WebVR: Use content CVC size for compositor rendering

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

Index: third_party/WebKit/Source/modules/vr/VRDisplay.cpp
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
index 4cf3973662823f203c01223e67c35aa38b26ad44..f2cebb033ce5d2f9fd8c7f4b3b3ca5becdf6a07f 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
@@ -4,6 +4,7 @@
 
 #include "modules/vr/VRDisplay.h"
 
+#include "core/css/StylePropertySet.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/FrameRequestCallback.h"
 #include "core/dom/Fullscreen.h"
@@ -336,8 +337,22 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
     // 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::requestFullscreen(*m_layer.source(),
-                                  Fullscreen::UnprefixedRequest);
+    auto canvas = m_layer.source();
+    auto inlineStyle = canvas->inlineStyle();
+    if (inlineStyle) {
+      m_fullscreenOrigWidth = inlineStyle->getPropertyValue(CSSPropertyWidth);

[mthiesse, 2016/11/16 21:30:41]

why are we changing CSS properties?

[mthiesse, 2016/11/16 21:31:35]

Just saw your comment in the CL description. Put it here too.

[klausw, 2016/11/16 23:37:39]

Done, with a bit more detail:

      // THREE.js's VREffect sets explicit style.width/height on its rendering
      // canvas based on the non-fullscreen window dimensions, and it keeps
      // those unchanged when presenting. Unfortunately it appears that a
      // fullscreened canvas just gets centered if it has explicitly set a
      // size smaller than the fullscreen dimensions. Manually set size to
      // 100% in this case and restore it when exiting fullscreen. This is a
      // stopgap measure since THREE.js's usage appears legal according to the
      // WebVR API spec. This will no longer be necessary once we can get rid
      // of this fullscreen hack.

+      if (!m_fullscreenOrigWidth.isNull()) {
+        canvas->setInlineStyleProperty(CSSPropertyWidth, "100%");
+      }
+      m_fullscreenOrigHeight = inlineStyle->getPropertyValue(CSSPropertyHeight);
+      if (!m_fullscreenOrigHeight.isNull()) {
+        canvas->setInlineStyleProperty(CSSPropertyHeight, "100%");
+      }
+    } else {
+      m_fullscreenOrigWidth = String();
+      m_fullscreenOrigHeight = String();
+    }
+    Fullscreen::requestFullscreen(*canvas, Fullscreen::UnprefixedRequest);
 
     // Check to see if the canvas is still the current fullscreen
     // element once per second.
@@ -435,8 +450,18 @@ void VRDisplay::beginPresent(ScriptPromiseResolver* resolver) {
 void VRDisplay::forceExitPresent() {
   if (m_isPresenting) {
     if (!m_capabilities->hasExternalDisplay()) {
-      Fullscreen::fullyExitFullscreen(m_layer.source()->document());
+      auto canvas = m_layer.source();
+      Fullscreen::fullyExitFullscreen(canvas->document());
       m_fullscreenCheckTimer.stop();
+      if (!m_fullscreenOrigWidth.isNull()) {

[bajones, 2016/11/16 21:23:52]

This is all so hacky anyway I don't know how much I care, but we risk resetting
this to an old value if the developer updates it while in VR presentation mode
(which would probably cause their content to break, but at that point it's on
their heads.) Maybe we should just check to see if it's currently set to "100%"
before restoring? Or we can just run with it like this because we intend for the
solution to be short-lived anyway.

[klausw, 2016/11/16 23:37:39]

I don't have strong feelings about this, but at this point I don't think making
the logic more complex has much benefit. Hopefully this code will all go away
soon.

+        canvas->setInlineStyleProperty(CSSPropertyWidth, m_fullscreenOrigWidth);
+        m_fullscreenOrigWidth = String();
+      }
+      if (!m_fullscreenOrigHeight.isNull()) {
+        canvas->setInlineStyleProperty(CSSPropertyWidth,
+                                       m_fullscreenOrigHeight);
+        m_fullscreenOrigHeight = String();
+      }
     } else {
       // Can't get into this presentation mode, so nothing to do here.
     }