Rework gfx::Font by moving platform-specific code into inner classes....

gfx/platform_font.h

+// Copyright (c) 2010 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 GFX_PLATFORM_FONT_
+#define GFX_PLATFORM_FONT_
+#pragma once
+
+#include <string>
+
+#include "base/ref_counted.h"
+#include "gfx/native_widget_types.h"
+
+namespace gfx {
+
+class Font;
+
+class PlatformFont : public base::RefCounted<PlatformFont> {
+ public:
+  // Create an appropriate PlatformFont implementation.
+  static PlatformFont* CreateDefault();
+  static PlatformFont* CreateFromFont(const Font& other);
+  static PlatformFont* CreateFromNativeFont(NativeFont native_font);
+  static PlatformFont* CreateFromNameAndSize(const std::wstring& font_name,
+                                             int font_size);
+
+  // Returns a new Font derived from the existing font.
+  // size_delta is the size to add to the current font. See the single
+  // argument version of this method for an example.
+  // The style parameter specifies the new style for the font, and is a
+  // bitmask of the values: BOLD, ITALIC and UNDERLINED.
+  virtual Font DeriveFont(int size_delta, int style) const = 0;
+
+  // Returns the number of vertical pixels needed to display characters from
+  // the specified font.  This may include some leading, i.e. height may be
+  // greater than just ascent + descent.  Specifically, the Windows and Mac
+  // implementations include leading and the Linux one does not.  This may
+  // need to be revisited in the future.
+  virtual int GetHeight() const = 0;
+
+  // Returns the baseline, or ascent, of the font.
+  virtual int GetBaseline() const = 0;
+
+  // Returns the average character width for the font.
+  virtual int GetAverageCharacterWidth() const = 0;
+
+  // Returns the number of horizontal pixels needed to display the specified
+  // string.
+  virtual int GetStringWidth(const std::wstring& text) const = 0;
+
+  // Returns the expected number of horizontal pixels needed to display the
+  // specified length of characters. Call GetStringWidth() to retrieve the
+  // actual number.
+  virtual int GetExpectedTextWidth(int length) const = 0;
+
+  // Returns the style of the font.
+  virtual int GetStyle() const = 0;
+
+  // Returns the font name.
+  virtual const std::wstring& GetFontName() const = 0;
+
+  // Returns the font size in pixels.
+  virtual int GetFontSize() const = 0;
+
+  // Returns the native font handle.
+  virtual NativeFont GetNativeFont() const = 0;
+
+ protected:
+  virtual ~PlatformFont() {}
+
+ private:
+  friend class base::RefCounted<PlatformFont>;
+};
+
+}  // namespace gfx
+
+#endif  // GFX_PLATFORM_FONT_
+