Increase tolerance for touch-snapping near the screen edges

ash/wm/workspace/workspace_window_resizer.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 "ash/wm/workspace/workspace_window_resizer.h"
 
 #include <algorithm>
 #include <cmath>
 #include <utility>
 #include <vector>
@@ skipping 980 matching lines @@
     if (i != map.rend())
       parent->StackChildBelow(i->second, window);
   }
 }
 
 SnapType WorkspaceWindowResizer::GetSnapType(
     const gfx::Point& location) const {
   // TODO: this likely only wants total display area, not the area of a single
   // display.
   gfx::Rect area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window()));
+  if (details_.source == aura::client::WINDOW_MOVE_SOURCE_TOUCH) {
+    // Increase tolerance for touch-snapping near the screen edges. This is only
+    // necessary when the work area left or right edge is same as screen edge.
+    gfx::Rect display_bounds(ScreenAsh::GetDisplayBoundsInParent(window()));
+    int inset_left = 0;
+    if (area.x() == display_bounds.x())
+      inset_left = kScreenEdgeInsetForTouchResize;
+    int inset_right = 0;
+    if (area.right() == display_bounds.right())
+      inset_right = kScreenEdgeInsetForTouchResize;
+    area.Inset(inset_left, 0, inset_right, 0);
+  }
   if (location.x() <= area.x())
     return SNAP_LEFT;
   if (location.x() >= area.right() - 1)
     return SNAP_RIGHT;
   return SNAP_NONE;
 }
 
 void WorkspaceWindowResizer::SetDraggedWindowDocked(bool should_dock) {
   if (should_dock &&
       dock_layout_->GetAlignmentOfWindow(window()) != DOCKED_ALIGNMENT_NONE) {
     if (!dock_layout_->is_dragged_window_docked())
       dock_layout_->DockDraggedWindow(window());
   } else {
     if (dock_layout_->is_dragged_window_docked())
       dock_layout_->UndockDraggedWindow();
   }
 }
 
 }  // namespace internal
 }  // namespace ash