Broke out layout metric information from ViewsDelegate to LayoutProvider

ui/views/layout/layout_provider.h

+// Copyright 2017 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 UI_VIEWS_LAYOUT_LAYOUT_PROVIDER_H_
+#define UI_VIEWS_LAYOUT_LAYOUT_PROVIDER_H_
+
+#include "base/macros.h"
+#include "ui/gfx/geometry/insets.h"
+#include "ui/views/style/typography_provider.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+
+enum InsetsMetric {
+  // Embedders can extend this enum with additional values that are understood
+  // by the LayoutProvider implementation. Embedders define enum values from
+  // VIEWS_INSETS_END. Values named beginning with "INSETS_" represent the
+  // actual Insets: the rest are markers.
+  VIEWS_INSETS_START = 0,
+
+  // The margins around the contents area of a bubble (popover)-style dialog.
+  INSETS_BUBBLE_CONTENTS = VIEWS_INSETS_START,
+  // The margins around the button row of a dialog.
+  INSETS_DIALOG_BUTTON,
+  // The margins around the icon/title of a dialog.
+  INSETS_DIALOG_TITLE,
+  // The margins that should be applied around a panel GridLayout.
+  INSETS_PANEL,
+  // Padding to add to vector image buttons to increase their click and touch
+  // target size.
+  INSETS_VECTOR_IMAGE_BUTTON,
+
+  // Embedders must start Insets enum values from this value.
+  VIEWS_INSETS_END,
+
+  // All Insets enum values must be below this value.
+  VIEWS_INSETS_MAX = 0x1000
+};
+
+enum DistanceMetric {
+  // DistanceMetric enum values must always be greater than any InsetsMetric
+  // value. This allows the code to verify at runtime that arguments of the
+  // two types have not been interchanged.
+  VIEWS_DISTANCE_START = VIEWS_INSETS_MAX,
+
+  // The default padding to add on each side of a button's label.
+  DISTANCE_BUTTON_HORIZONTAL_PADDING = VIEWS_DISTANCE_START,
+  // The distance between a dialog's edge and the close button in the upper
+  // trailing corner.
+  DISTANCE_CLOSE_BUTTON_MARGIN,
+  // The default minimum width of a dialog button.
+  DISTANCE_DIALOG_BUTTON_MINIMUM_WIDTH,
+  // The spacing between a pair of related horizontal buttons, used for
+  // dialog layout.
+  DISTANCE_RELATED_BUTTON_HORIZONTAL,
+  // Horizontal spacing between controls that are logically related.
+  DISTANCE_RELATED_CONTROL_HORIZONTAL,
+  // The spacing between a pair of related vertical controls, used for
+  // dialog layout.
+  DISTANCE_RELATED_CONTROL_VERTICAL,
+
+  // Embedders must start DistanceMetric enum values from here.
+  VIEWS_DISTANCE_END
+};
+
+class VIEWS_EXPORT LayoutProvider {
+ public:
+  LayoutProvider();
+  virtual ~LayoutProvider();
+
+  // This should never return nullptr.
+  static LayoutProvider* Get();
+
+  // Returns the insets metric according to the given enumeration element.
+  virtual gfx::Insets GetInsetsMetric(int metric) const;
+
+  // Returns the distance metric between elements according to the given
+  // enumeration element.
+  virtual int GetDistanceMetric(int metric) const;
+
+  // Returns the TypographyProvider, used to configure text properties such as
+  // font, weight, color, size, and line height. Never null.
+  virtual const TypographyProvider& GetTypographyProvider() const;
+
+ private:
+  DefaultTypographyProvider typography_provider_;
+
+  DISALLOW_COPY_AND_ASSIGN(LayoutProvider);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_LAYOUT_LAYOUT_PROVIDER_H_