commit d17d074f2bffbcb132d87b07eab256555f5bccf3
author lanwei <lanwei@chromium.org> Mon Dec 01 18:58:52 2014
committer Commit bot <commit-bot@chromium.org> Mon Dec 01 18:59:07 2014
tree 0922a12a02d296e8eae32edd6215b5027c6d0dbc
parent ed2f91a2995c4e64dc9564f914df0f171662ee49

Enable raw pixel scrolling for wheel events in web contents

We now support raw pixel scroll with touch pad on high resolution Chromebook.
The web content should be scrolled as smoothly as from touch screen even
after we do pinch-zoom. We changed wheel events to be scaled by page scale
same as gesture events.

BUG=344614

Review URL: https://codereview.chromium.org/613043003

Cr-Commit-Position: refs/heads/master@{#306218}

cc/trees/layer_tree_host_impl.cc

diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 7593965..ea30d85 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2551,10 +2551,14 @@
   return actual_viewport_end_point - viewport_point;
 }
 
-static gfx::Vector2dF ScrollLayerWithLocalDelta(LayerImpl* layer_impl,
-    const gfx::Vector2dF& local_delta) {
+static gfx::Vector2dF ScrollLayerWithLocalDelta(
+    LayerImpl* layer_impl,
+    const gfx::Vector2dF& local_delta,
+    float page_scale_factor) {
   gfx::Vector2dF previous_delta(layer_impl->ScrollDelta());
-  layer_impl->ScrollBy(local_delta);
+  gfx::Vector2dF delta = local_delta;
+  delta.Scale(1.f / page_scale_factor);
+  layer_impl->ScrollBy(delta);
   return layer_impl->ScrollDelta() - previous_delta;
 }
 
@@ -2632,7 +2636,8 @@
     // Gesture events need to be transformed from viewport coordinates to local
     // layer coordinates so that the scrolling contents exactly follow the
     // user's finger. In contrast, wheel events represent a fixed amount of
-    // scrolling so we can just apply them directly.
+    // scrolling so we can just apply them directly, but the page scale factor
+    // is applied to the scroll delta.
     if (!wheel_scrolling_) {
       float scale_from_viewport_to_screen_space = device_scale_factor_;
       applied_delta =
@@ -2640,7 +2645,8 @@
                                             scale_from_viewport_to_screen_space,
                                             viewport_point, pending_delta);
     } else {
-      applied_delta = ScrollLayerWithLocalDelta(layer_impl, pending_delta);
+      applied_delta = ScrollLayerWithLocalDelta(
+          layer_impl, pending_delta, active_tree_->total_page_scale_factor());
     }
 
     const float kEpsilon = 0.1f;
@@ -2762,7 +2768,8 @@
 
     gfx::Vector2dF delta = gfx::Vector2dF(0.f, page);
 
-    gfx::Vector2dF applied_delta = ScrollLayerWithLocalDelta(layer_impl, delta);
+    gfx::Vector2dF applied_delta =
+        ScrollLayerWithLocalDelta(layer_impl, delta, 1.f);
 
     if (!applied_delta.IsZero()) {
       client_->SetNeedsCommitOnImplThread();