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