[Ozone] Properly initialize multitouch slot values

ui/events/ozone/evdev/event_device_info.cc

 // Copyright 2013 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/ozone/evdev/event_device_info.h"
 
 #include <linux/input.h>
 
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 22 matching lines @@
 }
 
 bool GetAbsInfo(int fd, int code, struct input_absinfo* absinfo) {
   if (ioctl(fd, EVIOCGABS(code), absinfo)) {
     DLOG(ERROR) << "failed EVIOCGABS(" << code << ") on fd " << fd;
     return false;
   }
   return true;
 }
 
+// |request| needs to be the equivalent to:
+// struct input_mt_request_layout {
+//   uint32_t code;
+//   int32_t values[num_slots];
+// };
+//
+// |size| is num_slots + 1 (for code).
+bool GetSlotValues(int fd, int32_t* request, unsigned int size) {
+  if (ioctl(fd,
+            EVIOCGMTSLOTS(sizeof(int32_t) * size),
+            request) < 0) {
+    LOG(ERROR) << "failed EVIOCGMTSLOTS(" << request[0] << ") on fd " << fd;
+    return false;
+  }
+
+  return true;
+}
+
 }  // namespace
 
 EventDeviceInfo::EventDeviceInfo() {
   memset(ev_bits_, 0, sizeof(ev_bits_));
   memset(key_bits_, 0, sizeof(key_bits_));
   memset(rel_bits_, 0, sizeof(rel_bits_));
   memset(abs_bits_, 0, sizeof(abs_bits_));
   memset(msc_bits_, 0, sizeof(msc_bits_));
   memset(sw_bits_, 0, sizeof(sw_bits_));
   memset(led_bits_, 0, sizeof(led_bits_));
@@ skipping 26 matching lines @@
     return false;
 
   if (!GetPropBits(fd, prop_bits_, sizeof(prop_bits_)))
     return false;
 
   for (unsigned int i = 0; i < ABS_CNT; ++i)
     if (HasAbsEvent(i))
       if (!GetAbsInfo(fd, i, &abs_info_[i]))
         return false;
 
+  int max_num_slots = abs_info_[ABS_MT_SLOT].maximum + 1;
+  // |request| is MT code + slots.
+  int32_t request[max_num_slots + 1];
+  for (unsigned int i = ABS_MT_SLOT + 1; i < ABS_MAX; ++i) {
+    memset(request, 0, sizeof(request));
+    request[0] = i;
+    if (HasAbsEvent(i))
+      if (!GetSlotValues(fd, request, max_num_slots + 1))
+        return false;
+
+    slot_values_[i - ABS_MT_SLOT - 1].assign(
+        request + 1, request + max_num_slots + 1);
+  }
+
   return true;
 }
 
 bool EventDeviceInfo::HasEventType(unsigned int type) const {
   if (type > EV_MAX)
     return false;
   return EvdevBitIsSet(ev_bits_, type);
 }
 
 bool EventDeviceInfo::HasKeyEvent(unsigned int code) const {
@@ skipping 39 matching lines @@
 }
 
 int32 EventDeviceInfo::GetAbsMinimum(unsigned int code) const {
   return abs_info_[code].minimum;
 }
 
 int32 EventDeviceInfo::GetAbsMaximum(unsigned int code) const {
   return abs_info_[code].maximum;
 }
 
+int32 EventDeviceInfo::GetSlotValue(unsigned int code,
+                                    unsigned int slot) const {
+  const std::vector<int32_t>& slots = GetMtSlotsForCode(code);
+  DCHECK_LE(0u, slot) << slot << " is an invalid slot";
+  DCHECK_LT(slot, slots.size()) << slot << " is an invalid slot";
+  return slots[slot];
+}
+
 bool EventDeviceInfo::HasAbsXY() const {
   if (HasAbsEvent(ABS_X) && HasAbsEvent(ABS_Y))
     return true;
 
   if (HasAbsEvent(ABS_MT_POSITION_X) && HasAbsEvent(ABS_MT_POSITION_Y))
     return true;
 
   return false;
 }
 
@@ skipping 17 matching lines @@
 
   // Touchpads are not mapped to the screen.
   if (HasKeyEvent(BTN_LEFT) || HasKeyEvent(BTN_MIDDLE) ||
       HasKeyEvent(BTN_RIGHT) || HasKeyEvent(BTN_TOOL_FINGER))
     return false;
 
   // Touchscreens are mapped to the screen.
   return true;
 }
 
+const std::vector<int32_t>& EventDeviceInfo::GetMtSlotsForCode(int code) const {
+  int index = code - ABS_MT_SLOT - 1;
+  DCHECK_LE(0, index) << code << " is not a valid multi-touch code";
+  DCHECK_LT(index, EVDEV_ABS_MT_COUNT)
+      << code << " is not a valid multi-touch code";
+  return slot_values_[index];
+}
+
 }  // namespace ui