SkOnce in is_lcd_supported instead of hand rolled double-checked locking.

src/ports/SkFontHost_FreeType.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "SkAdvancedTypefaceMetrics.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkColorPriv.h"
 #include "SkDescriptor.h"
 #include "SkFDot6.h"
 #include "SkFloatingPoint.h"
 #include "SkFontHost.h"
 #include "SkFontHost_FreeType_common.h"
 #include "SkGlyph.h"
 #include "SkMask.h"
 #include "SkMaskGamma.h"
 #include "SkOTUtils.h"
-#include "SkAdvancedTypefaceMetrics.h"
+#include "SkOnce.h"
 #include "SkScalerContext.h"
 #include "SkStream.h"
 #include "SkString.h"
 #include "SkTemplates.h"
 #include "SkThread.h"
 
 #if defined(SK_CAN_USE_DLOPEN)
 #include <dlfcn.h>
 #endif
 #include <ft2build.h>
@@ skipping 121 matching lines @@
 #endif
     }
 #else
     gLCDSupport = false;
 #endif
     gLCDSupportValid = true;
 
     return true;
 }
 
+// Called while holding gFTMutex.
+static void determine_lcd_support(bool* lcdSupported) {
+    if (!gLCDSupportValid) {
+        // This will determine LCD support as a side effect.
+        InitFreetype();
+        FT_Done_FreeType(gFTLibrary);
+    }
+    SkASSERT(gLCDSupportValid);
+    *lcdSupported = gLCDSupport;
+}
+
 // Lazy, once, wrapper to ask the FreeType Library if it can support LCD text
 static bool is_lcd_supported() {
-    if (!gLCDSupportValid) {
-        SkAutoMutexAcquire  ac(gFTMutex);
-
-        if (!gLCDSupportValid) {
-            InitFreetype();
-            FT_Done_FreeType(gFTLibrary);
-        }
-    }
-    return gLCDSupport;
+    static bool lcdSupported = false;
+    SkOnce(&gLCDSupportValid, &gFTMutex, determine_lcd_support, &lcdSupported);
+    return lcdSupported;
 }
 
 class SkScalerContext_FreeType : public SkScalerContext_FreeType_Base {
 public:
     SkScalerContext_FreeType(SkTypeface*, const SkDescriptor* desc);
     virtual ~SkScalerContext_FreeType();
 
     bool success() const {
         return fFaceRec != NULL &&
                fFTSize != NULL &&
@@ skipping 1493 matching lines @@
         *style = (SkTypeface::Style) tempStyle;
     }
     if (isFixedPitch) {
         *isFixedPitch = FT_IS_FIXED_WIDTH(face);
     }
 
     FT_Done_Face(face);
     FT_Done_FreeType(library);
     return true;
 }