content/common/input/touch_event_stream_validator.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/common/input/touch_event_stream_validator.h"
   6
   7 #include "base/logging.h"
   8 #include "content/common/input/web_touch_event_traits.h"
   9
  10 using blink::WebInputEvent;
  11 using blink::WebTouchEvent;
  12 using blink::WebTouchPoint;
  13
  14 namespace content {
  15 namespace {
  16
  17 const WebTouchPoint* FindTouchPoint(const WebTouchEvent& event, int id) {
  18   for (unsigned i = 0; i < event.touchesLength; ++i) {
  19     if (event.touches[i].id == id)
  20       return &event.touches[i];
  21   }
  22   return NULL;
  23 }
  24
  25 }  // namespace
  26
  27 TouchEventStreamValidator::TouchEventStreamValidator() {
  28 }
  29
  30 TouchEventStreamValidator::~TouchEventStreamValidator() {
  31 }
  32
  33 bool TouchEventStreamValidator::Validate(const WebTouchEvent& event,
  34                                          std::string* error_msg) {
  35   DCHECK(error_msg);
  36   error_msg->clear();
  37
  38   WebTouchEvent previous_event = previous_event_;
  39   previous_event_ = event;
  40
  41   // Allow "hard" restarting of touch stream validation. This is necessary
  42   // in cases where touch event forwarding ceases in response to the event ack
  43   // or removal of touch handlers.
  44   if (WebTouchEventTraits::IsTouchSequenceStart(event))
  45     previous_event = WebTouchEvent();
  46
  47   // Unreleased points from the previous event should exist in the latest event.
  48   for (unsigned i = 0; i < previous_event.touchesLength; ++i) {
  49     const WebTouchPoint& previous_point = previous_event.touches[i];
  50     if (previous_point.state == WebTouchPoint::StateCancelled ||
  51         previous_point.state == WebTouchPoint::StateReleased)
  52       continue;
  53
  54     const WebTouchPoint* point = FindTouchPoint(event, previous_point.id);
  55     if (!point)
  56       error_msg->append("Previously active touch point not in new event.\n");
  57   }
  58
  59   for (unsigned i = 0; i < event.touchesLength; ++i) {
  60     const WebTouchPoint& point = event.touches[i];
  61     const WebTouchPoint* previous_point =
  62         FindTouchPoint(previous_event, point.id);
  63
  64     // The point should exist in the previous event if it is not a new point.
  65     if (!previous_point) {
  66       if (point.state != WebTouchPoint::StatePressed)
  67         error_msg->append("Active touch point not found in previous event.\n");
  68     } else {
  69       if (point.state == WebTouchPoint::StatePressed &&
  70           previous_point->state != WebTouchPoint::StateCancelled &&
  71           previous_point->state != WebTouchPoint::StateReleased) {
  72         error_msg->append("Pressed touch point id already exists.\n");
  73       }
  74     }
  75
  76     switch (point.state) {
  77       case WebTouchPoint::StateUndefined:
  78         error_msg->append("Undefined WebTouchPoint state.\n");
  79         break;
  80
  81       case WebTouchPoint::StateReleased:
  82         if (event.type != WebInputEvent::TouchEnd)
  83           error_msg->append("Released touch point outside touchend.\n");
  84         break;
  85
  86       case WebTouchPoint::StatePressed:
  87         if (event.type != WebInputEvent::TouchStart)
  88           error_msg->append("Pressed touch point outside touchstart.\n");
  89         break;
  90
  91       case WebTouchPoint::StateMoved:
  92         if (event.type != WebInputEvent::TouchMove)
  93           error_msg->append("Moved touch point outside touchmove.\n");
  94         break;
  95
  96       case WebTouchPoint::StateStationary:
  97         break;
  98
  99       case WebTouchPoint::StateCancelled:
 100         if (event.type != WebInputEvent::TouchCancel)
 101           error_msg->append("Cancelled touch point outside touchcancel.\n");
 102         break;
 103     }
 104   }
 105   return error_msg->empty();
 106 }
 107
 108 }  // namespace content