events: Introduce EventRewriter.

ui/events/event_rewriter_unittest.cc

Index: ui/events/event_rewriter_unittest.cc
diff --git a/ui/events/event_rewriter_unittest.cc b/ui/events/event_rewriter_unittest.cc
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+// Copyright (c) 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.
+
+#include "ui/events/event_rewriter.h"
+
+#include <list>
+#include <map>
+#include <set>
+#include <utility>
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/events/test/test_event_processor.h"
+
+namespace ui {
+
+namespace {
+
+// To test the handling of |EventRewriter|s through |EventSource|,
+// we rewrite and test event types.
+class TestEvent : public Event {
+ public:
+  explicit TestEvent(EventType type)
+      : Event(type, base::TimeDelta(), 0), unique_id_(next_unique_id_++) {}
+  ~TestEvent() {}
+  int unique_id() const { return unique_id_; }
+
+ private:
+  static int next_unique_id_;
+  int unique_id_;
+};
+
+int TestEvent::next_unique_id_ = 0;
+
+// TestEventRewriteProcessor is set up with a sequence of event types,
+// and fails if the events received via OnEventFromSource() do not match
+// this sequence. These expected event types are consumed on receipt.
+class TestEventRewriteProcessor : public test::TestEventProcessor {
+ public:
+  TestEventRewriteProcessor() {}
+  virtual ~TestEventRewriteProcessor() { CheckAllReceived(); }
+
+  void AddExpectedEvent(EventType type) { expected_events_.push_back(type); }
+  // Test that all expected events have been received.
+  void CheckAllReceived() { EXPECT_TRUE(expected_events_.empty()); }
+
+  // EventProcessor:
+  virtual EventDispatchDetails OnEventFromSource(Event* event) OVERRIDE {
+    EXPECT_FALSE(expected_events_.empty());
+    EXPECT_EQ(expected_events_.front(), event->type());
+    expected_events_.pop_front();
+    return EventDispatchDetails();
+  }
+
+ private:
+  std::list<EventType> expected_events_;
+  DISALLOW_COPY_AND_ASSIGN(TestEventRewriteProcessor);
+};
+
+// Trivial EventSource that does nothing but send events.
+class TestEventRewriteSource : public EventSource {
+ public:
+  explicit TestEventRewriteSource(EventProcessor* processor)
+      : processor_(processor) {}
+  virtual EventProcessor* GetEventProcessor() OVERRIDE { return processor_; }
+  void Send(EventType type) {
+    scoped_ptr<Event> event(new TestEvent(type));
+    (void)SendEventToProcessor(event.get());
+  }
+
+ private:
+  EventProcessor* processor_;
+};
+
+// This EventRewriter always returns the same status, and if rewriting, the
+// same event type; it is used to test simple rewriting, and rewriter addition,
+// removal, and sequencing. Consequently EVENT_REWRITE_DISPATCH_ANOTHER is not
+// supported here (calls to NextDispatchEvent() would continue indefinitely).
+class TestConstantEventRewriter : public EventRewriter {
+ public:
+  TestConstantEventRewriter(EventRewriteStatus status, EventType type)
+      : status_(status), type_(type) {
+    CHECK_NE(EVENT_REWRITE_DISPATCH_ANOTHER, status);
+  }
+
+  virtual EventRewriteStatus RewriteEvent(
+      const Event& event, scoped_ptr<Event>& rewritten_event) OVERRIDE {
+    if (status_ == EVENT_REWRITE_REWRITTEN) {
+      rewritten_event.reset(new TestEvent(type_));
+    }
+    return status_;
+  }
+  virtual EventRewriteStatus NextDispatchEvent(
+      const Event& last_event, scoped_ptr<Event>& new_event) OVERRIDE {
+    NOTREACHED();
+    return status_;
+  }
+
+ private:
+  EventRewriteStatus status_;
+  EventType type_;
+};
+
+// This EventRewriter runs a simple state machine; it is used to test
+// EVENT_REWRITE_DISPATCH_ANOTHER.
+class TestStateMachineEventRewriter : public EventRewriter {
+ public:
+  TestStateMachineEventRewriter() : last_rewritten_event_(0), state_(0) {}
+  void AddRule(int from_state, EventType from_type, int to_state,
+               EventType to_type, EventRewriteStatus to_status) {
+    RewriteResult r = {to_state, to_type, to_status};
+    rules_.insert(std::pair<RewriteCase, RewriteResult>(
+        RewriteCase(from_state, from_type), r));
+  }
+  virtual EventRewriteStatus RewriteEvent(
+      const Event& event, scoped_ptr<Event>& rewritten_event) OVERRIDE {
+    RewriteRules::iterator find =
+        rules_.find(RewriteCase(state_, event.type()));
+    if (find == rules_.end()) {
+      return EVENT_REWRITE_CONTINUE;
+    }
+    if ((find->second.status == EVENT_REWRITE_REWRITTEN) ||
+        (find->second.status == EVENT_REWRITE_DISPATCH_ANOTHER)) {
+      last_rewritten_event_ = new TestEvent(find->second.type);
+      rewritten_event.reset(last_rewritten_event_);
+    } else {
+      last_rewritten_event_ = 0;
+    }
+    state_ = find->second.state;
+    return find->second.status;
+  }
+  virtual EventRewriteStatus NextDispatchEvent(
+      const Event& last_event, scoped_ptr<Event>& new_event) OVERRIDE {
+    EXPECT_TRUE(last_rewritten_event_);
+    const TestEvent* arg_last = static_cast<const TestEvent*>(&last_event);
+    EXPECT_EQ(last_rewritten_event_->unique_id(), arg_last->unique_id());
+    const TestEvent* arg_new = static_cast<const TestEvent*>(new_event.get());
+    EXPECT_FALSE(new_event && arg_last->unique_id() == arg_new->unique_id());
+    return RewriteEvent(last_event, new_event);
+  }
+
+ private:
+  typedef std::pair<int, EventType> RewriteCase;
+  struct RewriteResult {
+    int state;
+    EventType type;
+    EventRewriteStatus status;
+  };
+  typedef std::map<RewriteCase, RewriteResult> RewriteRules;
+  RewriteRules rules_;
+  TestEvent* last_rewritten_event_;
+  int state_;
+};
+
+}  // namespace
+
+TEST(EventRewriterTest, EventRewriting) {
+  // TestEventRewriter r0 always rewrites events to ET_CANCEL_MODE;
+  // it is placed at the beginning of the chain and later removed,
+  // to verify that rewriter removal works.
+  TestConstantEventRewriter r0(EVENT_REWRITE_REWRITTEN, ET_CANCEL_MODE);
+
+  // TestEventRewriter r1 always returns EVENT_REWRITE_CONTINUE;
+  // it is placed at the beginning of the chain to verify that a
+  // later rewriter sees the events.
+  TestConstantEventRewriter r1(EVENT_REWRITE_CONTINUE, ET_UNKNOWN);
+
+  // TestEventRewriter r2 has a state machine, primarily to test
+  // |EVENT_REWRITE_DISPATCH_ANOTHER|.
+  TestStateMachineEventRewriter r2;
+
+  // TestEventRewriter r3 always rewrites events to ET_CANCEL_MODE;
+  // it is placed at the end of the chain to verify that previously
+  // rewritten events are not passed further down the chain.
+  TestConstantEventRewriter r3(EVENT_REWRITE_REWRITTEN, ET_CANCEL_MODE);
+
+  TestEventRewriteProcessor p;
+  TestEventRewriteSource s(&p);
+  s.AddEventRewriter(&r0);
+  s.AddEventRewriter(&r1);
+  s.AddEventRewriter(&r2);
+
+  // These events should be rewritten by r0 to ET_CANCEL_MODE.
+  p.AddExpectedEvent(ET_CANCEL_MODE);
+  s.Send(ET_MOUSE_DRAGGED);
+  p.AddExpectedEvent(ET_CANCEL_MODE);
+  s.Send(ET_MOUSE_PRESSED);
+  p.CheckAllReceived();
+
+  // Remove r0, and verify that it's gone and that events make it through.
+  s.AddEventRewriter(&r3);
+  s.RemoveEventRewriter(&r0);
+  r2.AddRule(0, ET_SCROLL_FLING_START, 0, ET_SCROLL_FLING_CANCEL,
+             EVENT_REWRITE_REWRITTEN);
+  p.AddExpectedEvent(ET_SCROLL_FLING_CANCEL);
+  s.Send(ET_SCROLL_FLING_START);
+  p.CheckAllReceived();
+  s.RemoveEventRewriter(&r3);
+
+  // Verify EVENT_REWRITE_DISPATCH_ANOTHER using a state machine
+  // (that happens to be analogous to sticky keys).
+  r2.AddRule(0, ET_KEY_PRESSED,
+             1, ET_KEY_PRESSED, EVENT_REWRITE_CONTINUE);
+  r2.AddRule(1, ET_MOUSE_PRESSED,
+             0, ET_MOUSE_PRESSED, EVENT_REWRITE_CONTINUE);
+  r2.AddRule(1, ET_KEY_RELEASED,
+             2, ET_KEY_RELEASED, EVENT_REWRITE_DISCARD);
+  r2.AddRule(2, ET_MOUSE_RELEASED,
+             3, ET_MOUSE_RELEASED, EVENT_REWRITE_DISPATCH_ANOTHER);
+  r2.AddRule(3, ET_MOUSE_RELEASED,
+             0, ET_KEY_RELEASED, EVENT_REWRITE_REWRITTEN);
+  p.AddExpectedEvent(ET_KEY_PRESSED);
+  s.Send(ET_KEY_PRESSED);
+  s.Send(ET_KEY_RELEASED);
+  p.AddExpectedEvent(ET_MOUSE_PRESSED);
+  s.Send(ET_MOUSE_PRESSED);
+
+  // Removing rewriters r1 and r3 shouldn't affect r2.
+  s.RemoveEventRewriter(&r1);
+  s.RemoveEventRewriter(&r3);
+
+  // Continue with the state-based rewriting.
+  p.AddExpectedEvent(ET_MOUSE_RELEASED);
+  p.AddExpectedEvent(ET_KEY_RELEASED);
+  s.Send(ET_MOUSE_RELEASED);
+  p.CheckAllReceived();
+}
+
+}  // namespace ui