events: Introduce EventRewriter.

ui/events/event_rewriter_unittest.cc

+// 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 change and test event type.
+
+// 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() { CheckAllReceived(); }

[sadrul, 2014/03/24 21:15:38]

virtual

+
+  // EventProcessor:
+  virtual EventDispatchDetails OnEventFromSource(Event* event) OVERRIDE {

[sadrul, 2014/03/24 21:15:38]

Overrides typically go at the end of the block. So this should be after
CheckAllReceived()

+    EXPECT_FALSE(expected_events_.empty());
+    EXPECT_EQ(expected_events_.front(), event->type());
+    expected_events_.pop_front();
+    return EventDispatchDetails();
+  }
+
+  void AddExpectedEvent(EventType type) { expected_events_.push_back(type); }
+  // Test that all expected events have been received.
+  void CheckAllReceived() { EXPECT_TRUE(expected_events_.empty()); }
+
+ private:
+  std::list<EventType> expected_events_;

[sadrul, 2014/03/24 21:15:38]

DISALLOW_COPY_AND_ASSIGN

+};
+
+// Allocates events, testing that none are leaked.
+class TestEventFactory {
+ public:
+  TestEventFactory() {}
+  ~TestEventFactory() { EXPECT_TRUE(events_.empty()); }
+
+  Event* New(EventType type) {

[sadrul, 2014/03/24 21:15:38]

This should return a scoped_ptr<>

+    Event* event = new TestEvent(*this, type);
+    EXPECT_TRUE(event);
+    events_.insert(event);
+    return event;
+  }
+  void Check(Event* event) { EXPECT_NE(events_.end(), events_.find(event)); }
+  void Delete(Event* event) {
+    EventList::iterator find = events_.find(event);
+    EXPECT_NE(events_.end(), find);
+    events_.erase(find);
+  }
+
+ private:
+  class TestEvent : public Event {
+   public:
+    TestEvent(TestEventFactory& factory, EventType type)
+        : Event(type, base::TimeDelta(), 0), factory_(factory) {}
+    ~TestEvent() { factory_.Delete(this); }
+
+   private:
+    TestEventFactory& factory_;
+  };
+  typedef std::set<Event*> EventList;
+  EventList events_;
+  DISALLOW_COPY_AND_ASSIGN(TestEventFactory);
+};
+
+// 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(event_factory_.New(type));
+    (void)SendEventToProcessor(event.get());

[sadrul, 2014/03/24 21:15:38]

You don't need to Delete the event in the event-factory?

+  }
+
+ private:
+  TestEventFactory event_factory_;
+  EventProcessor* processor_;
+};
+
+// This EventRewriter always returns the same status; it is used to test
+// simple rewriting, and rewriter addition, removal, and sequencing.
+// EVENT_REWRITE_DISPATCH_ANOTHER is not supported here.
+class TestConstantEventRewriter : public EventRewriter {
+ public:
+  TestConstantEventRewriter(EventRewriteStatus status, EventType type)
+      : status_(status), type_(type) {
+    EXPECT_NE(EVENT_REWRITE_DISPATCH_ANOTHER, status);

[sadrul, 2014/03/24 21:15:38]

CHECK instead

+  }
+
+  virtual EventRewriteStatus RewriteEvent(const Event& event,
+                                          Event** rewritten_event) OVERRIDE {
+    EXPECT_TRUE(rewritten_event);
+    if (status_ == EVENT_REWRITE_REWRITTEN) {
+      *rewritten_event = event_factory_.New(type_);
+    }
+    return status_;
+  }
+  virtual EventRewriteStatus NextDispatchEvent(const Event& last_event,
+                                               Event** new_event) OVERRIDE {
+    EXPECT_TRUE(false);

[sadrul, 2014/03/24 21:15:38]

Replace this with a NOTREACHED instead

+    return status_;
+  }
+
+ private:
+  EventRewriteStatus status_;
+  EventType type_;
+  TestEventFactory event_factory_;
+};
+
+// This EventRewriter runs a simple state machine; it is used to test
+// EVENT_REWRITE_DISPATCH_ANOTHER.
+class TestStateMachineEventRewriter : public EventRewriter {
+ public:
+  TestStateMachineEventRewriter() : state_(0), last_rewritten_event_(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,
+                                          Event** rewritten_event) OVERRIDE {
+    EXPECT_TRUE(rewritten_event);
+    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_ = event_factory_.New(find->second.type);
+      *rewritten_event = last_rewritten_event_;
+    }
+    state_ = find->second.state;
+    return find->second.status;
+  }
+  virtual EventRewriteStatus NextDispatchEvent(const Event& last_event,
+                                               Event** new_event) OVERRIDE {
+    EXPECT_TRUE(last_rewritten_event_);
+    EXPECT_EQ(last_rewritten_event_->type(), last_event.type());
+    event_factory_.Check(last_rewritten_event_);

[sadrul, 2014/03/24 21:15:38]

We should add a unique-identifer for each TestEvent, and compare that id here to
verify that the event rewritten by this rewriter is the one that comes back as
|last_event|.

This would allow us to get rid of EventFactory, and instead have just TestEvent
that the tests create directly where necessary.

[kpschoedel, 2014/03/25 18:12:01]

Is it really necessary to pass back last_event? If the caller passes in the same
scoped_ptr for new_event as it did previously (which is reasonable), then they
alias and last_event will be destroyed upon new_event.reset(), which could be
surprising.

[sadrul, 2014/03/25 18:24:35]

I am thinking the rewriter will need to maintain less internal state if we
include |last_event| in this call to NextDispatchEvent(). We should have the
source make sure that setting |new_event| doesn't invalidate |last_event|.

If we end up not needing |last_event| in the rewriter-implementations, then we
can come back and remove this. But I feel like we should start with it in place.

+    last_rewritten_event_ = 0;
+    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;
+
+  int state_;
+  RewriteRules rules_;
+  TestEventFactory event_factory_;
+  Event* last_rewritten_event_;
+};
+
+}  // 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