Fix a crash when views::HWNDMessageHandler::HandleTouchMessage

ui/views/win/hwnd_message_handler.cc

 // Copyright (c) 2012 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/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <oleacc.h>
 #include <shellapi.h>
 
@@ skipping 2332 matching lines @@
                                                int num_points,
                                                TouchEvents* touch_events) {
   for (int i = 0; i < num_points; ++i) {
     POINT point;
     point.x = TOUCH_COORD_TO_PIXEL(input[i].x);
     point.y = TOUCH_COORD_TO_PIXEL(input[i].y);
     gfx::Point point_location(point.x, point.y);
 
     ScreenToClient(hwnd(), &point);
 
+    // We set a check to assert that we do not receive any touch events from
+    // user's palm.
+    bool touch_event_from_palm = (input[i].dwFlags & TOUCHEVENTF_PALM) != 0;
+    CHECK(!touch_event_from_palm) << "There are touch events from user's palm";

[sadrul, 2015/05/19 23:38:12]

I don't think we should crash here? Why not just ignore this event?

[ananta, 2015/05/19 23:40:18]

Wanted to check if the missing touch downs are because of us receiving a touch
palm event. We register for palms as well. If this CHECK fires then we can treat
palms as downs.

[sadrul, 2015/05/19 23:51:13]

Should we keep the old CHECKs too then? If the palms are the downs we are
missing, then the we would trip this CHECK, and not the the one in 2399. But if
there are some other reason the downs are missing, we will miss that without the
CHECK below, right?

+
     // TOUCHEVENTF_DOWN cannot be combined with TOUCHEVENTF_MOVE or
     // TOUCHEVENTF_UP, but TOUCHEVENTF_MOVE and TOUCHEVENTF_UP can be combined
     // in one input.
     if (input[i].dwFlags & TOUCHEVENTF_DOWN) {
       touch_down_contexts_++;
       active_touch_point_count_++;
       GenerateTouchEvent(input[i].dwID, point_location, ui::ET_TOUCH_PRESSED,
                          touch_events);
     } else {
       if (input[i].dwFlags & TOUCHEVENTF_MOVE) {
@@ skipping 22 matching lines @@
   }
 
   TouchPoint& touch_point = touch_id_list_[touch_id];
   int flags = ui::GetModifiersFromKeyState();
 
   // The dwTime of every input in the WM_TOUCH message doesn't necessarily
   // relate to the system time at all, so use base::TimeTicks::Now() for
   // touchevent time.
   base::TimeDelta now = ui::EventTimeForNow();
 
-  // We set a check to assert that we do not have missing touch presses in
-  // every message.
-  bool has_missing_touch_press = touch_event_type != ui::ET_TOUCH_PRESSED &&
-      touch_point.in_touch_list == InTouchList::NotPresent;
-  CHECK(!has_missing_touch_press) << "There are missing touch presses";
-
   ui::TouchEvent event(touch_event_type, point_location, touch_id, now);
   event.set_flags(flags);
   event.latency()->AddLatencyNumberWithTimestamp(
       ui::INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT, 0, 0, base::TimeTicks::Now(),
       1);
   touch_events->push_back(event);
 
   // Mark the active touch pointers in the touch_id_list_ to be
   // InCurrentMessage, so we can track the ones which are missed in the
   // current message and release them.
@@ skipping 386 matching lines @@
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_HIDEWINDOW);
     SetWindowPos(hwnd(), NULL, 0, 0, 0, 0, flags | SWP_SHOWWINDOW);
   }
   // WM_DWMCOMPOSITIONCHANGED is only sent to top level windows, however we want
   // to notify our children too, since we can have MDI child windows who need to
   // update their appearance.
   EnumChildWindows(hwnd(), &SendDwmCompositionChanged, NULL);
 }
 
 }  // namespace views