ui/gfx/platform_font_win.h

   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/gtest_prod_util.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "ui/gfx/gfx_export.h"
  14 #include "ui/gfx/platform_font.h"
  15
  16 struct IDWriteFactory;
  17
  18 namespace gfx {
  19
  20 class GFX_EXPORT PlatformFontWin : public PlatformFont {
  21  public:
  22   PlatformFontWin();
  23   explicit PlatformFontWin(NativeFont native_font);
  24   PlatformFontWin(const std::string& font_name, int font_size);
  25
  26   // Dialog units to pixels conversion.
  27   // See http://support.microsoft.com/kb/145994 for details.
  28   int horizontal_dlus_to_pixels(int dlus) const {
  29     return dlus * font_ref_->GetDluBaseX() / 4;
  30   }
  31   int vertical_dlus_to_pixels(int dlus)  const {
  32     return dlus * font_ref_->height() / 8;
  33   }
  34
  35   // Callback that returns the minimum height that should be used for
  36   // gfx::Fonts. Optional. If not specified, the minimum font size is 0.
  37   typedef int (*GetMinimumFontSizeCallback)();
  38   static GetMinimumFontSizeCallback get_minimum_font_size_callback;
  39
  40   // Callback that adjusts a LOGFONT to meet suitability requirements of the
  41   // embedding application. Optional. If not specified, no adjustments are
  42   // performed other than clamping to a minimum font height if
  43   // |get_minimum_font_size_callback| is specified.
  44   typedef void (*AdjustFontCallback)(LOGFONT* lf);
  45   static AdjustFontCallback adjust_font_callback;
  46
  47   // Returns the font name for the system locale. Some fonts, particularly
  48   // East Asian fonts, have different names per locale. If the localized font
  49   // name could not be retrieved, returns GetFontName().
  50   std::string GetLocalizedFontName() const;
  51
  52   // Returns a derived Font with the specified |style| and maximum |height|.
  53   // The returned Font will be the largest font size with a height <= |height|,
  54   // since a size with the exact specified |height| may not necessarily exist.
  55   // GetMinimumFontSize() may impose a font size that is taller than |height|.
  56   Font DeriveFontWithHeight(int height, int style);
  57
  58   // Overridden from PlatformFont:
  59   Font DeriveFont(int size_delta, int style) const override;
  60   int GetHeight() const override;
  61   int GetBaseline() const override;
  62   int GetCapHeight() const override;
  63   int GetExpectedTextWidth(int length) const override;
  64   int GetStyle() const override;
  65   std::string GetFontName() const override;
  66   std::string GetActualFontNameForTesting() const override;
  67   int GetFontSize() const override;
  68   const FontRenderParams& GetFontRenderParams() override;
  69   NativeFont GetNativeFont() const override;
  70
  71   // Called once during initialization if we should be retrieving font metrics
  72   // from skia and DirectWrite.
  73   static void SetDirectWriteFactory(IDWriteFactory* factory);
  74
  75   // Returns the GDI metrics for the font passed in.
  76   static void GetTextMetricsForFont(HDC hdc,
  77                                     HFONT font,
  78                                     TEXTMETRIC* text_metrics);
  79
  80   // Returns the size of the font based on the font information passed in.
  81   static int GetFontSize(const LOGFONT& font_info);
  82
  83  private:
  84   FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_UniscribeFallback);
  85   FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, Metrics_SkiaVersusGDI);
  86   FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, DirectWriteFontSubstitution);
  87
  88   ~PlatformFontWin() override;
  89
  90   // Chrome text drawing bottoms out in the Windows GDI functions that take an
  91   // HFONT (an opaque handle into Windows). To avoid lots of GDI object
  92   // allocation and destruction, Font indirectly refers to the HFONT by way of
  93   // an HFontRef. That is, every Font has an HFontRef, which has an HFONT.
  94   //
  95   // HFontRef is reference counted. Upon deletion, it deletes the HFONT.
  96   // By making HFontRef maintain the reference to the HFONT, multiple
  97   // HFontRefs can share the same HFONT, and Font can provide value semantics.
  98   class GFX_EXPORT HFontRef : public base::RefCounted<HFontRef> {
  99    public:
 100     // This constructor takes control of the HFONT, and will delete it when
 101     // the HFontRef is deleted.
 102     HFontRef(HFONT hfont,
 103              int font_size,
 104              int height,
 105              int baseline,
 106              int cap_height,
 107              int ave_char_width,
 108              int style);
 109
 110     // Accessors
 111     HFONT hfont() const { return hfont_; }
 112     int height() const { return height_; }
 113     int baseline() const { return baseline_; }
 114     int cap_height() const { return cap_height_; }
 115     int ave_char_width() const { return ave_char_width_; }
 116     int style() const { return style_; }
 117     const std::string& font_name() const { return font_name_; }
 118     int font_size() const { return font_size_; }
 119     int requested_font_size() const { return requested_font_size_; }
 120
 121     // Returns the average character width in dialog units.
 122     int GetDluBaseX();
 123
 124     // Helper to return the average character width using the text extent
 125     // technique mentioned here. http://support.microsoft.com/kb/125681.
 126     static int GetAverageCharWidthInDialogUnits(HFONT gdi_font);
 127
 128    private:
 129     friend class base::RefCounted<HFontRef>;
 130     FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_UniscribeFallback);
 131     FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, Metrics_SkiaVersusGDI);
 132     FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, DirectWriteFontSubstitution);
 133
 134     ~HFontRef();
 135
 136     const HFONT hfont_;
 137     const int font_size_;
 138     const int height_;
 139     const int baseline_;
 140     const int cap_height_;
 141     const int ave_char_width_;
 142     const int style_;
 143     // Average character width in dialog units. This is queried lazily from the
 144     // system, with an initial value of -1 meaning it hasn't yet been queried.
 145     int dlu_base_x_;
 146     std::string font_name_;
 147
 148     // If the requested font size is not possible for the font, |font_size_|
 149     // will be different than |requested_font_size_|. This is stored separately
 150     // so that code that increases the font size in a loop will not cause the
 151     // loop to get stuck on the same size.
 152     int requested_font_size_;
 153
 154     DISALLOW_COPY_AND_ASSIGN(HFontRef);
 155   };
 156
 157   // Initializes this object with a copy of the specified HFONT.
 158   void InitWithCopyOfHFONT(HFONT hfont);
 159
 160   // Initializes this object with the specified font name and size.
 161   void InitWithFontNameAndSize(const std::string& font_name,
 162                                int font_size);
 163
 164   // Returns the base font ref. This should ONLY be invoked on the
 165   // UI thread.
 166   static HFontRef* GetBaseFontRef();
 167
 168   // Creates and returns a new HFontRef from the specified HFONT.
 169   static HFontRef* CreateHFontRef(HFONT font);
 170
 171   // Creates and returns a new HFontRef from the specified HFONT. Uses provided
 172   // |font_metrics| instead of calculating new one.
 173   static HFontRef* CreateHFontRefFromGDI(HFONT font,
 174                                          const TEXTMETRIC& font_metrics);
 175
 176   // Creates and returns a new HFontRef from the specified HFONT using metrics
 177   // from skia. Currently this is only used if we use DirectWrite for font
 178   // metrics.
 179   // |gdi_font| : Handle to the GDI font created via CreateFontIndirect.
 180   // |font_metrics| : The GDI font metrics retrieved via the GetTextMetrics
 181   // API. This is currently used to calculate the correct height of the font
 182   // in case we get a font created with a positive height.
 183   // A positive height represents the cell height (ascent + descent).
 184   // A negative height represents the character Em height which is cell
 185   // height minus the internal leading value.
 186   static PlatformFontWin::HFontRef* CreateHFontRefFromSkia(
 187       HFONT gdi_font,
 188       const TEXTMETRIC& font_metrics);
 189
 190   // Creates a new PlatformFontWin with the specified HFontRef. Used when
 191   // constructing a Font from a HFONT we don't want to copy.
 192   explicit PlatformFontWin(HFontRef* hfont_ref);
 193
 194     // Reference to the base font all fonts are derived from.
 195   static HFontRef* base_font_ref_;
 196
 197   // Indirect reference to the HFontRef, which references the underlying HFONT.
 198   scoped_refptr<HFontRef> font_ref_;
 199
 200   // Pointer to the global IDWriteFactory interface.
 201   static IDWriteFactory* direct_write_factory_;
 202
 203   DISALLOW_COPY_AND_ASSIGN(PlatformFontWin);
 204 };
 205
 206 }  // namespace gfx
 207
 208 #endif  // UI_GFX_PLATFORM_FONT_WIN_H_