ozone: events: Centralize & document our NativeEvent woes

ui/events/ozone/events_ozone.h

Index: ui/events/ozone/events_ozone.h
diff --git a/ui/events/ozone/events_ozone.h b/ui/events/ozone/events_ozone.h
new file mode 100644
index 0000000000000000000000000000000000000000..ad603cdadd9775370c4ac06e6e309bfa6d7a4b12
--- /dev/null
+++ b/ui/events/ozone/events_ozone.h
@@ -0,0 +1,39 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_EVENTS_OZONE_EVENTS_OZONE_H_
+#define UI_EVENTS_OZONE_EVENTS_OZONE_H_
+
+#include "base/callback.h"
+#include "base/event_types.h"
+#include "ui/events/events_export.h"
+
+namespace ui {
+
+class Event;
+
+// Wrap a "native" ui::Event in another ui::Event & dispatch it.
+//
+// This is really unfortunate, but exists for two reasons:
+//
+//   1. Some of the ui::Event constructors depend on global state that
+//   is only used when building from a "native" event. For example:
+//   last_click_event_ is used when constructing MouseEvent from
+//   NativeEvent to determine click count.
+//
+//   2. Events contain a reference to a "native event", which some code
+//   depends on. The ui::Event might get mutated during dispatch, but
+//   the native event won't. Some code depends on the fact that the
+//   "native" version of the event is unmodified.

[kpschoedel, 2014/09/11 21:23:19]

… and some code depends (for at least little longer) on the native event being
*modified* by event rewriting. Joy.

+//
+// We are trying to fix both of these issues, but in the meantime we
+// define NativeEvent == ui::Event.
+//
+EVENTS_EXPORT void DispatchEventFromNativeUiEvent(
+    const base::NativeEvent& native_event,
+    base::Callback<void(ui::Event*)> callback);
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_EVENTS_OZONE_H_