Home | History | Annotate | Download | only in gfx
      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_PLATFORM_FONT_WIN_H_
      6 #define UI_GFX_PLATFORM_FONT_WIN_H_
      7 
      8 #include <string>
      9 
     10 #include "base/compiler_specific.h"
     11 #include "base/memory/ref_counted.h"
     12 #include "ui/base/ui_export.h"
     13 #include "ui/gfx/platform_font.h"
     14 
     15 namespace gfx {
     16 
     17 class UI_EXPORT PlatformFontWin : public PlatformFont {
     18  public:
     19   PlatformFontWin();
     20   explicit PlatformFontWin(NativeFont native_font);
     21   PlatformFontWin(const std::string& font_name, int font_size);
     22 
     23   // Dialog units to pixels conversion.
     24   // See http://support.microsoft.com/kb/145994 for details.
     25   int horizontal_dlus_to_pixels(int dlus) const {
     26     return dlus * font_ref_->GetDluBaseX() / 4;
     27   }
     28   int vertical_dlus_to_pixels(int dlus)  const {
     29     return dlus * font_ref_->height() / 8;
     30   }
     31 
     32   // Callback that returns the minimum height that should be used for
     33   // gfx::Fonts. Optional. If not specified, the minimum font size is 0.
     34   typedef int (*GetMinimumFontSizeCallback)();
     35   static GetMinimumFontSizeCallback get_minimum_font_size_callback;
     36 
     37   // Callback that adjusts a LOGFONT to meet suitability requirements of the
     38   // embedding application. Optional. If not specified, no adjustments are
     39   // performed other than clamping to a minimum font height if
     40   // |get_minimum_font_size_callback| is specified.
     41   typedef void (*AdjustFontCallback)(LOGFONT* lf);
     42   static AdjustFontCallback adjust_font_callback;
     43 
     44   // Returns the font name for the system locale. Some fonts, particularly
     45   // East Asian fonts, have different names per locale. If the localized font
     46   // name could not be retrieved, returns GetFontName().
     47   std::string GetLocalizedFontName() const;
     48 
     49   // Returns a derived Font with the specified |style| and with height at most
     50   // |height|. If the height and style of the receiver already match, it is
     51   // returned. Otherwise, the returned Font will have the largest size such that
     52   // its height is less than or equal to |height| (since there may not exist a
     53   // size that matches the exact |height| specified).
     54   Font DeriveFontWithHeight(int height, int style);
     55 
     56   // Overridden from PlatformFont:
     57   virtual Font DeriveFont(int size_delta, int style) const OVERRIDE;
     58   virtual int GetHeight() const OVERRIDE;
     59   virtual int GetBaseline() const OVERRIDE;
     60   virtual int GetAverageCharacterWidth() const OVERRIDE;
     61   virtual int GetStringWidth(const base::string16& text) const OVERRIDE;
     62   virtual int GetExpectedTextWidth(int length) const OVERRIDE;
     63   virtual int GetStyle() const OVERRIDE;
     64   virtual std::string GetFontName() const OVERRIDE;
     65   virtual int GetFontSize() const OVERRIDE;
     66   virtual NativeFont GetNativeFont() const OVERRIDE;
     67 
     68  private:
     69   virtual ~PlatformFontWin() {}
     70 
     71   // Chrome text drawing bottoms out in the Windows GDI functions that take an
     72   // HFONT (an opaque handle into Windows). To avoid lots of GDI object
     73   // allocation and destruction, Font indirectly refers to the HFONT by way of
     74   // an HFontRef. That is, every Font has an HFontRef, which has an HFONT.
     75   //
     76   // HFontRef is reference counted. Upon deletion, it deletes the HFONT.
     77   // By making HFontRef maintain the reference to the HFONT, multiple
     78   // HFontRefs can share the same HFONT, and Font can provide value semantics.
     79   class HFontRef : public base::RefCounted<HFontRef> {
     80    public:
     81     // This constructor takes control of the HFONT, and will delete it when
     82     // the HFontRef is deleted.
     83     HFontRef(HFONT hfont,
     84              int font_size,
     85              int height,
     86              int baseline,
     87              int ave_char_width,
     88              int style);
     89 
     90     // Accessors
     91     HFONT hfont() const { return hfont_; }
     92     int height() const { return height_; }
     93     int baseline() const { return baseline_; }
     94     int ave_char_width() const { return ave_char_width_; }
     95     int style() const { return style_; }
     96     const std::string& font_name() const { return font_name_; }
     97     int font_size() const { return font_size_; }
     98     int requested_font_size() const { return requested_font_size_; }
     99 
    100     // Returns the average character width in dialog units.
    101     int GetDluBaseX();
    102 
    103    private:
    104     friend class base::RefCounted<HFontRef>;
    105 
    106     ~HFontRef();
    107 
    108     const HFONT hfont_;
    109     const int font_size_;
    110     const int height_;
    111     const int baseline_;
    112     const int ave_char_width_;
    113     const int style_;
    114     // Average character width in dialog units. This is queried lazily from the
    115     // system, with an initial value of -1 meaning it hasn't yet been queried.
    116     int dlu_base_x_;
    117     std::string font_name_;
    118 
    119     // If the requested font size is not possible for the font, |font_size_|
    120     // will be different than |requested_font_size_|. This is stored separately
    121     // so that code that increases the font size in a loop will not cause the
    122     // loop to get stuck on the same size.
    123     int requested_font_size_;
    124 
    125     DISALLOW_COPY_AND_ASSIGN(HFontRef);
    126   };
    127 
    128   // Initializes this object with a copy of the specified HFONT.
    129   void InitWithCopyOfHFONT(HFONT hfont);
    130 
    131   // Initializes this object with the specified font name and size.
    132   void InitWithFontNameAndSize(const std::string& font_name,
    133                                int font_size);
    134 
    135   // Returns the base font ref. This should ONLY be invoked on the
    136   // UI thread.
    137   static HFontRef* GetBaseFontRef();
    138 
    139   // Creates and returns a new HFONTRef from the specified HFONT.
    140   static HFontRef* CreateHFontRef(HFONT font);
    141 
    142   // Creates a new PlatformFontWin with the specified HFontRef. Used when
    143   // constructing a Font from a HFONT we don't want to copy.
    144   explicit PlatformFontWin(HFontRef* hfont_ref);
    145 
    146     // Reference to the base font all fonts are derived from.
    147   static HFontRef* base_font_ref_;
    148 
    149   // Indirect reference to the HFontRef, which references the underlying HFONT.
    150   scoped_refptr<HFontRef> font_ref_;
    151 
    152   DISALLOW_COPY_AND_ASSIGN(PlatformFontWin);
    153 };
    154 
    155 }  // namespace gfx
    156 
    157 #endif  // UI_GFX_PLATFORM_FONT_WIN_H_
    158 
    159