[gtk] migration guide: Improve warp-pointer entry

[Matthias Clasen <matthiasc src gnome org>]

commit 733271e09af3a05e324eb68593197e1a02beab28
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Mar 27 14:21:26 2019 -0400

    migration guide: Improve warp-pointer entry
    
    Mention platform APIs.

 docs/reference/gtk/migrating-3to4.xml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/docs/reference/gtk/migrating-3to4.xml b/docs/reference/gtk/migrating-3to4.xml
index 1d19d6bca1..60afd4d7c2 100644
--- a/docs/reference/gtk/migrating-3to4.xml
+++ b/docs/reference/gtk/migrating-3to4.xml
@@ -293,7 +293,10 @@
       <title>Stop using gdk_pointer_warp()</title>
       <para>
         Warping the pointer is disorienting and unfriendly to users.
-        GTK 4 does not support it.
+        GTK 4 does not support it. In special circumstances (such as when
+        implementing remote connection UIs) it can be necessary to
+        warp the pointer; in this case, use platform APIs such as XWarpPointer
+        directly.
       </para>
     </section>