Added common layout framework for system menu rows.

ash/common/system/tray/tray_popup_layout_factory.cc

+// Copyright 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.
+
+#include "ash/common/system/tray/tray_popup_layout_factory.h"
+
+#include "ash/common/material_design/material_design_controller.h"
+#include "ash/common/system/tray/three_view_layout.h"
+#include "ash/common/system/tray/tray_constants.h"
+#include "ui/views/controls/button/label_button.h"
+#include "ui/views/layout/box_layout.h"
+
+namespace ash {
+
+namespace {
+
+// Creates a layout manager that positions Views vertically. The Views will be
+// stretched horizontally and centered vertically.
+std::unique_ptr<views::LayoutManager> CreateDefaultCenterLayoutManager() {
+  // TODO(bruthig): Use constants instead of magic numbers.
+  views::BoxLayout* box_layout =
+      new views::BoxLayout(views::BoxLayout::kVertical, 4, 8, 4);
+  box_layout->set_main_axis_alignment(
+      views::BoxLayout::MAIN_AXIS_ALIGNMENT_CENTER);
+  box_layout->set_cross_axis_alignment(
+      views::BoxLayout::CROSS_AXIS_ALIGNMENT_STRETCH);
+  return std::unique_ptr<views::LayoutManager>(box_layout);
+}
+
+// Creates a layout manager that positions Views horizontally. The Views will be
+// centered along the horizontal and vertical axis.
+std::unique_ptr<views::LayoutManager> CreateDefaultEndsLayoutManager() {
+  views::BoxLayout* box_layout =
+      new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, 0);
+  box_layout->set_main_axis_alignment(
+      views::BoxLayout::MAIN_AXIS_ALIGNMENT_CENTER);
+  box_layout->set_cross_axis_alignment(
+      views::BoxLayout::CROSS_AXIS_ALIGNMENT_CENTER);
+  return std::unique_ptr<views::LayoutManager>(box_layout);
+}
+
+}  // namespace
+
+ThreeViewLayout* TrayPopupLayoutFactory::InstallDefaultLayout(
+    views::View* host) {
+  ThreeViewLayout* layout = new ThreeViewLayout(0 /* padding_between_items */);
+
+  // TODO(bruthig): views::BoxLayout::SetFlexForView() fails on a DCHECK() if it
+  // has not yet been installed on a View. Evaluate whether this is necessary or
+  // if it can be removed. This would allow us to drop the |host| parameter from
+  // this function.
+  host->SetLayoutManager(layout);
+
+  layout->SetInsets(gfx::Insets(0, GetTrayConstant(TRAY_POPUP_ITEM_LEFT_INSET),
+                                0,
+                                GetTrayConstant(TRAY_POPUP_ITEM_RIGHT_INSET)));
+  layout->SetMinCrossAxisSize(GetTrayConstant(TRAY_POPUP_ITEM_HEIGHT));
+
+  ConfigureDefaultLayout(layout, ThreeViewLayout::Container::START);
+  ConfigureDefaultLayout(layout, ThreeViewLayout::Container::CENTER);
+  ConfigureDefaultLayout(layout, ThreeViewLayout::Container::END);
+
+  return layout;
+}
+
+void TrayPopupLayoutFactory::ConfigureDefaultLayout(
+    ThreeViewLayout* layout,
+    ThreeViewLayout::Container container) {
+  switch (container) {
+    case ThreeViewLayout::Container::START:
+      layout->SetLayoutManager(ThreeViewLayout::Container::START,
+                               CreateDefaultEndsLayoutManager());
+      layout->SetMinSize(
+          ThreeViewLayout::Container::START,
+          gfx::Size(GetTrayConstant(TRAY_POPUP_ITEM_MIN_START_WIDTH), 0));
+      break;
+    case ThreeViewLayout::Container::CENTER:
+      layout->SetLayoutManager(ThreeViewLayout::Container::CENTER,
+                               CreateDefaultCenterLayoutManager());
+      layout->SetFlexForContainer(ThreeViewLayout::Container::CENTER, 1.f);
+      break;
+    case ThreeViewLayout::Container::END:
+      layout->SetLayoutManager(ThreeViewLayout::Container::END,
+                               CreateDefaultEndsLayoutManager());
+      layout->SetMinSize(
+          ThreeViewLayout::Container::END,
+          gfx::Size(GetTrayConstant(TRAY_POPUP_ITEM_MIN_END_WIDTH), 0));
+      break;
+  }
+}
+
+}  // namespace ash