Fix mouse wheel scrolling on PDFs.

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 625 matching lines @@
 WebInputEventResult WebViewImpl::handleMouseWheel(LocalFrame& mainFrame, const WebMouseWheelEvent& event)
 {
     // Halt an in-progress fling on a wheel tick.
     if (!event.hasPreciseScrollingDeltas)
         endActiveFlingAnimation();
 
     hidePopups();
     return PageWidgetEventHandler::handleMouseWheel(mainFrame, event);
 }
 
+void WebViewImpl::populateGestureScrollEventFromFling(WebInputEvent::Type type, WebGestureDevice sourceDevice, WebGestureEvent* gestureEvent)

[tdresser, 2016/03/29 19:16:03]

Why not just return a WebGestureEvent?

[dtapuska, 2016/03/29 19:42:05]

Done.

+{
+    gestureEvent->type = type;
+    gestureEvent->sourceDevice = sourceDevice;
+    gestureEvent->timeStampSeconds = WTF::monotonicallyIncreasingTime();
+    gestureEvent->x = m_positionOnFlingStart.x;
+    gestureEvent->y = m_positionOnFlingStart.y;
+    gestureEvent->globalX = m_globalPositionOnFlingStart.x;
+    gestureEvent->globalY = m_globalPositionOnFlingStart.y;
+    gestureEvent->modifiers = m_flingModifier;
+}
+
 bool WebViewImpl::scrollBy(const WebFloatSize& delta, const WebFloatSize& velocity)
 {
     ASSERT(m_flingSourceDevice != WebGestureDeviceUninitialized);
+    if (!m_page || !m_page->mainFrame() || !m_page->mainFrame()->isLocalFrame() || !m_page->deprecatedLocalMainFrame()->view())
+        return false;
+
     if (m_flingSourceDevice == WebGestureDeviceTouchpad) {
         WebMouseWheelEvent syntheticWheel;
         const float tickDivisor = WheelEvent::TickMultiplier;
 
         syntheticWheel.type = WebInputEvent::MouseWheel;
         syntheticWheel.timeStampSeconds = WTF::monotonicallyIncreasingTime();
         syntheticWheel.deltaX = delta.width;
         syntheticWheel.deltaY = delta.height;
         syntheticWheel.wheelTicksX = delta.width / tickDivisor;
         syntheticWheel.wheelTicksY = delta.height / tickDivisor;
         syntheticWheel.hasPreciseScrollingDeltas = true;
         syntheticWheel.x = m_positionOnFlingStart.x;
         syntheticWheel.y = m_positionOnFlingStart.y;
         syntheticWheel.globalX = m_globalPositionOnFlingStart.x;
         syntheticWheel.globalY = m_globalPositionOnFlingStart.y;
         syntheticWheel.modifiers = m_flingModifier;
 
-        if (m_page && m_page->mainFrame() && m_page->mainFrame()->isLocalFrame() && m_page->deprecatedLocalMainFrame()->view())
-            return handleMouseWheel(*m_page->deprecatedLocalMainFrame(), syntheticWheel) != WebInputEventResult::NotHandled;
+        if (handleMouseWheel(*m_page->deprecatedLocalMainFrame(), syntheticWheel) != WebInputEventResult::NotHandled)
+            return true;
+        if (!m_webSettings->wheelGesturesEnabled())
+            return false;
+
+        WebGestureEvent syntheticScrollBegin;
+        populateGestureScrollEventFromFling(WebInputEvent::GestureScrollBegin,
+            WebGestureDeviceTouchpad,
+            &syntheticScrollBegin);
+        syntheticScrollBegin.data.scrollBegin.deltaXHint = delta.width;
+        syntheticScrollBegin.data.scrollBegin.deltaYHint = delta.height;
+        syntheticScrollBegin.data.scrollBegin.inertial = true;
+        handleGestureEvent(syntheticScrollBegin);
+
+        WebGestureEvent syntheticScrollUpdate;
+        populateGestureScrollEventFromFling(WebInputEvent::GestureScrollUpdate,
+            WebGestureDeviceTouchpad,
+            &syntheticScrollUpdate);
+        syntheticScrollUpdate.data.scrollUpdate.deltaX = delta.width;
+        syntheticScrollUpdate.data.scrollUpdate.deltaY = delta.height;
+        syntheticScrollUpdate.data.scrollUpdate.velocityX = velocity.width;
+        syntheticScrollUpdate.data.scrollUpdate.velocityY = velocity.height;
+        syntheticScrollUpdate.data.scrollUpdate.inertial = true;
+        bool scrollUpdateHandled = handleGestureEvent(syntheticScrollUpdate) != WebInputEventResult::NotHandled;
+
+        WebGestureEvent syntheticScrollEnd;
+        populateGestureScrollEventFromFling(WebInputEvent::GestureScrollEnd,
+            WebGestureDeviceTouchpad,
+            &syntheticScrollUpdate);

[tdresser, 2016/03/29 19:16:03]

We're passing in syntheticGestureScrollUpdate here, instead of
syntheticGestureScrollEnd.

Probably means we need more thorough testing, too.

[dtapuska, 2016/03/29 19:42:05]

Ugh; this should fail in a debug build bot.

+        syntheticScrollEnd.data.scrollEnd.inertial = true;
+        handleGestureEvent(syntheticScrollEnd);
+        return scrollUpdateHandled;
     } else {
         WebGestureEvent syntheticGestureEvent;
-
-        syntheticGestureEvent.type = WebInputEvent::GestureScrollUpdate;
-        syntheticGestureEvent.timeStampSeconds = WTF::monotonicallyIncreasingTime();
+        populateGestureScrollEventFromFling(WebInputEvent::GestureScrollUpdate,
+            WebGestureDeviceTouchscreen,
+            &syntheticGestureEvent);
         syntheticGestureEvent.data.scrollUpdate.preventPropagation = true;
         syntheticGestureEvent.data.scrollUpdate.deltaX = delta.width;
         syntheticGestureEvent.data.scrollUpdate.deltaY = delta.height;
         syntheticGestureEvent.data.scrollUpdate.velocityX = velocity.width;
         syntheticGestureEvent.data.scrollUpdate.velocityY = velocity.height;
-        syntheticGestureEvent.x = m_positionOnFlingStart.x;
-        syntheticGestureEvent.y = m_positionOnFlingStart.y;
-        syntheticGestureEvent.globalX = m_globalPositionOnFlingStart.x;
-        syntheticGestureEvent.globalY = m_globalPositionOnFlingStart.y;
-        syntheticGestureEvent.modifiers = m_flingModifier;
-        syntheticGestureEvent.sourceDevice = WebGestureDeviceTouchscreen;
         syntheticGestureEvent.data.scrollUpdate.inertial = true;
 
-        if (m_page && m_page->mainFrame() && m_page->mainFrame()->isLocalFrame() && m_page->deprecatedLocalMainFrame()->view())
-            return handleGestureEvent(syntheticGestureEvent) != WebInputEventResult::NotHandled;
+        return handleGestureEvent(syntheticGestureEvent) != WebInputEventResult::NotHandled;
     }
-    return false;
 }
 
 WebInputEventResult WebViewImpl::handleGestureEvent(const WebGestureEvent& event)
 {
     if (!m_client)
         return WebInputEventResult::NotHandled;
 
     WebInputEventResult eventResult = WebInputEventResult::NotHandled;
     bool eventCancelled = false; // for disambiguation
 
@@ skipping 3864 matching lines @@
 {
     // TODO(oshima): Investigate if this should return the ScreenInfo's scale factor rather than
     // page's scale factor, which can be 1 in use-zoom-for-dsf mode.
     if (!page())
         return 1;
 
     return page()->deviceScaleFactor();
 }
 
 } // namespace blink