[gtk] Migration guide: Updates

[Matthias Clasen <matthiasc src gnome org>]

commit 141f758c5ce1eba8b1fabdb681c24349bf4d9d09
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Mar 27 02:18:36 2019 -0400

    Migration guide: Updates

 docs/reference/gtk/migrating-3to4.xml | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
---
diff --git a/docs/reference/gtk/migrating-3to4.xml b/docs/reference/gtk/migrating-3to4.xml
index 3a25b76ead..3e9ef096d6 100644
--- a/docs/reference/gtk/migrating-3to4.xml
+++ b/docs/reference/gtk/migrating-3to4.xml
@@ -289,6 +289,25 @@
       </para>
     </section>
 
+    <section>
+      <title>Stop using gdk_pointer_warp()</title>
+      <para>
+        Warping the pointer is disorienting and unfriendly to users.
+        GTK 4 does not support it.
+      </para>
+    </section>
+
+    <section>
+      <title>Adapt to coordinate api changes</title>
+      <para>
+        A number of coordinate apis in GTK 3 had _double variants: 
+        gdk_device_get_position(), gdk_device_get_surface_at_position(),
+        gdk_surface_get_device_position(). These have been changed to use
+        doubles, and the _double variants have been removed. Update your
+        code accordingly.
+      </para>
+    </section>
+
     <section>
       <title>Adapt to GdkKeymap API changes</title>
       <para>