Split default font settings into webkit and browser settings having separate flags to enable subpixel positioning.

Allows separately specifying subpixel positioning for webkit and browser UI. Adds a flag in about:flags to enable subpixel positioning in web pages.

BUG=145020
TEST=Run chrome with Webkit text subpixel positioning flag enabled and navigate to http://jsfiddle.net/ALd5F/21/, span widths should be non-integer values.


Review URL: https://chromiumcodereview.appspot.com/10916055

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154767 0039d316-1c4b-4281-b951-d872f2087c98

9 files changed, 57 insertions, 16 deletions

diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index ab32b02..4f430da 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -6056,6 +6056,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_DISABLE_ACCELERATED_VIDEO_DECODE_DESCRIPTION" desc="Description for the flag to disable accelerated video decode where available.">
         Disables hardware-accelerated video decode where available.
       </message>
+      <message name="IDS_FLAGS_ENABLE_WEBKIT_TEXT_SUBPIXEL_POSITIONING_NAME" desc="Name of the flag to enable subpixel text positioning on web pages.">
+        Enable webpage text sub-pixel positioning.
+      </message>
+      <message name="IDS_FLAGS_ENABLE_WEBKIT_TEXT_SUBPIXEL_POSITIONING_DESCRIPTION" desc="Description for the flag to set when subpixel text positioning is enabled on web pages.">
+        Allows text glyphs on web pages to have X positions which aren't snapped to the pixel grid.
+      </message>
 
       <!-- Crashes -->
       <message name="IDS_CRASHES_TITLE" desc="Title for the chrome://crashes page.">
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 00e35b1..6661e87 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -702,6 +702,13 @@ const Experiment kExperiments[] = {
     MULTI_VALUE_TYPE(kTouchOptimizedUIChoices)
   },
   {
+    "enable-webkit-text-subpixel-positioning",
+    IDS_FLAGS_ENABLE_WEBKIT_TEXT_SUBPIXEL_POSITIONING_NAME,
+    IDS_FLAGS_ENABLE_WEBKIT_TEXT_SUBPIXEL_POSITIONING_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(switches::kEnableWebkitTextSubpixelPositioning)
+  },
+  {
     "enable-touch-events",
     IDS_ENABLE_TOUCH_EVENTS_NAME,
     IDS_ENABLE_TOUCH_EVENTS_DESCRIPTION,
diff --git a/chrome/browser/renderer_preferences_util.cc b/chrome/browser/renderer_preferences_util.cc
index bb29ee2..f782b43 100644
--- a/chrome/browser/renderer_preferences_util.cc
+++ b/chrome/browser/renderer_preferences_util.cc
@@ -106,7 +106,7 @@ void UpdateFromSystemSettings(
 #endif
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
-  const gfx::FontRenderParams& params = gfx::GetDefaultFontRenderParams();
+  const gfx::FontRenderParams& params = gfx::GetDefaultWebKitFontRenderParams();
   prefs->should_antialias_text = params.antialiasing;
   prefs->use_subpixel_positioning = params.subpixel_positioning;
   prefs->hinting = GetRendererPreferencesHintingEnum(params.hinting);
diff --git a/content/browser/renderer_host/render_sandbox_host_linux.cc b/content/browser/renderer_host/render_sandbox_host_linux.cc
index 1ef8e71..0249836 100644
--- a/content/browser/renderer_host/render_sandbox_host_linux.cc
+++ b/content/browser/renderer_host/render_sandbox_host_linux.cc
@@ -76,7 +76,7 @@ class SandboxIPCProcess  {
         // positioning, so just pass false here to avoid the issue.
         false
 #else
-        gfx::GetDefaultFontRenderParams().subpixel_positioning
+        gfx::GetDefaultWebKitFontRenderParams().subpixel_positioning
 #endif
         );
   }
diff --git a/ui/base/ui_base_switches.cc b/ui/base/ui_base_switches.cc
index 50d9709..545189e 100644
--- a/ui/base/ui_base_switches.cc
+++ b/ui/base/ui_base_switches.cc
@@ -14,9 +14,10 @@ const char kEnableBezelTouch[] = "enable-bezel-touch";
 const char kDisableScalingInImageSkiaOperations[] =
     "disable-scaling-in-image-skia-operations";
 
-// Let text glyphs have X-positions that aren't snapped to the pixel grid.
-const char kEnableTextSubpixelPositioning[] =
-    "enable-text-subpixel-positioning";
+// Let text glyphs have X-positions that aren't snapped to the pixel grid in
+// the browser UI.
+const char kEnableBrowserTextSubpixelPositioning[] =
+    "enable-browser-text-subpixel-positioning";
 
 // Enable touch screen calibration.
 const char kEnableTouchCalibration[] = "enable-touch-calibration";
@@ -27,6 +28,11 @@ const char kEnableTouchEvents[] = "enable-touch-events";
 // Enables the Views textfield on Windows.
 const char kEnableViewsTextfield[] = "enable-views-textfield";
 
+// Enable text glyphs to have X-positions that aren't snapped to the pixel grid
+// in webkit renderers.
+const char kEnableWebkitTextSubpixelPositioning[] =
+    "enable-webkit-text-subpixel-positioning";
+
 // Overrides the device scale factor for the browser UI and the
 // contents.
 const char kForceDeviceScaleFactor[] = "force-device-scale-factor";
diff --git a/ui/base/ui_base_switches.h b/ui/base/ui_base_switches.h
index 2613fe8..0f522ce 100644
--- a/ui/base/ui_base_switches.h
+++ b/ui/base/ui_base_switches.h
@@ -14,10 +14,11 @@ namespace switches {
 
 UI_EXPORT extern const char kEnableBezelTouch[];
 UI_EXPORT extern const char kDisableScalingInImageSkiaOperations[];
-UI_EXPORT extern const char kEnableTextSubpixelPositioning[];
+UI_EXPORT extern const char kEnableBrowserTextSubpixelPositioning[];
 UI_EXPORT extern const char kEnableTouchCalibration[];
 UI_EXPORT extern const char kEnableTouchEvents[];
 UI_EXPORT extern const char kEnableViewsTextfield[];
+UI_EXPORT extern const char kEnableWebkitTextSubpixelPositioning[];
 UI_EXPORT extern const char kForceDeviceScaleFactor[];
 UI_EXPORT extern const char kHighlightMissing2xResources[];
 UI_EXPORT extern const char kLang[];
diff --git a/ui/gfx/font_render_params_android.cc b/ui/gfx/font_render_params_android.cc
index e3547e1..3dfd668 100644
--- a/ui/gfx/font_render_params_android.cc
+++ b/ui/gfx/font_render_params_android.cc
@@ -29,7 +29,12 @@ const FontRenderParams& GetDefaultFontRenderParams() {
   static FontRenderParams default_params;
   if (!loaded_defaults)
     LoadDefaults(&default_params);
+  loaded_defaults = true;
   return default_params;
 }
 
+const FontRenderParams& GetDefaultWebKitFontRenderParams() {
+  return GetDefaultFontRenderParams();
+}
+
 }  // namespace gfx
diff --git a/ui/gfx/font_render_params_linux.cc b/ui/gfx/font_render_params_linux.cc
index ddefc95..2b32c7b 100644
--- a/ui/gfx/font_render_params_linux.cc
+++ b/ui/gfx/font_render_params_linux.cc
@@ -18,8 +18,9 @@ namespace gfx {
 
 namespace {
 
-// Initializes |params| with the system's default settings.
-void LoadDefaults(FontRenderParams* params) {
+// Initializes |params| with the system's default settings. |renderer| is true
+// when setting WebKit renderer defaults.
+void LoadDefaults(FontRenderParams* params, bool renderer) {
 #if defined(TOOLKIT_GTK)
   params->antialiasing = true;
   params->subpixel_positioning = false;
@@ -105,15 +106,17 @@ void LoadDefaults(FontRenderParams* params) {
       params->subpixel_rendering = FontRenderParams::SUBPIXEL_RENDERING_NONE;
   }
 
-  if (CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kEnableTextSubpixelPositioning)) {
-    // To enable subpixel positioning, we need to disable hinting.
-    params->subpixel_positioning = true;
+  params->subpixel_positioning =
+      CommandLine::ForCurrentProcess()->HasSwitch(
+          renderer ?
+          switches::kEnableWebkitTextSubpixelPositioning :
+          switches::kEnableBrowserTextSubpixelPositioning);
+
+  // To enable subpixel positioning, we need to disable hinting.
+  if (params->subpixel_positioning)
     params->hinting = FontRenderParams::HINTING_NONE;
-  } else {
-    params->subpixel_positioning = false;
+  else
     params->hinting = FontRenderParams::HINTING_SLIGHT;
-  }
 #endif
 }
 
@@ -123,7 +126,17 @@ const FontRenderParams& GetDefaultFontRenderParams() {
   static bool loaded_defaults = false;
   static FontRenderParams default_params;
   if (!loaded_defaults)
-    LoadDefaults(&default_params);
+    LoadDefaults(&default_params, /* renderer */ false);
+  loaded_defaults = true;
+  return default_params;
+}
+
+const FontRenderParams& GetDefaultWebKitFontRenderParams() {
+  static bool loaded_defaults = false;
+  static FontRenderParams default_params;
+  if (!loaded_defaults)
+    LoadDefaults(&default_params, /* renderer */ true);
+  loaded_defaults = true;
   return default_params;
 }
 
diff --git a/ui/gfx/font_render_params_linux.h b/ui/gfx/font_render_params_linux.h
index 7a9339a..de15d01 100644
--- a/ui/gfx/font_render_params_linux.h
+++ b/ui/gfx/font_render_params_linux.h
@@ -56,6 +56,9 @@ struct UI_EXPORT FontRenderParams {
 // Returns the system's default parameters for font rendering.
 UI_EXPORT const FontRenderParams& GetDefaultFontRenderParams();
 
+// Returns the system's default parameters for WebKit font rendering.
+UI_EXPORT const FontRenderParams& GetDefaultWebKitFontRenderParams();
+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_RENDER_PARAMS_LINUX_H_