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