mojo VR interface simplified

device/vr/vr_service.mojom

 // Copyright 2015 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 device;
 
 // A field of view, given by 4 degrees describing the view from a center point.
 struct VRFieldOfView {
   float upDegrees;
   float downDegrees;
@@ skipping 31 matching lines @@
   uint32 renderHeight;
 };
 
 struct VRStageParameters {
   array<float, 16> standingTransform;
   float sizeX;
   float sizeZ;
 };
 
 struct VRDisplay {
    uint32 index;

[leonhsl(Using Gerrit), 2016/10/17 09:03:29]

I suppose our target is to avoid transferring the index.

[shaobo.yan, 2016/10/18 01:10:48]

Since WebVR spec need each VRDisplay should have an id attribute, I thought the
index could be setted as id directly. But if mojo really doesn't want index be
transferred, I'll remove it and use another id generation in blink side.

[leonhsl(Using Gerrit), 2016/10/18 07:12:10]

This is not requested by mojo. I think one motivate of the refactor is to avoid
specifying device<-->display pair by an index, and transferring index everywhere
seems be unnecessary at least for apis such as onDisplayChanged and
onDisplayConnected etc.

    string displayName;
    VRDisplayCapabilities capabilities;
    VRStageParameters? stageParameters;
    VREyeParameters leftEye;
    VREyeParameters rightEye;
 };
 
+struct VRDisplayWithService {
+   VRDisplay? display;

[leonhsl(Using Gerrit), 2016/10/17 09:03:29]

Does it make sense when VRDisplay is null? For what scenario?

+   VRDeviceService? service;

[leonhsl(Using Gerrit), 2016/10/17 09:03:29]

Same question with above, what scenario for the null VRDeviceService?

[shaobo.yan, 2016/10/18 01:10:48]

The VRDisplay should not be nullptr but the VRDeviceService could be.

The display and service should not be nullptr. Since all of them are related to
an VRDevice object and the object has been checked not null. So it should not be
nullptr.

+};
+
 struct VRLayerBounds {
    float left;
    float top;
    float width;
    float height;
 };
 
 interface VRService {
-  SetClient(VRServiceClient client);
-
-  GetDisplays() => (array<VRDisplay> displays);
-  [Sync]
-  GetPose(uint32 index) => (VRPose? pose);
-  ResetPose(uint32 index);
-
-  RequestPresent(uint32 index, bool secureOrigin) => (bool success);
-  ExitPresent(uint32 index);
-  SubmitFrame(uint32 index, VRPose? pose);
-  UpdateLayerBounds(uint32 index, VRLayerBounds leftBounds, VRLayerBounds rightBounds);
+  GetDisplays() => (array<VRDisplayWithService> displays);
 };
 
-interface VRServiceClient {
+interface VRDeviceService {

[leonhsl(Using Gerrit), 2016/10/17 09:03:29]

We should avoid such interface naming as XXXService, as it is not a real
service,, how about 'VRDevice'?

[shaobo.yan, 2016/10/18 01:10:48]

Oh, thx for the info ! We already have a class named VRDevice. This interface is
used by VRDisplay object to communicate with VRDevice object on blink side,
maybe VRDeviceClient could be a name.

[leonhsl(Using Gerrit), 2016/10/18 07:12:10]

You could change 'module device' to 'module device.mojom', this way generated
class will live under a nested namespace device::mojom, to avoid name collision.
I think (VRDevice, VRDeviceClient) pair is appropriate naming practice to align
with other mojo interfaces inside Chromium.

+  RegisterDisplayService(VRDisplayService display_service);
+
+  [Sync]
+  GetPose() => (VRPose? pose);
+  ResetPose();
+
+  RequestPresent(bool secureOrigin) => (bool success);
+  ExitPresent();
+  SubmitFrame(VRPose? pose);
+  UpdateLayerBounds(VRLayerBounds leftBounds, VRLayerBounds rightBounds);
+};
+
+//NOTE: this interface will be held by each VRDevice and VRDisplay pair.
+interface VRDisplayService {

[leonhsl(Using Gerrit), 2016/10/17 09:03:29]

Naming change: to 'VRDisplay' or 'VRDeviceClient'

[shaobo.yan, 2016/10/18 01:10:48]

This interface is used by VRDevice to inform event to VRDisplay on blink side.
I'll change it to VRDisplayClient.

   OnDisplayChanged(VRDisplay display);
-  OnExitPresent(uint32 index);
+  OnExitPresent();
   OnDisplayConnected(VRDisplay display);
-  OnDisplayDisconnected(uint32 index);
+  OnDisplayDisconnected();
 };