VR: Sending the fling event to the right target

chrome/browser/android/vr_shell/vr_shell_gl.cc

 // 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 "chrome/browser/android/vr_shell/vr_shell_gl.h"
 
 #include <chrono>
 #include <limits>
 #include <utility>
 
@@ skipping 635 matching lines @@
 
   for (auto& gesture : gesture_list) {
     gesture->x = pixel_x;
     gesture->y = pixel_y;
     auto movableGesture = base::MakeUnique<WebGestureEvent>(*gesture);
 
     switch (gesture->type()) {
       // Once the user starts scrolling send all the scroll events to this
       // element until the scrolling stops.
       case WebInputEvent::GestureScrollBegin:
-        current_scroll_target = input_target;
-        if (current_scroll_target != InputTarget::NONE) {
-          SendGesture(current_scroll_target, std::move(movableGesture));
+        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));
+        if (current_scroll_target_ != InputTarget::NONE) {
+          SendGesture(current_scroll_target_, std::move(movableGesture));
         }
-        current_scroll_target = InputTarget::NONE;
+        current_fling_target_ = current_scroll_target_;
+        current_scroll_target_ = InputTarget::NONE;
         break;
       case WebInputEvent::GestureScrollUpdate:
-      case WebInputEvent::GestureFlingCancel:
-      case WebInputEvent::GestureFlingStart:
-        if (current_scroll_target != InputTarget::NONE) {
-          SendGesture(current_scroll_target, std::move(movableGesture));
+        if (current_scroll_target_ != InputTarget::NONE) {
+          SendGesture(current_scroll_target_, std::move(movableGesture));
         }
         break;
+      case WebInputEvent::GestureFlingStart:
+        if (current_fling_target_ != InputTarget::NONE) {
+          SendGesture(current_fling_target_, std::move(movableGesture));
+        }
+        current_fling_target_ = InputTarget::NONE;
+        break;
+      case WebInputEvent::GestureFlingCancel:

[mthiesse, 2017/04/12 17:46:20]

Shouldn't FlingCancel do something like sending a cancel gesture to the
current_fling_target_? Why is it falling through to GestureTapDown?

[asimjour, 2017/04/12 18:00:58]

Fling cancel happens when user start to touch the touchpad during a fling. I
think it should only stop the fling if the laser is pointing to the same target
that fling was sent to.

[mthiesse, 2017/04/12 18:05:28]

Sure, but now we're sending a FlingCancel gesture to something that was probably
not in a fling. Just for clarity sake, even if we use the exact same logic in
the FlingCancel and TapDown cases, we shouldn't have it fall through because
they should be they're distinct events that might diverge in behaviour.

[asimjour1, 2017/04/12 18:15:32]

I repeated the code under FlingCancel and TapDown, and made the separate.

It is ok to send FlingCancel to a content that has not received a FlingStart
before.

       case WebInputEvent::GestureTapDown:
+        current_fling_target_ = InputTarget::NONE;
         if (input_target != InputTarget::NONE) {
           SendGesture(input_target, std::move(movableGesture));
         }
         break;
       case WebInputEvent::Undefined:
         break;
       default:
         NOTREACHED();
     }
   }
@@ skipping 591 matching lines @@
   // InitializeGl. Revisit if the initialization order changes.
   device::mojom::VRDisplayInfoPtr info =
       device::GvrDelegate::CreateVRDisplayInfo(gvr_api_.get(),
                                                webvr_surface_size_, device_id);
   main_thread_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&RunVRDisplayInfoCallback, callback, base::Passed(&info)));
 }
 
 }  // namespace vr_shell