change offset to xy for pixelref subsetting

BUG=
R=scroggo@google.com

Review URL: https://codereview.chromium.org/105893012

git-svn-id: http://skia.googlecode.com/svn/trunk@12958 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 44 insertions, 17 deletions

diff --git a/include/core/SkBitmap.h b/include/core/SkBitmap.h
index 2b900bef34..fe0fc0f9c1 100644
--- a/include/core/SkBitmap.h
+++ b/include/core/SkBitmap.h
@@ -347,18 +347,41 @@ public:
     */
     bool allocPixels(Allocator* allocator, SkColorTable* ctable);
 
-    /** Return the current pixelref object, if any
-    */
+    /**
+     *  Return the current pixelref object or NULL if there is none. This does
+     *  not affect the refcount of the pixelref.
+     */
     SkPixelRef* pixelRef() const { return fPixelRef; }
-    /** Return the offset into the pixelref, if any. Will return 0 if there is
-        no pixelref installed.
-    */
-    size_t pixelRefOffset() const { return fPixelRefOffset; }
-    /** Assign a pixelref and optional offset. Pixelrefs are reference counted,
-        so the existing one (if any) will be unref'd and the new one will be
-        ref'd.
-    */
-    SkPixelRef* setPixelRef(SkPixelRef* pr, size_t offset = 0);
+
+    /**
+     *  A bitmap can reference a subset of a pixelref's pixels. That means the
+     *  bitmap's width/height can be <= the dimensions of the pixelref. The
+     *  pixelref origin is the x,y location within the pixelref's pixels for
+     *  the bitmap's top/left corner. To be valid the following must be true:
+     *
+     *  origin_x + bitmap_width  <= pixelref_width
+     *  origin_y + bitmap_height <= pixelref_height
+     *
+     *  pixelRefOrigin() returns this origin, or (0,0) if there is no pixelRef.
+     */
+    SkIPoint pixelRefOrigin() const { return fPixelRefOrigin; }
+
+    /**
+     *  Assign a pixelref and origin to the bitmap. Pixelrefs are reference,
+     *  so the existing one (if any) will be unref'd and the new one will be
+     *  ref'd. (x,y) specify the offset within the pixelref's pixels for the
+     *  top/left corner of the bitmap. For a bitmap that encompases the entire
+     *  pixels of the pixelref, these will be (0,0).
+     */
+    SkPixelRef* setPixelRef(SkPixelRef* pr, int dx, int dy);
+
+    SkPixelRef* setPixelRef(SkPixelRef* pr, const SkIPoint& origin) {
+        return this->setPixelRef(pr, origin.fX, origin.fY);
+    }
+    
+    SkPixelRef* setPixelRef(SkPixelRef* pr) {
+        return this->setPixelRef(pr, 0, 0);
+    }
 
     /** Call this to ensure that the bitmap points to the current pixel address
         in the pixelref. Balance it with a call to unlockPixels(). These calls
@@ -665,13 +688,14 @@ private:
     mutable MipMap* fMipMap;
 
     mutable SkPixelRef* fPixelRef;
-    mutable size_t      fPixelRefOffset;
     mutable int         fPixelLockCount;
     // either user-specified (in which case it is not treated as mutable)
     // or a cache of the returned value from fPixelRef->lockPixels()
     mutable void*       fPixels;
     mutable SkColorTable* fColorTable;    // only meaningful for kIndex8
 
+    SkIPoint    fPixelRefOrigin;
+
     enum Flags {
         kImageIsOpaque_Flag     = 0x01,
         kImageIsVolatile_Flag   = 0x02,
diff --git a/include/core/SkBitmapDevice.h b/include/core/SkBitmapDevice.h
index f3d40d0ce8..a9208e20a0 100644
--- a/include/core/SkBitmapDevice.h
+++ b/include/core/SkBitmapDevice.h
@@ -199,8 +199,8 @@ protected:
 
     SkPixelRef* getPixelRef() const { return fBitmap.pixelRef(); }
     // just for subclasses, to assign a custom pixelref
-    SkPixelRef* setPixelRef(SkPixelRef* pr, size_t offset) {
-        fBitmap.setPixelRef(pr, offset);
+    SkPixelRef* setPixelRef(SkPixelRef* pr) {
+        fBitmap.setPixelRef(pr);
         return pr;
     }
 
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index a1d7644e53..4c7e4b3399 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -172,8 +172,8 @@ public:
      *  signature can be passed to serialize() and SkOrderedWriteBuffer.
      *  Returning NULL will tell the SkOrderedWriteBuffer to use
      *  SkBitmap::flatten() to store the bitmap.
-     *  @param pixelRefOffset Output parameter, telling the deserializer what
-     *      offset in the bm's pixelRef corresponds to the encoded data.
+     *
+     *  @param pixelRefOffset DEPRECATED -- caller assumes it will return 0.
      *  @return SkData If non-NULL, holds encoded data representing the passed
      *      in bitmap. The caller is responsible for calling unref().
      */
@@ -221,10 +221,11 @@ protected:
     // V15: Remove A1 bitmpa config (and renumber remaining configs)
     // V16: Move SkPath's isOval flag to SkPathRef
     // V17: SkPixelRef now writes SkImageInfo
+    // V18: SkBitmap now records x,y for its pixelref origin, instead of offset.
 #ifndef DELETE_THIS_CODE_WHEN_SKPS_ARE_REBUILT_AT_V16_AND_ALL_OTHER_INSTANCES_TOO
     static const uint32_t PRIOR_PICTURE_VERSION = 15;  // TODO: remove when .skps regenerated
 #endif
-    static const uint32_t PICTURE_VERSION = 17;
+    static const uint32_t PICTURE_VERSION = 18;
 
     // fPlayback, fRecord, fWidth & fHeight are protected to allow derived classes to
     // install their own SkPicturePlayback-derived players,SkPictureRecord-derived
diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index 4811435721..e0bf8866c6 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -69,6 +69,8 @@ public:
     */
     SkColorTable* colorTable() const { return fRec.fColorTable; }
 
+    size_t rowBytes() const { return fRec.fRowBytes; }
+
     /**
      *  To access the actual pixels of a pixelref, it must be "locked".
      *  Calling lockPixels returns a LockRec struct (on success).