Makes FontList light-weighted introducing FontListImpl.

Like Font class has scoped_refptr<PlatformFont>, makes FontList have scoped_refptr<FontListImpl>.  FontListImpl is almost the same as the old FontList and implements all functionalities.

There are two major benefits with this CL.
1. Copying a FontList to another FontList is very quick.  It just copies a scoped_refptr.
2. Calculated font metrics are shared among all FontList instances which refer to the same FontListImpl.

In addition, this CL may fix Issue 340396.  I don't fully understand the cause yet, but it seems that copying the object in a ctor is causing the issue (It's a little tricky, but I thought it should be okay).  This CL doesn't copy the object.  So I think this CL may fix the issue.

BUG=340396
TEST=Run ui_unittests, views_unittests and unit_tests.

Review URL: https://codereview.chromium.org/148773007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249976 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 123 insertions, 0 deletions

diff --git a/ui/gfx/font_list_impl.h b/ui/gfx/font_list_impl.h
new file mode 100644
index 0000000..94bb330
--- /dev/null
+++ b/ui/gfx/font_list_impl.h
@@ -0,0 +1,123 @@
+// Copyright 2014 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_GFX_FONT_LIST_IMPL_H_
+#define UI_GFX_FONT_LIST_IMPL_H_
+
+#include <string>
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+
+namespace gfx {
+
+class Font;
+
+// FontListImpl is designed to provide the implementation of FontList and
+// intended to be used only from FontList.  You must not use this class
+// directly.
+//
+// FontListImpl represents a list of fonts either in the form of Font vector or
+// in the form of a string representing font names, styles, and size.
+//
+// FontListImpl could be initialized either way without conversion to the other
+// form. The conversion to the other form is done only when asked to get the
+// other form.
+//
+// For the format of font description string, see font_list.h for details.
+class FontListImpl : public base::RefCounted<FontListImpl> {
+ public:
+  // Creates a font list from a string representing font names, styles, and
+  // size.
+  explicit FontListImpl(const std::string& font_description_string);
+
+  // Creates a font list from font names, styles and size.
+  FontListImpl(const std::vector<std::string>& font_names,
+               int font_style,
+               int font_size);
+
+  // Creates a font list from a Font vector.
+  // All fonts in this vector should have the same style and size.
+  explicit FontListImpl(const std::vector<Font>& fonts);
+
+  // Creates a font list from a Font.
+  explicit FontListImpl(const Font& font);
+
+  // Returns a new FontListImpl with the same font names but resized and the
+  // given style. |size_delta| is the size in pixels to add to the current font
+  // size. |font_style| specifies the new style, which is a bitmask of the
+  // values: Font::BOLD, Font::ITALIC and Font::UNDERLINE.
+  FontListImpl* Derive(int size_delta, int font_style) const;
+
+  // Returns the height of this font list, which is max(ascent) + max(descent)
+  // for all the fonts in the font list.
+  int GetHeight() const;
+
+  // Returns the baseline of this font list, which is max(baseline) for all the
+  // fonts in the font list.
+  int GetBaseline() const;
+
+  // Returns the cap height of this font list.
+  // Currently returns the cap height of the primary font.
+  int GetCapHeight() const;
+
+  // Returns the expected number of horizontal pixels needed to display the
+  // specified length of characters. Call GetStringWidth() to retrieve the
+  // actual number.
+  int GetExpectedTextWidth(int length) const;
+
+  // Returns the |gfx::Font::FontStyle| style flags for this font list.
+  int GetFontStyle() const;
+
+  // Returns a string representing font names, styles, and size. If the
+  // FontListImpl is initialized by a vector of Font, use the first font's style
+  // and size for the description.
+  const std::string& GetFontDescriptionString() const;
+
+  // Returns the font size in pixels.
+  int GetFontSize() const;
+
+  // Returns the Font vector.
+  const std::vector<Font>& GetFonts() const;
+
+  // Returns the first font in the list.
+  const Font& GetPrimaryFont() const;
+
+ private:
+  friend class base::RefCounted<FontListImpl>;
+
+  ~FontListImpl();
+
+  // Extracts common font height and baseline into |common_height_| and
+  // |common_baseline_|.
+  void CacheCommonFontHeightAndBaseline() const;
+
+  // Extracts font style and size into |font_style_| and |font_size_|.
+  void CacheFontStyleAndSize() const;
+
+  // A vector of Font. If FontListImpl is constructed with font description
+  // string, |fonts_| is not initialized during construction. Instead, it is
+  // computed lazily when user asked to get the font vector.
+  mutable std::vector<Font> fonts_;
+
+  // A string representing font names, styles, and sizes.
+  // Please refer to the comments before class declaration for details on string
+  // format.
+  // If FontListImpl is constructed with a vector of font,
+  // |font_description_string_| is not initialized during construction. Instead,
+  // it is computed lazily when user asked to get the font description string.
+  mutable std::string font_description_string_;
+
+  // The cached common height and baseline of the fonts in the font list.
+  mutable int common_height_;
+  mutable int common_baseline_;
+
+  // Cached font style and size.
+  mutable int font_style_;
+  mutable int font_size_;
+};
+
+}  // namespace gfx
+
+#endif  // UI_GFX_FONT_LIST_IMPL_H_