The key for SkBitmapCache can now be genID+SkIRect

src/core/SkBitmapCache.cpp

Index: src/core/SkBitmapCache.cpp
diff --git a/src/core/SkBitmapCache.cpp b/src/core/SkBitmapCache.cpp
index 8de8ab79edac2d8b0224bb3a0e140b81551964cc..a84ab97c4592bcf6f79f6028988088f075587943 100644
--- a/src/core/SkBitmapCache.cpp
+++ b/src/core/SkBitmapCache.cpp
@@ -56,7 +56,7 @@ struct BitmapRec : public SkResourceCache::Rec {
 
     BitmapKey   fKey;
     SkBitmap    fBitmap;
-    
+
     virtual const Key& getKey() const SK_OVERRIDE { return fKey; }
     virtual size_t bytesUsed() const SK_OVERRIDE { return sizeof(fKey) + fBitmap.getSize(); }
 };
@@ -101,16 +101,30 @@ void SkBitmapCache::Add(const SkBitmap& src, SkScalar invScaleX, SkScalar invSca
 }
 
 bool SkBitmapCache::Find(uint32_t genID, int width, int height, SkBitmap* result) {
-    BitmapKey key(genID, SK_Scalar1, SK_Scalar1, SkIRect::MakeWH(width, height));
-    return find_and_return(key, result);
+    return Find(genID, SkIRect::MakeWH(width, height), result);
 }
 
 void SkBitmapCache::Add(uint32_t genID, int width, int height, const SkBitmap& result) {
-    SkASSERT(result.isImmutable());
-    SkResourceCache::Add(SkNEW_ARGS(BitmapRec, (genID, SK_Scalar1, SK_Scalar1,
-                                                SkIRect::MakeWH(width, height), result)));
+    Add(genID, SkIRect::MakeWH(width, height), result);
+}
+
+bool SkBitmapCache::Find(uint32_t genID, const SkIRect& subset, SkBitmap* result) {
+    BitmapKey key(genID, SK_Scalar1, SK_Scalar1, subset);
+    return find_and_return(key, result);
 }
 
+void SkBitmapCache::Add(uint32_t genID, const SkIRect& subset, const SkBitmap& result) {
+    SkASSERT(result.isImmutable());
+
+    // We need to take only the width and height of 'subset' to compute the intersection

[reed1, 2014/09/02 20:38:45]

Actually the subset rect is very interesting because it can have non-zero
left/top (in the general case). Why are you explicitly zapping those?

[Rémi Piotaix, 2014/09/02 20:48:44]

Because the given subset is relative to the original bitmap from which the
'result' has been extracted.
If we extract, from a 100x100 bitmap, a subset at 90,90 of width 10x10, we will
have:
intersect(rect(0, 0, 10, 10), rect(90, 90, 10, 10)) which will be always empty.

+    SkIRect localSubset = SkIRect::MakeWH(subset.width(), subset.height());
+    SkIRect bitmapBounds = SkIRect::MakeWH(result.width(), result.height());
+
+    if (localSubset.intersect(bitmapBounds)) {
+        SkResourceCache::Add(SkNEW_ARGS(BitmapRec, (genID, SK_Scalar1, SK_Scalar1,
+                                                    localSubset, result)));
+    }
+}
 //////////////////////////////////////////////////////////////////////////////////////////
 
 struct MipMapRec : public SkResourceCache::Rec {
@@ -125,7 +139,7 @@ struct MipMapRec : public SkResourceCache::Rec {
 
     BitmapKey       fKey;
     const SkMipMap* fMipMap;
-    
+
     virtual const Key& getKey() const SK_OVERRIDE { return fKey; }
     virtual size_t bytesUsed() const SK_OVERRIDE { return sizeof(fKey) + fMipMap->getSize(); }
 };