Don't send touch move to renderer while scrolling

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 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 "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 42 matching lines @@
 #include "ui/aura/window.h"
 #include "ui/aura/window_destruction_observer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/base/clipboard/scoped_clipboard_writer.h"
 #include "ui/base/events/event.h"
 #include "ui/base/events/event_utils.h"
 #include "ui/base/gestures/gesture_recognizer.h"
 #include "ui/base/hit_test.h"
 #include "ui/base/ime/input_method.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/compositor/layer.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/screen.h"
 #include "ui/gfx/size_conversions.h"
 #include "ui/gfx/skia_util.h"
 
 #if defined(OS_WIN)
@@ skipping 2394 matching lines @@
   WebKit::WebGestureEvent gesture = MakeWebGestureEvent(event);
   if (event->type() == ui::ET_GESTURE_TAP_DOWN) {
     // Webkit does not stop a fling-scroll on tap-down. So explicitly send an
     // event to stop any in-progress flings.
     WebKit::WebGestureEvent fling_cancel = gesture;
     fling_cancel.type = WebKit::WebInputEvent::GestureFlingCancel;
     fling_cancel.sourceDevice = WebKit::WebGestureEvent::Touchscreen;
     host_->ForwardGestureEvent(fling_cancel);
   }
 
+  if (switches::IsTouchCancelAfterScrollEnabled()) {

[Rick Byers, 2013/05/30 01:53:29]

This code should apply to windows (non-aura) as well (and perhaps there's even
some opportunity to share logic with Android).  So it probably doesn't belong in
an Aura specific file.  

I know you and Sadrul are discussing where best to put this - I'm not sure
myself which option I think is best.

[Yufeng Shen (Slow to review), 2013/05/30 22:34:38]

Moved the logic to render_widget_host_impl.cc

+    // When there is touch handler on the page, once scrolling is started,
+    // we send a touch cancel to the page, and stops forwarding touch moves to
+    // the renderer. This is to align with Chrome on Android behavior.
+    if (event->type() == ui::ET_GESTURE_SCROLL_UPDATE &&
+        host_->ShouldForwardTouchEvent() &&
+        !host_->scroll_update_in_progress()) {
+      host_->scroll_update_in_progress() = true;

[sadrul, 2013/05/30 02:44:16]

ew no

[Yufeng Shen (Slow to review), 2013/05/30 22:34:38]

Done.

+      // Insert a TouchCancel event.
+      WebKit::WebTouchEvent cancel_event;
+      cancel_event.type = WebKit::WebInputEvent::TouchCancel;
+      cancel_event.timeStampSeconds = event->time_stamp().InSecondsF();
+      int id = event->GetLowestTouchId();
+      if (id != -1) {
+        cancel_event.touchesLength = 1;
+        cancel_event.touches[0].id = id;
+        cancel_event.touches[0].state = WebKit::WebTouchPoint::StateCancelled;
+        host_->skip_next_acked_touch_cancel() = true;

[sadrul, 2013/05/30 02:44:16]

ew no

[Yufeng Shen (Slow to review), 2013/05/30 22:34:38]

Done.

+        host_->ForwardTouchEvent(cancel_event);
+      }
+    }
+
+    if (event->type() == ui::ET_GESTURE_SCROLL_END ||
+        event->type() == ui::ET_SCROLL_FLING_START) {
+      host_->scroll_update_in_progress() = false;

[sadrul, 2013/05/30 02:44:16]

stahp

[Yufeng Shen (Slow to review), 2013/05/30 22:34:38]

Done.

+    }
+  }

[sadrul, 2013/05/30 02:44:16]

There may be a few more touch-move events in the touch-event queue when
scrolling starts. So it is necessary to flush all those events to the GR
immediately when this happens.

This is not a good place for doing this. It would be better to do this in
GestureEventFilter (although still a little awkward, perhaps), or near that part
of the code.

[Yufeng Shen (Slow to review), 2013/05/30 22:34:38]

moved to render_widge_host_impl.cc

+
   if (gesture.type != WebKit::WebInputEvent::Undefined) {
     host_->ForwardGestureEvent(gesture);
 
     if (event->type() == ui::ET_GESTURE_SCROLL_BEGIN ||
         event->type() == ui::ET_GESTURE_SCROLL_UPDATE ||
         event->type() == ui::ET_GESTURE_SCROLL_END) {
       RecordAction(UserMetricsAction("TouchscreenScroll"));
     } else if (event->type() == ui::ET_SCROLL_FLING_START) {
       RecordAction(UserMetricsAction("TouchscreenScrollFling"));
     }
@@ skipping 469 matching lines @@
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewAura(widget);
 }
 
 // static
 void RenderWidgetHostViewPort::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content