[gtk/focus-active: 1/3] Define GTK_CROSSING_ACTIVE

[Matthias Clasen <matthiasc src gnome org>]

commit 12170acf464ab203e7a6a099ae7334de070d19e9
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Jul 30 13:21:28 2020 -0400

    Define GTK_CROSSING_ACTIVE
    
    Document the different crossing event kinds that we use,
    and add GTK_CROSSING_ACTIVE. We are going to use it in
    the future when the active window changes.

 gtk/gtkeventcontrollerprivate.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
---
diff --git a/gtk/gtkeventcontrollerprivate.h b/gtk/gtkeventcontrollerprivate.h
index c997f7951e..e639e2d82a 100644
--- a/gtk/gtkeventcontrollerprivate.h
+++ b/gtk/gtkeventcontrollerprivate.h
@@ -22,12 +22,29 @@
 
 #include "gtkeventcontroller.h"
 
+/* GdkCrossingType:
+ * @GTK_CROSSING_FOCUS: Focus moved from one widget to another
+ * @GTK_CROSSING_ACTIVE: The active window changed (the crossing
+ *    events in this case leave from the old active window's focus
+ *    location to the new active window's one.
+ * @GTK_CROSSING_POINTER: The pointer moved from one widget to another
+ * @GTK_CROSSING_POINTER: An active drag moved from one widget to another
+ *
+ * We emit various kinds of crossing events when the target widget
+ * for keyboard or pointer events changes.
+ */
 typedef enum {
   GTK_CROSSING_FOCUS,
+  GTK_CROSSING_ACTIVE,
   GTK_CROSSING_POINTER,
   GTK_CROSSING_DROP
 } GtkCrossingType;
 
+/*
+ * GdkCrossingirection:
+ * @GTK_CROSSING_IN: the event is on the downward slope, towards the new target
+ * @GTK_CROSSING_OUT: the event is on the upward slope, away from the old target
+ */
 typedef enum {
   GTK_CROSSING_IN,
   GTK_CROSSING_OUT