Part 1 of the arrow button implementation

This CL is the first part of code to implement the arrow button in
the overflow bubble view.
See more details from the below doc link:
https://docs.google.com/document/d/1dO4H_4T6ttWFc75nCNi2Uh18k-3_M8-eOHcfMTcNwd0/edit?usp=sharing

Bug: 918024
Change-Id: I6f8bf2dfe4871e2457947468696834adbd5d264d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1686782
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676253}

ash/resources/vector_icons/BUILD.gn

@@ -105,6 +105,8 @@ aggregate_vector_icons("ash_vector_icons") {
     "notification_timer.icon",
     "overview_window_close.icon",
     "overview_drop_target_plus.icon",
+    "overflow_shelf_left.icon",
+    "overflow_shelf_right.icon",
     "palette_action_capture_region.icon",
     "palette_action_capture_screen.icon",
     "palette_action_create_note.icon",

ash/resources/vector_icons/overflow_shelf_left.icon

+// Copyright 2019 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.
+
+CANVAS_DIMENSIONS, 20,
+MOVE_TO, 13.34f, 13.83f,
+LINE_TO, 12.07f, 15,
+LINE_TO, 6.67f, 10,
+R_LINE_TO, 5.4f, -5,
+R_LINE_TO, 1.27f, 1.18f,
+LINE_TO, 9.22f, 10,
+CLOSE

ash/resources/vector_icons/overflow_shelf_right.icon

+// Copyright 2019 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.
+
+CANVAS_DIMENSIONS, 20,
+MOVE_TO, 6.67f, 13.83f,
+LINE_TO, 10.79f, 10,
+LINE_TO, 6.67f, 6.18f,
+LINE_TO, 7.94f, 5,
+R_LINE_TO, 5.4f, 5,
+R_LINE_TO, -5.4f, 5,
+CLOSE

ash/shelf/overflow_bubble_view.h

@@ -17,6 +17,21 @@ class ShelfView;
 // Exports to access this class from OverflowBubbleViewTestAPI.
 class ASH_EXPORT OverflowBubbleView : public ShelfBubble {
  public:
+  enum LayoutStrategy {
+    // The arrow buttons are not shown. It means that there is enough space to
+    // accommodate all of shelf icons.
+    NOT_SHOW_ARROW_BUTTON,
+
+    // Only the left arrow button is shown.
+    SHOW_LEFT_ARROW_BUTTON,
+
+    // Only the right arrow button is shown.
+    SHOW_RIGHT_ARROW_BUTTON,
+
+    // Both buttons are shown.
+    SHOW_BUTTONS
+  };
+
   // |anchor| is the overflow button on the main shelf. |shelf_view| is the
   // ShelfView containing the overflow items.
   OverflowBubbleView(ShelfView* shelf_view,
@@ -36,7 +51,10 @@ class ASH_EXPORT OverflowBubbleView : public ShelfBubble {
   gfx::Rect GetBubbleBounds() override;
   bool CanActivate() const override;
 
-  ShelfView* shelf_view() { return shelf_view_; }
+  ShelfView* shelf_view() { return shelf_container_view_->shelf_view(); }
+  View* left_arrow() { return left_arrow_; }
+  View* right_arrow() { return right_arrow_; }
+  LayoutStrategy layout_strategy() { return layout_strategy_; }
 
   // ShelfBubble:
   bool ShouldCloseOnPressDown() override;
@@ -45,6 +63,56 @@ class ASH_EXPORT OverflowBubbleView : public ShelfBubble {
  private:
   friend class OverflowBubbleViewTestAPI;
 
+  class ScrollArrowView : public views::View {
+   public:
+    enum ArrowType { LEFT, RIGHT };
+    ScrollArrowView(ArrowType arrow_type, bool is_horizontal_alignment);
+    ~ScrollArrowView() override = default;
+
+    // Overridden from views::View:
+    void OnPaint(gfx::Canvas* canvas) override;
+    const char* GetClassName() const override;
+
+   private:
+    ArrowType arrow_type_;
+    bool is_horizontal_alignment_;
+  };
+
+  class OverflowShelfContainerView : public views::View {
+   public:
+    explicit OverflowShelfContainerView(ShelfView* shelf_view);
+    ~OverflowShelfContainerView() override = default;
+
+    void Initialize();
+
+    // Translate |shelf_view_| by |offset|.
+    void TranslateShelfView(const gfx::Vector2d& offset);
+
+    // views::View:
+    gfx::Size CalculatePreferredSize() const override;
+    void ChildPreferredSizeChanged(views::View* child) override;
+    void Layout() override;
+    const char* GetClassName() const override;
+
+    ShelfView* shelf_view() { return shelf_view_; }
+
+   private:
+    ShelfView* shelf_view_;
+  };
+
+  // Returns the maximum scroll distance.
+  int CalculateScrollUpperBound() const;
+
+  // Updates the overflow bubble view's layout strategy after scrolling by the
+  // distance of |scroll|. Returns the adapted scroll offset.
+  int CalculateLayoutStrategyAfterScroll(int scroll);
+
+  // Ensures that the width of |bubble_bounds| (if it is not horizontally
+  // aligned, adjust |bubble_bounds|'s height) is the multiple of the sum
+  // between kShelfButtonSize and kShelfButtonSpacing. It helps that all of
+  // shelf icons are fully visible.
+  void AdjustToEnsureIconsFullyVisible(gfx::Rect* bubble_bounds) const;
+
   // views::View:
   gfx::Size CalculatePreferredSize() const override;
   void Layout() override;
@@ -55,8 +123,14 @@ class ASH_EXPORT OverflowBubbleView : public ShelfBubble {
   // ui::EventHandler:
   void OnScrollEvent(ui::ScrollEvent* event) override;
 
+  mutable LayoutStrategy layout_strategy_;
+
+  // Child views Owned by views hierarchy.
+  ScrollArrowView* left_arrow_ = nullptr;
+  ScrollArrowView* right_arrow_ = nullptr;
+  OverflowShelfContainerView* shelf_container_view_ = nullptr;
+
   Shelf* shelf_;
-  ShelfView* shelf_view_;  // Owned by views hierarchy.
   gfx::Vector2d scroll_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(OverflowBubbleView);

ash/shelf/overflow_bubble_view_test_api.cc

@@ -16,7 +16,7 @@ OverflowBubbleViewTestAPI::OverflowBubbleViewTestAPI(
 OverflowBubbleViewTestAPI::~OverflowBubbleViewTestAPI() = default;
 
 gfx::Size OverflowBubbleViewTestAPI::GetContentsSize() {
-  return bubble_view_->shelf_view_->GetPreferredSize();
+  return bubble_view_->shelf_view()->GetPreferredSize();
 }
 
 void OverflowBubbleViewTestAPI::ScrollByXOffset(int x_offset) {

ash/shelf/shelf_view_unittest.cc

@@ -1654,12 +1654,13 @@ TEST_F(ShelfViewTest, CheckDragInsertBoundsOfScrolledOverflowBubble) {
 
   ASSERT_TRUE(shelf_view_->IsShowingOverflowBubble());
 
-  ShelfViewTestAPI test_for_overflow_view(
-      test_api_->overflow_bubble()->bubble_view()->shelf_view());
+  ShelfViewTestAPI test_for_overflow_view(bubble_view->shelf_view());
   const ShelfView* overflow_shelf_view = shelf_view_->overflow_shelf();
   int first_index = overflow_shelf_view->first_visible_index();
   int last_index = overflow_shelf_view->last_visible_index();
 
+  views::View* left_arrow_button = bubble_view->left_arrow();
+  views::View* right_arrow_button = bubble_view->right_arrow();
   ShelfAppButton* first_button = test_for_overflow_view.GetButton(first_index);
   ShelfAppButton* last_button = test_for_overflow_view.GetButton(last_index);
   gfx::Point first_point = first_button->GetBoundsInScreen().CenterPoint();
@@ -1669,6 +1670,20 @@ TEST_F(ShelfViewTest, CheckDragInsertBoundsOfScrolledOverflowBubble) {
   EXPECT_TRUE(drag_reinsert_bounds.Contains(first_point));
   EXPECT_FALSE(drag_reinsert_bounds.Contains(last_point));
 
+  // Verfies that at the beginning, the left button is invisible while the right
+  // button shows.
+  EXPECT_EQ(OverflowBubbleView::SHOW_RIGHT_ARROW_BUTTON,
+            bubble_view->layout_strategy());
+  EXPECT_FALSE(left_arrow_button->GetVisible());
+  EXPECT_TRUE(right_arrow_button->GetVisible());
+
+  // Scroll the overflow shelf view a little bit. Then verifies that both arrow
+  // buttons show.
+  bubble_view_api.ScrollByXOffset(item_width);
+  EXPECT_EQ(OverflowBubbleView::SHOW_BUTTONS, bubble_view->layout_strategy());
+  EXPECT_TRUE(left_arrow_button->GetVisible());
+  EXPECT_TRUE(right_arrow_button->GetVisible());
+
   // Scroll sufficiently to completely show last item.
   bubble_view_api.ScrollByXOffset(bubble_view_api.GetContentsSize().width() -
                                   bubble_view->GetContentsBounds().width());
@@ -1678,6 +1693,13 @@ TEST_F(ShelfViewTest, CheckDragInsertBoundsOfScrolledOverflowBubble) {
   last_point = last_button->GetBoundsInScreen().CenterPoint();
   EXPECT_FALSE(drag_reinsert_bounds.Contains(first_point));
   EXPECT_TRUE(drag_reinsert_bounds.Contains(last_point));
+
+  // Verifies that when the last item shows, the right arrow button is invisible
+  // while the left one shows.
+  EXPECT_EQ(OverflowBubbleView::SHOW_LEFT_ARROW_BUTTON,
+            bubble_view->layout_strategy());
+  EXPECT_TRUE(left_arrow_button->GetVisible());
+  EXPECT_FALSE(right_arrow_button->GetVisible());
 }
 
 // Check the drag insertion bounds of shelf view in multi monitor environment.