From 82d5f12914d198b403bf14b19219581de3c6199f Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Mon, 20 Sep 2021 11:58:49 +0200
Subject: [PATCH] Add -Dnoscanout debug option

This can help debugging direct scan-out issues, such as [1].

[1]: https://github.com/swaywm/wlroots/issues/3185
---
 include/sway/server.h | 1 +
 sway/desktop/output.c | 2 +-
 sway/main.c           | 2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/sway/server.h b/include/sway/server.h
index f3522a49..88dda097 100644
--- a/include/sway/server.h
+++ b/include/sway/server.h
@@ -119,6 +119,7 @@ struct sway_debug {
 	bool noatomic;         // Ignore atomic layout updates
 	bool txn_timings;      // Log verbose messages about transactions
 	bool txn_wait;         // Always wait for the timeout before applying
+	bool noscanout;        // Disable direct scan-out
 
 	enum {
 		DAMAGE_DEFAULT,    // Default behaviour
diff --git a/sway/desktop/output.c b/sway/desktop/output.c
index a980e958..8cdd47f5 100644
--- a/sway/desktop/output.c
+++ b/sway/desktop/output.c
@@ -507,7 +507,7 @@ static int output_repaint_timer_handler(void *data) {
 		fullscreen_con = workspace->current.fullscreen;
 	}
 
-	if (fullscreen_con && fullscreen_con->view) {
+	if (fullscreen_con && fullscreen_con->view && !debug.noscanout) {
 		// Try to scan-out the fullscreen view
 		static bool last_scanned_out = false;
 		bool scanned_out =
diff --git a/sway/main.c b/sway/main.c
index 0611e80b..e960c4e2 100644
--- a/sway/main.c
+++ b/sway/main.c
@@ -182,6 +182,8 @@ void enable_debug_flag(const char *flag) {
 		debug.txn_timings = true;
 	} else if (strncmp(flag, "txn-timeout=", 12) == 0) {
 		server.txn_timeout_ms = atoi(&flag[12]);
+	} else if (strcmp(flag, "noscanout") == 0) {
+		debug.noscanout = true;
 	} else {
 		sway_log(SWAY_ERROR, "Unknown debug flag: %s", flag);
 	}