SDL: Fix flickering of window when using desktop-fullscreen and borderless window on multiple monitors on Linux. Closes #8186.

SDL Commits
1 
From 2de2e9d031cf7195ccdcf434538ea6b742035ca4 Mon Sep 17 00:00:00 2001
From: Dan Ginsburg <[EMAIL REDACTED]>
Date: Fri, 1 Sep 2023 16:21:44 -0400
Subject: [PATCH] Fix flickering of window when using desktop-fullscreen and
 borderless window on multiple monitors on Linux.  Closes #8186.

---
 src/video/x11/SDL_x11window.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/video/x11/SDL_x11window.c b/src/video/x11/SDL_x11window.c
index 7c211de23d4c..a1c5bb82198a 100644
--- a/src/video/x11/SDL_x11window.c
+++ b/src/video/x11/SDL_x11window.c
@@ -604,8 +604,14 @@ int X11_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window)
         return SDL_SetError("Couldn't create window");
     }
 
-    SetWindowBordered(display, screen, w,
-                      !(window->flags & SDL_WINDOW_BORDERLESS));
+    /* Do not set borderless window if in desktop fullscreen, this causes
+       flickering in multi-monitor setups */
+    if (!((window->pending_flags & SDL_WINDOW_FULLSCREEN) &&
+          (window->flags & SDL_WINDOW_BORDERLESS) &&
+          !window->fullscreen_exclusive)) {
+        SetWindowBordered(display, screen, w,
+                          !(window->flags & SDL_WINDOW_BORDERLESS));
+    }
 
     sizehints = X11_XAllocSizeHints();
     /* Setup the normal size hints */