7 @@ screen_redraw_screen(struct client *c)
 
 	flags = screen_redraw_update(c, c->flags);
 	screen_redraw_set_context(c, &ctx);
+	tty_sync_start(&c->tty);
 
 	if (flags & (CLIENT_REDRAWWINDOW|CLIENT_REDRAWBORDERS)) {
 		if (ctx.pane_status != PANE_STATUS_OFF)
@@ -448,7 +449,9 @@ screen_redraw_screen(struct client *c)
 		screen_redraw_draw_status(&ctx);
 	if (c->overlay_draw != NULL && (flags & CLIENT_REDRAWOVERLAY))
 		c->overlay_draw(c, &ctx);
+
 	tty_reset(&c->tty);
+	tty_sync_end(&c->tty);
 }
 
 /* Redraw a single pane. */
@@ -461,9 +464,12 @@ screen_redraw_pane(struct client *c, struct window_pane *wp)
 		return;
 
 	screen_redraw_set_context(c, &ctx);
+	tty_sync_start(&c->tty);
 
 	screen_redraw_draw_pane(&ctx, wp);
+
 	tty_reset(&c->tty);
+	tty_sync_end(&c->tty);
 }
 
 /* Draw a border cell. */
diff --git a/screen-write.c b/screen-write.c
index b2f9e223..3e7fa66b 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -100,7 +100,8 @@ void
 screen_write_start(struct screen_write_ctx *ctx, struct window_pane *wp,
     struct screen *s)
 {
-	u_int	y;
+	struct tty_ctx	ttyctx;
+	u_int		y;
 
 	memset(ctx, 0, sizeof *ctx);
 
@@ -129,18 +130,26 @@ screen_write_start(struct screen_write_ctx *ctx, struct window_pane *wp,
 			    screen_size_y(ctx->s));
 		}
 	}
+
+	screen_write_initctx(ctx, &ttyctx);
+	tty_write(tty_cmd_syncstart, &ttyctx);
 }
 
 /* Finish writing. */
 void
 screen_write_stop(struct screen_write_ctx *ctx)
 {
+	struct tty_ctx	ttyctx;
+
 	screen_write_collect_end(ctx);
 	screen_write_collect_flush(ctx, 0);
 
 	log_debug("%s: %u cells (%u written, %u skipped)", __func__,
 	    ctx->cells, ctx->written, ctx->skipped);
 
+	screen_write_initctx(ctx, &ttyctx);
+	tty_write(tty_cmd_syncend, &ttyctx);
+
 	free(ctx->item);
 	free(ctx->list); /* flush will have emptied */
 }
diff --git a/tmux.1 b/tmux.1
index 81a5c613..fd022c9e 100644
--- a/tmux.1
+++ b/tmux.1
@@ -5511,6 +5511,8 @@ $ printf '\e033[4 q'
 If
 .Em Se
 is not set, \&Ss with argument 0 will be used to reset the cursor style instead.
+.It Em \&Sync
+Show that the terminal supports synchronized updates.
 .It Em \&Tc
 Indicate that the terminal supports the
 .Ql direct colour
diff --git a/tmux.h b/tmux.h
index 98d78a63..87d38ef3 100644
--- a/tmux.h
+++ b/tmux.h
@@ -452,6 +452,7 @@ enum tty_code_code {
 	TTYC_SMUL,
 	TTYC_SMXX,
 	TTYC_SS,
+	TTYC_SYNC,
 	TTYC_TC,
 	TTYC_TSL,
 	TTYC_U8,
@@ -1181,6 +1182,7 @@ struct tty_term {
 #define TERM_DECSLRM 0x4
 #define TERM_DECFRA 0x8
 #define TERM_RGBCOLOURS 0x10
+#define TERM_SYNC 0x20
 	int		 flags;
 
 	LIST_ENTRY(tty_term) entry;
@@ -1949,6 +1951,8 @@ void	tty_set_title(struct tty *, const char *);
 void	tty_update_mode(struct tty *, int, struct screen *);
 void	tty_draw_line(struct tty *, struct window_pane *, struct screen *,
 	    u_int, u_int, u_int, u_int, u_int);
+void	tty_sync_start(struct tty *);
+void	tty_sync_end(struct tty *);
 int	tty_open(struct tty *, char **);
 void	tty_close(struct tty *);
 void	tty_free(struct tty *);
@@ -1976,6 +1980,8 @@ void	tty_cmd_scrolldown(struct tty *, const struct tty_ctx *);
 void	tty_cmd_reverseindex(struct tty *, const struct tty_ctx *);
 void	tty_cmd_setselection(struct tty *, const struct tty_ctx *);
 void	tty_cmd_rawstring(struct tty *, const struct tty_ctx *);
+void	tty_cmd_syncstart(struct tty *, const struct tty_ctx *);
+void	tty_cmd_syncend(struct tty *, const struct tty_ctx *);
 
 /* tty-term.c */
 extern struct tty_terms tty_terms;
diff --git a/tty-keys.c b/tty-keys.c
index 064f2172..1fcc74b8 100644
--- a/tty-keys.c
+++ b/tty-keys.c
@@ -1117,7 +1117,7 @@ tty_keys_device_status_report(struct tty *tty, const char *buf, size_t len,
 
 	/* Set terminal flags. */
 	if (strncmp(tmp, "ITERM2 ", 7) == 0)
-		flags |= (TERM_DECSLRM|TERM_256COLOURS|TERM_RGBCOLOURS);
+		flags |= (TERM_DECSLRM|TERM_256COLOURS|TERM_RGBCOLOURS|TERM_SYNC);
 	if (strncmp(tmp, "TMUX ", 5) == 0)
 		flags |= (TERM_256COLOURS|TERM_RGBCOLOURS);
 	log_debug("%s: received DSR %.*s", c->name, (int)*size, buf);
diff --git a/tty-term.c b/tty-term.c
index ef7d7905..d6faa6ff 100644
--- a/tty-term.c
+++ b/tty-term.c
@@ -260,6 +260,7 @@ static const struct tty_term_code_entry tty_term_codes[] = {
 	[TTYC_SMUL] = { TTYCODE_STRING, "smul" },
 	[TTYC_SMXX] =  { TTYCODE_STRING, "smxx" },
 	[TTYC_SS] = { TTYCODE_STRING, "Ss" },
+	[TTYC_SYNC] = { TTYCODE_FLAG, "Sync" },
 	[TTYC_TC] = { TTYCODE_FLAG, "Tc" },
 	[TTYC_TSL] = { TTYCODE_STRING, "tsl" },
 	[TTYC_U8] = { TTYCODE_NUMBER, "U8" },
@@ -532,6 +533,10 @@ tty_term_find(char *name, int fd, char **cause)
 	    tty_term_has(term, TTYC_SETRGBB)))
 		term->flags |= TERM_RGBCOLOURS;
 
+	/* Set flag if terminal has synchronized updates. */
+	if (tty_term_flag(term, TTYC_SYNC))
+		term->flags |= TERM_SYNC;
+
 	/*
 	 * Terminals without xenl (eat newline glitch) wrap at at $COLUMNS - 1
 	 * rather than $COLUMNS (the cursor can never be beyond $COLUMNS - 1).
diff --git a/tty.c b/tty.c
index a7607cba..95c16fb8 100644
--- a/tty.c
+++ b/tty.c
@@ -1426,6 +1426,20 @@ tty_draw_line(struct tty *tty, struct window_pane *wp, struct screen *s,
 	tty_update_mode(tty, tty->mode, s);
 }
 
+void
+tty_sync_start(struct tty *tty)
+{
+	if ((tty->term->flags|tty->term_flags) & TERM_SYNC)
+		tty_puts(tty, "\033P=1s\033\\");
+}
+
+void
+tty_sync_end(struct tty *tty)
+{
+	if ((tty->term->flags|tty->term_flags) & TERM_SYNC)
+		tty_puts(tty, "\033P=2s\033\\");
+}
+
 static int
 tty_client_ready(struct client *c, struct window_pane *wp)
 {
@@ -1919,6 +1933,18 @@ tty_cmd_rawstring(struct tty *tty, const struct tty_ctx *ctx)
 	tty_invalidate(tty);
 }
 
+void
+tty_cmd_syncstart(struct tty *tty, __unused const struct tty_ctx *ctx)
+{
+	tty_sync_start(tty);
+}
+
+void
+tty_cmd_syncend(struct tty *tty, __unused const struct tty_ctx *ctx)
+{
+	tty_sync_end(tty);
+}
+
 static void
 tty_cell(struct tty *tty, const struct grid_cell *gc, struct window_pane *wp)
 {

From 4744aa43af47815a9c4c110cceb3959b1662e54b Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Thu, 16 Apr 2020 14:03:51 +0000
Subject: [PATCH 2/3] Add a helper function to get the terminal flags.

---
 tmux.h |  1 +
 tty.c  | 44 ++++++++++++++++++++++++++------------------
 2 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/tmux.h b/tmux.h
index 87d38ef3..dbf3244f 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1957,6 +1957,7 @@ int	tty_open(struct tty *, char **);
 void	tty_close(struct tty *);
 void	tty_free(struct tty *);
 void	tty_set_flags(struct tty *, int);
+int	tty_get_flags(struct tty *);
 void	tty_write(void (*)(struct tty *, const struct tty_ctx *),
 	    struct tty_ctx *);
 void	tty_cmd_alignmenttest(struct tty *, const struct tty_ctx *);
diff --git a/tty.c b/tty.c
index 95c16fb8..a068c1a6 100644
--- a/tty.c
+++ b/tty.c
@@ -74,7 +74,7 @@ static void	tty_default_attributes(struct tty *, struct window_pane *,
 		    u_int);
 
 #define tty_use_margin(tty) \
-	((tty->term->flags|tty->term_flags) & TERM_DECSLRM)
+	(tty_get_flags(tty) & TERM_DECSLRM)
 
 #define tty_pane_full_width(tty, ctx) \
 	((ctx)->xoff == 0 && screen_size_x((ctx)->wp->screen) >= (tty)->sx)
@@ -478,6 +478,14 @@ tty_set_flags(struct tty *tty, int flags)
 		tty_puts(tty, "\033[?69h"); /* DECLRMM */
 }
 
+int
+tty_get_flags(struct tty *tty)
+{
+	if (tty->term != NULL)
+		return (tty->term->flags|tty->term_flags);
+	return (tty->term_flags);
+}
+
 void
 tty_raw(struct tty *tty, const char *s)
 {
@@ -575,7 +583,7 @@ tty_putc(struct tty *tty, u_char ch)
 {
 	const char	*acs;
 
-	if ((tty->term->flags & TERM_NOXENL) &&
+	if ((tty_get_flags(tty) & TERM_NOXENL) &&
 	    ch >= 0x20 && ch != 0x7f &&
 	    tty->cy == tty->sy - 1 &&
 	    tty->cx + 1 >= tty->sx)
@@ -601,7 +609,7 @@ tty_putc(struct tty *tty, u_char ch)
 			 * where we think it should be after a line wrap - this
 			 * means it works on sensible terminals as well.
 			 */
-			if (tty->term->flags & TERM_NOXENL)
+			if (tty_get_flags(tty) & TERM_NOXENL)
 				tty_putcode2(tty, TTYC_CUP, tty->cy, tty->cx);
 		} else
 			tty->cx++;
@@ -611,7 +619,7 @@ tty_putc(struct tty *tty, u_char ch)
 void
 tty_putn(struct tty *tty, const void *buf, size_t len, u_int width)
 {
-	if ((tty->term->flags & TERM_NOXENL) &&
+	if ((tty_get_flags(tty) & TERM_NOXENL) &&
 	    tty->cy == tty->sy - 1 &&
 	    tty->cx + len >= tty->sx)
 		len = tty->sx - tty->cx - 1;
@@ -1167,7 +1175,7 @@ tty_clear_area(struct tty *tty, struct window_pane *wp, u_int py, u_int ny,
 		 * background colour isn't default (because it doesn't work
 		 * after SGR 0).
 		 */
-		if (((tty->term->flags|tty->term_flags) & TERM_DECFRA) &&
+		if ((tty_get_flags(tty) & TERM_DECFRA) &&
 		    !COLOUR_DEFAULT(bg)) {
 			xsnprintf(tmp, sizeof tmp, "\033[32;%u;%u;%u;%u$x",
 			    py + 1, px + 1, py + ny, px + nx);
@@ -1429,14 +1437,14 @@ tty_draw_line(struct tty *tty, struct window_pane *wp, struct screen *s,
 void
 tty_sync_start(struct tty *tty)
 {
-	if ((tty->term->flags|tty->term_flags) & TERM_SYNC)
+	if (tty_get_flags(tty) & TERM_SYNC)
 		tty_puts(tty, "\033P=1s\033\\");
 }
 
 void
 tty_sync_end(struct tty *tty)
 {
-	if ((tty->term->flags|tty->term_flags) & TERM_SYNC)
+	if (tty_get_flags(tty) & TERM_SYNC)
 		tty_puts(tty, "\033P=2s\033\\");
 }
 
@@ -1890,7 +1898,7 @@ tty_cmd_cells(struct tty *tty, const struct tty_ctx *ctx)
 	    ctx->xoff + ctx->ocx + ctx->num > ctx->ox + ctx->sx)) {
 		if (!ctx->wrapped ||
 		    !tty_pane_full_width(tty, ctx) ||
-		    (tty->term->flags & TERM_NOXENL) ||
+		    (tty_get_flags(tty) & TERM_NOXENL) ||
 		    ctx->xoff + ctx->ocx != 0 ||
 		    ctx->yoff + ctx->ocy != tty->cy + 1 ||
 		    tty->cx < tty->sx ||
@@ -1951,7 +1959,7 @@ tty_cell(struct tty *tty, const struct grid_cell *gc, struct window_pane *wp)
 	const struct grid_cell	*gcp;
 
 	/* Skip last character if terminal is stupid. */
-	if ((tty->term->flags & TERM_NOXENL) &&
+	if ((tty_get_flags(tty) & TERM_NOXENL) &&
 	    tty->cy == tty->sy - 1 &&
 	    tty->cx == tty->sx - 1)
 		return;
@@ -2110,7 +2118,7 @@ tty_cursor_pane_unless_wrap(struct tty *tty, const struct tty_ctx *ctx,
 {
 	if (!ctx->wrapped ||
 	    !tty_pane_full_width(tty, ctx) ||
-	    (tty->term->flags & TERM_NOXENL) ||
+	    (tty_get_flags(tty) & TERM_NOXENL) ||
 	    ctx->xoff + cx != 0 ||
 	    ctx->yoff + cy != tty->cy + 1 ||
 	    tty->cx < tty->sx ||
@@ -2447,14 +2455,14 @@ tty_check_fg(struct tty *tty, struct window_pane *wp, struct grid_cell *gc)
 	/* Is this a 24-bit colour? */
 	if (gc->fg & COLOUR_FLAG_RGB) {
 		/* Not a 24-bit terminal? Translate to 256-colour palette. */
-		if ((tty->term->flags|tty->term_flags) & TERM_RGBCOLOURS)
+		if (tty_get_flags(tty) & TERM_RGBCOLOURS)
 			return;
 		colour_split_rgb(gc->fg, &r, &g, &b);
 		gc->fg = colour_find_rgb(r, g, b);
 	}
 
 	/* How many colours does this terminal have? */
-	if ((tty->term->flags|tty->term_flags) & TERM_256COLOURS)
+	if (tty_get_flags(tty) & TERM_256COLOURS)
 		colours = 256;
 	else
 		colours = tty_term_number(tty->term, TTYC_COLORS);
@@ -2496,14 +2504,14 @@ tty_check_bg(struct tty *tty, struct window_pane *wp, struct grid_cell *gc)
 	/* Is this a 24-bit colour? */
 	if (gc->bg & COLOUR_FLAG_RGB) {
 		/* Not a 24-bit terminal? Translate to 256-colour palette. */
-		if ((tty->term->flags|tty->term_flags) & TERM_RGBCOLOURS)
+		if (tty_get_flags(tty) & TERM_RGBCOLOURS)
 			return;
 		colour_split_rgb(gc->bg, &r, &g, &b);
 		gc->bg = colour_find_rgb(r, g, b);
 	}
 
 	/* How many colours does this terminal have? */
-	if ((tty->term->flags|tty->term_flags) & TERM_256COLOURS)
+	if (tty_get_flags(tty) & TERM_256COLOURS)
 		colours = 256;
 	else
 		colours = tty_term_number(tty->term, TTYC_COLORS);
@@ -2564,7 +2572,7 @@ tty_colours_fg(struct tty *tty, const struct grid_cell *gc)
 
 	/* Is this an aixterm bright colour? */
 	if (gc->fg >= 90 && gc->fg <= 97) {
-		if (tty->term_flags & TERM_256COLOURS) {
+		if (tty_get_flags(tty) & TERM_256COLOURS) {
 			xsnprintf(s, sizeof s, "\033[%dm", gc->fg);
 			tty_puts(tty, s);
 		} else
@@ -2596,7 +2604,7 @@ tty_colours_bg(struct tty *tty, const struct grid_cell *gc)
 
 	/* Is this an aixterm bright colour? */
 	if (gc->bg >= 90 && gc->bg <= 97) {
-		if (tty->term_flags & TERM_256COLOURS) {
+		if (tty_get_flags(tty) & TERM_256COLOURS) {
 			xsnprintf(s, sizeof s, "\033[%dm", gc->bg + 10);
 			tty_puts(tty, s);
 		} else
@@ -2652,7 +2660,7 @@ tty_try_colour(struct tty *tty, int colour, const char *type)
 		 * Also if RGB is set, setaf and setab do not support the 256
 		 * colour palette so use the sequences directly there too.
 		 */
-		if ((tty->term_flags & TERM_256COLOURS) ||
+		if ((tty_get_flags(tty) & TERM_256COLOURS) ||
 		    tty_term_has(tty->term, TTYC_RGB))
 			goto fallback_256;
 
@@ -2660,7 +2668,7 @@ tty_try_colour(struct tty *tty, int colour, const char *type)
 		 * If the terminfo entry has 256 colours and setaf and setab
 		 * exist, assume that they work correctly.
 		 */
-		if (tty->term->flags & TERM_256COLOURS) {
+		if (tty_get_flags(tty) & TERM_256COLOURS) {
 			if (*type == '3') {
 				if (!tty_term_has(tty->term, TTYC_SETAF))
 					goto fallback_256;

From 5ec80bd249a37147207ec2ef420086336ccf78a8 Mon Sep 17 00:00:00 2001
From: nicm <nicm>
Date: Thu, 16 Apr 2020 14:25:35 +0000
Subject: [PATCH 3/3] Move the UTF-8 flag to terminal flags.

---
 format.c        | 2 +-
 server-client.c | 2 +-
 tmux.h          | 3 ++-
 tty-acs.c       | 2 +-
 tty.c           | 2 +-
 5 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/format.c b/format.c
index fd3b45b9..f2387f7a 100644
--- a/format.c
+++ b/format.c
@@ -2569,7 +2569,7 @@ format_defaults_client(struct format_tree *ft, struct client *c)
 		format_add(ft, "client_prefix", "%d", 1);
 	format_add(ft, "client_key_table", "%s", c->keytable->name);
 
-	if (tty->flags & TTY_UTF8)
+	if (tty_get_flags(tty) & TERM_UTF8)
 		format_add(ft, "client_utf8", "%d", 1);
 	else
 		format_add(ft, "client_utf8", "%d", 0);
diff --git a/server-client.c b/server-client.c
index 8042da9a..1b27ae20 100644
--- a/server-client.c
+++ b/server-client.c
@@ -2056,7 +2056,7 @@ server_client_dispatch_identify(struct client *c, struct imsg *imsg)
 			c->fd = -1;
 		} else {
 			if (c->flags & CLIENT_UTF8)
-				c->tty.flags |= TTY_UTF8;
+				c->tty.term_flags |= TERM_UTF8;
 			if (c->flags & CLIENT_256COLOURS)
 				c->tty.term_flags |= TERM_256COLOURS;
 			tty_resize(&c->tty);
diff --git a/tmux.h b/tmux.h
index dbf3244f..58840108 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1183,6 +1183,7 @@ struct tty_term {
 #define TERM_DECFRA 0x8
 #define TERM_RGBCOLOURS 0x10
 #define TERM_SYNC 0x20
+#define TERM_UTF8 0x40
 	int		 flags;
 
 	LIST_ENTRY(tty_term) entry;
@@ -1235,7 +1236,7 @@ struct tty {
 #define TTY_NOCURSOR 0x1
 #define TTY_FREEZE 0x2
 #define TTY_TIMER 0x4
-#define TTY_UTF8 0x8
+/* 0x8 unused */
 #define TTY_STARTED 0x10
 #define TTY_OPENED 0x20
 #define TTY_FOCUS 0x40
diff --git a/tty-acs.c b/tty-acs.c
index 14634120..f5352d3e 100644
--- a/tty-acs.c
+++ b/tty-acs.c
@@ -99,7 +99,7 @@ tty_acs_needed(struct tty *tty)
 	    tty_term_number(tty->term, TTYC_U8) == 0)
 		return (1);
 
-	if (tty->flags & TTY_UTF8)
+	if (tty_get_flags(tty) & TERM_UTF8)
 		return (0);
 	return (1);
 }
diff --git a/tty.c b/tty.c
index a068c1a6..239d1cde 100644
--- a/tty.c
+++ b/tty.c
@@ -1255,7 +1255,7 @@ tty_check_codeset(struct tty *tty, const struct grid_cell *gc)
 		return (gc);
 
 	/* UTF-8 terminal and a UTF-8 character - fine. */
-	if (tty->flags & TTY_UTF8)
+	if (tty_get_flags(tty) & TERM_UTF8)
 		return (gc);
 
 	/* Replace by the right number of underscores. */