Merge 176231: x11: Add a hack to detect touch-cancel events from X11.

> 
> The touch-end event chrome receives from X does not contain enough
> information to know whether the event came because the user lifted
> the finger, or something else happened in the system that triggered
> the event. So add some hack to figure out whether to generate a
> touch-release event or a touch-cancel event from the X touch-end event.
> 
> BUG=169177
> 
> Review URL: https://codereview.chromium.org/11819054

TBR=sadrul@chromium.org
Review URL: https://codereview.chromium.org/11975054

git-svn-id: svn://svn.chromium.org/chrome/branches/1364/src@177445 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 41 insertions, 3 deletions

diff --git a/ui/aura/root_window.cc b/ui/aura/root_window.cc
index d79c6ec..2449873 100644
--- a/ui/aura/root_window.cc
+++ b/ui/aura/root_window.cc
@@ -803,7 +803,11 @@ bool RootWindow::OnHostTouchEvent(ui::TouchEvent* event) {
       Env::GetInstance()->set_touch_down(touch_ids_down_ != 0);
       break;
 
-    // Don't handle ET_TOUCH_CANCELLED since we always get a ET_TOUCH_RELEASED.
+    // Handle ET_TOUCH_CANCELLED only if it has a native event.
+    case ui::ET_TOUCH_CANCELLED:
+      if (!event->HasNativeEvent())
+        break;
+      // fallthrough
     case ui::ET_TOUCH_RELEASED:
       touch_ids_down_ = (touch_ids_down_ | (1 << event->touch_id())) ^
                         (1 << event->touch_id());
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index c15fad9..e3ececa 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -868,6 +868,7 @@ void RootWindowHostLinux::DispatchXI2Event(const base::NativeEvent& event) {
         xev = &last_event;
       // fallthrough
     case ui::ET_TOUCH_PRESSED:
+    case ui::ET_TOUCH_CANCELLED:
     case ui::ET_TOUCH_RELEASED: {
       ui::TouchEvent touchev(xev);
 #if defined(OS_CHROMEOS)
diff --git a/ui/base/x/events_x.cc b/ui/base/x/events_x.cc
index 116b867..14b8da1 100644
--- a/ui/base/x/events_x.cc
+++ b/ui/base/x/events_x.cc
@@ -479,6 +479,37 @@ class XModifierStateWatcher{
   DISALLOW_COPY_AND_ASSIGN(XModifierStateWatcher);
 };
 
+#if defined(USE_XI2_MT)
+// Detects if a touch event is a driver-generated 'special event'.
+// A 'special event' is a touch release or move event with maximum radius and
+// pressure at location (0, 0).
+// This needs to be done in a cleaner way: http://crbug.com/169256
+bool TouchEventIsGeneratedHack(const base::NativeEvent& native_event) {
+  XIDeviceEvent* event =
+      static_cast<XIDeviceEvent*>(native_event->xcookie.data);
+  CHECK(event->evtype == XI_TouchUpdate ||
+        event->evtype == XI_TouchEnd);
+
+  // Force is normalized to [0, 1].
+  if (ui::GetTouchForce(native_event) < 1.0f)
+    return false;
+
+  if (ui::EventLocationFromNative(native_event) != gfx::Point())
+    return false;
+
+  // Radius is in pixels, and the valuator is the diameter in pixels.
+  float radius = ui::GetTouchRadiusX(native_event), min, max;
+  unsigned int deviceid =
+      static_cast<XIDeviceEvent*>(native_event->xcookie.data)->sourceid;
+  if (!ui::ValuatorTracker::GetInstance()->GetValuatorRange(
+      deviceid, ui::ValuatorTracker::VAL_TOUCH_MAJOR, &min, &max)) {
+    return false;
+  }
+
+  return radius * 2 == max;
+}
+#endif
+
 int GetEventFlagsFromXState(unsigned int state) {
   int flags = 0;
   if (state & ControlMask)
@@ -539,9 +570,11 @@ ui::EventType GetTouchEventType(const base::NativeEvent& native_event) {
     case XI_TouchBegin:
       return ui::ET_TOUCH_PRESSED;
     case XI_TouchUpdate:
-      return ui::ET_TOUCH_MOVED;
+      return TouchEventIsGeneratedHack(native_event) ? ui::ET_UNKNOWN :
+                                                       ui::ET_TOUCH_MOVED;
     case XI_TouchEnd:
-      return ui::ET_TOUCH_RELEASED;
+      return TouchEventIsGeneratedHack(native_event) ? ui::ET_TOUCH_CANCELLED :
+                                                       ui::ET_TOUCH_RELEASED;
   }
 
   return ui::ET_UNKNOWN;