Updates subpixel positioning and hinting when DSF is changed

ui/gfx/font_render_params.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_FONT_RENDER_PARAMS_H_
 #define UI_GFX_FONT_RENDER_PARAMS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 66 matching lines @@
   std::vector<std::string> families;
 
   // Font size in pixels or points, or 0 if unset.
   int pixel_size;
   int point_size;
 
   // gfx::Font::FontStyle bit field, or -1 if unset.
   int style;
 };
 
+// This class is used to modify the FontRenderParams based on the current
+// status of the system.
+class GFX_EXPORT FontRenderParamsRewriter {

[Daniel Erat, 2014/12/09 16:24:35]

i don't think i like this being a general interface, or the additional
complexity it adds to FontRenderParams -- it feels very chrome-os-specific. if
we need to do customization, why can't it be done within GetFontRenderParams()
(e.g. after adding necessary additional fields to FontRenderParamsQuery)?

[Jun Mukai, 2014/12/12 00:04:49]

Removed this class.

+ public:
+  // Gets/sets/removes the singleton instance. These are safe if instance is not
+  // set yet.
+  static FontRenderParamsRewriter* GetInstance();
+  static void SetInstance(FontRenderParamsRewriter* instance);
+  static void Shutdown();
+
+  virtual ~FontRenderParamsRewriter();
+
+  // Rewrite the FontRenderParams based on the current system configuration.
+  virtual void RewriteParams(FontRenderParams* params) = 0;
+};
+
 // Returns the appropriate parameters for rendering the font described by
 // |query|. If |family_out| is non-NULL, it will be updated to contain the
 // recommended font family from |query.families|.
-GFX_EXPORT FontRenderParams GetFontRenderParams(
-    const FontRenderParamsQuery& query,
-    std::string* family_out);
+// The return value should not be cached, because the result is already
+// rewritten by the current FontRenderParamsRewriter instance. To cache the
+// parameters, consider using GetSystemFontRenderParams() below and rewrite
+// the result by yourself.
+GFX_EXPORT FontRenderParams
+GetCurrentFontRenderParams(const FontRenderParamsQuery& query,
+                           std::string* family_out);
+
+// Returns the appropriate parameters for rendering the font described by
+// |query|. This is similar to GetCurrentFontRenderParams(), but the return
+// value is not yet rewritten by FontRenderParamsRewirter, hence it can be
+// cached.
+GFX_EXPORT FontRenderParams
+GetSystemFontRenderParams(const FontRenderParamsQuery& query,
+                          std::string* family_out);
 
 // Clears GetFontRenderParams()'s cache. Intended to be called by tests that are
 // changing Fontconfig's configuration.
 // TODO(derat): This is only defined for Linux, but OS_LINUX doesn't seem to be
 // set when font_render_params_linux_unittest.cc includes this header. Figure
 // out what's going on here.
 GFX_EXPORT void ClearFontRenderParamsCacheForTest();
 
 #if defined(OS_CHROMEOS)
 // Sets the device scale factor for FontRenderParams to decide
 // if it should enable subpixel positioning.
 GFX_EXPORT void SetFontRenderParamsDeviceScaleFactor(
     float device_scale_factor);
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_RENDER_PARAMS_H_