[libhandy] Document shadows drawn beyond the rounded corners

[Alexander Mikhaylenko <alexm src gnome org>]

commit c3bba30a8807262367ad75adf125d0064aff65d0
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Jul 1 11:44:34 2020 +0200

    Document shadows drawn beyond the rounded corners

 doc/hdy-migrating-0-0-to-1.xml | 8 ++++++++
 src/hdy-deck.c                 | 6 ++++++
 src/hdy-leaflet.c              | 6 ++++++
 3 files changed, 20 insertions(+)
---
diff --git a/doc/hdy-migrating-0-0-to-1.xml b/doc/hdy-migrating-0-0-to-1.xml
index cbe3e049..955a87f0 100644
--- a/doc/hdy-migrating-0-0-to-1.xml
+++ b/doc/hdy-migrating-0-0-to-1.xml
@@ -139,6 +139,14 @@
         hdy_leaflet_set_homogeneous() accessors take a boolean parameter instead
         of a #HdyFold.
       </para>
+      <para>
+        The “over” and “under” transitions can draw their shadow on top of the
+        window's transparent areas, like the rounded corners.
+        This is a side-effect of allowing shadows to be drawn on top of OpenGL
+        areas.
+        It can be mitigated by using #HdyWindow or #HdyApplicationWindow as they
+        will crop anything drawn beyond the rounded corners.
+      </para>
     </refsect3>
 
     <refsect3>
diff --git a/src/hdy-deck.c b/src/hdy-deck.c
index d887af46..62baf4bc 100644
--- a/src/hdy-deck.c
+++ b/src/hdy-deck.c
@@ -21,6 +21,12 @@
  * #GtkStack. The children are strictly ordered and can be navigated using
  * swipe gestures.
  *
+ * The “over” and “under” transitions can draw their shadow on top of the
+ * window's transparent areas, like the rounded corners. This is a side-effect
+ * of allowing shadows to be drawn on top of OpenGL areas. It can be mitigated
+ * by using #HdyWindow or #HdyApplicationWindow as they will crop anything drawn
+ * beyond the rounded corners.
+ *
  * # CSS nodes
  *
  * #HdyDeck has a single CSS node with name deck.
diff --git a/src/hdy-leaflet.c b/src/hdy-leaflet.c
index c91891db..d64d0418 100644
--- a/src/hdy-leaflet.c
+++ b/src/hdy-leaflet.c
@@ -25,6 +25,12 @@
  * only one is displayed. The threshold is dictated by the preferred minimum
  * sizes of the children.
  *
+ * The “over” and “under” transitions can draw their shadow on top of the
+ * window's transparent areas, like the rounded corners. This is a side-effect
+ * of allowing shadows to be drawn on top of OpenGL areas. It can be mitigated
+ * by using #HdyWindow or #HdyApplicationWindow as they will crop anything drawn
+ * beyond the rounded corners.
+ *
  * # CSS nodes
  *
  * #HdyLeaflet has a single CSS node with name leaflet. The node will get the