Respect the system ClearType setting in RenderTextWin.

ui/gfx/font_smoothing_win.cc

Index: ui/gfx/font_smoothing_win.cc
===================================================================
--- ui/gfx/font_smoothing_win.cc	(revision 0)
+++ ui/gfx/font_smoothing_win.cc	(revision 0)
@@ -0,0 +1,111 @@
+// 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/bind.h"
+#include "base/callback.h"
+#include "base/memory/singleton.h"
+#include "ui/base/win/singleton_hwnd.h"
+
+namespace {
+
+// Helper class to cache font smoothing settings and listen for WM_SETTINGCHANGE
+// notifications to re-query them from the system.
+class CachedFontSmoothingSettings {
+ public:
+  // Singleton getter.
+  static CachedFontSmoothingSettings* GetInstance();
+
+  // Returns the cached screen compatible DC or creates one if needed.
+  void GetFontSmoothingSettings(bool* smoothing_enabled,
+                                bool* cleartype_enabled);
+
+  // Listener for WM_SETTINGCHANGE notifications.
+  void OnWndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam);
+
+ private:
+  friend struct DefaultSingletonTraits<CachedFontSmoothingSettings>;
+
+  CachedFontSmoothingSettings();
+  ~CachedFontSmoothingSettings();
+
+  // Queries the font settings from the system.
+  void QueryFontSettings();
+
+  // Indicates whether the listener has been registered with the SingletonHwnd.
+  bool listener_registered_;
+
+  // 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);
+};
+
+CachedFontSmoothingSettings::CachedFontSmoothingSettings()
+    : listener_registered_(false),
+      smoothing_enabled_(false),
+      cleartype_enabled_(false) {
+}
+
+CachedFontSmoothingSettings::~CachedFontSmoothingSettings() {
+}
+
+// static
+CachedFontSmoothingSettings* CachedFontSmoothingSettings::GetInstance() {
+  return Singleton<CachedFontSmoothingSettings>::get();
+}
+
+void CachedFontSmoothingSettings::OnWndProc(HWND hwnd,
+                                            UINT message,
+                                            WPARAM wparam,
+                                            LPARAM lparam) {
+  if (message == WM_SETTINGCHANGE)
+    QueryFontSettings();
+}
+
+// Returns the cached screen compatible DC or creates one if needed.

[msw, 2012/02/15 00:33:16]

This comment just seems incorrect.

[asvitkine_google, 2012/02/15 15:10:44]

Oops. Fixed.

+void CachedFontSmoothingSettings::GetFontSmoothingSettings(
+    bool* smoothing_enabled,
+    bool* cleartype_enabled) {
+  if (!listener_registered_) {
+    ui::WndProcCallback callback =
+        base::Bind(&CachedFontSmoothingSettings::OnWndProc,
+                   base::Unretained(this));
+    ui::SingletonHwnd::GetInstance()->RegisterListener(callback);
+    QueryFontSettings();
+    listener_registered_ = true;

[msw, 2012/02/15 00:33:16]

Bad advice?: I don't expect re-entrance here, but you can help win a race by
putting this at the top of the block.

[asvitkine_google, 2012/02/15 15:10:44]

If folks are calling this on different threads, there's bigger problems than
this race. But since this is in ui, the assumption is that this will only be
called on the UI thread.

(I would add a DCHECK() for the thread affinity, but knowledge of browser
threads is in content/, which ui/ can't depend on.)

+  }
+  *smoothing_enabled = smoothing_enabled_;
+  *cleartype_enabled = cleartype_enabled_;
+}
+
+void CachedFontSmoothingSettings::QueryFontSettings() {
+  smoothing_enabled_ = false;
+  cleartype_enabled_ = false;
+
+  BOOL enabled;

[msw, 2012/02/15 00:33:16]

You should explicitly init this local.

[asvitkine_google, 2012/02/15 15:10:44]

Done.

+  if (SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &enabled, 0) && enabled) {

[msw, 2012/02/15 00:33:16]

Should we explicitly check for the BOOL to != 0?

[asvitkine_google, 2012/02/15 15:10:44]

If we treat it like 'bool', we shouldn't..

+    smoothing_enabled_ = true;
+
+    UINT smooth_type;

[msw, 2012/02/15 00:33:16]

You should explicitly init this local.

[asvitkine_google, 2012/02/15 15:10:44]

Done.

+    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);

[msw, 2012/02/15 00:33:16]

These params should each be on their own lines.

[asvitkine_google, 2012/02/15 15:10:44]

Done.

+}
+
+}  // namespace gfx