ui/gfx/font_smoothing_win.cc

   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 #include "ui/gfx/font_smoothing_win.h"
   6
   7 #include "base/memory/singleton.h"
   8 #include "ui/base/win/singleton_hwnd.h"
   9
  10 namespace {
  11
  12 // Helper class to cache font smoothing settings and listen for notifications
  13 // to re-query them from the system.
  14 class CachedFontSmoothingSettings : public ui::SingletonHwnd::Observer {
  15  public:
  16   static CachedFontSmoothingSettings* GetInstance();
  17
  18   // Returns the cached Windows font smoothing settings. Queries the settings
  19   // via Windows APIs and begins listening for changes when called for the
  20   // first time.
  21   void GetFontSmoothingSettings(bool* smoothing_enabled,
  22                                 bool* cleartype_enabled);
  23
  24  private:
  25   friend struct DefaultSingletonTraits<CachedFontSmoothingSettings>;
  26
  27   CachedFontSmoothingSettings();
  28   virtual ~CachedFontSmoothingSettings();
  29
  30   // Listener for WM_SETTINGCHANGE notifications.
  31   virtual void OnWndProc(HWND hwnd,
  32                          UINT message,
  33                          WPARAM wparam,
  34                          LPARAM lparam) OVERRIDE;
  35
  36   // Queries the font settings from the system.
  37   void QueryFontSettings();
  38
  39   // Indicates whether the MessagePumpObserver has been registered.
  40   bool observer_added_;
  41
  42   // Indicates whether |smoothing_enabled_| and |cleartype_enabled_| are valid
  43   // or need to be re-queried from the system.
  44   bool need_to_query_settings_;
  45
  46   // Indicates that font smoothing is enabled.
  47   bool smoothing_enabled_;
  48
  49   // Indicates that the ClearType font smoothing is enabled.
  50   bool cleartype_enabled_;
  51
  52   DISALLOW_COPY_AND_ASSIGN(CachedFontSmoothingSettings);
  53 };
  54
  55 // static
  56 CachedFontSmoothingSettings* CachedFontSmoothingSettings::GetInstance() {
  57   return Singleton<CachedFontSmoothingSettings>::get();
  58 }
  59
  60 void CachedFontSmoothingSettings::GetFontSmoothingSettings(
  61     bool* smoothing_enabled,
  62     bool* cleartype_enabled) {
  63   // If cached settings are stale, query them from the OS.
  64   if (need_to_query_settings_) {
  65     QueryFontSettings();
  66     need_to_query_settings_ = false;
  67   }
  68   if (!observer_added_) {
  69     ui::SingletonHwnd::GetInstance()->AddObserver(this);
  70     observer_added_ = true;
  71   }
  72   *smoothing_enabled = smoothing_enabled_;
  73   *cleartype_enabled = cleartype_enabled_;
  74 }
  75
  76 CachedFontSmoothingSettings::CachedFontSmoothingSettings()
  77     : observer_added_(false),
  78       need_to_query_settings_(true),
  79       smoothing_enabled_(false),
  80       cleartype_enabled_(false) {
  81 }
  82
  83 CachedFontSmoothingSettings::~CachedFontSmoothingSettings() {
  84   // Can't remove the SingletonHwnd observer here since SingletonHwnd may have
  85   // been destroyed already (both singletons).
  86 }
  87
  88 void CachedFontSmoothingSettings::OnWndProc(HWND hwnd,
  89                                             UINT message,
  90                                             WPARAM wparam,
  91                                             LPARAM lparam) {
  92   if (message == WM_SETTINGCHANGE)
  93     need_to_query_settings_ = true;
  94 }
  95
  96 void CachedFontSmoothingSettings::QueryFontSettings() {
  97   smoothing_enabled_ = false;
  98   cleartype_enabled_ = false;
  99
 100   BOOL enabled = false;
 101   if (SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &enabled, 0) && enabled) {
 102     smoothing_enabled_ = true;
 103
 104     UINT smooth_type = 0;
 105     if (SystemParametersInfo(SPI_GETFONTSMOOTHINGTYPE, 0, &smooth_type, 0))
 106       cleartype_enabled_ = (smooth_type == FE_FONTSMOOTHINGCLEARTYPE);
 107   }
 108 }
 109
 110 }  // namespace
 111
 112 namespace gfx {
 113
 114 void GetCachedFontSmoothingSettings(bool* smoothing_enabled,
 115                                     bool* cleartype_enabled) {
 116   CachedFontSmoothingSettings::GetInstance()->GetFontSmoothingSettings(
 117       smoothing_enabled,
 118       cleartype_enabled);
 119 }
 120
 121 }  // namespace gfx