Enable scrolling of UI elements.

chrome/browser/android/vr_shell/vr_shell_gl.cc

Index: chrome/browser/android/vr_shell/vr_shell_gl.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.cc b/chrome/browser/android/vr_shell/vr_shell_gl.cc
index 4564af0162f5c35aab779ce0b28045de7f093c98..4c147ccd22bd5c3e0444ee77e5c34ae2199c0ae0 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.cc
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.cc
@@ -529,8 +529,19 @@ void VrShellGl::UpdateController(const gvr::Vec3f& forward_vector) {
 
       target_point_ = plane_intersection_point;
       target_element_ = plane.get();
-      input_target = (plane->fill == Fill::CONTENT) ? InputTarget::CONTENT
-                                                    : InputTarget::UI;
+      // For now treat UI elements, which do not show web content, as NONE input

[cjgrant, 2017/02/14 14:08:25]

General comment on comments: It's usually best to leave out "For now",
"temporarily", etc, as we have no idea how long this code might live.

[tiborg, 2017/02/14 21:44:23]

Done.

+      // targets since they cannot make use of the input anyway.
+      switch (plane->fill) {

[cjgrant, 2017/02/14 14:08:25]

The loop is responsible for finding target_element_, so this switch should live
after the loop and use target_element_.

[tiborg, 2017/02/14 21:44:23]

Done.

+        case Fill::CONTENT:
+          input_target = InputTarget::CONTENT;
+          break;
+        case Fill::SPRITE:
+          input_target = InputTarget::UI;
+          break;
+        default:
+          input_target = InputTarget::NONE;
+          break;
+      }
     }
   }
   SendEventsToTarget(input_target, pixel_x, pixel_y);
@@ -554,21 +565,36 @@ void VrShellGl::SendEventsToTarget(InputTarget input_target,
   }
 
   for (const auto& gesture : gesture_list) {
+    gesture->x = pixel_x;

[cjgrant, 2017/02/14 14:08:25]

So here we change gesture, but a line above, gesture is a const reference. Is
the const-ness broken through unique_ptr?

[tiborg, 2017/02/14 21:44:23]

I think the const is referring to the unique_ptr and not the referenced type,
i.e. const std::unique_ptr<...>. So, you cannot let the unique_ptr point to some
other object but you can modify the pointed to object. To make the pointed to
object const you would need std::unique_ptr<const ...>.

[cjgrant, 2017/02/14 22:37:41]

Michael, thoughts on this?  The const is misleading here IMO - I'd ditch it.

[tiborg, 2017/02/14 23:13:52]

Ditched const.

+    gesture->y = pixel_y;
+    auto movableGesture = base::WrapUnique(new WebGestureEvent(*gesture));

[cjgrant, 2017/02/14 14:08:24]

This should use MakeUnique() (ie. the new preferred style).

[tiborg, 2017/02/14 21:44:23]

Done.

+
     switch (gesture->type()) {
+      // Once the user starts scrolling sed all the scroll events to this

[cjgrant, 2017/02/14 14:08:24]

/sed/send/

[tiborg, 2017/02/14 21:44:23]

Done.

+      // element until the scrolling stops.
       case WebInputEvent::GestureScrollBegin:
-      case WebInputEvent::GestureScrollUpdate:
+        current_scroll_target = input_target;
+        if (current_scroll_target != InputTarget::NONE) {
+          SendGesture(current_scroll_target, std::move(movableGesture));
+        }
+        break;
       case WebInputEvent::GestureScrollEnd:
+        if (current_scroll_target != InputTarget::NONE) {
+          SendGesture(current_scroll_target, std::move(movableGesture));
+        }
+        current_scroll_target = InputTarget::NONE;
+        break;
+      case WebInputEvent::GestureScrollUpdate:
       case WebInputEvent::GestureFlingCancel:
       case WebInputEvent::GestureFlingStart:
-        SendGesture(InputTarget::CONTENT,
-                    base::WrapUnique(new WebGestureEvent(*gesture)));
+        if (current_scroll_target != InputTarget::NONE) {
+          SendGesture(current_scroll_target, std::move(movableGesture));
+        }
         break;
       case WebInputEvent::GestureTapDown:
-        gesture->x = pixel_x;
-        gesture->y = pixel_y;
-        if (input_target != InputTarget::NONE)
-          SendGesture(input_target,
-                      base::WrapUnique(new WebGestureEvent(*gesture)));
+        if (input_target != InputTarget::NONE) {
+          SendGesture(input_target, std::move(movableGesture));
+        }
         break;
       case WebInputEvent::Undefined:
         break;