Optimize CSS box-shadow performance

src/core/SkMaskCache.cpp

Index: src/core/SkMaskCache.cpp
diff --git a/src/core/SkMaskCache.cpp b/src/core/SkMaskCache.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..29c91b1abcd66003629425dd33b3a452cb735e54
--- /dev/null
+++ b/src/core/SkMaskCache.cpp
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkMaskCache.h"
+
+struct RRectBlurKey : public SkScaledImageCache::Key {
+public:
+    RRectBlurKey(SkScalar sigma, const SkRRect rrect)
+        : fSigma(sigma)
+        , fRRect(rrect) {
+        this->init(sizeof(fSigma) + sizeof(fRRect));
+    }
+
+    SkScalar    fSigma;
+    SkRRect     fRRect;
+};
+
+struct RectsBlurKey : public SkScaledImageCache::Key {
+public:
+    RectsBlurKey(SkScalar sigma, int32_t count, const SkRect rects[])
+        : fSigma(sigma)
+        , fRecCount(count) {
+        for (int i = 0; i < count; i++) {
+            fRects[i] = rects[i];
+        }
+        this->init(sizeof(fSigma) + sizeof(fRecCount) + sizeof(SkRect) * fRecCount);
+    }
+
+    SkScalar    fSigma;
+    int32_t     fRecCount;
+    SkRect      fRects[2];
+};
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
+SkMaskCache::ID* SkMaskCache::FindAndLock(SkScalar sigma,
+                                                   const SkRRect rrect,
+                                                   SkMask* result) {
+    RRectBlurKey key(sigma, rrect);
+    SkBitmap bitmap;
+    ID* cacheId = SkScaledImageCache::FindAndLock(key, &bitmap);
+    if (cacheId) {
+        SkAutoLockPixels autoLockPixels(bitmap);
+        result->fBounds.set(0, 0, bitmap.width(), bitmap.height());
+        result->fRowBytes = result->fBounds.width();
+        result->fFormat = SkMask::kA8_Format;
+        result->fImage = static_cast<uint8_t*>(bitmap.getPixels());
+    }
+
+    return cacheId;
+}
+
+SkMaskCache::ID* SkMaskCache::AddAndLock(SkScalar sigma,
+                                                  const SkRRect rrect,
+                                                  const SkMask& mask) {
+    SkBitmap bitmap;
+    bitmap.installMaskPixels(mask);

[reed1, 2014/08/25 11:58:42]

installMaskPixels does not copy the memory for the pixels, but the caller of
this will free those pixels when the mask goes away.

[qiankun, 2014/08/26 08:36:33]

The pixels owned by mask won't be freed in this blurMask case when mask goes
away. Or I can do a deepCopyTo for bitmap. I am looking forward to your
solution.

+    RRectBlurKey key(sigma, rrect);
+    return SkScaledImageCache::AddAndLock(key, bitmap);
+}
+
+////
+
+SkMaskCache::ID* SkMaskCache::FindAndLock(SkScalar sigma,
+                                                   unsigned count,
+                                                   const SkRect rects[],
+                                                   SkMask* result) {
+    RectsBlurKey key(sigma, count, rects);
+    SkBitmap bitmap;
+    ID* cacheId = SkScaledImageCache::FindAndLock(key, &bitmap);
+    if (cacheId) {
+        SkAutoLockPixels autoLockPixels(bitmap);
+        result->fBounds.set(0, 0, bitmap.width(), bitmap.height());
+        result->fRowBytes = result->fBounds.width();
+        result->fFormat = SkMask::kA8_Format;
+        result->fImage = static_cast<uint8_t*>(bitmap.getPixels());
+    }
+
+    return cacheId;
+}
+
+SkMaskCache::ID* SkMaskCache::AddAndLock(SkScalar sigma,
+                                                  unsigned count,
+                                                  const SkRect rects[],
+                                                  const SkMask& mask) {
+    SkBitmap bitmap;
+    bitmap.installMaskPixels(mask);
+    RectsBlurKey key(sigma, count, rects);
+    return SkScaledImageCache::AddAndLock(key, bitmap);
+}
+