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 "base/strings/stringprintf.h"
   9 #include "content/common/input/web_input_event_traits.h"
  10 #include "content/common/input/web_touch_event_traits.h"
  11
  12 using base::StringPrintf;
  13 using blink::WebInputEvent;
  14 using blink::WebTouchEvent;
  15 using blink::WebTouchPoint;
  16
  17 namespace content {
  18 namespace {
  19
  20 const WebTouchPoint* FindTouchPoint(const WebTouchEvent& event, int id) {
  21   for (unsigned i = 0; i < event.touchesLength; ++i) {
  22     if (event.touches[i].id == id)
  23       return &event.touches[i];
  24   }
  25   return NULL;
  26 }
  27
  28 std::string TouchPointIdsToString(const WebTouchEvent& event) {
  29   std::stringstream ss;
  30   for (unsigned i = 0; i < event.touchesLength; ++i) {
  31     if (i)
  32       ss << ",";
  33     ss << event.touches[i].id;
  34   }
  35   return ss.str();
  36 }
  37
  38 }  // namespace
  39
  40 TouchEventStreamValidator::TouchEventStreamValidator() {
  41 }
  42
  43 TouchEventStreamValidator::~TouchEventStreamValidator() {
  44 }
  45
  46 bool TouchEventStreamValidator::Validate(const WebTouchEvent& event,
  47                                          std::string* error_msg) {
  48   DCHECK(error_msg);
  49   error_msg->clear();
  50
  51   WebTouchEvent previous_event = previous_event_;
  52   previous_event_ = event;
  53
  54   if (!event.touchesLength) {
  55     error_msg->append("Touch event is empty.\n");
  56     return false;
  57   }
  58
  59   if (!WebInputEvent::isTouchEventType(event.type)) {
  60     error_msg->append(StringPrintf("Touch event has invalid type: %s\n",
  61                                    WebInputEventTraits::GetName(event.type)));
  62   }
  63
  64   // Allow "hard" restarting of touch stream validation. This is necessary
  65   // in cases where touch event forwarding ceases in response to the event ack
  66   // or removal of touch handlers.
  67   if (WebTouchEventTraits::IsTouchSequenceStart(event))
  68     previous_event = WebTouchEvent();
  69
  70   // Unreleased points from the previous event should exist in the latest event.
  71   for (unsigned i = 0; i < previous_event.touchesLength; ++i) {
  72     const WebTouchPoint& previous_point = previous_event.touches[i];
  73     if (previous_point.state == WebTouchPoint::StateCancelled ||
  74         previous_point.state == WebTouchPoint::StateReleased)
  75       continue;
  76
  77     const WebTouchPoint* point = FindTouchPoint(event, previous_point.id);
  78     if (!point) {
  79       error_msg->append(StringPrintf(
  80           "Previously active touch point (id=%d) not in new event (ids=%s).\n",
  81           previous_point.id, TouchPointIdsToString(event).c_str()));
  82     }
  83   }
  84
  85   bool found_valid_state_for_type = false;
  86   for (unsigned i = 0; i < event.touchesLength; ++i) {
  87     const WebTouchPoint& point = event.touches[i];
  88     const WebTouchPoint* previous_point =
  89         FindTouchPoint(previous_event, point.id);
  90
  91     // The point should exist in the previous event if it is not a new point.
  92     if (!previous_point) {
  93       if (point.state != WebTouchPoint::StatePressed)
  94         error_msg->append(StringPrintf(
  95             "Active touch point (id=%d) not in previous event (ids=%s).\n",
  96             point.id, TouchPointIdsToString(previous_event).c_str()));
  97     } else {
  98       if (point.state == WebTouchPoint::StatePressed &&
  99           previous_point->state != WebTouchPoint::StateCancelled &&
 100           previous_point->state != WebTouchPoint::StateReleased) {
 101         error_msg->append(StringPrintf(
 102             "Pressed touch point (id=%d) already exists in previous event "
 103             "(ids=%s).\n",
 104             point.id, TouchPointIdsToString(previous_event).c_str()));
 105       }
 106     }
 107
 108     switch (point.state) {
 109       case WebTouchPoint::StateUndefined:
 110         error_msg->append(
 111             StringPrintf("Undefined touch point state (id=%d).\n", point.id));
 112         break;
 113
 114       case WebTouchPoint::StateReleased:
 115         if (event.type != WebInputEvent::TouchEnd) {
 116           error_msg->append(StringPrintf(
 117               "Released touch point (id=%d) outside touchend.\n", point.id));
 118         } else {
 119           found_valid_state_for_type = true;
 120         }
 121         break;
 122
 123       case WebTouchPoint::StatePressed:
 124         if (event.type != WebInputEvent::TouchStart) {
 125           error_msg->append(StringPrintf(
 126               "Pressed touch point (id=%d) outside touchstart.\n", point.id));
 127         } else {
 128           found_valid_state_for_type = true;
 129         }
 130         break;
 131
 132       case WebTouchPoint::StateMoved:
 133         if (event.type != WebInputEvent::TouchMove) {
 134           error_msg->append(StringPrintf(
 135               "Moved touch point (id=%d) outside touchmove.\n", point.id));
 136         } else {
 137           found_valid_state_for_type = true;
 138         }
 139         break;
 140
 141       case WebTouchPoint::StateStationary:
 142         break;
 143
 144       case WebTouchPoint::StateCancelled:
 145         if (event.type != WebInputEvent::TouchCancel) {
 146           error_msg->append(StringPrintf(
 147               "Cancelled touch point (id=%d) outside touchcancel.\n",
 148               point.id));
 149         } else {
 150           found_valid_state_for_type = true;
 151         }
 152         break;
 153     }
 154   }
 155
 156   if (!found_valid_state_for_type) {
 157     error_msg->append(
 158         StringPrintf("No valid touch point corresponding to event type: %s\n",
 159                      WebInputEventTraits::GetName(event.type)));
 160   }
 161
 162   return error_msg->empty();
 163 }
 164
 165 }  // namespace content