Mention global coordinates in the migration guide

diff --git a/docs/reference/gtk/migrating-3to4.xml b/docs/reference/gtk/migrating-3to4.xml
index a1d9dd08b518d21f2d281859fdf50d55c359ba05..1e3a9079eb7c48326eb61a01aadca480694c7f68 100644 (file)
--- a/docs/reference/gtk/migrating-3to4.xml
+++ b/docs/reference/gtk/migrating-3to4.xml
@@ -314,8 +314,15 @@
         doubles, and the _double variants have been removed. Update your
         code accordingly.
       </para>
+      <para>
+        Any APIs that deal with global (or root) coordinates have been
+        removed in GTK4, since not all backends support them. You should
+        replace your use of such APIs with surface-relative equivalents.
+        Examples of this are gdk_surfae_get_origin(), gdk_surface_move()
+        or gdk_event_get_root_coords().
+      </para>
     </section>
-
+ 
     <section>
       <title>Adapt to GdkKeymap API changes</title>
       <para>