events: Introduce EventRewriter.

ui/events/event_source.cc

Index: ui/events/event_source.cc
diff --git a/ui/events/event_source.cc b/ui/events/event_source.cc
index a40813079d837398644acc295b54fba54f865f6c..0f3dfb80a0a4baa867e436aae2ba4b130a00eedb 100644
--- a/ui/events/event_source.cc
+++ b/ui/events/event_source.cc
@@ -4,11 +4,70 @@
 
 #include "ui/events/event_source.h"
 
+#include <algorithm>
+
 #include "ui/events/event_processor.h"
+#include "ui/events/event_rewriter.h"
 
 namespace ui {
 
+EventSource::EventSource() {}
+
+EventSource::~EventSource() {}
+
+void EventSource::AddEventRewriter(EventRewriter* rewriter) {
+  DCHECK(rewriter);
+  DCHECK(rewriter_list_.end() ==
+         std::find(rewriter_list_.begin(), rewriter_list_.end(), rewriter));
+  rewriter_list_.push_back(rewriter);
+}
+
+void EventSource::RemoveEventRewriter(EventRewriter* rewriter) {
+  EventRewriterList::iterator find =
+      std::find(rewriter_list_.begin(), rewriter_list_.end(), rewriter);
+  if (find != rewriter_list_.end())
+    rewriter_list_.erase(find);
+}
+
 EventDispatchDetails EventSource::SendEventToProcessor(Event* event) {
+  scoped_ptr<Event> rewritten_event;
+  EventRewriteStatus status = EVENT_REWRITE_CONTINUE;
+  EventRewriterList::const_iterator it = rewriter_list_.begin(),
+                                    end = rewriter_list_.end();
+  for (; it != end; ++it) {
+    status = (*it)->RewriteEvent(*event, &rewritten_event);
+    if (status == EVENT_REWRITE_DISCARD) {
+      CHECK(!rewritten_event);
+      return EventDispatchDetails();
+    }
+    if (status == EVENT_REWRITE_CONTINUE) {
+      CHECK(!rewritten_event);
+      continue;
+    }
+    break;
+  }
+  CHECK((it == end && !rewritten_event) || rewritten_event);
+  EventDispatchDetails details =
+      DeliverEventToProcessor(rewritten_event ? rewritten_event.get() : event);
+  if (details.dispatcher_destroyed)
+    return details;
+
+  while (status == EVENT_REWRITE_DISPATCH_ANOTHER) {
+    scoped_ptr<Event> new_event;
+    status = (*it)->NextDispatchEvent(*rewritten_event, &new_event);
+    if (status == EVENT_REWRITE_DISCARD)
+      return EventDispatchDetails();
+    CHECK_NE(EVENT_REWRITE_CONTINUE, status);
+    CHECK(new_event);
+    details = DeliverEventToProcessor(new_event.get());
+    if (details.dispatcher_destroyed)
+      return details;
+    rewritten_event.reset(new_event.release());
+  }
+  return EventDispatchDetails();
+}
+
+EventDispatchDetails EventSource::DeliverEventToProcessor(Event* event) {
   EventProcessor* processor = GetEventProcessor();
   CHECK(processor);
   return processor->OnEventFromSource(event);