[ash-md] Adds support for gesture to move selection in overview mode

ash/common/wm/overview/window_selector.cc

 // Copyright 2013 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 "ash/common/wm/overview/window_selector.h"
 
 #include <algorithm>
 #include <functional>
 #include <set>
 #include <utility>
@@ skipping 236 matching lines @@
   std::sort(root_windows.begin(), root_windows.end(),
             [](const WmWindow* a, const WmWindow* b) {
               // Since we don't know if windows are vertically or horizontally
               // oriented we use both x and y position. This may be confusing
               // if you have 3 or more monitors which are not strictly
               // horizontal or vertical but that case is not yet supported.
               return (a->GetBoundsInScreen().x() + a->GetBoundsInScreen().y()) <
                      (b->GetBoundsInScreen().x() + b->GetBoundsInScreen().y());
             });
 
+  bool first_grid = true;
   for (WmWindow* root : root_windows) {
     // Observed switchable containers for newly created windows on all root
     // windows.
     for (size_t i = 0; i < wm::kSwitchableWindowContainerIdsLength; ++i) {
       WmWindow* container =
           root->GetChildByShellWindowId(wm::kSwitchableWindowContainerIds[i]);
       container->AddObserver(this);
       observed_windows_.insert(container);
     }
 
     // Hide the callout widgets for panels. It is safe to call this for
     // root windows that don't contain any panel windows.
     PanelLayoutManager::Get(root)->SetShowCalloutWidgets(false);
 
     std::unique_ptr<WindowGrid> grid(new WindowGrid(root, windows, this));
     if (grid->empty())
       continue;
+    if (first_grid) {

[tdanderson, 2017/02/10 16:05:19]

I'm not 100% convinced this is the right thing to do, actually - what's your
reasoning for skipping the first item? Is this to be consistent with Alt+Tab?
There may be a user expectation (especially from an a11y point of view) to be
able to cycle through the MRU beginning with the current window.

[varkha, 2017/02/10 17:34:30]

Yes, I'll take this offline.

+      grid->set_skip_first(true);
+      first_grid = false;
+    }
     num_items_ += grid->size();
     grid_list_.push_back(std::move(grid));
   }
 
   {
     // The calls to WindowGrid::PrepareForOverview() and CreateTextFilter(...)
     // requires some LayoutManagers (ie PanelLayoutManager) to perform layouts
     // so that windows are correctly visible and properly animated in overview
     // mode. Otherwise these layouts should be suppressed during overview mode
     // so they don't conflict with overview mode animations. The
@@ skipping 113 matching lines @@
     selected_grid_index_--;
     // If the grid which became empty was the one with the selected window, we
     // need to select a window on the newly selected grid.
     if (selected_grid_index_ == index - 1)
       Move(LEFT, true);
   }
   if (grid_list_.empty())
     CancelSelection();
 }
 
+void WindowSelector::IncrementSelection(int increment) {
+  const Direction direction =
+      increment > 0 ? WindowSelector::RIGHT : WindowSelector::LEFT;
+  for (int step = 0; step < abs(increment); ++step)
+    Move(direction, true);
+}
+
+bool WindowSelector::AcceptSelection() {
+  if (!grid_list_[selected_grid_index_]->is_selecting())
+    return false;
+  SelectWindow(grid_list_[selected_grid_index_]->SelectedWindow());
+  return true;
+}
+
 void WindowSelector::SelectWindow(WindowSelectorItem* item) {
   WmWindow* window = item->GetWindow();
   std::vector<WmWindow*> window_list =
       WmShell::Get()->mru_window_tracker()->BuildMruWindowList();
   if (!window_list.empty()) {
     // Record UMA_WINDOW_OVERVIEW_ACTIVE_WINDOW_CHANGED if the user is selecting
     // a window other than the window that was active prior to entering overview
     // mode (i.e., the window at the front of the MRU list).
     if (window_list[0] != window) {
       WmShell::Get()->RecordUserMetricsAction(
@@ skipping 246 matching lines @@
   for (size_t i = 0; i <= grid_list_.size() &&
                      grid_list_[selected_grid_index_]->Move(direction, animate);
        i++) {
     selected_grid_index_ =
         (selected_grid_index_ + display_direction + grid_list_.size()) %
         grid_list_.size();
   }
 }
 
 }  // namespace ash