Support FontRenderParams on Win; fix RenderTextHarfBuzz.

ui/gfx/font_render_params_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_render_params.h"
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/singleton.h"
+#include "ui/gfx/win/singleton_hwnd.h"
+
+namespace gfx {
+
+namespace {
+
+// Caches font render params and updates them on system notifications.
+class CachedFontRenderParams : public gfx::SingletonHwnd::Observer {
+ public:
+  static CachedFontRenderParams* GetInstance() {
+    return Singleton<CachedFontRenderParams>::get();
+  }
+
+  const FontRenderParams& GetParams() {
+    if (params_)
+      return *params_;
+
+    params_.reset(new FontRenderParams());
+    params_->antialiasing = false;
+    params_->subpixel_positioning = false;
+    params_->subpixel_rendering = FontRenderParams::SUBPIXEL_RENDERING_NONE;
+
+    BOOL enabled = false;
+    if (SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &enabled, 0) && enabled) {
+      params_->antialiasing = true;
+      params_->subpixel_positioning = true;
+
+      UINT type = 0;
+      if (SystemParametersInfo(SPI_GETFONTSMOOTHINGTYPE, 0, &type, 0) &&
+          type == FE_FONTSMOOTHINGCLEARTYPE) {
+        params_->subpixel_rendering = FontRenderParams::SUBPIXEL_RENDERING_RGB;
+      }
+    }
+    gfx::SingletonHwnd::GetInstance()->AddObserver(this);
+    return *params_;
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<CachedFontRenderParams>;
+
+  CachedFontRenderParams() {}
+  virtual ~CachedFontRenderParams() {
+    // Can't remove the SingletonHwnd observer here since SingletonHwnd may have
+    // been destroyed already (both singletons).
+  }
+
+  virtual void OnWndProc(HWND hwnd,
+                         UINT message,
+                         WPARAM wparam,
+                         LPARAM lparam) OVERRIDE {
+    if (message == WM_SETTINGCHANGE) {
+      params_.reset();
+      gfx::SingletonHwnd::GetInstance()->RemoveObserver(this);

[Alexei Svitkine (slow), 2014/07/14 15:00:53]

Wait, what if the settings change again? Wouldn't the observer have been removed
and we wouldn't see it?

[ckocagil, 2014/07/14 16:13:47]

There's no need to invalidate the already invalidated |params_| (i.e when
params_ is NULL). GetParams() adds the observer back, so the observer is alive
whenever |params_| is valid.

[Alexei Svitkine (slow), 2014/07/14 16:32:21]

Ah, got it!

+    }
+  }
+
+  scoped_ptr<FontRenderParams> params_;
+
+  DISALLOW_COPY_AND_ASSIGN(CachedFontRenderParams);
+};
+
+}  // namespace
+
+const FontRenderParams& GetDefaultFontRenderParams() {
+  return CachedFontRenderParams::GetInstance()->GetParams();
+}
+
+const FontRenderParams& GetDefaultWebKitFontRenderParams() {
+  return GetDefaultFontRenderParams();
+}
+
+}  // namespace gfx