New AppListView Scroll Behavior.

ui/app_list/views/app_list_view.cc

Index: ui/app_list/views/app_list_view.cc
diff --git a/ui/app_list/views/app_list_view.cc b/ui/app_list/views/app_list_view.cc
index 48a26d9691f3574d9d65d1e07384ba03e8c7dac8..2db73ddfe8ada1982962a4cf4f0a279c6ca27a0d 100644
--- a/ui/app_list/views/app_list_view.cc
+++ b/ui/app_list/views/app_list_view.cc
@@ -35,6 +35,7 @@
 #include "ui/display/screen.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/insets.h"
+#include "ui/gfx/geometry/vector2d_conversions.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/path.h"
 #include "ui/gfx/skia_util.h"
@@ -72,6 +73,9 @@ constexpr int kAppListThresholdDenominator = 3;
 // state, measured in DIPs/event.
 constexpr int kAppListDragVelocityThreshold = 25;
 
+// The scroll offset in order to transition from PEEKING to FULLSCREEN
+constexpr int kAppListMinScrollToSwitchStates = 20;
+
 // The DIP distance from the bezel that a drag event must end within to transfer
 // the |app_list_state_|.
 constexpr int kAppListBezelMargin = 50;
@@ -664,6 +668,30 @@ void AppListView::OnMaximizeModeChanged(bool started) {
   }
 }
 
+bool AppListView::HandleScroll(const ui::Event* event) {
+  if (app_list_state_ != PEEKING)
+    return false;
+
+  switch (event->type()) {
+    case ui::ET_MOUSEWHEEL:
+      SetState(event->AsMouseWheelEvent()->y_offset() < 0 ? FULLSCREEN_ALL_APPS
+                                                          : CLOSED);
+      return true;
+    case ui::ET_SCROLL:
+    case ui::ET_SCROLL_FLING_START: {
+      int offset = event->AsScrollEvent()->y_offset();

[khmel, 2017/07/14 18:10:01]

 nit const int or even better inline

[newcomer, 2017/07/17 21:38:10]

Done.

+      if (abs(offset) > kAppListMinScrollToSwitchStates) {
+        SetState(offset < 0 ? FULLSCREEN_ALL_APPS : CLOSED);
+        return true;
+      }
+      break;
+    }
+    default:
+      break;
+  }
+  return false;
+}
+
 void AppListView::OnBeforeBubbleWidgetInit(views::Widget::InitParams* params,
                                            views::Widget* widget) const {
   if (!params->native_widget) {
@@ -697,6 +725,19 @@ void AppListView::GetWidgetHitTestMask(gfx::Path* mask) const {
   mask->addRect(gfx::RectToSkRect(GetBubbleFrameView()->GetContentsBounds()));
 }
 
+void AppListView::OnScrollEvent(ui::ScrollEvent* event) {
+  if (!is_fullscreen_app_list_enabled_)
+    return;
+
+  if (event->type() == ui::ET_SCROLL_FLING_CANCEL)
+    return;
+
+  if (HandleScroll(event)) {

[khmel, 2017/07/14 18:10:01]

nit: 
we prefer following style:
if (!HandleScroll(event))
  return;
....

[newcomer, 2017/07/17 21:38:10]

Done.

+    event->SetHandled();
+    event->StopPropagation();
+  }
+}
+
 void AppListView::OnMouseEvent(ui::MouseEvent* event) {
   if (!is_fullscreen_app_list_enabled_)
     return;
@@ -714,6 +755,11 @@ void AppListView::OnMouseEvent(ui::MouseEvent* event) {
       EndDrag(event->location());
       event->SetHandled();
       break;
+    case ui::ET_MOUSEWHEEL: {
+      if (HandleScroll(event))
+        event->SetHandled();
+      break;
+    }
     default:
       break;
   }
@@ -765,8 +811,8 @@ bool AppListView::AcceleratorPressed(const ui::Accelerator& accelerator) {
 void AppListView::Layout() {
   const gfx::Rect contents_bounds = GetContentsBounds();
 
-  // Make sure to layout |app_list_main_view_| and |speech_view_| at the center
-  // of the widget.
+  // Make sure to layout |app_list_main_view_| and |speech_view_| at the
+  // center of the widget.
   gfx::Rect centered_bounds = contents_bounds;
   centered_bounds.ClampToCenteredSize(gfx::Size(
       app_list_main_view_->contents_view()->GetDefaultContentsBounds().width(),
@@ -948,8 +994,9 @@ void AppListView::OnSpeechRecognitionStateChanged(
   } else {
     app_list_main_view_->SetVisible(true);
     // Refocus the search box. However, if the app list widget does not have
-    // focus, it means another window has already taken focus, and we *must not*
-    // focus the search box (or we would steal focus back into the app list).
+    // focus, it means another window has already taken focus, and we *must
+    // not* focus the search box (or we would steal focus back into the app
+    // list).
     if (GetWidget()->IsActive())
       search_box_view_->search_box()->RequestFocus();
   }