[ash-md] Makes Wi-Fi header row sticky when network list is scrolled

ash/common/system/tray/header_list_scroll_view.h

+// Copyright (c) 2016 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.
+
+#ifndef ASH_COMMON_SYSTEM_TRAY_HEADER_LIST_SCROLL_VIEW_H_
+#define ASH_COMMON_SYSTEM_TRAY_HEADER_LIST_SCROLL_VIEW_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "ui/views/controls/button/button.h"
+#include "ui/views/view.h"
+
+namespace ash {
+
+// A view that is used as ScrollView contents. It supports designating some of
+// the children as sticky header rows. The sticky header rows are not scrolled
+// above the top of the visible viewport and are stacked above other children.
+// To indicate that a child is a sticky header row use set_id(kHeaderRowId).

[sadrul, 2016/11/01 18:50:16]

Where is kHeaderRowId() defined?

[varkha, 2016/11/02 02:03:21]

Acknowledged.

+class HeaderListScrollView : public views::View {
+ public:
+  HeaderListScrollView();
+  ~HeaderListScrollView() override;
+
+  // Sets |view| as a sticky header view for all items with the same group.
+  void SetHeaderView(views::View* child);

[sadrul, 2016/11/01 18:50:16]

This seems odd with the class level description. There can be more than one
sticky headers, right? What does this do? Do you mean 'AddHeaderView()'? If the
user should explicitly add the header views, I guess that means the special
view-id is not necessary?

[varkha, 2016/11/02 02:03:21]

Acknowledged.

+
+ protected:
+  // views::View.
+  void Layout() override;
+  void OnBoundsChanged(const gfx::Rect& previous_bounds) override;
+  void ViewHierarchyChanged(
+      const ViewHierarchyChangedDetails& details) override;
+  const char* GetClassName() const override;
+
+ private:
+  class HeaderListLayout;
+
+  class Header {
+   public:
+    explicit Header(views::View* header)
+        : view(header), offset(header->bounds().y()) {}
+    bool operator==(views::View* other) { return view == other; }
+
+    views::View* view;
+    int offset;
+  };
+
+  // Sets decorations on a header row to indicate whether it is sticky.
+  static void ShowHeaderSticky(views::View* header, bool show_sticky);
+
+  // Adjusts y-position of header rows allowing one or two rows to stick to the
+  // top of the visible viewport.
+  void ScrollChildren();
+
+  // Header child views that stick to the top of visible viewport when scrolled.
+  std::vector<Header> headers_;
+  HeaderListLayout* header_list_layout_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(HeaderListScrollView);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_TRAY_HEADER_LIST_SCROLL_VIEW_H_