docs: Mention the ::damage-event signal in the migration guide

There is no replacement for damage event tracking.

diff --git a/docs/reference/gtk/migrating-3to4.md b/docs/reference/gtk/migrating-3to4.md
index f286fc72dce19ef80132d5a08bc41b9b6e526e9d..0ffe95a8b5c5ba501956f162db3492e7b36a0e41 100644 (file)
--- a/docs/reference/gtk/migrating-3to4.md
+++ b/docs/reference/gtk/migrating-3to4.md
@@ -200,6 +200,9 @@ on a one-by-one basis:
  - If you were using `::map-event` and `::unmap-event` to track a window
    being mapped, you should use property notification for the
    [property@Gdk.Surface:mapped] property instead.
+ - The `::damage-event` signal has no replacement, as the only consumer
+   of damage events were the offscreen GDK surfaces, which have no
+   replacement in GTK 4.x.
 
 ### Set a proper application ID