Respect the system ClearType setting in RenderTextWin.

ui/gfx/font_smoothing_win.cc

+// Copyright (c) 2012 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.
+
+#include "ui/gfx/font_smoothing_win.h"
+
+#include "base/memory/singleton.h"
+#include "ui/base/win/singleton_hwnd.h"
+
+namespace {
+
+// Helper class to cache font smoothing settings and listen for notifications
+// to re-query them from the system.
+class CachedFontSmoothingSettings : public ui::SingletonHwnd::Observer {
+ public:
+  static CachedFontSmoothingSettings* GetInstance();
+
+  // Returns the cached Windows font smoothing settings. Queries the settings
+  // via Windows APIs and begins listening for changes when called for the
+  // first time.
+  void GetFontSmoothingSettings(bool* smoothing_enabled,
+                                bool* cleartype_enabled);
+
+ private:
+  friend struct DefaultSingletonTraits<CachedFontSmoothingSettings>;
+
+  CachedFontSmoothingSettings();
+  virtual ~CachedFontSmoothingSettings();
+
+  // Listener for WM_SETTINGCHANGE notifications.
+  virtual void OnWndProc(HWND hwnd,
+                         UINT message,
+                         WPARAM wparam,
+                         LPARAM lparam) OVERRIDE;
+
+  // Queries the font settings from the system.
+  void QueryFontSettings();
+
+  // Indicates whether the MessagePumpObserver has been registered.
+  bool observer_added_;
+
+  // Indicates whether |smoothing_enabled_| and |cleartype_enabled_| are valid
+  // or need to be re-queried from the system.
+  bool need_to_query_settings_;
+
+  // Indicates that font smoothing is enabled.
+  bool smoothing_enabled_;
+
+  // Indicates that the ClearType font smoothing is enabled.
+  bool cleartype_enabled_;
+
+  DISALLOW_COPY_AND_ASSIGN(CachedFontSmoothingSettings);
+};
+
+// static
+CachedFontSmoothingSettings* CachedFontSmoothingSettings::GetInstance() {
+  return Singleton<CachedFontSmoothingSettings>::get();
+}
+
+void CachedFontSmoothingSettings::GetFontSmoothingSettings(
+    bool* smoothing_enabled,
+    bool* cleartype_enabled) {
+  // If cached settings are stale, query them from the OS.
+  if (need_to_query_settings_) {
+    QueryFontSettings();
+    need_to_query_settings_ = false;
+  }
+  if (!observer_added_) {
+    ui::SingletonHwnd::GetInstance()->AddObserver(this);
+    observer_added_ = true;
+  }
+  *smoothing_enabled = smoothing_enabled_;
+  *cleartype_enabled = cleartype_enabled_;
+}
+
+CachedFontSmoothingSettings::CachedFontSmoothingSettings()
+    : observer_added_(false),
+      need_to_query_settings_(true),
+      smoothing_enabled_(false),
+      cleartype_enabled_(false) {
+}
+
+CachedFontSmoothingSettings::~CachedFontSmoothingSettings() {
+  // Can't remove the SingletonHwnd observer here since SingletonHwnd may have
+  // been destroyed already (both singletons).
+}
+
+void CachedFontSmoothingSettings::OnWndProc(HWND hwnd,
+                                            UINT message,
+                                            WPARAM wparam,
+                                            LPARAM lparam) {
+  if (message == WM_SETTINGCHANGE)
+    need_to_query_settings_ = true;
+}
+
+void CachedFontSmoothingSettings::QueryFontSettings() {
+  smoothing_enabled_ = false;
+  cleartype_enabled_ = false;
+
+  BOOL enabled = false;
+  if (SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &enabled, 0) && enabled) {
+    smoothing_enabled_ = true;
+
+    UINT smooth_type = 0;
+    if (SystemParametersInfo(SPI_GETFONTSMOOTHINGTYPE, 0, &smooth_type, 0))
+      cleartype_enabled_ = (smooth_type == FE_FONTSMOOTHINGCLEARTYPE);
+  }
+}
+
+}  // namespace
+
+namespace gfx {
+
+void GetCachedFontSmoothingSettings(bool* smoothing_enabled,
+                                    bool* cleartype_enabled) {
+  CachedFontSmoothingSettings::GetInstance()->GetFontSmoothingSettings(
+      smoothing_enabled,
+      cleartype_enabled);
+}
+
+}  // namespace gfx