events: Add gdk_event_[gs]et_device_tool()

This getter/setter will manage the tool pointer in GdkEventPrivate. The
setter should be most notably used by backends.

docs/reference/gdk/gdk3-sections.txt

@@ -888,6 +888,8 @@ gdk_event_get_device
 gdk_event_set_device
 gdk_event_get_source_device
 gdk_event_set_source_device
+gdk_event_get_device_tool
+gdk_event_set_device_tool
 
 <SUBSECTION>
 gdk_setting_get

gdk/gdkevents.c

@@ -650,6 +650,7 @@ gdk_event_copy (const GdkEvent *event)
       new_private->device = private->device ? g_object_ref (private->device) : NULL;
       new_private->source_device = private->source_device ? g_object_ref (private->source_device) : NULL;
       new_private->seat = private->seat;
+      new_private->tool = private->tool;
     }
 
   switch (event->any.type)
@@ -2412,3 +2413,54 @@ gdk_event_set_seat (GdkEvent *event,
       priv->seat = seat;
     }
 }
+
+/**
+ * gdk_event_get_device_tool:
+ * @event: a #GdkEvent
+ *
+ * If the event was generated by a device that supports
+ * different tools (eg. a tablet), this function will
+ * return a #GdkDeviceTool representing the tool that
+ * caused the event. Otherwise, %NULL will be returned.
+ *
+ * Note: the #GdkDeviceTool<!-- -->s will be constant during
+ * the application lifetime, if settings must be stored
+ * persistently across runs, see gdk_device_tool_get_serial()
+ *
+ * Returns: (transfer none): The current device tool, or %NULL
+ *
+ * Since: 3.22
+ **/
+GdkDeviceTool *
+gdk_event_get_device_tool (const GdkEvent *event)
+{
+  GdkEventPrivate *private;
+
+  if (!gdk_event_is_allocated (event))
+    return NULL;
+
+  private = (GdkEventPrivate *) event;
+  return private->tool;
+}
+
+/**
+ * gdk_event_set_device_tool:
+ * @event: a #GdkEvent
+ * @tool: (nullable): tool to set on the event, or %NULL
+ *
+ * Sets the device tool for this event, should be rarely used.
+ *
+ * Since: 3.22
+ **/
+void
+gdk_event_set_device_tool (GdkEvent      *event,
+                           GdkDeviceTool *tool)
+{
+  GdkEventPrivate *private;
+
+  if (!gdk_event_is_allocated (event))
+    return;
+
+  private = (GdkEventPrivate *) event;
+  private->tool = tool;
+}

gdk/gdkevents.h

@@ -1443,6 +1443,13 @@ GDK_AVAILABLE_IN_ALL
 gboolean gdk_setting_get                (const gchar    *name,
                                          GValue         *value);
 
+GDK_AVAILABLE_IN_3_16
+GdkDeviceTool *gdk_event_get_device_tool (const GdkEvent *event);
+
+GDK_AVAILABLE_IN_3_16
+void           gdk_event_set_device_tool (GdkEvent       *event,
+                                          GdkDeviceTool  *tool);
+
 G_END_DECLS
 
 #endif /* __GDK_EVENTS_H__ */

gdk/gdkinternals.h

@@ -189,6 +189,7 @@ struct _GdkEventPrivate
   GdkDevice *device;
   GdkDevice *source_device;
   GdkSeat   *seat;
+  GdkDeviceTool *tool;
 };
 
 typedef struct _GdkWindowPaint GdkWindowPaint;