add extractSubset and SkAutoPixmapStorage

include/core/SkPixmap.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPixmap_DEFINED
 #define SkPixmap_DEFINED
 
 #include "SkImageInfo.h"
 
 class SkColorTable;
+struct SkMask;
 
 /**
  *  Pairs SkImageInfo with actual pixels and rowbytes. This class does not try to manage the
  *  lifetime of the pixel memory (nor the colortable if provided).
  */
 class SkPixmap {
 public:
     SkPixmap()
         : fPixels(NULL), fCTable(NULL), fRowBytes(0), fInfo(SkImageInfo::MakeUnknown(0, 0))
     {}
 
     SkPixmap(const SkImageInfo& info, const void* addr, size_t rowBytes,
              SkColorTable* ctable = NULL)
         : fPixels(addr), fCTable(ctable), fRowBytes(rowBytes), fInfo(info)
     {
         if (kIndex_8_SkColorType == info.colorType()) {
             SkASSERT(ctable);
         } else {
             SkASSERT(NULL == ctable);
         }
     }
 
     void reset();
     void reset(const SkImageInfo& info, const void* addr, size_t rowBytes,
                SkColorTable* ctable = NULL);
+    void reset(const SkImageInfo& info) {
+        this->reset(info, NULL, 0, NULL);
+    }
+
+    /**
+     *  If supported, set this pixmap to point to the pixels in the specified mask and return true.
+     *  On failure, return false and set this pixmap to empty.
+     */
+    bool SK_WARN_UNUSED_RESULT reset(const SkMask&);
+
+    /**
+     *  Computes the intersection of area and this pixmap. If that intersection is non-empty,
+     *  set subset to that intersection and return true.
+     *
+     *  On failure, return false and ignore the subset parameter.
+     */
+    bool SK_WARN_UNUSED_RESULT extractSubset(SkPixmap* subset, const SkIRect& area) const;
 
     const SkImageInfo& info() const { return fInfo; }
     size_t rowBytes() const { return fRowBytes; }
     const void* addr() const { return fPixels; }
     SkColorTable* ctable() const { return fCTable; }
 
     int width() const { return fInfo.width(); }
     int height() const { return fInfo.height(); }
     SkColorType colorType() const { return fInfo.colorType(); }
     SkAlphaType alphaType() const { return fInfo.alphaType(); }
@@ skipping 68 matching lines @@
 
 private:
     const void*     fPixels;
     SkColorTable*   fCTable;
     size_t          fRowBytes;
     SkImageInfo     fInfo;
 };
 
 /////////////////////////////////////////////////////////////////////////////////////////////
 
+class SkAutoPixmapStorage : public SkPixmap {
+public:
+    SkAutoPixmapStorage();
+    ~SkAutoPixmapStorage();
+
+    /**
+     *  Try to allocate memory for the pixels needed to match the specified Info. On success
+     *  return true and fill out the pixmap to point to that memory. The storage will be freed
+     *  when this object is destroyed, or if another call to tryAlloc() or alloc() is made.
+     *
+     *  On failure, return false and reset() the pixmap to empty.
+     */
+    bool tryAlloc(const SkImageInfo&);
+
+    /**
+     *  Allocate memory for the pixels needed to match the specified Info and fill out the pixmap
+     *  to point to that memory. The storage will be freed when this object is destroyed,
+     *  or if another call to tryAlloc() or alloc() is made.
+     *
+     *  If the memory cannot be allocated, calls sk_throw().
+     */
+    void alloc(const SkImageInfo&);
+
+private:
+    void*   fStorage;
+};
+
+/////////////////////////////////////////////////////////////////////////////////////////////
+
 class SkAutoPixmapUnlock : ::SkNoncopyable {
 public:
     SkAutoPixmapUnlock() : fUnlockProc(NULL), fIsLocked(false) {}
     SkAutoPixmapUnlock(const SkPixmap& pm, void (*unlock)(void*), void* ctx)
         : fUnlockProc(unlock), fUnlockContext(ctx), fPixmap(pm), fIsLocked(true)
     {}
     ~SkAutoPixmapUnlock() { this->unlock(); }
 
     /**
      *  Return the currently locked pixmap. Undefined if it has been unlocked.
@@ skipping 27 matching lines @@
 private:
     void        (*fUnlockProc)(void*);
     void*       fUnlockContext;
     SkPixmap    fPixmap;
     bool        fIsLocked;
 
     friend class SkBitmap;
 };
 
 #endif