bluetooth: web: web_bluetooth.mojom comments and UUID type fix.

third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom

 // Copyright 2016 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.
 
 module blink.mojom;
 
 import "device/bluetooth/public/interfaces/uuid.mojom";
 
-// Result codes that can occur during Web Bluetooth execution, which are
-// transformed to a DOMException in Source/modules/bluetooth/BluetoothError.cpp.
+// Instance ID Note:
+//
+// Structs and parameters use 'instance_id' string values as unique identifiers
+// for GATT objects. Subsequent calls from and to the client code use the ids
+// to refer to previously disclosed objects.

[dcheng, 2017/01/14 10:23:45]

Nit: Perhaps expand GATT the first time it's written (Generic ATTribute is my
assumption for what it stands for, based on my searching).

For people who aren't familiar with Bluetooth, it might be nice to explain other
terminology or provide a pointer to a resource that does: I don't really know
what a characteristic or descriptor is, for example, and I assume that devices
can provide services, but I have no clue =)

[scheib, 2017/01/17 19:20:43]

Done.

+//
+// Device IDs are exposed to web content, valid to persist, and have a dedicated
+// type, WebBluetoothDeviceId. See comments on that struct.
+//
+// Service, characteristic, and descriptor IDs are simply strings not exposed to
+// web content and use platform specific values. They are only used for
+// comparison and not intended to be parsed by code, serialized, or exposed to
+// web content.
+//
+// For example:
+// RemoteServerGetPrimaryServices() may return a struct of type
+// WebBluetoothRemoteGATTService with an instance_id of "service1".
+// To retrieve characteristics of that service use that id when calling
+// RemoteServiceGetCharacteristics("service1", ...).
+
+// Result codes that can occur during Web Bluetooth execution.
+// Transformed to a DOMException in Source/modules/bluetooth/BluetoothError.cpp.
 //
 // These errors all produce constant message strings. If a particular message
 // needs a dynamic component, we should add a separate enum so type-checking the
 // IPC ensures the dynamic component is passed.
 enum WebBluetoothResult {
   SUCCESS,
   // AbortError:
   // InvalidModificationError:
   GATT_INVALID_ATTRIBUTE_LENGTH,
   // InvalidStateError:
@@ skipping 65 matching lines @@
   bool accept_all_devices;
 };
 
 // Indicates if the function will return a single or multiple
 // GATT objects.
 enum WebBluetoothGATTQueryQuantity {
   SINGLE,
   MULTIPLE
 };
 
+// An identifier uniquely identifying a Bluetooth device. This identifier is
+// safe to provide to web content and is unique per origin, even if referring
+// to a common device. Web content may persist this identifier for future
+// sessions to identify the same device.
 struct WebBluetoothDeviceId {
   string device_id;
 };
 
 struct WebBluetoothDevice {
   WebBluetoothDeviceId id;
   string? name;
 };
 
 struct WebBluetoothRemoteGATTService {
-  string instance_id;
+  string instance_id; // See Instance ID Note above.
   string uuid;

[dcheng, 2017/01/14 10:23:45]

Why does this need both uuid and instance_id? Also, what's the difference
between string uuid and bluetooth.mojom.UUID?

[scheib, 2017/01/17 19:20:43]

I added comments.
I changed the types to use the new bluetooth.mojom.UUID.

 };
 
 struct WebBluetoothRemoteGATTCharacteristic {
-  string instance_id;
+  string instance_id; // See Instance ID Note above.
   string uuid;
   uint32 properties;
 };
 
 struct WebBluetoothRemoteGATTDescriptor {
-  string instance_id;
+  string instance_id; // See Instance ID Note above.
   string uuid;
 };
 
 // Web Bluetooth Interface that Blink can use to perform
 // Bluetooth GATT Operations on Bluetooth Devices.
 interface WebBluetoothService {
   // Sets the client for this WebBluetoothService. The service will notify the
   // client of device events e.g. when a Characteristic's value changes or when
   // a device disconnects.
   SetClient(associated WebBluetoothServiceClient client);
 
   RequestDevice(WebBluetoothRequestDeviceOptions options)
     => (WebBluetoothResult result, WebBluetoothDevice? device);
 
-  // Creates a GATT Connection to a Bluetooth Device with |device_id| if a
-  // connection to the device didn't exist already. If a GATT connection existed
-  // already then this function increases the ref count to keep that connection
-  // alive.
+  // Creates a GATT Connection to a Bluetooth Device identified by |device_id|
+  // if a connection to the device didn't exist already. If a GATT connection
+  // existed already then this function increases the ref count to keep that
+  // connection alive.
   RemoteServerConnect(WebBluetoothDeviceId device_id) => (WebBluetoothResult result);
 
-  // If a GATT connection exists for Device with |device_id| then decreases
-  // the ref count for that connection.
+  // If a GATT connection exists for Device identified by |device_id| then
+  // decreases the ref count for that connection.
   RemoteServerDisconnect(WebBluetoothDeviceId device_id);
 
-  // If |services_uuid| is present, returns services with |services_uuid|.
+  // Returns the Services of a GATT Device identified by |device_id|.
+  // If |services_uuid| is present, filters services by |services_uuid|.
   // Otherwise returns all non-blocklisted services.
-  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, only one
+  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, at most one
   // service will be returned.
   RemoteServerGetPrimaryServices(
     WebBluetoothDeviceId device_id,
     WebBluetoothGATTQueryQuantity quantity,
     bluetooth.mojom.UUID? services_uuid) => (
       WebBluetoothResult result,
       array<WebBluetoothRemoteGATTService>? services);
 
-  // Returns the Characteristics of a GATT Service with |service_instance_id|.
-  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, only one
+  // Returns the Characteristics of a GATT Service identified by
+  // |service_instance_id|.
+  // If |characteristics_uuid| is present, filters characteristics by
+  // |characteristics_uuid|. Otherwise returns all non-blocklisted services.
+  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, at most one
   // characteristic will be returned.
   RemoteServiceGetCharacteristics(
     string service_instance_id,
     WebBluetoothGATTQueryQuantity quantity,
     bluetooth.mojom.UUID? characteristics_uuid) => (
       WebBluetoothResult result,
       array<WebBluetoothRemoteGATTCharacteristic>? characteristics);
 
-  // Reads the value for characteristic with
+  // Reads the value for the characteristic identified by
   // |characteristic_instance_id|. If the value is successfully read the
   // callback will be run with WebBluetoothResult::SUCCESS and the
   // characteristic's value. If the value is not successfully read the
   // callback with be run with the corresponding error and nullptr for value.
   RemoteCharacteristicReadValue(
     string characteristic_instance_id) => (
     WebBluetoothResult result,
     array<uint8>? value);
 
-  // Writes a value to the characteristic with
+  // Writes a value to the characteristic identified by
   // |characteristic_instance_id|. The callback is run with
   // WebBluetoothResult::SUCCESS if the value was successfully
   // written.
   RemoteCharacteristicWriteValue(
     string characteristic_instance_id,
     array<uint8> value) => (WebBluetoothResult result);
 
-  // Starts notifications for the characteristic with
+  // Starts notifications for the characteristic identified by
   // |characteristic_instance_id|.
   RemoteCharacteristicStartNotifications(
     string characteristic_instance_id) => (WebBluetoothResult result);
 
-  // Stops notifications for the characteristic with
+  // Stops notifications for the characteristic identified by
   // |characteristic_instance_id|.
   RemoteCharacteristicStopNotifications(
     string characteristic_instance_id) => ();
 
-  // Returns the Descriptors of a GATT Characteristic with
+  // Returns the Descriptors of a GATT Characteristic identified by
   // |characteristics_instance_id|.
-  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, only one descriptor
-  // will be returned.
+  // If |descriptor_uuid| is present, filters descriptors by
+  // |descriptor_uuid|. Otherwise returns all non-blocklisted descriptors.
+  // If |quantity| == WebBluetoothGATTQueryQuantity::SINGLE, at most one
+  // characteristic will be returned.
   RemoteCharacteristicGetDescriptors(
     string characteristics_instance_id,
     WebBluetoothGATTQueryQuantity quantity,
     bluetooth.mojom.UUID? descriptor_uuid) => (
       WebBluetoothResult result,
       array<WebBluetoothRemoteGATTDescriptor>? descriptors);
 };
 
 // Classes should implement this interface and pass an associated pointer
 // bound to them to the WebBluetoothService by using SetClient. Classes
 // that do this will be notified of device events e.g. device disconnection.

[dcheng, 2017/01/14 10:23:45]

Btw, is it expected this will be a 1:1 sort of relationship? i.e. is something
that connects to the bluetooth service expected to provide this client?

[scheib, 2017/01/17 19:20:43]

1:1,

WebBluetoothServiceClient is only used in interface WebBluetoothService
SetClient which comments that "Sets the client for this WebBluetoothService." 

[dcheng, 2017/01/17 23:39:15]

If it's always 1:1, would you be willing to file a bug/explore making sure this
invariant always hold? The current way to do that is using a factory interface,
though Mojo may explore alternatives if there's enough demand (see
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-mojo/j-kiK17V-Qc)

 interface WebBluetoothServiceClient {
+  // The characteristic identified by |characteristic_instance_id| has received
+  // a notification of value change.
   RemoteCharacteristicValueChanged(string characteristic_instance_id,
                                    array<uint8> value);
+
+  // The device identified by |device_id| has been disconnected.
   GattServerDisconnected(WebBluetoothDeviceId device_id);
 };