ui/gfx/font_render_params.h

   1 // Copyright 2014 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_RENDER_PARAMS_H_
   6 #define UI_GFX_FONT_RENDER_PARAMS_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "third_party/skia/include/core/SkFontHost.h"
  12 #include "ui/gfx/gfx_export.h"
  13
  14 namespace gfx {
  15
  16 // A collection of parameters describing how text should be rendered on Linux.
  17 struct GFX_EXPORT FontRenderParams {
  18   FontRenderParams();
  19   ~FontRenderParams();
  20
  21   // Level of hinting to be applied.
  22   enum Hinting {
  23     HINTING_NONE = 0,
  24     HINTING_SLIGHT,
  25     HINTING_MEDIUM,
  26     HINTING_FULL,
  27
  28     HINTING_MAX = HINTING_FULL,
  29   };
  30
  31   // Different subpixel orders to be used for subpixel rendering.
  32   enum SubpixelRendering {
  33     SUBPIXEL_RENDERING_NONE = 0,
  34     SUBPIXEL_RENDERING_RGB,
  35     SUBPIXEL_RENDERING_BGR,
  36     SUBPIXEL_RENDERING_VRGB,
  37     SUBPIXEL_RENDERING_VBGR,
  38
  39     SUBPIXEL_RENDERING_MAX = SUBPIXEL_RENDERING_VBGR,
  40   };
  41
  42   // Antialiasing (grayscale if |subpixel_rendering| is SUBPIXEL_RENDERING_NONE
  43   // and RGBA otherwise).
  44   bool antialiasing;
  45
  46   // Should subpixel positioning (i.e. fractional X positions for glyphs) be
  47   // used?
  48   // TODO(derat): Remove this; we don't set it in the browser and mostly ignore
  49   // it in Blink: http://crbug.com/396659
  50   bool subpixel_positioning;
  51
  52   // Should FreeType's autohinter be used (as opposed to Freetype's bytecode
  53   // interpreter, which uses fonts' own hinting instructions)?
  54   bool autohinter;
  55
  56   // Should embedded bitmaps in fonts should be used?
  57   bool use_bitmaps;
  58
  59   // Hinting level.
  60   Hinting hinting;
  61
  62   // Whether subpixel rendering should be used or not, and if so, the display's
  63   // subpixel order.
  64   SubpixelRendering subpixel_rendering;
  65
  66   static SkFontHost::LCDOrder SubpixelRenderingToSkiaLCDOrder(
  67       SubpixelRendering subpixel_rendering);
  68   static SkFontHost::LCDOrientation SubpixelRenderingToSkiaLCDOrientation(
  69       SubpixelRendering subpixel_rendering);
  70 };
  71
  72 // A query used to determine the appropriate FontRenderParams.
  73 struct GFX_EXPORT FontRenderParamsQuery {
  74   FontRenderParamsQuery();
  75   ~FontRenderParamsQuery();
  76
  77   bool is_empty() const {
  78     return families.empty() && pixel_size <= 0 && point_size <= 0 && style < 0;
  79   }
  80
  81   // Requested font families, or empty if unset.
  82   std::vector<std::string> families;
  83
  84   // Font size in pixels or points, or 0 if unset.
  85   int pixel_size;
  86   int point_size;
  87
  88   // gfx::Font::FontStyle bit field, or -1 if unset.
  89   int style;
  90
  91   // The device scale factor of the display, or 0 if unset.
  92   float device_scale_factor;
  93 };
  94
  95 // Returns the appropriate parameters for rendering the font described by
  96 // |query|. If |family_out| is non-NULL, it will be updated to contain the
  97 // recommended font family from |query.families|.
  98 GFX_EXPORT FontRenderParams GetFontRenderParams(
  99     const FontRenderParamsQuery& query,
 100     std::string* family_out);
 101
 102 // Clears GetFontRenderParams()'s cache. Intended to be called by tests that are
 103 // changing Fontconfig's configuration.
 104 // TODO(derat): This is only defined for Linux, but OS_LINUX doesn't seem to be
 105 // set when font_render_params_linux_unittest.cc includes this header. Figure
 106 // out what's going on here.
 107 GFX_EXPORT void ClearFontRenderParamsCacheForTest();
 108
 109 #if defined(OS_CHROMEOS)
 110 // Gets the device scale factor to query the FontRenderParams.
 111 float GetFontRenderParamsDeviceScaleFactor();
 112
 113 // Sets the device scale factor for FontRenderParams to decide
 114 // if it should enable subpixel positioning.
 115 GFX_EXPORT void SetFontRenderParamsDeviceScaleFactor(
 116     float device_scale_factor);
 117 #endif
 118
 119 }  // namespace gfx
 120
 121 #endif  // UI_GFX_FONT_RENDER_PARAMS_H_