Give Alt+Tab shield rounded corners when it's narrower than the screen.

ash/common/wm/window_cycle_list.cc

 // Copyright 2014 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/window_cycle_list.h"
 
 #include <list>
 #include <map>
 
 #include "ash/common/wm/mru_window_tracker.h"
@@ skipping 17 matching lines @@
 #include "ui/views/widget/widget.h"
 #include "ui/views/widget/widget_delegate.h"
 #include "ui/wm/core/visibility_controller.h"
 
 namespace ash {
 
 namespace {
 
 bool g_disable_initial_delay = false;
 
+// Used for the highlight view and the shield (black background).
+constexpr float kBackgroundCornerRadius = 4.f;
+
 // Returns the window immediately below |window| in the current container.
 WmWindow* GetWindowBelow(WmWindow* window) {
   WmWindow* parent = window->GetParent();
   if (!parent)
     return nullptr;
   const WmWindow::Windows children = parent->GetChildren();
   auto iter = std::find(children.begin(), children.end(), window);
   CHECK(*iter == window);
   return (iter != children.begin()) ? *(iter - 1) : nullptr;
 }
@@ skipping 225 matching lines @@
     mirror_container_->SetPaintToLayer(true);
     mirror_container_->layer()->SetFillsBoundsOpaquely(false);
 
     for (WmWindow* window : windows) {
       // |mirror_container_| owns |view|.
       views::View* view = new WindowPreviewView(window);
       window_view_map_[window] = view;
       mirror_container_->AddChildView(view);
     }
 
-    const float kHighlightCornerRadius = 4;
     // The background needs to be painted to fill the layer, not the View,
     // because the layer animates bounds changes but the View's bounds change
     // immediately.
     highlight_view_->set_background(new LayerFillBackgroundPainter(
         base::WrapUnique(views::Painter::CreateRoundRectWith1PxBorderPainter(
             SkColorSetA(SK_ColorWHITE, 0x4D), SkColorSetA(SK_ColorWHITE, 0x33),
-            kHighlightCornerRadius))));
+            kBackgroundCornerRadius))));
     highlight_view_->SetPaintToLayer(true);
     highlight_view_->layer()->SetFillsBoundsOpaquely(false);
 
     AddChildView(highlight_view_);
     AddChildView(mirror_container_);
   }
 
   ~WindowCycleView() override {}
 
   void SetTargetWindow(WmWindow* target) {
@@ skipping 87 matching lines @@
     }
   }
 
   void OnMouseCaptureLost() override {
     WmShell::Get()->window_cycle_controller()->StopCycling();
   }
 
   void OnPaintBackground(gfx::Canvas* canvas) override {
     // We can't set a bg on the mirror container itself because the highlight
     // view needs to be on top of the bg but behind the target windows.
-    canvas->FillRect(mirror_container_->bounds(),
-                     SkColorSetA(SK_ColorBLACK, 0xE6));
+    const gfx::RectF shield_bounds(mirror_container_->bounds());
+    SkPaint paint;
+    paint.setColor(SkColorSetA(SK_ColorBLACK, 0xE6));
+    paint.setStyle(SkPaint::kFill_Style);
+    float corner_radius = 0.f;
+    if (shield_bounds.width() < width()) {
+      paint.setAntiAlias(true);
+      corner_radius = kBackgroundCornerRadius;
+    }
+    canvas->DrawRoundRect(shield_bounds, corner_radius, paint);
   }
 
   View* GetInitiallyFocusedView() override {
     return window_view_map_[target_window_];
   }
 
   WmWindow* target_window() { return target_window_; }
 
  private:
   std::map<WmWindow*, views::View*> window_view_map_;
@@ skipping 218 matching lines @@
   widget->Init(params);
 
   screen_observer_.Add(display::Screen::GetScreen());
   widget->Show();
   widget->SetCapture(cycle_view_);
   widget->set_auto_release_capture(false);
   cycle_ui_widget_ = widget;
 }
 
 }  // namespace ash