Backport upstream patch to fix outdated screen state on screenshots.

Closes: #1031112.

debian/patches/Mark-surface-as-dirty-before-flushing-it.patch

@@ -0,0 +1,40 @@
+From: Emmanuele Bassi <ebassi@gnome.org>
+Date: Sun, 12 Feb 2023 19:18:00 +0000
+Subject: Mark surface as dirty before flushing it
+
+If we're trying to read back the contents of a GdkWindow that was
+created from a foreign windowing system surface, we are going to
+forcibly mark it as dirty before flushing the Cairo state.
+
+To avoid regressing any further in the future of the 3.x branch, let's
+leave a comment.
+
+Bug: https://gitlab.gnome.org/GNOME/gtk/-/issues/5482
+Bug-Debian: https://bugs.debian.org/1031112
+Origin: upstream, 3.24.37, commit:fba09dbfc7
+---
+ gdk/gdkpixbuf-drawable.c | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+diff --git a/gdk/gdkpixbuf-drawable.c b/gdk/gdkpixbuf-drawable.c
+index e63c3a8..ee88abe 100644
+--- a/gdk/gdkpixbuf-drawable.c
++++ b/gdk/gdkpixbuf-drawable.c
+@@ -102,8 +102,17 @@ gdk_pixbuf_get_from_window (GdkWindow *src,
+   /* We do not know what happened to this surface outside of GDK.
+    * Especially for foreign windows, they will have been modified
+    * by external applications.
++   *
+    * So be on the safe side and:
++   * - mark the surface as dirty, in case the GdkWindow was
++   *   created from a foreign X11 surface
++   * - flush the Cairo state
++   *
++   * For reference, see:
++   * - https://bugzilla.gnome.org/show_bug.cgi?id=754952
++   * - https://gitlab.gnome.org/GNOME/gtk/-/issues/4456
+    */
++  cairo_surface_mark_dirty (surface);
+   cairo_surface_flush (surface);
+ 
+   if (cairo_surface_get_content (surface) & CAIRO_CONTENT_ALPHA)

debian/patches/series

@@ -23,3 +23,4 @@ reftest_compare_surfaces-Report-how-much-the-images-diffe.patch
 reftests-Allow-minor-differences-to-be-tolerated.patch
 window-focus-on-window-show-for-wayland-activation.patch
 gdk-wayland-save-custom-xdg-activation-startup_id.patch
+Mark-surface-as-dirty-before-flushing-it.patch