Only allow VR presentation in response to a user gesture

third_party/WebKit/Source/modules/vr/VRDisplay.cpp

 // 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.
 
 #include "modules/vr/VRDisplay.h"
 
 #include "core/dom/DOMException.h"
 #include "core/dom/Fullscreen.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "modules/vr/NavigatorVR.h"
 #include "modules/vr/VRController.h"
 #include "modules/vr/VRDisplayCapabilities.h"
 #include "modules/vr/VREyeParameters.h"
 #include "modules/vr/VRLayer.h"
 #include "modules/vr/VRPose.h"
 #include "modules/vr/VRStageParameters.h"
 #include "modules/webgl/WebGLRenderingContextBase.h"
+#include "platform/UserGestureIndicator.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
 
 namespace {
 
 VREye stringToVREye(const String& whichEye)
 {
     if (whichEye == "left")
         return VREyeLeft;
@@ skipping 98 matching lines @@
 {
     if (Document* document = m_navigatorVR->document())
         document->cancelAnimationFrame(id);
 }
 
 ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState, const HeapVector<VRLayer>& layers)
 {
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
-    m_isPresenting = false;
-
+    // If the VRDisplay does not advertise the ability to present reject the request.
     if (!m_capabilities->canPresent()) {
-        DOMException* exception = DOMException::create(InvalidStateError, "VRDisplay cannot present");
+        DOMException* exception = DOMException::create(InvalidStateError, "VRDisplay cannot present.");
         resolver->reject(exception);
         return promise;
     }
 
+    // Initiating VR presentation is only allowed in response to a user gesture.
+    // If the VRDisplay is already presenting, however, repeated calls are
+    // allowed outside a user gesture so that the presented content may be
+    // updated.
+    if (!m_isPresenting && !UserGestureIndicator::utilizeUserGesture()) {
+        DOMException* exception = DOMException::create(InvalidStateError, "API can only be initiated by a user gesture.");
+        resolver->reject(exception);
+        return promise;
+    }
+
+    m_isPresenting = false;
+
+    // A valid number of layers must be provided in order to present.
     if (layers.size() == 0 || layers.size() > m_capabilities->maxLayers()) {
         DOMException* exception = DOMException::create(InvalidStateError, "Invalid number of layers.");
         if (m_isPresenting) {
             exitPresent(scriptState);
         }
         resolver->reject(exception);
         return promise;
     }
 
     m_layer = layers[0];
 
     if (m_layer.source()) {
         if (!m_capabilities->hasExternalDisplay()) {
             // TODO: Need a proper VR compositor, but for the moment on mobile
             // we'll just make the canvas fullscreen so that VrShell can pick it
             // up through the standard (high latency) compositing path.
             Fullscreen::from(m_layer.source()->document()).requestFullscreen(*m_layer.source(), Fullscreen::UnprefixedRequest);
 
             m_isPresenting = true;
 
             resolver->resolve();
 
             m_navigatorVR->fireVRDisplayPresentChange(this);
 
             // Check to see if the canvas is still the current fullscreen
             // element once per second.
             m_fullscreenCheckTimer.startRepeating(1.0, BLINK_FROM_HERE);
         } else {
-            DOMException* exception = DOMException::create(InvalidStateError, "VR Presentation not implemented for this VRDisplay");
+            DOMException* exception = DOMException::create(InvalidStateError, "VR Presentation not implemented for this VRDisplay.");
             resolver->reject(exception);
         }
     } else {
-        DOMException* exception = DOMException::create(InvalidStateError, "Invalid layer source");
+        DOMException* exception = DOMException::create(InvalidStateError, "Invalid layer source.");
         resolver->reject(exception);
     }
 
     return promise;
 }
 
 ScriptPromise VRDisplay::exitPresent(ScriptState* scriptState)
 {
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
     if (!m_isPresenting) {
         // Can't stop presenting if we're not presenting.
-        DOMException* exception = DOMException::create(InvalidStateError, "VRDisplay is not presenting");
+        DOMException* exception = DOMException::create(InvalidStateError, "VRDisplay is not presenting.");
         resolver->reject(exception);
         return promise;
     }
 
     if (!m_capabilities->hasExternalDisplay()) {
         Fullscreen::fullyExitFullscreen(m_layer.source()->document());
         m_fullscreenCheckTimer.stop();
     } else {
         // Can't get into this presentation mode, so nothing to do here.
     }
@@ skipping 51 matching lines @@
     visitor->trace(m_navigatorVR);
     visitor->trace(m_capabilities);
     visitor->trace(m_stageParameters);
     visitor->trace(m_eyeParametersLeft);
     visitor->trace(m_eyeParametersRight);
     visitor->trace(m_framePose);
     visitor->trace(m_layer);
 }
 
 } // namespace blink