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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef UI_GFX_FONT_H_
      6 #define UI_GFX_FONT_H_
      7 
      8 #include <string>
      9 
     10 #include "base/memory/ref_counted.h"
     11 #include "base/strings/string16.h"
     12 #include "ui/gfx/gfx_export.h"
     13 #include "ui/gfx/native_widget_types.h"
     14 
     15 namespace gfx {
     16 
     17 class PlatformFont;
     18 
     19 // Font provides a wrapper around an underlying font. Copy and assignment
     20 // operators are explicitly allowed, and cheap.
     21 //
     22 // Figure of font metrics:
     23 //   +--------+-------------------+------------------+
     24 //   |        |                   | internal leading |
     25 //   |        | ascent (baseline) +------------------+
     26 //   | height |                   | cap height       |
     27 //   |        |-------------------+------------------+
     28 //   |        | descent (height - baseline)          |
     29 //   +--------+--------------------------------------+
     30 class GFX_EXPORT Font {
     31  public:
     32   // The following constants indicate the font style.
     33   enum FontStyle {
     34     NORMAL = 0,
     35     BOLD = 1,
     36     ITALIC = 2,
     37     UNDERLINE = 4,
     38   };
     39 
     40   // Creates a font with the default name and style.
     41   Font();
     42 
     43   // Creates a font that is a clone of another font object.
     44   Font(const Font& other);
     45   gfx::Font& operator=(const Font& other);
     46 
     47   // Creates a font from the specified native font.
     48   explicit Font(NativeFont native_font);
     49 
     50   // Constructs a Font object with the specified PlatformFont object. The Font
     51   // object takes ownership of the PlatformFont object.
     52   explicit Font(PlatformFont* platform_font);
     53 
     54   // Creates a font with the specified name in UTF-8 and size in pixels.
     55   Font(const std::string& font_name, int font_size);
     56 
     57   ~Font();
     58 
     59   // Returns a new Font derived from the existing font.
     60   // |size_deta| is the size in pixels to add to the current font. For example,
     61   // a value of 5 results in a font 5 pixels bigger than this font.
     62   Font DeriveFont(int size_delta) const;
     63 
     64   // Returns a new Font derived from the existing font.
     65   // |size_delta| is the size in pixels to add to the current font. See the
     66   // single argument version of this method for an example.
     67   // The style parameter specifies the new style for the font, and is a
     68   // bitmask of the values: BOLD, ITALIC and UNDERLINE.
     69   Font DeriveFont(int size_delta, int style) const;
     70 
     71   // Returns the number of vertical pixels needed to display characters from
     72   // the specified font.  This may include some leading, i.e. height may be
     73   // greater than just ascent + descent.  Specifically, the Windows and Mac
     74   // implementations include leading and the Linux one does not.  This may
     75   // need to be revisited in the future.
     76   int GetHeight() const;
     77 
     78   // Returns the baseline, or ascent, of the font.
     79   int GetBaseline() const;
     80 
     81   // Returns the cap height of the font.
     82   int GetCapHeight() const;
     83 
     84   // Returns the average character width for the font.
     85   int GetAverageCharacterWidth() const;
     86 
     87   // Returns the number of horizontal pixels needed to display the specified
     88   // string.
     89   int GetStringWidth(const base::string16& text) const;
     90 
     91   // Returns the expected number of horizontal pixels needed to display the
     92   // specified length of characters. Call GetStringWidth() to retrieve the
     93   // actual number.
     94   int GetExpectedTextWidth(int length) const;
     95 
     96   // Returns the style of the font.
     97   int GetStyle() const;
     98 
     99   // Returns the specified font name in UTF-8.
    100   std::string GetFontName() const;
    101 
    102   // Returns the actually used font name in UTF-8.
    103   std::string GetActualFontNameForTesting() const;
    104 
    105   // Returns the font size in pixels.
    106   int GetFontSize() const;
    107 
    108   // Returns the native font handle.
    109   // Lifetime lore:
    110   // Windows: This handle is owned by the Font object, and should not be
    111   //          destroyed by the caller.
    112   // Mac:     The object is owned by the system and should not be released.
    113   // Gtk:     This handle is created on demand, and must be freed by calling
    114   //          pango_font_description_free() when the caller is done using it or
    115   //          by using ScopedPangoFontDescription.
    116   NativeFont GetNativeFont() const;
    117 
    118   // Raw access to the underlying platform font implementation. Can be
    119   // static_cast to a known implementation type if needed.
    120   PlatformFont* platform_font() const { return platform_font_.get(); }
    121 
    122  private:
    123   // Wrapped platform font implementation.
    124   scoped_refptr<PlatformFont> platform_font_;
    125 };
    126 
    127 }  // namespace gfx
    128 
    129 #endif  // UI_GFX_FONT_H_
    130