Add palm suppression feature to EventConverterEvdev

ui/events/ozone/evdev/input_device_factory_evdev.cc

Index: ui/events/ozone/evdev/input_device_factory_evdev.cc
diff --git a/ui/events/ozone/evdev/input_device_factory_evdev.cc b/ui/events/ozone/evdev/input_device_factory_evdev.cc
index 95f3867bc1d19a769da09e576096e9018d42d1e3..c810de36dd488fb279592d11a3348451224460ad 100644
--- a/ui/events/ozone/evdev/input_device_factory_evdev.cc
+++ b/ui/events/ozone/evdev/input_device_factory_evdev.cc
@@ -342,20 +342,34 @@ void InputDeviceFactoryEvdev::ApplyInputDeviceSettings() {
   SetBoolPropertyForOneType(DT_TOUCHPAD, "Tap Paused",
                             input_device_settings_.tap_to_click_paused);
 
+  EventConverterEvdev* internal_pen = nullptr;
   for (const auto& it : converters_) {
     EventConverterEvdev* converter = it.second;
-    converter->SetEnabled(IsDeviceEnabled(converter));
-
-    if (converter->type() == InputDeviceType::INPUT_DEVICE_INTERNAL &&
-        converter->HasKeyboard()) {
-      converter->SetKeyFilter(
-          input_device_settings_.enable_internal_keyboard_filter,
-          input_device_settings_.internal_keyboard_allowed_keys);
+    bool enabled = IsDeviceEnabled(converter);
+
+    if (converter->type() == InputDeviceType::INPUT_DEVICE_INTERNAL) {
+      if (converter->HasPen()) {
+        converter->SetPalmSuppressionCallback(base::Callback<void(bool)>());

[spang, 2016/08/26 00:58:34]

This call isn't conditional on settings, can you do it just once when the device
is plugged in?

[denniskempin, 2016/08/26 21:56:02]

Done.

I was a little paranoid about the theoretical possibility that we might have two
internal pen devices.
In which case they would both be using the same callback and potentially cause
issues. So I did this here where we can iterate over all converter and pick just
one pen.
Doing this right during init is much simpler though, and having multiple
internal touchscreens and pen devices would probably cause a whole bunch of
other issues anyway. 

+        internal_pen = converter;
+      } else if (converter->HasTouchscreen()) {
+        enabled &= !palm_suppression_enabled_;
+      }
+
+      if (converter->HasKeyboard()) {
+        converter->SetKeyFilter(
+            input_device_settings_.enable_internal_keyboard_filter,
+            input_device_settings_.internal_keyboard_allowed_keys);
+      }
     }
-
+    converter->SetEnabled(enabled);
     converter->SetTouchEventLoggingEnabled(
         input_device_settings_.touch_event_logging_enabled);
   }
+  if (internal_pen) {
+    internal_pen->SetPalmSuppressionCallback(

[spang, 2016/08/26 00:58:34]

Also this one. Unless it uses settings, it doesn't really need to run every time
settings change.

[denniskempin, 2016/08/26 21:56:02]

Done.

+        base::Bind(&InputDeviceFactoryEvdev::EnablePalmSuppression,
+                   base::Unretained(this)));
+  }
 }
 
 void InputDeviceFactoryEvdev::ApplyCapsLockLed() {
@@ -491,4 +505,19 @@ void InputDeviceFactoryEvdev::SetBoolPropertyForOneType(
 #endif
 }
 
+void InputDeviceFactoryEvdev::EnablePalmSuppression(bool enabled) {
+  if (enabled == palm_suppression_enabled_)
+    return;
+
+  for (const auto& it : converters_) {
+    EventConverterEvdev* converter = it.second;
+    if (converter->type() == InputDeviceType::INPUT_DEVICE_INTERNAL &&
+        converter->HasTouchscreen() && !converter->HasPen()) {
+      converter->SetEnabled(!enabled);

[spang, 2016/08/26 00:58:34]

The way to disable a device is to change the implementation of IsDeviceEnabled()
to check your condition and return "false". The policy is handled centrally, to
avoid multiple features fighting over ownership of the "enabled" status, causing
funny behavior.

If you do call SetEnabled() here directly, then as soon as settings change, or a
device is plugged or unplugged, it'll get enabled again. But you want it to stay
disabled while the stylus is active.

[denniskempin, 2016/08/26 21:56:02]

Done.

+    }
+  }
+
+  palm_suppression_enabled_ = enabled;
+}
+
 }  // namespace ui